{"version":1,"generatedAt":"2026-10-26T06:42:31.735Z","count":49,"records":[{"kind":"equipment","family":"boilers","manufacturer":"Honeywell","manufacturerSlug":"honeywell","model":"7800 Series","modelSlug":"7800-series","title":"Honeywell 7800 Series Burner Control Troubleshooting","description":"How Honeywell 7800 Series relay modules (RM7800 and family) report lockouts, the six-lockout fault history, the burner sequence, and every fault code from 1 to 127.","summary":"The Honeywell 7800 Series is a family of microprocessor burner control relay modules, such as the RM7800, usually fitted with the S7800 Keyboard Display Module. On a lockout the display shows a numbered fault code, a message and the sequence step the burner was in, which together narrow down the cause.","faultReporting":["The Keyboard Display Module shows the fault code number, a fault message and the burner sequence status at the time of the fault.","The relay module stores the six most recent lockouts in non-volatile memory, each with the cycle count, operating hour, fault code, message and burner status.","A lockout is not cleared by switching power off and on; it needs a reset.","Fault codes run from 1 to 127. Codes 105–127 are mainly relay-module self-test faults shown as *Call Service*.","Some codes apply only to particular modules (for example RM7838B or EC/RM7850); check the model on the relay module label."],"sequence":[{"name":"INITIATE / STANDBY","text":"The module checks itself and waits for a call for heat; limits and interlocks must be proven."},{"name":"PURGE","text":"Combustion air purges the furnace; the airflow interlock must be proven."},{"name":"PILOT IGN (PFEP)","text":"Pilot Flame Establishing Period: the igniter and pilot valve are energised and flame must be proven."},{"name":"MAIN IGN (MFEP)","text":"Main Flame Establishing Period: the main fuel valve opens and main flame must be proven."},{"name":"RUN","text":"The burner fires under its modulation control with flame supervised."},{"name":"POSTPURGE","text":"Air purges the furnace after the burner shuts down."}],"evidence":["Photo of the Keyboard Display Module showing code, message and sequence step","The fault history (six most recent lockouts)","Relay module model and flame amplifier type","Flame signal reading during a normal start"],"codeIndex":[{"code":"1","name":"*No Purge Card*: purge card missing"},{"code":"2–5","name":"AC supply faults: noise, line dropout, frequency or low line voltage"},{"code":"6","name":"*Purge Card Error*: purge card timing changed"},{"code":"7–8","name":"*Flame Amplifier* / *Flame Amp/Shutr*: flame sensed when none expected, amplifier or shutter check"},{"code":"9","name":"*Flame Detected*: flame sensed in STANDBY with the shutter open"},{"code":"10","name":"*Pre-Ignition ILK*: pre-ignition interlock fault in STANDBY"},{"code":"11–12","name":"*Running ILK On* / *Lockout ILK On*: interlock powered at the wrong point"},{"code":"13","name":"*Airflow Sw. On*: airflow interlock closed in STANDBY"},{"code":"14","name":"*High Fire Sw.*: high fire switch not closed in PREPURGE"},{"code":"15","name":"*Flame Detected*: flame sensed in STANDBY"},{"code":"16","name":"*Flame-Out Timer*: no flame during PFEP"},{"code":"17","name":"*Main Flame Fail*: main flame lost in RUN after at least 10 s"},{"code":"18","name":"*Flame Detected*: flame sensed in PREPURGE"},{"code":"19","name":"*Main Flame Ign.*: flame lost in MFEP or the first 10 s of RUN"},{"code":"20","name":"*Low Fire Sw. Off*: low fire switch not closed"},{"code":"21–22","name":"*Running ILK* / *Lockout ILK*: interlock fault in PREPURGE"},{"code":"23","name":"*Airflow Switch*: airflow interlock fault in PREPURGE"},{"code":"24–25","name":"*Call Service*: internal flame interlock in the wrong state"},{"code":"26–27","name":"Manual open valve or start switch faults (RM7838 only)"},{"code":"28","name":"*Pilot Flame Fail*: pilot flame failure"},{"code":"29–30","name":"*Lockout ILK* / *Running ILK*: interlock fault"},{"code":"31","name":"*Low Fire Sw. Off*: low fire switch open in RUN (RM7838B)"},{"code":"32","name":"*Airflow Switch*: combustion airflow interlock fault"},{"code":"33","name":"*Pre-Ignition ILK*: pre-ignition interlock fault"},{"code":"34","name":"*Control On*: control input energised at the wrong time (wiring)"},{"code":"35–40","name":"*Call Service*: safety relay or output terminal in the wrong state"},{"code":"41–44","name":"Main valve, pilot valve, ignition or V2S terminal on when it should be off (explosion hazard warning in the manual)"},{"code":"45","name":"*Low Fire Sw. Off*: low fire switch failed to close or stay closed"},{"code":"46","name":"*Flame Amp Type*: amplifier type or response time not valid for the module"},{"code":"47","name":"*Jumpers Changed*: configuration jumpers differ from startup"},{"code":"48–49","name":"Delayed main valve or manual-open switch on when it should be off"},{"code":"50","name":"*Jumpers Wrong*: illegal jumper combination"},{"code":"51","name":"*Flame Too Strong*: flame signal above the valid range"},{"code":"52–57","name":"Pilot valve 2, lockout switch and Fulton pulse combustion faults"},{"code":"67","name":"*AC Phase*: L1 and L2 miswired"},{"code":"68","name":"*Pre-Ignition ILK*: pre-ignition interlock fault (EC/RM7810, 7820, 7830, 7850)"},{"code":"71–75","name":"Firing-rate switch, special function and flame-proven feedback faults (model specific)"},{"code":"76–93","name":"*Accessory Fault*: accessory and valve proving faults"},{"code":"105–127","name":"*Call Service*: relay module self-test, ground, jumper and safety relay checks"}],"sources":[{"title":"7800 SERIES Relay Modules: Checkout and Test","publisher":"Honeywell","docId":"65-0229-2","revision":"M.S. Rev. 02-06","url":"https://docuthek.kromschroeder.com/download.php?lang=de&doc=66089","section":"Keyboard Display Module messages; Table 2; Table 3 Hold and Fault Message Summary","page":"6–16"},{"title":"RM7800 Relay Module installation instructions","publisher":"Honeywell","docId":"66-1085-3","section":"Sequence of Operation; Table 6","page":"11–12","url":"https://www.stromquist.com/customer/docs/honeywell/RM7800spec.pdf"}],"review":{"status":"extracted","checks":["No step asks the reader to bypass, jumper or disable a flame safeguard, limit or interlock.","Electrical and fuel-train checks are framed for qualified personnel only.","Every code range and message in the index matches Table 3 of 65-0229-2 and the current Honeywell documentation."]},"updatedAt":"2026-10-26","url":"https://induqt.ai/troubleshoot/boilers/honeywell/7800-series"},{"kind":"fault","family":"boilers","manufacturerSlug":"honeywell","modelSlug":"7800-series","controller":"Honeywell 7800 Series relay module (RM7800, RM7840, EC7800 family)","severity":"lockout","code":"13","name":"Airflow Sw. On","title":"Honeywell 7800 Fault 13: Airflow Switch On in Standby","description":"Honeywell 7800 fault 13 means the combustion airflow interlock was closed during STANDBY, before the fan should be proving air. Causes, checks and evidence.","meaning":"In STANDBY the relay module expects the combustion airflow interlock to be open, because the fan has not been asked to run. Fault 13 means the module saw that circuit closed at a point where no air flow should exist, so it cannot trust the switch to prove air during purge.","operatingStates":["STANDBY, before the call for heat starts the fan","Often seen right after a previous cycle, while the fan is still running down"],"functions":["air-proving","limit-supervision"],"relatedComponents":["air-switch","combustion-fan","burner-controller"],"causes":[{"cause":"Air switch contacts stuck or welded closed","signs":"Fault appears on every start; the switch reads closed with the fan stopped.","check":"With the fan stopped and power isolated, check the switch contacts for continuity and inspect for a jumper left from previous work.","component":"air-switch","mechanism":"contact-welded"},{"cause":"Air still moving through the boiler with the fan off","signs":"Intermittent, worse in windy weather, with a tall stack or when another fan shares the breeching.","check":"Read the pressure at the switch sensing point with the fan off; compare with the switch setpoint and the burner maker’s draft limits.","component":"air-switch","mechanism":"switch-drift"},{"cause":"Fan running when it should be off","signs":"Fan can be heard in STANDBY; motor contactor or fan VSD stays on.","check":"Check the fan contactor, starter auxiliaries and any VSD run command; confirm the fan stops when the module drops the motor output.","component":"combustion-fan","mechanism":"contact-welded"},{"cause":"Wiring error feeding the airflow input","signs":"Line voltage present on the interlock input with the switch open.","check":"Table 3 groups 11, 12 and 13 together and directs a voltage check on the interlock terminals with the controller off; a qualified technician should trace any unexpected feed.","component":"burner-controller","mechanism":"contact-welded"}],"distinguish":["Fault 13 is the switch closed when it should be open (STANDBY). Fault 23 and fault 32 are the opposite: air not proven when it should be.","Faults 11 and 12 (running or lockout interlock on at the wrong point) share the same checks; read which message appears before resetting."],"evidence":["Photo of the display with code 13 and the sequence status","Whether the fan is audibly running in STANDBY","Air switch model, setpoint and sensing-line routing","Pressure at the sensing point with the fan off"],"related":["23","32"],"sources":[{"title":"7800 SERIES Relay Modules: Checkout and Test","publisher":"Honeywell","docId":"65-0229-2","revision":"M.S. Rev. 02-06","url":"https://docuthek.kromschroeder.com/download.php?lang=de&doc=66089","section":"Table 3, Hold and Fault Message Summary: fault 13","page":"10"},{"title":"RM7800 Relay Module installation instructions","publisher":"Honeywell","docId":"66-1085-3","section":"Sequence of Operation; Table 6","page":"11–12","url":"https://www.stromquist.com/customer/docs/honeywell/RM7800spec.pdf"}],"review":{"status":"extracted","checks":["No step asks the reader to bypass, jumper or disable a flame safeguard, limit or interlock.","Electrical and fuel-train checks are framed for qualified personnel only.","Code 13, its message and the sequence point match Table 3 of 65-0229-2 for the installed relay module."]},"updatedAt":"2026-10-26","url":"https://induqt.ai/troubleshoot/boilers/honeywell/7800-series/13"},{"kind":"fault","family":"boilers","manufacturerSlug":"honeywell","modelSlug":"7800-series","controller":"Honeywell 7800 Series relay module (RM7800, RM7840, EC7800 family)","severity":"lockout","code":"14","name":"High Fire Sw.","title":"Honeywell 7800 Fault 14: High Fire Switch Not Closed","description":"Honeywell 7800 fault 14: the high fire (purge position) switch did not close during PREPURGE. How to tell a stuck actuator from a misadjusted switch.","meaning":"During PREPURGE the module drives the firing-rate motor to high fire so the furnace is purged with full air, and waits for the high fire switch to prove it. Fault 14 means that proof never arrived within the allowed time.","operatingStates":["PREPURGE, while driving to high fire"],"functions":["purge","positioning"],"relatedComponents":["position-switches","air-damper"],"causes":[{"cause":"Actuator does not reach high fire","signs":"Damper stops short of full open; motor hums or stalls.","check":"Watch the actuator and damper during PREPURGE; check the drive signal, linkage and any mechanical stop.","component":"air-damper","mechanism":"actuator-feedback-fault"},{"cause":"High fire switch cam out of adjustment","signs":"Actuator reaches full travel but the switch does not make; appeared after linkage or motor work.","check":"Table 3 describes holding the sequence at high fire with the Run/Test switch and confirming line voltage at the high fire switch input; adjust the cam to the burner maker’s setting.","component":"position-switches","mechanism":"switch-drift"},{"cause":"Linkage slip between actuator and damper","signs":"Switch makes but air flow at purge is low, or damper position does not match the actuator shaft.","check":"Mark the shaft and damper and check for slip at couplings and set screws.","component":"air-damper","mechanism":"linkage-slip"}],"distinguish":["Fault 14 is high fire not proven in PREPURGE; fault 20 is low fire not proven before ignition.","If the actuator moves but no switch ever makes, compare both switches: a wiring fault often affects both."],"evidence":["Code 14 and sequence status","Actuator model and whether it reached full travel","Any recent linkage or actuator work"],"related":["20"],"sources":[{"title":"7800 SERIES Relay Modules: Checkout and Test","publisher":"Honeywell","docId":"65-0229-2","revision":"M.S. Rev. 02-06","url":"https://docuthek.kromschroeder.com/download.php?lang=de&doc=66089","section":"Table 3, Hold and Fault Message Summary: fault 14","page":"10"}],"review":{"status":"extracted","checks":["No step asks the reader to bypass, jumper or disable a flame safeguard, limit or interlock.","Electrical and fuel-train checks are framed for qualified personnel only.","Code 14, its message and the sequence point match Table 3 of 65-0229-2 for the installed relay module."]},"updatedAt":"2026-10-26","url":"https://induqt.ai/troubleshoot/boilers/honeywell/7800-series/14"},{"kind":"fault","family":"boilers","manufacturerSlug":"honeywell","modelSlug":"7800-series","controller":"Honeywell 7800 Series relay module (RM7800, RM7840, EC7800 family)","severity":"lockout","code":"15","name":"Flame Detected","title":"Honeywell 7800 Fault 15: Flame Detected in Standby","description":"Honeywell 7800 fault 15 means a flame signal was present in STANDBY when no flame should exist. Real flame, detector faults and noise, and how to separate them.","meaning":"The relay module checks for flame before every start. Fault 15 means it saw a flame signal during STANDBY. Either fuel is still burning in the furnace, or the detector, amplifier or wiring is producing a signal without a flame. Both are treated as unsafe, so the module locks out.","operatingStates":["STANDBY (faults 9 and 18 are the related codes for STANDBY with a shutter check and for PREPURGE)"],"functions":["flame-supervision"],"relatedComponents":["flame-scanner","flame-amplifier","main-fuel-valves"],"causes":[{"cause":"Real flame after shutdown","signs":"Flame visible through the sight glass after the cycle ends; burning oil drips or a leaking valve.","check":"Look into the furnace; if flame persists, close manual fuel valves and have the safety shutoff valves tightness-tested.","component":"main-fuel-valves","mechanism":"valve-seat-leak"},{"cause":"Infrared scanner seeing hot refractory","signs":"Only after long high-fire runs; IR detector; clears once the furnace cools.","check":"The checkout publication warns that IR detectors can respond to hot refractory; re-sight the scanner so it sees the flame, not glowing brick.","component":"flame-scanner","mechanism":"sighting-shift"},{"cause":"Failed UV tube or amplifier","signs":"Flame signal present in a cold, dark furnace; amplifier is old or a non-self-checking type.","check":"Measure the flame signal with the burner off and the scanner covered; replace the detector or amplifier if a signal remains.","component":"flame-amplifier","mechanism":"detector-ageing"},{"cause":"Noise on the flame lead","signs":"Signal flickers with ignition or nearby motor starts; detector wires share conduit with power wiring.","check":"Route the flame detector leads separately from ignition and power wiring as Table 3 directs.","component":"flame-scanner","mechanism":"signal-noise"}],"distinguish":["Fault 15 (STANDBY) and fault 18 (PREPURGE) are both flame where none should be; fault 9 is the shutter-check version during STANDBY.","Fault 51 (Flame Too Strong) is a signal above the valid range during firing, not flame at the wrong time."],"evidence":["Code and sequence status","Flame signal reading with the burner off","Detector type (UV, self-checking UV, IR, flame rod) and amplifier model","Whether flame is visible after shutdown"],"related":["51","17"],"sources":[{"title":"7800 SERIES Relay Modules: Checkout and Test","publisher":"Honeywell","docId":"65-0229-2","revision":"M.S. Rev. 02-06","url":"https://docuthek.kromschroeder.com/download.php?lang=de&doc=66089","section":"Table 3, Hold and Fault Message Summary: fault 15","page":"10"},{"title":"7800 SERIES Relay Modules: Checkout and Test","publisher":"Honeywell","docId":"65-0229-2","revision":"M.S. Rev. 02-06","url":"https://docuthek.kromschroeder.com/download.php?lang=de&doc=66089","section":"Flame signal checks: infrared detector and hot refractory","page":"5"},{"title":"7800 SERIES Relay Modules: Checkout and Test","publisher":"Honeywell","docId":"65-0229-2","revision":"M.S. Rev. 02-06","url":"https://docuthek.kromschroeder.com/download.php?lang=de&doc=66089","section":"Safety shutdown tests: detection of flame in STANDBY and PREPURGE","page":"6"}],"review":{"status":"extracted","checks":["No step asks the reader to bypass, jumper or disable a flame safeguard, limit or interlock.","Electrical and fuel-train checks are framed for qualified personnel only.","Code 15, its message and the sequence point match Table 3 of 65-0229-2 for the installed relay module."]},"updatedAt":"2026-10-26","url":"https://induqt.ai/troubleshoot/boilers/honeywell/7800-series/15"},{"kind":"fault","family":"boilers","manufacturerSlug":"honeywell","modelSlug":"7800-series","controller":"Honeywell 7800 Series relay module (RM7800, RM7840, EC7800 family)","severity":"lockout","code":"16","name":"Flame-Out Timer","title":"Honeywell 7800 Fault 16: No Flame in Pilot Trial (PFEP)","description":"Honeywell 7800 fault 16 means no flame was proven during the Pilot Flame Establishing Period. Split ignition, pilot fuel and detection problems with one observed start.","meaning":"During the Pilot Flame Establishing Period (PFEP) the module energises the igniter and pilot valve and expects the flame detector to prove a pilot flame before the period ends. Fault 16 means the period expired without a usable flame signal, so the main valves never opened.","operatingStates":["PILOT IGN (PFEP), the pilot trial for ignition"],"functions":["ignition","flame-supervision"],"relatedComponents":["igniter","pilot-train","flame-scanner","flame-amplifier","air-damper"],"causes":[{"cause":"No spark or a weak spark","signs":"No ignition sound or visible spark through the sight glass.","check":"Inspect the electrode tip, insulator and gap; check the transformer output and high-voltage lead per the burner manual.","component":"igniter","mechanism":"electrode-wear"},{"cause":"Pilot gas not arriving","signs":"Spark present but no pilot flame; pilot regulator or valve recently serviced.","check":"Read pilot gas pressure during the trial; confirm the pilot valve opens and the manual pilot cock is open.","component":"pilot-train","mechanism":"valve-not-opening"},{"cause":"Detector does not see the pilot","signs":"Pilot visible but flame signal stays below the minimum.","check":"Measure the flame signal at the test jack during the pilot trial. The checkout publication uses 1.25 Vdc as the minimum flame signal for a reliable pilot or main flame on the 7800 test jack (65-0229-2, Flame signal and pilot turndown tests). Clean and re-sight the scanner, or check flame rod position.","component":"flame-scanner","mechanism":"sighting-shift"},{"cause":"Amplifier and detector not compatible","signs":"After a detector or amplifier was replaced.","check":"Confirm the plug-in amplifier type matches the detector, as Table 3 directs.","component":"flame-amplifier","mechanism":"amplifier-mismatch"},{"cause":"Too much light-off air","signs":"Pilot lights then blows out; after damper or low-fire position work.","check":"Check the light-off damper position against the commissioning record.","component":"air-damper","mechanism":"air-fuel-ratio-drift"}],"distinguish":["Faults 16 and 28 both point at the pilot trial. The checkout publication’s “failure to ignite pilot” safety test is documented as producing fault 28; use the same spark → pilot fuel → detection split for either.","If the pilot proves but the burner trips once the main valve opens, the code becomes 19."],"evidence":["Code 16 and sequence status (PILOT IGN)","Flame signal (Vdc) during the pilot trial","Pilot gas pressure during the trial","Detector and amplifier model numbers","Observation of spark and pilot through the sight glass"],"related":["28","19"],"sources":[{"title":"7800 SERIES Relay Modules: Checkout and Test","publisher":"Honeywell","docId":"65-0229-2","revision":"M.S. Rev. 02-06","url":"https://docuthek.kromschroeder.com/download.php?lang=de&doc=66089","section":"Table 3, Hold and Fault Message Summary: fault 16","page":"10"},{"title":"7800 SERIES Relay Modules: Checkout and Test","publisher":"Honeywell","docId":"65-0229-2","revision":"M.S. Rev. 02-06","url":"https://docuthek.kromschroeder.com/download.php?lang=de&doc=66089","section":"Initial lightoff checks: pilot; Pilot turndown test","page":"2–4"}],"review":{"status":"extracted","checks":["No step asks the reader to bypass, jumper or disable a flame safeguard, limit or interlock.","Electrical and fuel-train checks are framed for qualified personnel only.","Code 16, its message and the sequence point match Table 3 of 65-0229-2 for the installed relay module."]},"updatedAt":"2026-10-26","url":"https://induqt.ai/troubleshoot/boilers/honeywell/7800-series/16"},{"kind":"fault","family":"boilers","manufacturerSlug":"honeywell","modelSlug":"7800-series","controller":"Honeywell 7800 Series relay module (RM7800, RM7840, EC7800 family)","severity":"lockout","code":"17","name":"Main Flame Fail","title":"Honeywell 7800 Fault 17: Main Flame Failure in RUN","description":"Honeywell 7800 fault 17 means the main flame was lost in RUN after it had been established for at least 10 seconds. Fuel, air and flame detection checks, with trend evidence.","meaning":"Fault 17 means the burner lit and ran normally, then the flame signal dropped out during RUN, at least 10 seconds after the main flame was established. Because light-off succeeded, look for something that changes while firing: fuel pressure, air flow, firing rate or the detector’s view of the flame.","operatingStates":["RUN, at least 10 seconds after main flame was established","Often at load changes, high fire or when other fuel users start"],"functions":["flame-supervision","fuel-delivery","positioning"],"relatedComponents":["fuel-supply","main-fuel-valves","flame-scanner","air-damper","fuel-actuator"],"causes":[{"cause":"Fuel pressure dips while firing","signs":"Trips at high fire or when another large gas user starts; low gas pressure events near the trip.","check":"Trend burner gas (or oil) pressure across a full modulation cycle; compare with the burner’s required pressure at high fire.","component":"fuel-supply","mechanism":"supply-pressure-droop"},{"cause":"Main valve partially closing or chattering","signs":"Valve actuator noise, voltage dips on the valve circuit, or a trip that coincides with vibration.","check":"Inspect main valve wiring and terminations; check the valve actuator and supply voltage during firing.","component":"main-fuel-valves","mechanism":"valve-not-opening"},{"cause":"Detector loses sight of the flame at some firing rates","signs":"Flame signal good at low fire but weak at high fire, or the reverse.","check":"Record the flame signal at low fire, high fire and while modulating, as the checkout publication suggests. The checkout publication uses 1.25 Vdc as the minimum flame signal for a reliable pilot or main flame on the 7800 test jack (65-0229-2, Flame signal and pilot turndown tests).","component":"flame-scanner","mechanism":"sighting-shift"},{"cause":"Air/fuel ratio drift makes the flame unstable","signs":"Trips follow a tune-up, linkage work or seasonal air temperature change; flame looks lifting or smoky.","check":"Combustion-test across the firing range and check linkage for slip.","component":"air-damper","mechanism":"air-fuel-ratio-drift"}],"distinguish":["Fault 17 is loss of flame after 10 seconds of RUN. Loss during the main trial or the first 10 seconds of RUN is fault 19.","A falling flame signal over weeks before the first trip points to detection; a sudden trip with a pressure dip points to fuel supply."],"evidence":["Code 17 with the fault history (cycle and hour of each lockout)","Gas or oil pressure trend around the trip","Firing rate or damper position at the trip","Flame signal at low and high fire"],"related":["19","16"],"sources":[{"title":"7800 SERIES Relay Modules: Checkout and Test","publisher":"Honeywell","docId":"65-0229-2","revision":"M.S. Rev. 02-06","url":"https://docuthek.kromschroeder.com/download.php?lang=de&doc=66089","section":"Table 3, Hold and Fault Message Summary: fault 17","page":"10"},{"title":"7800 SERIES Relay Modules: Checkout and Test","publisher":"Honeywell","docId":"65-0229-2","revision":"M.S. Rev. 02-06","url":"https://docuthek.kromschroeder.com/download.php?lang=de&doc=66089","section":"Safety shutdown tests: loss of flame during RUN","page":"6"}],"review":{"status":"extracted","checks":["No step asks the reader to bypass, jumper or disable a flame safeguard, limit or interlock.","Electrical and fuel-train checks are framed for qualified personnel only.","Code 17, its message and the sequence point match Table 3 of 65-0229-2 for the installed relay module."]},"updatedAt":"2026-10-26","url":"https://induqt.ai/troubleshoot/boilers/honeywell/7800-series/17"},{"kind":"fault","family":"boilers","manufacturerSlug":"honeywell","modelSlug":"7800-series","controller":"Honeywell 7800 Series relay module (RM7800, RM7840, EC7800 family)","severity":"lockout","code":"19","name":"Main Flame Ign.","title":"Honeywell 7800 Fault 19: Flame Lost at Main Light-Off","description":"Honeywell 7800 fault 19 means flame was lost during the Main Flame Establishing Period or the first 10 seconds of RUN. What fails at main light-off and how to check it.","meaning":"The pilot was proven, the main fuel valve opened, and then the flame signal was lost during the Main Flame Establishing Period (MFEP) or within the first 10 seconds of RUN. The transition from pilot to main flame is where this burner is failing.","operatingStates":["MAIN IGN (MFEP)","First 10 seconds of RUN"],"functions":["fuel-delivery","flame-supervision","ignition"],"relatedComponents":["main-fuel-valves","fuel-supply","flame-scanner","pilot-train","air-damper"],"causes":[{"cause":"Main fuel not reaching the burner in time","signs":"Pilot holds, main flame never appears; valve recently replaced or rewired.","check":"Confirm the main valve opens when energised and that the manual main cock is open; check valve wiring.","component":"main-fuel-valves","mechanism":"valve-not-opening"},{"cause":"Pressure sag when the main valve opens","signs":"Main flame lights then dies; gas pressure drops sharply at light-off.","check":"Record gas pressure at the burner during light-off; check regulator response and supply capacity.","component":"fuel-supply","mechanism":"supply-pressure-droop"},{"cause":"Pilot too small to light the main flame","signs":"Rough or delayed main light-off.","check":"The checkout publication’s pilot turndown test checks that the smallest pilot that holds the flame relay will still light the main burner smoothly; repeat it.","component":"pilot-train","mechanism":"regulator-drift"},{"cause":"Detector sighted on the pilot only","signs":"Flame signal falls when the interrupted pilot shuts off, even though main flame is burning.","check":"Measure the flame signal with main flame alone. The checkout publication uses 1.25 Vdc as the minimum flame signal for a reliable pilot or main flame on the 7800 test jack (65-0229-2, Flame signal and pilot turndown tests).","component":"flame-scanner","mechanism":"sighting-shift"}],"distinguish":["Fault 19 is at main light-off; fault 16 or 28 is earlier (pilot trial) and fault 17 is later (after 10 s of RUN)."],"evidence":["Code 19 and sequence status","Gas pressure trend during light-off","Flame signal with pilot alone and main alone","Pilot type (interrupted or intermittent)"],"related":["17","16","28"],"sources":[{"title":"7800 SERIES Relay Modules: Checkout and Test","publisher":"Honeywell","docId":"65-0229-2","revision":"M.S. Rev. 02-06","url":"https://docuthek.kromschroeder.com/download.php?lang=de&doc=66089","section":"Table 3, Hold and Fault Message Summary: fault 19","page":"10"},{"title":"7800 SERIES Relay Modules: Checkout and Test","publisher":"Honeywell","docId":"65-0229-2","revision":"M.S. Rev. 02-06","url":"https://docuthek.kromschroeder.com/download.php?lang=de&doc=66089","section":"Safety shutdown tests: failure to ignite main","page":"6"}],"review":{"status":"extracted","checks":["No step asks the reader to bypass, jumper or disable a flame safeguard, limit or interlock.","Electrical and fuel-train checks are framed for qualified personnel only.","Code 19, its message and the sequence point match Table 3 of 65-0229-2 for the installed relay module."]},"updatedAt":"2026-10-26","url":"https://induqt.ai/troubleshoot/boilers/honeywell/7800-series/19"},{"kind":"fault","family":"boilers","manufacturerSlug":"honeywell","modelSlug":"7800-series","controller":"Honeywell 7800 Series relay module (RM7800, RM7840, EC7800 family)","severity":"lockout","code":"20","name":"Low Fire Sw. Off","title":"Honeywell 7800 Fault 20: Low Fire Switch Not Closed","description":"Honeywell 7800 fault 20: the low fire switch did not close after PREPURGE. Actuator travel, switch adjustment and linkage checks before light-off.","meaning":"After purge the module drives the firing-rate motor back to low fire so the burner lights at a safe, low input, and waits for the low fire switch to prove it. Fault 20 means the switch did not close in time.","operatingStates":["PREPURGE, while driving to low fire before ignition"],"functions":["positioning"],"relatedComponents":["position-switches","air-damper","fuel-actuator"],"causes":[{"cause":"Actuator does not return to low fire","signs":"Damper stays partly open; modulating signal still calling for load.","check":"Watch the actuator return; check the drive signal and that nothing holds the linkage.","component":"air-damper","mechanism":"actuator-feedback-fault"},{"cause":"Low fire switch out of adjustment","signs":"Actuator reaches its end stop but the switch does not make.","check":"Use the Run/Test switch to hold at low fire and confirm line voltage at the low fire switch input, as Table 3 describes; adjust to the burner maker’s setting.","component":"position-switches","mechanism":"switch-drift"}],"distinguish":["Fault 20 is low fire not proven before ignition; faults 31 and 45 are the low fire switch opening later (RM7838B and others).","Fault 14 is the high fire (purge) switch."],"evidence":["Code 20 and sequence status","Actuator position at the fault","Recent linkage, cam or actuator work"],"related":["14"],"sources":[{"title":"7800 SERIES Relay Modules: Checkout and Test","publisher":"Honeywell","docId":"65-0229-2","revision":"M.S. Rev. 02-06","url":"https://docuthek.kromschroeder.com/download.php?lang=de&doc=66089","section":"Table 3, Hold and Fault Message Summary: fault 20","page":"11"}],"review":{"status":"extracted","checks":["No step asks the reader to bypass, jumper or disable a flame safeguard, limit or interlock.","Electrical and fuel-train checks are framed for qualified personnel only.","Code 20, its message and the sequence point match Table 3 of 65-0229-2 for the installed relay module."]},"updatedAt":"2026-10-26","url":"https://induqt.ai/troubleshoot/boilers/honeywell/7800-series/20"},{"kind":"fault","family":"boilers","manufacturerSlug":"honeywell","modelSlug":"7800-series","controller":"Honeywell 7800 Series relay module (RM7800, RM7840, EC7800 family)","severity":"lockout","code":"23","name":"Airflow Switch","title":"Honeywell 7800 Fault 23: Airflow Not Proven in Prepurge","description":"Honeywell 7800 fault 23 means the combustion airflow interlock opened or did not prove during PREPURGE. Fan, air path and switch checks.","meaning":"Fault 23 means that during PREPURGE the module did not see the combustion airflow interlock closed. Without proven air the furnace cannot be purged, so the module locks out before any fuel valve opens.","operatingStates":["PREPURGE"],"functions":["air-proving","purge"],"relatedComponents":["combustion-fan","air-switch","air-damper"],"causes":[{"cause":"Fan not producing enough air","signs":"Fan slow to start, overload trips, belt slipping, or VSD not reaching purge speed.","check":"Confirm the fan runs at full speed in purge; check motor current, belts and VSD settings.","component":"combustion-fan","mechanism":"fan-drive-fault"},{"cause":"Air path restricted","signs":"Gradual onset; dirty intake screen, closed inlet damper or blocked flue.","check":"Inspect the air intake, fan wheel and damper; Table 3 directs checking the fan intake for blockage.","component":"combustion-fan","mechanism":"blocked-air-path"},{"cause":"Air switch setpoint or sensing line","signs":"Air flow is good but the switch does not make; water in the sensing tube.","check":"Measure the differential at the switch during purge and compare with its setpoint; clear and re-route the sensing tube.","component":"air-switch","mechanism":"switch-drift"}],"distinguish":["Fault 23 is air not proven during PREPURGE; fault 32 is the general airflow interlock fault and fault 13 is air proven when it should not be.","Faults 21 and 22 (running or lockout interlock in PREPURGE) share the same checks."],"evidence":["Code 23 and sequence status","Fan motor current and speed in purge","Differential pressure at the air switch during purge","Air switch setpoint"],"related":["32","13"],"sources":[{"title":"7800 SERIES Relay Modules: Checkout and Test","publisher":"Honeywell","docId":"65-0229-2","revision":"M.S. Rev. 02-06","url":"https://docuthek.kromschroeder.com/download.php?lang=de&doc=66089","section":"Table 3, Hold and Fault Message Summary: fault 23","page":"11"}],"review":{"status":"extracted","checks":["No step asks the reader to bypass, jumper or disable a flame safeguard, limit or interlock.","Electrical and fuel-train checks are framed for qualified personnel only.","Code 23, its message and the sequence point match Table 3 of 65-0229-2 for the installed relay module."]},"updatedAt":"2026-10-26","url":"https://induqt.ai/troubleshoot/boilers/honeywell/7800-series/23"},{"kind":"fault","family":"boilers","manufacturerSlug":"honeywell","modelSlug":"7800-series","controller":"Honeywell 7800 Series relay module (RM7800, RM7840, EC7800 family)","severity":"lockout","code":"28","name":"Pilot Flame Fail","title":"Honeywell 7800 Fault 28: Pilot Flame Failure","description":"Honeywell 7800 fault 28 means the pilot flame was not proven. Pilot valve, pilot pressure, ignition and flame detection checks in the right order.","meaning":"Fault 28 means the pilot flame failed. In Honeywell’s own safety shutdown test, a pilot that cannot light produces fault 28 four or ten seconds after the pilot valve opens, depending on the PFEP jumper setting. The main valves never opened.","operatingStates":["PILOT IGN (PFEP), 4 or 10 seconds after the pilot valve opens depending on the PFEP jumper"],"functions":["ignition","flame-supervision"],"relatedComponents":["pilot-train","igniter","flame-scanner","flame-amplifier"],"causes":[{"cause":"Pilot valve not opening","signs":"No pilot flame and no change in pilot pressure when the valve is energised.","check":"Check pilot valve wiring and that the valve actuates; Table 3 lists this first.","component":"pilot-train","mechanism":"valve-not-opening"},{"cause":"Pilot pressure wrong","signs":"Small, lazy or lifting pilot; regulator recently adjusted.","check":"Measure pilot pressure and repeat the pilot turndown test from the checkout publication.","component":"pilot-train","mechanism":"regulator-drift"},{"cause":"Ignition problem","signs":"No spark, or spark in the wrong place.","check":"Inspect the ignition transformer and electrode.","component":"igniter","mechanism":"electrode-wear"},{"cause":"Detector or sighting","signs":"Pilot visible but flame signal low.","check":"Check detector sighting and amplifier. The checkout publication uses 1.25 Vdc as the minimum flame signal for a reliable pilot or main flame on the 7800 test jack (65-0229-2, Flame signal and pilot turndown tests).","component":"flame-scanner","mechanism":"sighting-shift"}],"distinguish":["See fault 16, which also points at the pilot trial.","If the pilot proves and the trip follows main valve opening, the code is 19."],"evidence":["Code 28 and sequence status","PFEP jumper setting (4 or 10 s)","Pilot gas pressure and flame signal during the trial"],"related":["16","19"],"sources":[{"title":"7800 SERIES Relay Modules: Checkout and Test","publisher":"Honeywell","docId":"65-0229-2","revision":"M.S. Rev. 02-06","url":"https://docuthek.kromschroeder.com/download.php?lang=de&doc=66089","section":"Table 3, Hold and Fault Message Summary: fault 28","page":"11"},{"title":"7800 SERIES Relay Modules: Checkout and Test","publisher":"Honeywell","docId":"65-0229-2","revision":"M.S. Rev. 02-06","url":"https://docuthek.kromschroeder.com/download.php?lang=de&doc=66089","section":"Safety shutdown tests: failure to ignite pilot","page":"6"}],"review":{"status":"extracted","checks":["No step asks the reader to bypass, jumper or disable a flame safeguard, limit or interlock.","Electrical and fuel-train checks are framed for qualified personnel only.","Code 28, its message and the sequence point match Table 3 of 65-0229-2 for the installed relay module."]},"updatedAt":"2026-10-26","url":"https://induqt.ai/troubleshoot/boilers/honeywell/7800-series/28"},{"kind":"fault","family":"boilers","manufacturerSlug":"honeywell","modelSlug":"7800-series","controller":"Honeywell 7800 Series relay module (RM7800, RM7840, EC7800 family)","severity":"lockout","code":"32","name":"Airflow Switch","title":"Honeywell 7800 Fault 32: Combustion Airflow Interlock","description":"Honeywell 7800 fault 32 is a combustion airflow interlock fault. Separate fan, air path and switch problems using the sequence point and a purge-time check.","meaning":"Fault 32 means the combustion airflow interlock was not in the state the module required. Unlike fault 23 it is not tied to PREPURGE, so note the sequence step shown with it: an airflow loss while firing points to a different cause than one before light-off.","operatingStates":["Any state where air must be proven: PREPURGE, ignition trials or RUN"],"functions":["air-proving"],"relatedComponents":["air-switch","combustion-fan","air-damper"],"causes":[{"cause":"Air pressure falls near the switch setpoint while firing","signs":"Trips at low fire or during modulation; marginal differential at the switch.","check":"Measure the differential at the switch across the firing range; a setpoint close to the low-fire differential will chatter.","component":"air-switch","mechanism":"switch-drift"},{"cause":"Fan or air path problem","signs":"Fan noise change, overload or VSD fault near the trip.","check":"Inspect the fan and intake as Table 3 directs; check VSD fault history.","component":"combustion-fan","mechanism":"fan-drive-fault"},{"cause":"Wiring or dirty contacts on the interlock","signs":"Intermittent with vibration; no change in air flow.","check":"With the sequence held in PREPURGE (Run/Test switch), confirm line voltage at the interlock input; clean or replace switch contacts.","component":"air-switch","mechanism":"contact-welded"}],"distinguish":["Fault 23 is the PREPURGE-specific airflow fault; fault 13 is airflow proven in STANDBY.","Fault 30 (Running ILK) covers the whole running interlock string, which includes the airflow switch on many burners."],"evidence":["Code 32 and sequence step","Air switch differential at low and high fire","Fan VSD or starter fault history"],"related":["23","13"],"sources":[{"title":"7800 SERIES Relay Modules: Checkout and Test","publisher":"Honeywell","docId":"65-0229-2","revision":"M.S. Rev. 02-06","url":"https://docuthek.kromschroeder.com/download.php?lang=de&doc=66089","section":"Table 3, Hold and Fault Message Summary: fault 32","page":"12"}],"review":{"status":"extracted","checks":["No step asks the reader to bypass, jumper or disable a flame safeguard, limit or interlock.","Electrical and fuel-train checks are framed for qualified personnel only.","Code 32, its message and the sequence point match Table 3 of 65-0229-2 for the installed relay module."]},"updatedAt":"2026-10-26","url":"https://induqt.ai/troubleshoot/boilers/honeywell/7800-series/32"},{"kind":"fault","family":"boilers","manufacturerSlug":"honeywell","modelSlug":"7800-series","controller":"Honeywell 7800 Series relay module (RM7800, RM7840, EC7800 family)","severity":"lockout","code":"33","name":"Pre-Ignition ILK","title":"Honeywell 7800 Fault 33: Pre-Ignition Interlock","description":"Honeywell 7800 fault 33: the pre-ignition interlock (valve proof of closure) was not proven. Valve closing time, POC switch and wiring checks.","meaning":"The pre-ignition interlock is usually the proof-of-closure switch on the safety shutoff valves. Fault 33 means the module did not see it proven when required, so it cannot confirm the fuel valves are shut before purge or ignition.","operatingStates":["STANDBY or PREPURGE","After the first five seconds of POSTPURGE (safety shutdown test)"],"functions":["valve-proving"],"relatedComponents":["main-fuel-valves"],"causes":[{"cause":"Valve closing slowly","signs":"Fault appears just after a shutdown; valve actuator sluggish.","check":"Table 3 states the valve must close within five seconds; time the valve closing and service or replace the actuator.","component":"main-fuel-valves","mechanism":"valve-seat-leak"},{"cause":"Proof-of-closure switch out of adjustment or failed","signs":"Valve closes fully but the switch does not make.","check":"Check the POC switch contacts and adjustment per the valve maker; confirm line voltage at the pre-ignition interlock input in STANDBY.","component":"main-fuel-valves","mechanism":"switch-drift"}],"distinguish":["Fault 10 is the pre-ignition interlock fault reported during STANDBY on RM7800, 7840 and 7838B; fault 68 is the equivalent on EC/RM7810, 7820, 7830 and 7850."],"evidence":["Code 33 and sequence status","Valve and actuator model, POC switch type","Measured valve closing time"],"related":[],"sources":[{"title":"7800 SERIES Relay Modules: Checkout and Test","publisher":"Honeywell","docId":"65-0229-2","revision":"M.S. Rev. 02-06","url":"https://docuthek.kromschroeder.com/download.php?lang=de&doc=66089","section":"Table 3, Hold and Fault Message Summary: fault 33","page":"12"},{"title":"7800 SERIES Relay Modules: Checkout and Test","publisher":"Honeywell","docId":"65-0229-2","revision":"M.S. Rev. 02-06","url":"https://docuthek.kromschroeder.com/download.php?lang=de&doc=66089","section":"Safety shutdown tests: opening a pre-ignition interlock","page":"6"}],"review":{"status":"extracted","checks":["No step asks the reader to bypass, jumper or disable a flame safeguard, limit or interlock.","Electrical and fuel-train checks are framed for qualified personnel only.","Code 33, its message and the sequence point match Table 3 of 65-0229-2 for the installed relay module."]},"updatedAt":"2026-10-26","url":"https://induqt.ai/troubleshoot/boilers/honeywell/7800-series/33"},{"kind":"fault","family":"boilers","manufacturerSlug":"honeywell","modelSlug":"7800-series","controller":"Honeywell 7800 Series relay module (RM7800, RM7840, EC7800 family)","severity":"lockout","code":"51","name":"Flame Too Strong","title":"Honeywell 7800 Fault 51: Flame Signal Too Strong","description":"Honeywell 7800 fault 51 means the flame signal is above the valid range. Usually ignition noise, a wrong amplifier or a detector fault rather than a real flame.","meaning":"Fault 51 means the flame signal reached a value too high to be a genuine flame reading. The module treats the signal as untrustworthy, which usually points at ignition interference, an incompatible amplifier or a failing detector.","operatingStates":["Any state with a flame signal, most often during ignition trials while the spark is on"],"functions":["flame-supervision"],"relatedComponents":["flame-amplifier","flame-scanner","igniter"],"causes":[{"cause":"Ignition noise on the flame lead","signs":"Appears only while the igniter is energised.","check":"Check that the F lead is routed away from ignition wiring and in its own conduit, as Table 3 directs.","component":"flame-scanner","mechanism":"signal-noise"},{"cause":"Amplifier and detector mismatch","signs":"After an amplifier or detector change.","check":"Confirm compatibility and reseat the amplifier.","component":"flame-amplifier","mechanism":"amplifier-mismatch"},{"cause":"Detector failing","signs":"High reading even with a small flame.","check":"Follow the flame detector checkout procedure and replace the detector or amplifier if the reading stays out of range.","component":"flame-amplifier","mechanism":"detector-ageing"}],"distinguish":["Fault 51 is a signal too high to be valid; faults 9, 15 and 18 are flame present when none should be."],"evidence":["Code 51 and sequence step","Flame signal reading and when it peaks","Detector and amplifier model","Flame lead routing"],"related":["15"],"sources":[{"title":"7800 SERIES Relay Modules: Checkout and Test","publisher":"Honeywell","docId":"65-0229-2","revision":"M.S. Rev. 02-06","url":"https://docuthek.kromschroeder.com/download.php?lang=de&doc=66089","section":"Table 3, Hold and Fault Message Summary: fault 51","page":"14"}],"review":{"status":"extracted","checks":["No step asks the reader to bypass, jumper or disable a flame safeguard, limit or interlock.","Electrical and fuel-train checks are framed for qualified personnel only.","Code 51, its message and the sequence point match Table 3 of 65-0229-2 for the installed relay module."]},"updatedAt":"2026-10-26","url":"https://induqt.ai/troubleshoot/boilers/honeywell/7800-series/51"},{"kind":"equipment","family":"boilers","manufacturer":"Fireye","manufacturerSlug":"fireye","modelSlug":"nx6300","firmware":"Firmware 1.4","model":"NX6300 (Nexus)","title":"Fireye NX6300 Fault Codes and Lockout Diagnosis","description":"How the Fireye Nexus NX6300 burner control shows current, cleared and limit faults, how to read subsets and the 128-event history, and what each fault code means.","summary":"The Fireye NX6300 is a single-fuel integrated burner control in the Nexus range, combining flame safeguard and fuel/air positioning. Its fault numbers carry a letter prefix that tells you whether the fault is still present, has cleared, or is a limit, and it keeps a long event history, so the history is usually more useful than the single fault on screen.","faultReporting":["Each fault number has a prefix: F means the fault occurred and is still present, C means it occurred and has cleared, L means a programmed limit was exceeded.","Many faults cause a non-volatile lockout that survives a power cycle; some faults and limits only raise a warning.","Most faults carry a subset read on the Engineer’s Key screen. Subsets are bit sums (1, 2, 4 … 128) or, for flame and air faults, the burner status number.","The display stores the last 128 events and faults with status data, kept through power loss. View them via the Engineer’s Key screen (F4 LOG), the touchscreen Menu > Fault/Event Log, or ComFire2 software."],"sequence":[{"name":"00 Non-volatile lockout","text":"Fuel valves off, alarm on until muted; stays locked out until faults clear."},{"name":"01–02 Burner off, wait for purge","text":"Valves proven closed, no flame and no air pressure; waits for burner select and a profile."},{"name":"03–05 Leak test and prove closed","text":"Optional gas valve leak test starts; drives move to closed and are compared with commissioned positions."},{"name":"06–08 Prove air, purge positions, pre-purge","text":"Fan starts; air pressure must be proven after t1; drives reach purge positions and pre-purge t2 runs."},{"name":"09–10 Ignition position, pre-ignition","text":"Drives move to ignition positions; igniter energised for t3."},{"name":"11–12 Pilot ignition","text":"Pilot valve opens; flame must be proven by the end of safety time t4."},{"name":"13–14 Main ignition","text":"Main valves open for safety time t6, then the main flame interval t7; flame and air must stay proven."},{"name":"15–16 Low fire, modulation","text":"Low fire hold t8, then modulation on demand with flame and air supervised."},{"name":"17–18 Post-purge","text":"Fuel closes; air drives move to post-purge before returning to 01."}],"evidence":["Photo of the fault with its F/C/L prefix","Subset from the Engineer’s Key screen","The event log around the lockout","Flame scanner type and signal"],"codeIndex":[{"code":"F01–F06","name":"External alarm from low-voltage inputs 1 to 6"},{"code":"F10","name":"Flame Failure: no flame seen when one should be present"},{"code":"F11","name":"False Flame: flame seen when none should be present"},{"code":"F12–F13","name":"External alarm from high-voltage input 12 or 13"},{"code":"F14","name":"Main combustion air pressure not detected"},{"code":"F15","name":"Main combustion air pressure detected when it should not be"},{"code":"F18","name":"Not enough set points entered in the profile"},{"code":"F19","name":"Circuit board voltage reference fault"},{"code":"F20–F23","name":"Drive 0 to 3 position fault"},{"code":"F32","name":"Safety input fault (low-voltage inputs)"},{"code":"F33","name":"Burner input fault (high-voltage inputs)"},{"code":"F34","name":"Primary relay fault"},{"code":"F35","name":"ADC fault"},{"code":"F36","name":"Reset fault: too many resets with no fault present"},{"code":"F37–F39","name":"RAM, program memory or profile table check failed"},{"code":"F41","name":"Boiler sensor fault or safety limit exceeded"},{"code":"F42","name":"Valve prove (leak) test fault"},{"code":"F46","name":"EEPROM memory check failed"},{"code":"F50","name":"Oxygen probe heater fault"},{"code":"L52–L53","name":"Oxygen low or high limit alarm"},{"code":"F54","name":"Oxygen probes mismatch, or CO high limit"},{"code":"L55","name":"Trim limit alarm"},{"code":"F57","name":"Auto trim commissioning fault"},{"code":"L58–L59","name":"Flue temperature low or high alarm"},{"code":"F61","name":"Air pressure level fault"},{"code":"F63","name":"Option parameters uploaded: check and confirm"},{"code":"F64","name":"Profile Invalid"},{"code":"F65","name":"Power-up lockout"},{"code":"F66","name":"Flame Test: dark test failed"},{"code":"F67–F69","name":"Secondary relay, program memory or watchdog fault"},{"code":"F70–F79","name":"User faults from the programmable logic"},{"code":"L89","name":"FGR input fault"}],"sources":[{"title":"NX6300 Single Fuel Integrated Burner Control Commissioning Manual","publisher":"Fireye","docId":"NEX-6301","revision":"2025-03-19, Commissioning Manual 1.4, firmware 1.4","url":"https://www.fireye.com/downloads/NEX-6301-NX6300_Commissioning_Manual_English_2025-3-19-Web.pdf","section":"Section 5: 1.1–1.6, Faults and fault finding","page":"5-1 to 5-14"},{"title":"NX6300 Single Fuel Integrated Burner Control Commissioning Manual","publisher":"Fireye","docId":"NEX-6301","revision":"2025-03-19, Commissioning Manual 1.4, firmware 1.4","url":"https://www.fireye.com/downloads/NEX-6301-NX6300_Commissioning_Manual_English_2025-3-19-Web.pdf","section":"Section 1, 2.3 The Start-up Sequence","page":"1-19 to 1-20"}],"review":{"status":"extracted","checks":["No step asks the reader to bypass, jumper or disable a flame safeguard, limit or interlock.","Electrical and fuel-train checks are framed for qualified personnel only.","Prefix meanings, event history, sequence states and the code index match NEX-6301 for the installed firmware."]},"updatedAt":"2026-10-26","url":"https://induqt.ai/troubleshoot/boilers/fireye/nx6300"},{"kind":"fault","family":"boilers","manufacturerSlug":"fireye","modelSlug":"nx6300","controller":"Fireye NX6300 single-fuel integrated burner control (Nexus)","firmware":"Firmware 1.4","severity":"lockout","code":"F10","name":"Flame Failure","meaning":"F10 means the flame detector did not register a flame at a point in the sequence where the controller requires one. The subset tells you which flame input and which burner status the controller was in, which is the fastest way to narrow the cause: a failure at pilot ignition has different causes from a flame lost during modulation.","operatingStates":["Status 11–12: pilot ignition and pilot interval","Status 13–14: main ignition and waiting for main flame","Status 15: moving to or holding at low fire","Status 16: modulation"],"subsets":[{"value":"1xx","meaning":"Flame 1 (the first flame input); the last two digits are the burner status number"},{"value":"2xx","meaning":"Flame 2 (the second flame input)"},{"value":"x11, x12","meaning":"Pilot ignition (safety time t4) or pilot ignition interval (t5): flame never proven or pilot lost"},{"value":"x13, x14","meaning":"Main ignition (t6) or waiting for main flame (t7): lost at the change from pilot to main flame"},{"value":"x15","meaning":"Moving to low fire or low fire hold (t8)"},{"value":"x16","meaning":"Modulation: lost while firing"}],"functions":["flame-supervision","ignition","fuel-delivery"],"relatedComponents":["flame-scanner","flame-amplifier","igniter","pilot-train","fuel-supply","air-damper"],"causes":[{"cause":"No pilot flame at ignition (subset x11–x12)","signs":"Repeated F10 at pilot status; no spark or no pilot through the sight glass.","check":"Observe a start with a qualified technician: spark, pilot flame and the flame signal on the overview screen.","component":"igniter","mechanism":"electrode-wear"},{"cause":"Pilot gas pressure or regulator (subset x11–x12)","signs":"Spark present, pilot weak or absent.","check":"Read pilot gas pressure during the trial and confirm the pilot valve opens.","component":"pilot-train","mechanism":"regulator-drift"},{"cause":"Main flame does not take over (subset x13–x14)","signs":"Pilot proves, then F10 as main valves open; gas pressure sags at light-off.","check":"Trend gas pressure during main ignition; check the ignition position of the fuel and air drives against the commissioned profile.","component":"fuel-supply","mechanism":"supply-pressure-droop"},{"cause":"Flame lost while firing (subset x15–x16)","signs":"Trips at load changes or high fire; L-prefixed limits or drive faults near the event.","check":"Use the event log and any fuel pressure, air pressure or oxygen readings to see what moved before the trip.","component":"air-damper","mechanism":"air-fuel-ratio-drift"},{"cause":"Flame present but not seen","signs":"Flame visible; signal low or falling over weeks. The manual’s first instruction is to check wiring if there is a flame.","check":"Check scanner wiring, lens and sighting; compare the flame signal with earlier starts.","component":"flame-scanner","mechanism":"lens-fouling"}],"distinguish":["F10 is no flame when expected; F11 is flame when none should be present; F66 is the flame test (dark check) failing.","C10 in the event log means the flame failure happened and has since cleared, which is normal after the lockout; F10 means it is still present."],"evidence":["Photo of the fault with its F/C prefix and the subset from the Engineer’s Key screen","The event log around the lockout","Flame scanner type and flame signal during a normal start","Gas pressure at light-off and while firing"],"related":["F11","F66","F14"],"title":"Fireye NX6300 F10 Flame Failure: Subsets and Causes","description":"Fireye NX6300 F10 means no flame was seen when one should be present. How to read the subset (burner status), and the checks for each stage.","sources":[{"title":"NX6300 Single Fuel Integrated Burner Control Commissioning Manual","publisher":"Fireye","docId":"NEX-6301","revision":"2025-03-19, Commissioning Manual 1.4, firmware 1.4","url":"https://www.fireye.com/downloads/NEX-6301-NX6300_Commissioning_Manual_English_2025-3-19-Web.pdf","section":"Section 5, 1.5 List of Fault Code Numbers: F10","page":"5-4"},{"title":"NX6300 Single Fuel Integrated Burner Control Commissioning Manual","publisher":"Fireye","docId":"NEX-6301","revision":"2025-03-19, Commissioning Manual 1.4, firmware 1.4","url":"https://www.fireye.com/downloads/NEX-6301-NX6300_Commissioning_Manual_English_2025-3-19-Web.pdf","section":"Section 1, 2.3 The Start-up Sequence","page":"1-19 to 1-20"}],"review":{"status":"extracted","checks":["No step asks the reader to bypass, jumper or disable a flame safeguard, limit or interlock.","Electrical and fuel-train checks are framed for qualified personnel only.","F10, its display text and subsets match section 5 of NEX-6301 for the installed firmware."]},"updatedAt":"2026-10-26","url":"https://induqt.ai/troubleshoot/boilers/fireye/nx6300/f10"},{"kind":"fault","family":"boilers","manufacturerSlug":"fireye","modelSlug":"nx6300","controller":"Fireye NX6300 single-fuel integrated burner control (Nexus)","firmware":"Firmware 1.4","severity":"lockout","code":"F11","name":"False Flame","meaning":"F11 means the controller saw a flame signal when there should be no flame, for example before purge, during purge or after shutdown, or while a shuttered scanner’s shutter was closed. The controller cannot tell a real flame from a faulty signal, so it locks out.","operatingStates":["Status 01–02: burner off or waiting for purge","Status 05–09: proving positions and pre-purge","Status 10: pre-ignition","Status 17–18: post-purge"],"subsets":[{"value":"1xx","meaning":"Flame 1 (the first flame input); the last two digits are the burner status number"},{"value":"2xx","meaning":"Flame 2 (the second flame input)"},{"value":"x01, x02","meaning":"Burner off or waiting to purge: flame seen at rest"},{"value":"x05 to x09","meaning":"During closed/air/purge position proving or pre-purge"},{"value":"x10","meaning":"Pre-ignition, with the igniter on but no fuel"},{"value":"x17, x18","meaning":"Post-purge, after the fuel valves closed"}],"functions":["flame-supervision"],"relatedComponents":["flame-scanner","flame-amplifier","main-fuel-valves"],"causes":[{"cause":"Fuel still burning after shutdown (subset x17–x18 or x01)","signs":"Visible flame after the cycle; oil after-drip or leaking safety valve.","check":"Look into the furnace. If flame persists, close the manual fuel valves and have the safety shutoff valves tightness-tested; the valve leak test (if fitted) helps here.","component":"main-fuel-valves","mechanism":"valve-seat-leak"},{"cause":"Detector seeing ignition spark (subset x10)","signs":"Only at pre-ignition when the spark starts.","check":"Re-sight the scanner so it cannot view the spark; check scanner and ignition cable routing.","component":"flame-scanner","mechanism":"sighting-shift"},{"cause":"Failing UV tube or self-check detector","signs":"Signal in a dark, cold furnace; often accompanied by F66 events.","check":"Cover the scanner with the burner off; any remaining signal means a detector or input fault.","component":"flame-amplifier","mechanism":"detector-ageing"},{"cause":"Noise pickup on the flame input","signs":"Intermittent, coinciding with motor or ignition switching.","check":"Check screen termination and separation of the scanner cable from power and ignition wiring.","component":"flame-scanner","mechanism":"signal-noise"}],"distinguish":["F11 is flame when none is expected; F66 is the controller’s own dark test failing, which can precede F11 as a UV tube fails."],"evidence":["Fault prefix and subset","Event log","Scanner model (UV, self-check UV, IR)","Whether flame is visible in the furnace at the time"],"related":["F10","F66"],"title":"Fireye NX6300 F11 False Flame: Causes and Checks","description":"Fireye NX6300 F11 means a flame was registered when none should be present, or with the shutter closed. Real flame, detector faults and how the subset helps.","sources":[{"title":"NX6300 Single Fuel Integrated Burner Control Commissioning Manual","publisher":"Fireye","docId":"NEX-6301","revision":"2025-03-19, Commissioning Manual 1.4, firmware 1.4","url":"https://www.fireye.com/downloads/NEX-6301-NX6300_Commissioning_Manual_English_2025-3-19-Web.pdf","section":"Section 5, 1.5 List of Fault Code Numbers: F11","page":"5-4"},{"title":"NX6300 Single Fuel Integrated Burner Control Commissioning Manual","publisher":"Fireye","docId":"NEX-6301","revision":"2025-03-19, Commissioning Manual 1.4, firmware 1.4","url":"https://www.fireye.com/downloads/NEX-6301-NX6300_Commissioning_Manual_English_2025-3-19-Web.pdf","section":"Section 1, 2.3 The Start-up Sequence","page":"1-19 to 1-20"}],"review":{"status":"extracted","checks":["No step asks the reader to bypass, jumper or disable a flame safeguard, limit or interlock.","Electrical and fuel-train checks are framed for qualified personnel only.","F11, its display text and subsets match section 5 of NEX-6301 for the installed firmware."]},"updatedAt":"2026-10-26","url":"https://induqt.ai/troubleshoot/boilers/fireye/nx6300/f11"},{"kind":"fault","family":"boilers","manufacturerSlug":"fireye","modelSlug":"nx6300","controller":"Fireye NX6300 single-fuel integrated burner control (Nexus)","firmware":"Firmware 1.4","severity":"lockout","code":"F14","name":"Combustion air pressure not detected","meaning":"F14 means the main (secondary) combustion air pressure switch did not register air pressure at a point where the controller requires it. The subset is the burner status number, which tells you whether air was never proven at the start of purge or was lost later while firing.","operatingStates":["Status 07: proving purge positions, after the air pressure prove time t1","Status 08–16: purge, ignition and firing, where air must stay proven"],"subsets":[{"value":"07","meaning":"Air not proven when the air prove time ended, before purge"},{"value":"08 to 16","meaning":"Air pressure lost during purge, ignition or firing"}],"functions":["air-proving","purge"],"relatedComponents":["combustion-fan","air-switch","air-damper"],"causes":[{"cause":"Fan not running or slow (subset 07)","signs":"Fan does not start, overload trips, or a fan VSD ramps slowly.","check":"Confirm the burner motor output, starter and any VSD run signal; check the fan reaches purge speed.","component":"combustion-fan","mechanism":"fan-drive-fault"},{"cause":"Air path restricted","signs":"Gradual onset; dirty inlet, closed damper, flue restriction.","check":"Inspect intake, fan wheel, damper travel and flue.","component":"combustion-fan","mechanism":"blocked-air-path"},{"cause":"Switch setpoint too close to the low-fire differential (subset 15–16)","signs":"Trips at low fire or on modulation down.","check":"Measure the differential at the switch across the firing range and compare with its setpoint.","component":"air-switch","mechanism":"switch-drift"}],"distinguish":["F14 is air not proven when required; F15 is air proven when it should not be."],"evidence":["Subset (burner status)","Fan motor or VSD status at the fault","Air pressure at the switch at low and high fire"],"related":["F15","F10"],"title":"Fireye NX6300 F14: Combustion Air Pressure Not Proven","description":"Fireye NX6300 F14 means the main combustion air pressure switch did not prove air when it should. Fan, air path and switch checks by burner status.","sources":[{"title":"NX6300 Single Fuel Integrated Burner Control Commissioning Manual","publisher":"Fireye","docId":"NEX-6301","revision":"2025-03-19, Commissioning Manual 1.4, firmware 1.4","url":"https://www.fireye.com/downloads/NEX-6301-NX6300_Commissioning_Manual_English_2025-3-19-Web.pdf","section":"Section 5, 1.5 List of Fault Code Numbers: F14","page":"5-4"},{"title":"NX6300 Single Fuel Integrated Burner Control Commissioning Manual","publisher":"Fireye","docId":"NEX-6301","revision":"2025-03-19, Commissioning Manual 1.4, firmware 1.4","url":"https://www.fireye.com/downloads/NEX-6301-NX6300_Commissioning_Manual_English_2025-3-19-Web.pdf","section":"Section 1, 2.3 The Start-up Sequence","page":"1-19 to 1-20"}],"review":{"status":"extracted","checks":["No step asks the reader to bypass, jumper or disable a flame safeguard, limit or interlock.","Electrical and fuel-train checks are framed for qualified personnel only.","F14, its display text and subsets match section 5 of NEX-6301 for the installed firmware."]},"updatedAt":"2026-10-26","url":"https://induqt.ai/troubleshoot/boilers/fireye/nx6300/f14"},{"kind":"fault","family":"boilers","manufacturerSlug":"fireye","modelSlug":"nx6300","controller":"Fireye NX6300 single-fuel integrated burner control (Nexus)","firmware":"Firmware 1.4","severity":"lockout","code":"F15","name":"Combustion air pressure detected when it should not be","meaning":"F15 means the main combustion air pressure switch registered air when the controller expected none. Subset 1 means air was seen at the wrong time; subset 2 means the switch still showed air more than three minutes after the burner turned off. The manual also notes F15 appears if the air-switch option (Opt 6.x) is not set.","operatingStates":["Status 01: burner off, before the fan starts","After shutdown, while the fan runs down"],"subsets":[{"value":"1","meaning":"Air pressure registered when it should not be present"},{"value":"2","meaning":"Air pressure still registered more than 3 minutes after the burner turned off"}],"functions":["air-proving"],"relatedComponents":["air-switch","combustion-fan","burner-controller"],"causes":[{"cause":"Switch contacts stuck or a jumper left in","signs":"Every start; switch reads closed with the fan stopped.","check":"Check the switch with the fan off and isolated; look for jumpers from previous work.","component":"air-switch","mechanism":"contact-welded"},{"cause":"Fan still running or windmilling (subset 2)","signs":"Fan keeps turning after shutdown; shared breeching or strong stack draft.","check":"Confirm the fan stops; read pressure at the sensing point with the fan off.","component":"combustion-fan","mechanism":"contact-welded"},{"cause":"Option parameter not set","signs":"New installation or after parameter changes.","check":"Have the commissioning engineer confirm the Opt 6.x air switch settings.","component":"burner-controller","mechanism":"configuration-change"}],"distinguish":["F15 is air when there should be none; F14 is no air when there should be."],"evidence":["Subset (1 or 2)","Whether the fan is turning with the burner off","Air switch wiring and any recent parameter changes"],"related":["F14"],"title":"Fireye NX6300 F15: Air Pressure Detected When Off","description":"Fireye NX6300 F15 means the combustion air switch showed pressure when it should not. Subset 1 and 2 explained, with fan run-down and switch checks.","sources":[{"title":"NX6300 Single Fuel Integrated Burner Control Commissioning Manual","publisher":"Fireye","docId":"NEX-6301","revision":"2025-03-19, Commissioning Manual 1.4, firmware 1.4","url":"https://www.fireye.com/downloads/NEX-6301-NX6300_Commissioning_Manual_English_2025-3-19-Web.pdf","section":"Section 5, 1.5 List of Fault Code Numbers: F15","page":"5-5"}],"review":{"status":"extracted","checks":["No step asks the reader to bypass, jumper or disable a flame safeguard, limit or interlock.","Electrical and fuel-train checks are framed for qualified personnel only.","F15, its display text and subsets match section 5 of NEX-6301 for the installed firmware."]},"updatedAt":"2026-10-26","url":"https://induqt.ai/troubleshoot/boilers/fireye/nx6300/f15"},{"kind":"fault","family":"boilers","manufacturerSlug":"fireye","modelSlug":"nx6300","controller":"Fireye NX6300 single-fuel integrated burner control (Nexus)","firmware":"Firmware 1.4","severity":"lockout","code":"F20","name":"Drive position fault","meaning":"A drive position fault means a fuel or air drive (servo, or fan VSD) was not where the commissioned profile says it should be. F20 is drive 0; the following numbers are the other drives. The controller checks the close and purge positions during start-up and the fuel/air ratio while firing, so the subset tells you whether the problem is mechanical, communication or inside the servo.","operatingStates":["Status 05: proving closed positions","Status 07: proving purge positions","Status 08–15: pre-purge, ignition and post-purge, if a drive moves off its set point","Status 16: modulation, if a drive leaves the commissioned curve"],"subsets":[{"value":"000 to 016","meaning":"Burner status when the fault occurred (position error)"},{"value":"032 to 048","meaning":"CANbus communication error; the display shows ERR1 under the drive name"},{"value":"above 64","meaning":"Internal servo fault; the display shows ERR2 to ERR7 under the drive name"}],"functions":["positioning"],"relatedComponents":["air-damper","fuel-actuator","comms-network","combustion-fan"],"causes":[{"cause":"Linkage or damper binding (subset 000–016)","signs":"Fault at purge or during modulation; actuator labours or stalls.","check":"Disconnect and stroke the damper or valve by hand (burner off, qualified personnel) to check for binding; check couplings for slip.","component":"air-damper","mechanism":"linkage-slip"},{"cause":"Stored close or purge position no longer reachable","signs":"Fault before the drives reach purge, after mechanical work or servo replacement.","check":"The manual’s troubleshooting table points to feedback potentiometers and motor micro-switches, then resetting close and purge positions in Commission Ratio mode.","component":"fuel-actuator","mechanism":"actuator-feedback-fault"},{"cause":"CANbus fault (subset 032–048, ERR1)","signs":"ERR1 under the drive name; display slow or freezing.","check":"Check CANbus wiring, screens and termination to the servo.","component":"comms-network","mechanism":"network-fault"},{"cause":"Servo internal fault (subset above 64, ERR2–ERR7)","signs":"Repeats on the same servo.","check":"Replace the servo; a replacement servo invalidates profiles that used it (F64) until re-commissioned.","component":"fuel-actuator","mechanism":"actuator-feedback-fault"},{"cause":"Fan VSD outside its error band","signs":"Fault on the VSD drive while modulating; VSD current-limiting or slow ramp.","check":"Check the VSD ramp times and that its own PID is disabled, as the manual’s inverter section describes.","component":"combustion-fan","mechanism":"fan-drive-fault"}],"distinguish":["Position faults are drive-specific: note the drive number (F20 = drive 0) and its subset.","A profile that will not run at all after a servo change is F64, not a position fault."],"evidence":["Fault number (which drive) and subset","ERR code under the drive name, if shown","Any recent servo, linkage or VSD work"],"related":["F64"],"title":"Fireye NX6300 F20–F2x Drive Position Fault: Subsets","description":"Fireye NX6300 drive position faults (F20 for drive 0 and up) explained: close, purge and profile position errors, CANbus and servo subsets, and what to check.","sources":[{"title":"NX6300 Single Fuel Integrated Burner Control Commissioning Manual","publisher":"Fireye","docId":"NEX-6301","revision":"2025-03-19, Commissioning Manual 1.4, firmware 1.4","url":"https://www.fireye.com/downloads/NEX-6301-NX6300_Commissioning_Manual_English_2025-3-19-Web.pdf","section":"Section 5, 1.5 List of Fault Code Numbers: F20","page":"5-6"},{"title":"NX6300 Single Fuel Integrated Burner Control Commissioning Manual","publisher":"Fireye","docId":"NEX-6301","revision":"2025-03-19, Commissioning Manual 1.4, firmware 1.4","url":"https://www.fireye.com/downloads/NEX-6301-NX6300_Commissioning_Manual_English_2025-3-19-Web.pdf","section":"Section 5, 1.7.2 Startup problems; 1.7.5 Modulation problems","page":"5-25 to 5-28"}],"review":{"status":"extracted","checks":["No step asks the reader to bypass, jumper or disable a flame safeguard, limit or interlock.","Electrical and fuel-train checks are framed for qualified personnel only.","F20, its display text and subsets match section 5 of NEX-6301 for the installed firmware.","Troubleshooting page numbers for 1.7.2 and 1.7.5 match the installed manual issue."]},"updatedAt":"2026-10-26","url":"https://induqt.ai/troubleshoot/boilers/fireye/nx6300/f20"},{"kind":"fault","family":"boilers","manufacturerSlug":"fireye","modelSlug":"nx6300","controller":"Fireye NX6300 single-fuel integrated burner control (Nexus)","firmware":"Firmware 1.4","severity":"lockout","code":"F41","name":"Boiler sensor fault or safety limit exceeded","meaning":"F41 covers two very different situations: the measured boiler pressure or temperature went above the controller’s safety limit, or the sensor stopped responding correctly. The subset separates them, and only subset 4 is a real limit exceedance.","operatingStates":["Any status; most often while firing at high load or as load drops suddenly"],"subsets":[{"value":"1","meaning":"Sensor feedback below 1 V"},{"value":"2","meaning":"Sensor feedback above 5 V"},{"value":"3","meaning":"Sensor failed during its test"},{"value":"4","meaning":"Safety limit exceeded"},{"value":"255","meaning":"CANbus communication fault to the sensor"}],"functions":["limit-supervision"],"relatedComponents":["pressure-sensor","limit-string","comms-network"],"causes":[{"cause":"Real over-pressure or over-temperature (subset 4)","signs":"Steam demand dropped suddenly or the burner stayed at high fire; pressure trend rises to the limit.","check":"Trend steam pressure or water temperature and firing rate before the trip; check the modulation setpoint and PID against the safety limit.","component":"limit-string","mechanism":"limit-trip"},{"cause":"Sensor or wiring fault (subsets 1–3)","signs":"Pressure reading jumps or reads full scale or zero.","check":"Check sensor wiring and supply, and that no analog input exceeds 5 V.","component":"pressure-sensor","mechanism":"sensor-failure"},{"cause":"CANbus fault (subset 255)","signs":"Other CAN devices also show errors.","check":"Check CANbus wiring and termination to the sensor.","component":"comms-network","mechanism":"network-fault"}],"distinguish":["Subset 4 is a process event; subsets 1–3 and 255 are instrument faults. Treat a subset 4 trip as a real over-pressure until proven otherwise."],"evidence":["Subset","Steam pressure or water temperature trend before the trip","Firing rate trend","Sensor model and wiring"],"related":[],"title":"Fireye NX6300 F41: Boiler Pressure or Temperature Limit","description":"Fireye NX6300 F41 means the boiler pressure or temperature exceeded the safety limit, or its sensor failed. How the subset separates a real limit trip from a sensor fault.","sources":[{"title":"NX6300 Single Fuel Integrated Burner Control Commissioning Manual","publisher":"Fireye","docId":"NEX-6301","revision":"2025-03-19, Commissioning Manual 1.4, firmware 1.4","url":"https://www.fireye.com/downloads/NEX-6301-NX6300_Commissioning_Manual_English_2025-3-19-Web.pdf","section":"Section 5, 1.5 List of Fault Code Numbers: F41","page":"5-8"}],"review":{"status":"extracted","checks":["No step asks the reader to bypass, jumper or disable a flame safeguard, limit or interlock.","Electrical and fuel-train checks are framed for qualified personnel only.","F41, its display text and subsets match section 5 of NEX-6301 for the installed firmware."]},"updatedAt":"2026-10-26","url":"https://induqt.ai/troubleshoot/boilers/fireye/nx6300/f41"},{"kind":"fault","family":"boilers","manufacturerSlug":"fireye","modelSlug":"nx6300","controller":"Fireye NX6300 single-fuel integrated burner control (Nexus)","firmware":"Firmware 1.4","severity":"lockout","code":"F42","name":"Valve prove (leak) test fault","meaning":"When valve proving is enabled, the controller tests the gas safety shutoff valves during start-up by trapping gas between them and watching the pressure. F42 means the pressure did not behave as expected, which can mean a valve seat leaking, a valve not opening for the test, or a wrongly set test.","operatingStates":["Status 03–09: the leak test runs in parallel with the start-up sequence"],"subsets":[{"value":"Valve prove status number","meaning":"The step of the leak test that failed; the manual’s valve proving section lists the steps"}],"functions":["valve-proving"],"relatedComponents":["main-fuel-valves","fuel-supply"],"causes":[{"cause":"Upstream or downstream valve seat leaking","signs":"Fails at the same step every time; pressure decays or builds in the test section.","check":"Have the valves tightness-tested by a qualified technician against the valve maker’s procedure.","component":"main-fuel-valves","mechanism":"valve-seat-leak"},{"cause":"Supply pressure low or unstable","signs":"Fails intermittently, often when other users are on.","check":"Check supply pressure during the test against the nominal pressure set in the controller.","component":"fuel-supply","mechanism":"supply-pressure-droop"},{"cause":"Test parameters wrong","signs":"New installation or changed gas train; the test takes a long time.","check":"The troubleshooting table points to the valve-proving option parameters (nominal pressure, test volume, leak rate).","component":"burner-controller","mechanism":"configuration-change"}],"distinguish":["F42 is the controller’s own leak test. A separate proof-of-closure fault (NX6100 F30) is a valve-position switch problem."],"evidence":["Subset (valve prove status)","Gas supply pressure during the test","Valve train make and model"],"related":[],"title":"Fireye NX6300 F42: Gas Valve Leak Test Failed","description":"Fireye NX6300 F42 means the gas valve proving (leak) test measured the wrong pressure. What the test checks and how to separate a leaking valve from a setup problem.","sources":[{"title":"NX6300 Single Fuel Integrated Burner Control Commissioning Manual","publisher":"Fireye","docId":"NEX-6301","revision":"2025-03-19, Commissioning Manual 1.4, firmware 1.4","url":"https://www.fireye.com/downloads/NEX-6301-NX6300_Commissioning_Manual_English_2025-3-19-Web.pdf","section":"Section 5, 1.5 List of Fault Code Numbers: F42","page":"5-8"}],"review":{"status":"extracted","checks":["No step asks the reader to bypass, jumper or disable a flame safeguard, limit or interlock.","Electrical and fuel-train checks are framed for qualified personnel only.","F42, its display text and subsets match section 5 of NEX-6301 for the installed firmware."]},"updatedAt":"2026-10-26","url":"https://induqt.ai/troubleshoot/boilers/fireye/nx6300/f42"},{"kind":"fault","family":"boilers","manufacturerSlug":"fireye","modelSlug":"nx6300","controller":"Fireye NX6300 single-fuel integrated burner control (Nexus)","firmware":"Firmware 1.4","severity":"lockout","code":"F64","name":"Profile Invalid","meaning":"F64 means the controller will not fire the selected fuel/air profile because its data no longer matches the burner configuration. This is a deliberate safety block: a drive was deselected, a servo was replaced, or the profile was uploaded from a PC and not yet verified on this burner.","operatingStates":["Before start-up, when the profile is selected"],"subsets":[{"value":"Drive number","meaning":"A drive used in the profile has since been deselected"},{"value":"Profile + 100","meaning":"The profile uses a servo that was replaced, or was uploaded and not verified"}],"functions":["positioning","controller-integrity"],"relatedComponents":["burner-controller","fuel-actuator","air-damper"],"causes":[{"cause":"Servo replaced","signs":"After a servo swap; subset is the profile number plus 100.","check":"A qualified commissioning engineer checks the new servo is mounted the same way and re-commissions the profile, acknowledging every point up to high fire.","component":"fuel-actuator","mechanism":"configuration-change"},{"cause":"Drive deselected","signs":"After option parameter changes; subset is a drive number.","check":"Restore the drive selection or re-commission the profile without it.","component":"burner-controller","mechanism":"configuration-change"},{"cause":"Profile uploaded but not verified","signs":"After restoring settings from ComFire2 or a PC.","check":"Verify the profile on the burner in Commission Ratio mode.","component":"burner-controller","mechanism":"configuration-change"}],"distinguish":["F64 blocks a profile before firing; a drive position fault (F20 and up) happens when a valid profile’s drive misses its set point."],"evidence":["Subset","Recent servo, parameter or profile changes"],"related":["F20"],"title":"Fireye NX6300 F64 Profile Invalid: Causes and Fix","description":"Fireye NX6300 F64 means the selected fuel/air profile no longer matches the burner, often after a servo change or a profile upload. Subsets and what re-commissioning involves.","sources":[{"title":"NX6300 Single Fuel Integrated Burner Control Commissioning Manual","publisher":"Fireye","docId":"NEX-6301","revision":"2025-03-19, Commissioning Manual 1.4, firmware 1.4","url":"https://www.fireye.com/downloads/NEX-6301-NX6300_Commissioning_Manual_English_2025-3-19-Web.pdf","section":"Section 5, 1.5 List of Fault Code Numbers: F64","page":"5-11"}],"review":{"status":"extracted","checks":["No step asks the reader to bypass, jumper or disable a flame safeguard, limit or interlock.","Electrical and fuel-train checks are framed for qualified personnel only.","F64, its display text and subsets match section 5 of NEX-6301 for the installed firmware."]},"updatedAt":"2026-10-26","url":"https://induqt.ai/troubleshoot/boilers/fireye/nx6300/f64"},{"kind":"fault","family":"boilers","manufacturerSlug":"fireye","modelSlug":"nx6300","controller":"Fireye NX6300 single-fuel integrated burner control (Nexus)","firmware":"Firmware 1.4","severity":"lockout","code":"F66","name":"Flame Test","meaning":"The controller regularly checks that its flame input reads \"no flame\" when it should, using the scanner shutter or the detector’s own self-check. F66 means that test failed, so the controller can no longer trust the flame input. Left alone, a failing UV tube can show flame that is not there.","operatingStates":["Any status where the dark check runs; with shuttered or self-check scanners this includes firing"],"subsets":[{"value":"1","meaning":"Shutter not detected (shuttered UV)"},{"value":"2","meaning":"Flame input circuit failure"},{"value":"3","meaning":"Input stuck on, or terminals short-circuited"},{"value":"1xx / 2xx","meaning":"Self-check detector on flame 1 or flame 2 (when the scanner option is set for it), followed by the codes below"},{"value":"+1","meaning":"CANbus time-out: check wiring"},{"value":"+2 to +4","meaning":"Detector memory fault: replace the detector"},{"value":"+5, +6","meaning":"Detector internal fault: replace the detector"},{"value":"+7","meaning":"Shutter or dark check failed, or UV tube failed: check the detector out of the burner"}],"functions":["flame-supervision","controller-integrity"],"relatedComponents":["flame-scanner","flame-amplifier","comms-network"],"causes":[{"cause":"UV tube failing or shutter stuck","signs":"Subset 1 or +7; may be preceded by F11 events.","check":"Test the scanner outside the burner as the manual directs; replace if the dark check still fails.","component":"flame-scanner","mechanism":"detector-ageing"},{"cause":"Flame input wiring short","signs":"Subset 3; after wiring work or cable damage.","check":"Check the scanner cable and terminals for shorts.","component":"flame-amplifier","mechanism":"signal-noise"},{"cause":"Self-check detector fault","signs":"Subsets x02–x06.","check":"The manual directs replacing the detector for memory or internal faults.","component":"flame-scanner","mechanism":"detector-ageing"},{"cause":"CANbus to the detector","signs":"Subset x01.","check":"Check CANbus wiring to the detector.","component":"comms-network","mechanism":"network-fault"}],"distinguish":["F66 is the controller’s test of the flame input; F11 is a flame actually being registered at the wrong time."],"evidence":["Subset","Scanner model and option setting","Any recent F11 events in the log"],"related":["F11","F10"],"title":"Fireye NX6300 F66 Flame Test Failed: Subsets","description":"Fireye NX6300 F66 means the flame test (dark check) failed. Subsets for shuttered UV scanners and self-check detectors, and when to replace the detector.","sources":[{"title":"NX6300 Single Fuel Integrated Burner Control Commissioning Manual","publisher":"Fireye","docId":"NEX-6301","revision":"2025-03-19, Commissioning Manual 1.4, firmware 1.4","url":"https://www.fireye.com/downloads/NEX-6301-NX6300_Commissioning_Manual_English_2025-3-19-Web.pdf","section":"Section 5, 1.5 List of Fault Code Numbers: F66","page":"5-12"}],"review":{"status":"extracted","checks":["No step asks the reader to bypass, jumper or disable a flame safeguard, limit or interlock.","Electrical and fuel-train checks are framed for qualified personnel only.","F66, its display text and subsets match section 5 of NEX-6301 for the installed firmware."]},"updatedAt":"2026-10-26","url":"https://induqt.ai/troubleshoot/boilers/fireye/nx6300/f66"},{"kind":"equipment","family":"boilers","manufacturer":"Fireye","manufacturerSlug":"fireye","modelSlug":"nx6100","firmware":"Commissioning Manual 1.4 (Section 5 issue 1pt4D)","model":"NX6100 (Nexus)","title":"Fireye NX6100 Fault Codes and Lockout Diagnosis","description":"How the Fireye Nexus NX6100 integrated burner controller reports faults, subsets and its event history, and what the F, C and L fault codes mean.","summary":"The Fireye NX6100 is a Nexus integrated controller that combines flame safeguard, burner sequencing and parallel fuel/air positioning. It shares the Nexus fault numbering with the NX6300 but supports more drives and inputs, and adds faults for a second air switch, valve proof of closure and gas pressure supervision.","faultReporting":["Each fault number has a prefix: F means the fault occurred and is still present, C means it occurred and has cleared, L means a programmed limit was exceeded.","Many faults cause a non-volatile lockout that survives a power cycle; some faults and limits only raise a warning.","Most faults carry a subset read on the Engineer’s Key screen. Subsets are bit sums (1, 2, 4 … 128) or, for flame and air faults, the burner status number.","The 2-line text display stores the last 128 events and faults; the touchscreen display stores thousands. ComFire2 software shows the full set."],"sequence":[{"name":"00 Non-volatile lockout","text":"Fuel valves off, alarm on until muted; stays locked out until faults clear."},{"name":"01–02 Burner off, wait for purge","text":"Valves proven closed, no flame and no air pressure; waits for burner select and a profile."},{"name":"03–05 Leak test and prove closed","text":"Optional gas valve leak test starts; drives move to closed and are compared with commissioned positions."},{"name":"06–08 Prove air, purge positions, pre-purge","text":"Fan starts; air pressure must be proven after t1; drives reach purge positions and pre-purge t2 runs."},{"name":"09–10 Ignition position, pre-ignition","text":"Drives move to ignition positions; igniter energised for t3."},{"name":"11–12 Pilot ignition","text":"Pilot valve opens; flame must be proven by the end of safety time t4."},{"name":"13–14 Main ignition","text":"Main valves open for safety time t6, then the main flame interval t7; flame and air must stay proven."},{"name":"15–16 Low fire, modulation","text":"Low fire hold t8, then modulation on demand with flame and air supervised."},{"name":"17–18 Post-purge","text":"Fuel closes; air drives move to post-purge before returning to 01."}],"evidence":["Photo of the fault with its F/C/L prefix","Subset from the Engineer’s Key screen","The event log around the lockout","Flame scanner type and signal"],"codeIndex":[{"code":"F01–F09","name":"External alarm from low-voltage inputs 1 to 9"},{"code":"F10","name":"Flame Failure: no flame seen when one should be present"},{"code":"F11","name":"False Flame: flame seen when none should be present"},{"code":"F12–F13","name":"External alarm from high-voltage input 12 or 13"},{"code":"F14","name":"Main combustion air pressure not detected"},{"code":"F15","name":"Main combustion air pressure detected when it should not be"},{"code":"F16","name":"Optional second (primary) air pressure not detected"},{"code":"F17","name":"Optional second (primary) air pressure detected when it should not be"},{"code":"F18","name":"Not enough set points entered in the profile"},{"code":"F19","name":"Circuit board voltage reference fault"},{"code":"F20–F29","name":"Drive 0 to 9 position fault"},{"code":"F30","name":"Gas proof of closure fault"},{"code":"F31","name":"Oil proof of closure fault"},{"code":"F32","name":"Safety input fault (low-voltage inputs)"},{"code":"F33","name":"Burner input fault (high-voltage inputs)"},{"code":"F34","name":"Primary relay fault"},{"code":"F35","name":"ADC fault"},{"code":"F36","name":"Reset fault: too many resets with no fault present"},{"code":"F37–F39","name":"RAM, program memory or profile table check failed"},{"code":"F40","name":"Single fuel only fault: profile fuel not available on this unit"},{"code":"F41","name":"Boiler sensor fault or safety limit exceeded"},{"code":"F42","name":"Valve prove (leak) test fault"},{"code":"F43","name":"Gas pressure limit exceeded, or sensor fault"},{"code":"F45","name":"Low cup speed"},{"code":"F46","name":"EEPROM memory check failed"},{"code":"F50","name":"Oxygen probe heater fault"},{"code":"L52–L53","name":"Oxygen low or high limit alarm"},{"code":"F54","name":"Oxygen probes mismatch, or CO high limit"},{"code":"L55","name":"Trim limit alarm"},{"code":"F57","name":"Auto trim commissioning fault"},{"code":"L58–L59","name":"Flue temperature low or high alarm"},{"code":"F61","name":"Air pressure level fault"},{"code":"F63","name":"Option parameters uploaded: check and confirm"},{"code":"F64","name":"Profile Invalid"},{"code":"F65","name":"Power-up lockout"},{"code":"F66","name":"Flame Test: dark test failed"},{"code":"F67–F69","name":"Secondary relay, program memory or watchdog fault"},{"code":"F70–F79","name":"User faults from the programmable logic"},{"code":"L89","name":"FGR input fault"}],"sources":[{"title":"NX6100 Integrated Burner Controller Commissioning Manual","publisher":"Fireye","docId":"NEX-6101","revision":"2025-02-21, Commissioning Manual 1.4, Section 5 issue 1pt4D","url":"https://www.fireye.com/downloads/NEX-6101-NX6100_Series_Integrated_Burner_Controller_English_2025-21-02.pdf","section":"Section 5: 1.1–1.6, Faults and fault finding","page":"5-1 to 5-14"},{"title":"NX6100 Integrated Burner Controller Commissioning Manual","publisher":"Fireye","docId":"NEX-6101","revision":"2025-02-21, Commissioning Manual 1.4, Section 5 issue 1pt4D","url":"https://www.fireye.com/downloads/NEX-6101-NX6100_Series_Integrated_Burner_Controller_English_2025-21-02.pdf","section":"Section 1, 2.4 The Start-up Sequence","page":"1-29 to 1-30"}],"review":{"status":"extracted","checks":["No step asks the reader to bypass, jumper or disable a flame safeguard, limit or interlock.","Electrical and fuel-train checks are framed for qualified personnel only.","Prefix meanings, event history, sequence states and the code index match NEX-6101 for the installed firmware."]},"updatedAt":"2026-10-26","url":"https://induqt.ai/troubleshoot/boilers/fireye/nx6100"},{"kind":"fault","family":"boilers","manufacturerSlug":"fireye","modelSlug":"nx6100","controller":"Fireye NX6100 integrated burner controller (Nexus)","firmware":"Commissioning Manual 1.4 (Section 5 issue 1pt4D)","severity":"lockout","code":"F10","name":"Flame Failure","meaning":"F10 means the flame detector did not register a flame at a point in the sequence where the controller requires one. The subset tells you which flame input and which burner status the controller was in, which is the fastest way to narrow the cause: a failure at pilot ignition has different causes from a flame lost during modulation.","operatingStates":["Status 11–12: pilot ignition and pilot interval","Status 13–14: main ignition and waiting for main flame","Status 15: moving to or holding at low fire","Status 16: modulation"],"subsets":[{"value":"1xx","meaning":"Flame 1 (the first flame input); the last two digits are the burner status number"},{"value":"2xx","meaning":"Flame 2 (the second flame input)"},{"value":"x11, x12","meaning":"Pilot ignition (safety time t4) or pilot ignition interval (t5): flame never proven or pilot lost"},{"value":"x13, x14","meaning":"Main ignition (t6) or waiting for main flame (t7): lost at the change from pilot to main flame"},{"value":"x15","meaning":"Moving to low fire or low fire hold (t8)"},{"value":"x16","meaning":"Modulation: lost while firing"}],"functions":["flame-supervision","ignition","fuel-delivery"],"relatedComponents":["flame-scanner","flame-amplifier","igniter","pilot-train","fuel-supply","air-damper"],"causes":[{"cause":"No pilot flame at ignition (subset x11–x12)","signs":"Repeated F10 at pilot status; no spark or no pilot through the sight glass.","check":"Observe a start with a qualified technician: spark, pilot flame and the flame signal on the overview screen.","component":"igniter","mechanism":"electrode-wear"},{"cause":"Pilot gas pressure or regulator (subset x11–x12)","signs":"Spark present, pilot weak or absent.","check":"Read pilot gas pressure during the trial and confirm the pilot valve opens.","component":"pilot-train","mechanism":"regulator-drift"},{"cause":"Main flame does not take over (subset x13–x14)","signs":"Pilot proves, then F10 as main valves open; gas pressure sags at light-off.","check":"Trend gas pressure during main ignition; check the ignition position of the fuel and air drives against the commissioned profile.","component":"fuel-supply","mechanism":"supply-pressure-droop"},{"cause":"Flame lost while firing (subset x15–x16)","signs":"Trips at load changes or high fire; L-prefixed limits or drive faults near the event.","check":"Use the event log and any fuel pressure, air pressure or oxygen readings to see what moved before the trip.","component":"air-damper","mechanism":"air-fuel-ratio-drift"},{"cause":"Flame present but not seen","signs":"Flame visible; signal low or falling over weeks. The manual’s first instruction is to check wiring if there is a flame.","check":"Check scanner wiring, lens and sighting; compare the flame signal with earlier starts.","component":"flame-scanner","mechanism":"lens-fouling"}],"distinguish":["F10 is no flame when expected; F11 is flame when none should be present; F66 is the flame test (dark check) failing.","C10 in the event log means the flame failure happened and has since cleared, which is normal after the lockout; F10 means it is still present."],"evidence":["Photo of the fault with its F/C prefix and the subset from the Engineer’s Key screen","The event log around the lockout","Flame scanner type and flame signal during a normal start","Gas pressure at light-off and while firing"],"related":["F11","F66","F14"],"title":"Fireye NX6100 F10 Flame Failure: Subsets and Causes","description":"Fireye NX6100 F10 means no flame was seen when one should be present. How to read the subset (burner status), and the checks for each stage.","sources":[{"title":"NX6100 Integrated Burner Controller Commissioning Manual","publisher":"Fireye","docId":"NEX-6101","revision":"2025-02-21, Commissioning Manual 1.4, Section 5 issue 1pt4D","url":"https://www.fireye.com/downloads/NEX-6101-NX6100_Series_Integrated_Burner_Controller_English_2025-21-02.pdf","section":"Section 5, 1.5 List of Fault Code Numbers: F10","page":"5-4"},{"title":"NX6100 Integrated Burner Controller Commissioning Manual","publisher":"Fireye","docId":"NEX-6101","revision":"2025-02-21, Commissioning Manual 1.4, Section 5 issue 1pt4D","url":"https://www.fireye.com/downloads/NEX-6101-NX6100_Series_Integrated_Burner_Controller_English_2025-21-02.pdf","section":"Section 1, 2.4 The Start-up Sequence","page":"1-29 to 1-30"}],"review":{"status":"extracted","checks":["No step asks the reader to bypass, jumper or disable a flame safeguard, limit or interlock.","Electrical and fuel-train checks are framed for qualified personnel only.","F10, its display text and subsets match section 5 of NEX-6101 for the installed firmware."]},"updatedAt":"2026-10-26","url":"https://induqt.ai/troubleshoot/boilers/fireye/nx6100/f10"},{"kind":"fault","family":"boilers","manufacturerSlug":"fireye","modelSlug":"nx6100","controller":"Fireye NX6100 integrated burner controller (Nexus)","firmware":"Commissioning Manual 1.4 (Section 5 issue 1pt4D)","severity":"lockout","code":"F11","name":"False Flame","meaning":"F11 means the controller saw a flame signal when there should be no flame, for example before purge, during purge or after shutdown, or while a shuttered scanner’s shutter was closed. The controller cannot tell a real flame from a faulty signal, so it locks out.","operatingStates":["Status 01–02: burner off or waiting for purge","Status 05–09: proving positions and pre-purge","Status 10: pre-ignition","Status 17–18: post-purge"],"subsets":[{"value":"1xx","meaning":"Flame 1 (the first flame input); the last two digits are the burner status number"},{"value":"2xx","meaning":"Flame 2 (the second flame input)"},{"value":"x01, x02","meaning":"Burner off or waiting to purge: flame seen at rest"},{"value":"x05 to x09","meaning":"During closed/air/purge position proving or pre-purge"},{"value":"x10","meaning":"Pre-ignition, with the igniter on but no fuel"},{"value":"x17, x18","meaning":"Post-purge, after the fuel valves closed"}],"functions":["flame-supervision"],"relatedComponents":["flame-scanner","flame-amplifier","main-fuel-valves"],"causes":[{"cause":"Fuel still burning after shutdown (subset x17–x18 or x01)","signs":"Visible flame after the cycle; oil after-drip or leaking safety valve.","check":"Look into the furnace. If flame persists, close the manual fuel valves and have the safety shutoff valves tightness-tested; the valve leak test (if fitted) helps here.","component":"main-fuel-valves","mechanism":"valve-seat-leak"},{"cause":"Detector seeing ignition spark (subset x10)","signs":"Only at pre-ignition when the spark starts.","check":"Re-sight the scanner so it cannot view the spark; check scanner and ignition cable routing.","component":"flame-scanner","mechanism":"sighting-shift"},{"cause":"Failing UV tube or self-check detector","signs":"Signal in a dark, cold furnace; often accompanied by F66 events.","check":"Cover the scanner with the burner off; any remaining signal means a detector or input fault.","component":"flame-amplifier","mechanism":"detector-ageing"},{"cause":"Noise pickup on the flame input","signs":"Intermittent, coinciding with motor or ignition switching.","check":"Check screen termination and separation of the scanner cable from power and ignition wiring.","component":"flame-scanner","mechanism":"signal-noise"}],"distinguish":["F11 is flame when none is expected; F66 is the controller’s own dark test failing, which can precede F11 as a UV tube fails."],"evidence":["Fault prefix and subset","Event log","Scanner model (UV, self-check UV, IR)","Whether flame is visible in the furnace at the time"],"related":["F10","F66"],"title":"Fireye NX6100 F11 False Flame: Causes and Checks","description":"Fireye NX6100 F11 means a flame was registered when none should be present, or with the shutter closed. Real flame, detector faults and how the subset helps.","sources":[{"title":"NX6100 Integrated Burner Controller Commissioning Manual","publisher":"Fireye","docId":"NEX-6101","revision":"2025-02-21, Commissioning Manual 1.4, Section 5 issue 1pt4D","url":"https://www.fireye.com/downloads/NEX-6101-NX6100_Series_Integrated_Burner_Controller_English_2025-21-02.pdf","section":"Section 5, 1.5 List of Fault Code Numbers: F11","page":"5-4"},{"title":"NX6100 Integrated Burner Controller Commissioning Manual","publisher":"Fireye","docId":"NEX-6101","revision":"2025-02-21, Commissioning Manual 1.4, Section 5 issue 1pt4D","url":"https://www.fireye.com/downloads/NEX-6101-NX6100_Series_Integrated_Burner_Controller_English_2025-21-02.pdf","section":"Section 1, 2.4 The Start-up Sequence","page":"1-29 to 1-30"}],"review":{"status":"extracted","checks":["No step asks the reader to bypass, jumper or disable a flame safeguard, limit or interlock.","Electrical and fuel-train checks are framed for qualified personnel only.","F11, its display text and subsets match section 5 of NEX-6101 for the installed firmware."]},"updatedAt":"2026-10-26","url":"https://induqt.ai/troubleshoot/boilers/fireye/nx6100/f11"},{"kind":"fault","family":"boilers","manufacturerSlug":"fireye","modelSlug":"nx6100","controller":"Fireye NX6100 integrated burner controller (Nexus)","firmware":"Commissioning Manual 1.4 (Section 5 issue 1pt4D)","severity":"lockout","code":"F14","name":"Combustion air pressure not detected","meaning":"F14 means the main (secondary) combustion air pressure switch did not register air pressure at a point where the controller requires it. The subset is the burner status number, which tells you whether air was never proven at the start of purge or was lost later while firing.","operatingStates":["Status 07: proving purge positions, after the air pressure prove time t1","Status 08–16: purge, ignition and firing, where air must stay proven"],"subsets":[{"value":"07","meaning":"Air not proven when the air prove time ended, before purge"},{"value":"08 to 16","meaning":"Air pressure lost during purge, ignition or firing"}],"functions":["air-proving","purge"],"relatedComponents":["combustion-fan","air-switch","air-damper"],"causes":[{"cause":"Fan not running or slow (subset 07)","signs":"Fan does not start, overload trips, or a fan VSD ramps slowly.","check":"Confirm the burner motor output, starter and any VSD run signal; check the fan reaches purge speed.","component":"combustion-fan","mechanism":"fan-drive-fault"},{"cause":"Air path restricted","signs":"Gradual onset; dirty inlet, closed damper, flue restriction.","check":"Inspect intake, fan wheel, damper travel and flue.","component":"combustion-fan","mechanism":"blocked-air-path"},{"cause":"Switch setpoint too close to the low-fire differential (subset 15–16)","signs":"Trips at low fire or on modulation down.","check":"Measure the differential at the switch across the firing range and compare with its setpoint.","component":"air-switch","mechanism":"switch-drift"}],"distinguish":["F14 is air not proven when required; F15 is air proven when it should not be."],"evidence":["Subset (burner status)","Fan motor or VSD status at the fault","Air pressure at the switch at low and high fire"],"related":["F15","F10"],"title":"Fireye NX6100 F14: Combustion Air Pressure Not Proven","description":"Fireye NX6100 F14 means the main combustion air pressure switch did not prove air when it should. Fan, air path and switch checks by burner status.","sources":[{"title":"NX6100 Integrated Burner Controller Commissioning Manual","publisher":"Fireye","docId":"NEX-6101","revision":"2025-02-21, Commissioning Manual 1.4, Section 5 issue 1pt4D","url":"https://www.fireye.com/downloads/NEX-6101-NX6100_Series_Integrated_Burner_Controller_English_2025-21-02.pdf","section":"Section 5, 1.5 List of Fault Code Numbers: F14","page":"5-4"},{"title":"NX6100 Integrated Burner Controller Commissioning Manual","publisher":"Fireye","docId":"NEX-6101","revision":"2025-02-21, Commissioning Manual 1.4, Section 5 issue 1pt4D","url":"https://www.fireye.com/downloads/NEX-6101-NX6100_Series_Integrated_Burner_Controller_English_2025-21-02.pdf","section":"Section 1, 2.4 The Start-up Sequence","page":"1-29 to 1-30"}],"review":{"status":"extracted","checks":["No step asks the reader to bypass, jumper or disable a flame safeguard, limit or interlock.","Electrical and fuel-train checks are framed for qualified personnel only.","F14, its display text and subsets match section 5 of NEX-6101 for the installed firmware."]},"updatedAt":"2026-10-26","url":"https://induqt.ai/troubleshoot/boilers/fireye/nx6100/f14"},{"kind":"fault","family":"boilers","manufacturerSlug":"fireye","modelSlug":"nx6100","controller":"Fireye NX6100 integrated burner controller (Nexus)","firmware":"Commissioning Manual 1.4 (Section 5 issue 1pt4D)","severity":"lockout","code":"F15","name":"Combustion air pressure detected when it should not be","meaning":"F15 means the main combustion air pressure switch registered air when the controller expected none. Subset 1 means air was seen at the wrong time; subset 2 means the switch still showed air more than three minutes after the burner turned off. The manual also notes F15 appears if the air-switch option (Opt 6.x) is not set.","operatingStates":["Status 01: burner off, before the fan starts","After shutdown, while the fan runs down"],"subsets":[{"value":"1","meaning":"Air pressure registered when it should not be present"},{"value":"2","meaning":"Air pressure still registered more than 3 minutes after the burner turned off"}],"functions":["air-proving"],"relatedComponents":["air-switch","combustion-fan","burner-controller"],"causes":[{"cause":"Switch contacts stuck or a jumper left in","signs":"Every start; switch reads closed with the fan stopped.","check":"Check the switch with the fan off and isolated; look for jumpers from previous work.","component":"air-switch","mechanism":"contact-welded"},{"cause":"Fan still running or windmilling (subset 2)","signs":"Fan keeps turning after shutdown; shared breeching or strong stack draft.","check":"Confirm the fan stops; read pressure at the sensing point with the fan off.","component":"combustion-fan","mechanism":"contact-welded"},{"cause":"Option parameter not set","signs":"New installation or after parameter changes.","check":"Have the commissioning engineer confirm the Opt 6.x air switch settings.","component":"burner-controller","mechanism":"configuration-change"}],"distinguish":["F15 is air when there should be none; F14 is no air when there should be."],"evidence":["Subset (1 or 2)","Whether the fan is turning with the burner off","Air switch wiring and any recent parameter changes"],"related":["F14"],"title":"Fireye NX6100 F15: Air Pressure Detected When Off","description":"Fireye NX6100 F15 means the combustion air switch showed pressure when it should not. Subset 1 and 2 explained, with fan run-down and switch checks.","sources":[{"title":"NX6100 Integrated Burner Controller Commissioning Manual","publisher":"Fireye","docId":"NEX-6101","revision":"2025-02-21, Commissioning Manual 1.4, Section 5 issue 1pt4D","url":"https://www.fireye.com/downloads/NEX-6101-NX6100_Series_Integrated_Burner_Controller_English_2025-21-02.pdf","section":"Section 5, 1.5 List of Fault Code Numbers: F15","page":"5-4"}],"review":{"status":"extracted","checks":["No step asks the reader to bypass, jumper or disable a flame safeguard, limit or interlock.","Electrical and fuel-train checks are framed for qualified personnel only.","F15, its display text and subsets match section 5 of NEX-6101 for the installed firmware."]},"updatedAt":"2026-10-26","url":"https://induqt.ai/troubleshoot/boilers/fireye/nx6100/f15"},{"kind":"fault","family":"boilers","manufacturerSlug":"fireye","modelSlug":"nx6100","controller":"Fireye NX6100 integrated burner controller (Nexus)","firmware":"Commissioning Manual 1.4 (Section 5 issue 1pt4D)","severity":"lockout","code":"F20","name":"Drive position fault","meaning":"A drive position fault means a fuel or air drive (servo, or fan VSD) was not where the commissioned profile says it should be. F20 is drive 0; the following numbers are the other drives. The controller checks the close and purge positions during start-up and the fuel/air ratio while firing, so the subset tells you whether the problem is mechanical, communication or inside the servo.","operatingStates":["Status 05: proving closed positions","Status 07: proving purge positions","Status 08–15: pre-purge, ignition and post-purge, if a drive moves off its set point","Status 16: modulation, if a drive leaves the commissioned curve"],"subsets":[{"value":"000 to 016","meaning":"Burner status when the fault occurred (position error)"},{"value":"032 to 048","meaning":"CANbus communication error; the display shows ERR1 under the drive name"},{"value":"above 64","meaning":"Internal servo fault; the display shows ERR2 to ERR7 under the drive name"}],"functions":["positioning"],"relatedComponents":["air-damper","fuel-actuator","comms-network","combustion-fan"],"causes":[{"cause":"Linkage or damper binding (subset 000–016)","signs":"Fault at purge or during modulation; actuator labours or stalls.","check":"Disconnect and stroke the damper or valve by hand (burner off, qualified personnel) to check for binding; check couplings for slip.","component":"air-damper","mechanism":"linkage-slip"},{"cause":"Stored close or purge position no longer reachable","signs":"Fault before the drives reach purge, after mechanical work or servo replacement.","check":"The manual’s troubleshooting table points to feedback potentiometers and motor micro-switches, then resetting close and purge positions in Commission Ratio mode.","component":"fuel-actuator","mechanism":"actuator-feedback-fault"},{"cause":"CANbus fault (subset 032–048, ERR1)","signs":"ERR1 under the drive name; display slow or freezing.","check":"Check CANbus wiring, screens and termination to the servo.","component":"comms-network","mechanism":"network-fault"},{"cause":"Servo internal fault (subset above 64, ERR2–ERR7)","signs":"Repeats on the same servo.","check":"Replace the servo; a replacement servo invalidates profiles that used it (F64) until re-commissioned.","component":"fuel-actuator","mechanism":"actuator-feedback-fault"},{"cause":"Fan VSD outside its error band","signs":"Fault on the VSD drive while modulating; VSD current-limiting or slow ramp.","check":"Check the VSD ramp times and that its own PID is disabled, as the manual’s inverter section describes.","component":"combustion-fan","mechanism":"fan-drive-fault"}],"distinguish":["Position faults are drive-specific: note the drive number (F20 = drive 0) and its subset.","A profile that will not run at all after a servo change is F64, not a position fault."],"evidence":["Fault number (which drive) and subset","ERR code under the drive name, if shown","Any recent servo, linkage or VSD work"],"related":["F64"],"title":"Fireye NX6100 F20–F2x Drive Position Fault: Subsets","description":"Fireye NX6100 drive position faults (F20 for drive 0 and up) explained: close, purge and profile position errors, CANbus and servo subsets, and what to check.","sources":[{"title":"NX6100 Integrated Burner Controller Commissioning Manual","publisher":"Fireye","docId":"NEX-6101","revision":"2025-02-21, Commissioning Manual 1.4, Section 5 issue 1pt4D","url":"https://www.fireye.com/downloads/NEX-6101-NX6100_Series_Integrated_Burner_Controller_English_2025-21-02.pdf","section":"Section 5, 1.5 List of Fault Code Numbers: F20","page":"5-6"},{"title":"NX6100 Integrated Burner Controller Commissioning Manual","publisher":"Fireye","docId":"NEX-6101","revision":"2025-02-21, Commissioning Manual 1.4, Section 5 issue 1pt4D","url":"https://www.fireye.com/downloads/NEX-6101-NX6100_Series_Integrated_Burner_Controller_English_2025-21-02.pdf","section":"Section 5, 1.7.2 Startup problems; 1.7.5 Modulation problems","page":"5-25 to 5-28"}],"review":{"status":"extracted","checks":["No step asks the reader to bypass, jumper or disable a flame safeguard, limit or interlock.","Electrical and fuel-train checks are framed for qualified personnel only.","F20, its display text and subsets match section 5 of NEX-6101 for the installed firmware.","Troubleshooting page numbers for 1.7.2 and 1.7.5 match the installed manual issue."]},"updatedAt":"2026-10-26","url":"https://induqt.ai/troubleshoot/boilers/fireye/nx6100/f20"},{"kind":"fault","family":"boilers","manufacturerSlug":"fireye","modelSlug":"nx6100","controller":"Fireye NX6100 integrated burner controller (Nexus)","firmware":"Commissioning Manual 1.4 (Section 5 issue 1pt4D)","severity":"lockout","code":"F41","name":"Boiler sensor fault or safety limit exceeded","meaning":"F41 covers two very different situations: the measured boiler pressure or temperature went above the controller’s safety limit, or the sensor stopped responding correctly. The subset separates them, and only subset 4 is a real limit exceedance.","operatingStates":["Any status; most often while firing at high load or as load drops suddenly"],"subsets":[{"value":"1","meaning":"Sensor feedback below 1 V"},{"value":"2","meaning":"Sensor feedback above 5 V"},{"value":"3","meaning":"Sensor failed during its test"},{"value":"4","meaning":"Safety limit exceeded"},{"value":"255","meaning":"CANbus communication fault to the sensor"}],"functions":["limit-supervision"],"relatedComponents":["pressure-sensor","limit-string","comms-network"],"causes":[{"cause":"Real over-pressure or over-temperature (subset 4)","signs":"Steam demand dropped suddenly or the burner stayed at high fire; pressure trend rises to the limit.","check":"Trend steam pressure or water temperature and firing rate before the trip; check the modulation setpoint and PID against the safety limit.","component":"limit-string","mechanism":"limit-trip"},{"cause":"Sensor or wiring fault (subsets 1–3)","signs":"Pressure reading jumps or reads full scale or zero.","check":"Check sensor wiring and supply, and that no analog input exceeds 5 V.","component":"pressure-sensor","mechanism":"sensor-failure"},{"cause":"CANbus fault (subset 255)","signs":"Other CAN devices also show errors.","check":"Check CANbus wiring and termination to the sensor.","component":"comms-network","mechanism":"network-fault"}],"distinguish":["Subset 4 is a process event; subsets 1–3 and 255 are instrument faults. Treat a subset 4 trip as a real over-pressure until proven otherwise."],"evidence":["Subset","Steam pressure or water temperature trend before the trip","Firing rate trend","Sensor model and wiring"],"related":[],"title":"Fireye NX6100 F41: Boiler Pressure or Temperature Limit","description":"Fireye NX6100 F41 means the boiler pressure or temperature exceeded the safety limit, or its sensor failed. How the subset separates a real limit trip from a sensor fault.","sources":[{"title":"NX6100 Integrated Burner Controller Commissioning Manual","publisher":"Fireye","docId":"NEX-6101","revision":"2025-02-21, Commissioning Manual 1.4, Section 5 issue 1pt4D","url":"https://www.fireye.com/downloads/NEX-6101-NX6100_Series_Integrated_Burner_Controller_English_2025-21-02.pdf","section":"Section 5, 1.5 List of Fault Code Numbers: F41","page":"5-8"}],"review":{"status":"extracted","checks":["No step asks the reader to bypass, jumper or disable a flame safeguard, limit or interlock.","Electrical and fuel-train checks are framed for qualified personnel only.","F41, its display text and subsets match section 5 of NEX-6101 for the installed firmware."]},"updatedAt":"2026-10-26","url":"https://induqt.ai/troubleshoot/boilers/fireye/nx6100/f41"},{"kind":"fault","family":"boilers","manufacturerSlug":"fireye","modelSlug":"nx6100","controller":"Fireye NX6100 integrated burner controller (Nexus)","firmware":"Commissioning Manual 1.4 (Section 5 issue 1pt4D)","severity":"lockout","code":"F42","name":"Valve prove (leak) test fault","meaning":"When valve proving is enabled, the controller tests the gas safety shutoff valves during start-up by trapping gas between them and watching the pressure. F42 means the pressure did not behave as expected, which can mean a valve seat leaking, a valve not opening for the test, or a wrongly set test.","operatingStates":["Status 03–09: the leak test runs in parallel with the start-up sequence"],"subsets":[{"value":"Valve prove status number","meaning":"The step of the leak test that failed; the manual’s valve proving section lists the steps"}],"functions":["valve-proving"],"relatedComponents":["main-fuel-valves","fuel-supply"],"causes":[{"cause":"Upstream or downstream valve seat leaking","signs":"Fails at the same step every time; pressure decays or builds in the test section.","check":"Have the valves tightness-tested by a qualified technician against the valve maker’s procedure.","component":"main-fuel-valves","mechanism":"valve-seat-leak"},{"cause":"Supply pressure low or unstable","signs":"Fails intermittently, often when other users are on.","check":"Check supply pressure during the test against the nominal pressure set in the controller.","component":"fuel-supply","mechanism":"supply-pressure-droop"},{"cause":"Test parameters wrong","signs":"New installation or changed gas train; the test takes a long time.","check":"The troubleshooting table points to the valve-proving option parameters (nominal pressure, test volume, leak rate).","component":"burner-controller","mechanism":"configuration-change"}],"distinguish":["F42 is the controller’s own leak test. A separate proof-of-closure fault (NX6100 F30) is a valve-position switch problem."],"evidence":["Subset (valve prove status)","Gas supply pressure during the test","Valve train make and model"],"related":[],"title":"Fireye NX6100 F42: Gas Valve Leak Test Failed","description":"Fireye NX6100 F42 means the gas valve proving (leak) test measured the wrong pressure. What the test checks and how to separate a leaking valve from a setup problem.","sources":[{"title":"NX6100 Integrated Burner Controller Commissioning Manual","publisher":"Fireye","docId":"NEX-6101","revision":"2025-02-21, Commissioning Manual 1.4, Section 5 issue 1pt4D","url":"https://www.fireye.com/downloads/NEX-6101-NX6100_Series_Integrated_Burner_Controller_English_2025-21-02.pdf","section":"Section 5, 1.5 List of Fault Code Numbers: F42","page":"5-8"}],"review":{"status":"extracted","checks":["No step asks the reader to bypass, jumper or disable a flame safeguard, limit or interlock.","Electrical and fuel-train checks are framed for qualified personnel only.","F42, its display text and subsets match section 5 of NEX-6101 for the installed firmware."]},"updatedAt":"2026-10-26","url":"https://induqt.ai/troubleshoot/boilers/fireye/nx6100/f42"},{"kind":"fault","family":"boilers","manufacturerSlug":"fireye","modelSlug":"nx6100","controller":"Fireye NX6100 integrated burner controller (Nexus)","firmware":"Commissioning Manual 1.4 (Section 5 issue 1pt4D)","severity":"lockout","code":"F64","name":"Profile Invalid","meaning":"F64 means the controller will not fire the selected fuel/air profile because its data no longer matches the burner configuration. This is a deliberate safety block: a drive was deselected, a servo was replaced, or the profile was uploaded from a PC and not yet verified on this burner.","operatingStates":["Before start-up, when the profile is selected"],"subsets":[{"value":"Drive number","meaning":"A drive used in the profile has since been deselected"},{"value":"Profile + 100","meaning":"The profile uses a servo that was replaced, or was uploaded and not verified"}],"functions":["positioning","controller-integrity"],"relatedComponents":["burner-controller","fuel-actuator","air-damper"],"causes":[{"cause":"Servo replaced","signs":"After a servo swap; subset is the profile number plus 100.","check":"A qualified commissioning engineer checks the new servo is mounted the same way and re-commissions the profile, acknowledging every point up to high fire.","component":"fuel-actuator","mechanism":"configuration-change"},{"cause":"Drive deselected","signs":"After option parameter changes; subset is a drive number.","check":"Restore the drive selection or re-commission the profile without it.","component":"burner-controller","mechanism":"configuration-change"},{"cause":"Profile uploaded but not verified","signs":"After restoring settings from ComFire2 or a PC.","check":"Verify the profile on the burner in Commission Ratio mode.","component":"burner-controller","mechanism":"configuration-change"}],"distinguish":["F64 blocks a profile before firing; a drive position fault (F20 and up) happens when a valid profile’s drive misses its set point."],"evidence":["Subset","Recent servo, parameter or profile changes"],"related":["F20"],"title":"Fireye NX6100 F64 Profile Invalid: Causes and Fix","description":"Fireye NX6100 F64 means the selected fuel/air profile no longer matches the burner, often after a servo change or a profile upload. Subsets and what re-commissioning involves.","sources":[{"title":"NX6100 Integrated Burner Controller Commissioning Manual","publisher":"Fireye","docId":"NEX-6101","revision":"2025-02-21, Commissioning Manual 1.4, Section 5 issue 1pt4D","url":"https://www.fireye.com/downloads/NEX-6101-NX6100_Series_Integrated_Burner_Controller_English_2025-21-02.pdf","section":"Section 5, 1.5 List of Fault Code Numbers: F64","page":"5-11"}],"review":{"status":"extracted","checks":["No step asks the reader to bypass, jumper or disable a flame safeguard, limit or interlock.","Electrical and fuel-train checks are framed for qualified personnel only.","F64, its display text and subsets match section 5 of NEX-6101 for the installed firmware."]},"updatedAt":"2026-10-26","url":"https://induqt.ai/troubleshoot/boilers/fireye/nx6100/f64"},{"kind":"fault","family":"boilers","manufacturerSlug":"fireye","modelSlug":"nx6100","controller":"Fireye NX6100 integrated burner controller (Nexus)","firmware":"Commissioning Manual 1.4 (Section 5 issue 1pt4D)","severity":"lockout","code":"F66","name":"Flame Test","meaning":"The controller regularly checks that its flame input reads \"no flame\" when it should, using the scanner shutter or the detector’s own self-check. F66 means that test failed, so the controller can no longer trust the flame input. Left alone, a failing UV tube can show flame that is not there.","operatingStates":["Any status where the dark check runs; with shuttered or self-check scanners this includes firing"],"subsets":[{"value":"1","meaning":"Shutter not detected (shuttered UV)"},{"value":"2","meaning":"Flame input circuit failure"},{"value":"3","meaning":"Input stuck on, or terminals short-circuited"},{"value":"1xx / 2xx","meaning":"Self-check detector on flame 1 or flame 2 (when the scanner option is set for it), followed by the codes below"},{"value":"+1","meaning":"CANbus time-out: check wiring"},{"value":"+2 to +4","meaning":"Detector memory fault: replace the detector"},{"value":"+5, +6","meaning":"Detector internal fault: replace the detector"},{"value":"+7","meaning":"Shutter or dark check failed, or UV tube failed: check the detector out of the burner"}],"functions":["flame-supervision","controller-integrity"],"relatedComponents":["flame-scanner","flame-amplifier","comms-network"],"causes":[{"cause":"UV tube failing or shutter stuck","signs":"Subset 1 or +7; may be preceded by F11 events.","check":"Test the scanner outside the burner as the manual directs; replace if the dark check still fails.","component":"flame-scanner","mechanism":"detector-ageing"},{"cause":"Flame input wiring short","signs":"Subset 3; after wiring work or cable damage.","check":"Check the scanner cable and terminals for shorts.","component":"flame-amplifier","mechanism":"signal-noise"},{"cause":"Self-check detector fault","signs":"Subsets x02–x06.","check":"The manual directs replacing the detector for memory or internal faults.","component":"flame-scanner","mechanism":"detector-ageing"},{"cause":"CANbus to the detector","signs":"Subset x01.","check":"Check CANbus wiring to the detector.","component":"comms-network","mechanism":"network-fault"}],"distinguish":["F66 is the controller’s test of the flame input; F11 is a flame actually being registered at the wrong time."],"evidence":["Subset","Scanner model and option setting","Any recent F11 events in the log"],"related":["F11","F10"],"title":"Fireye NX6100 F66 Flame Test Failed: Subsets","description":"Fireye NX6100 F66 means the flame test (dark check) failed. Subsets for shuttered UV scanners and self-check detectors, and when to replace the detector.","sources":[{"title":"NX6100 Integrated Burner Controller Commissioning Manual","publisher":"Fireye","docId":"NEX-6101","revision":"2025-02-21, Commissioning Manual 1.4, Section 5 issue 1pt4D","url":"https://www.fireye.com/downloads/NEX-6101-NX6100_Series_Integrated_Burner_Controller_English_2025-21-02.pdf","section":"Section 5, 1.5 List of Fault Code Numbers: F66","page":"5-12"}],"review":{"status":"extracted","checks":["No step asks the reader to bypass, jumper or disable a flame safeguard, limit or interlock.","Electrical and fuel-train checks are framed for qualified personnel only.","F66, its display text and subsets match section 5 of NEX-6101 for the installed firmware."]},"updatedAt":"2026-10-26","url":"https://induqt.ai/troubleshoot/boilers/fireye/nx6100/f66"},{"kind":"fault","family":"boilers","manufacturerSlug":"fireye","modelSlug":"nx6100","controller":"Fireye NX6100 integrated burner controller (Nexus)","firmware":"Commissioning Manual 1.4 (Section 5 issue 1pt4D)","severity":"lockout","code":"F16","name":"Second (primary) air pressure not detected","meaning":"Some burners have a second, primary air pressure switch as well as the main combustion air switch. F16 means that optional primary switch did not register air when the controller required it. The subset is the burner status number.","operatingStates":["Status 07 onwards, wherever primary air must be proven"],"subsets":[{"value":"Burner status number","meaning":"Where in the sequence primary air was not proven"}],"functions":["air-proving"],"relatedComponents":["air-switch","combustion-fan"],"causes":[{"cause":"Primary air fan or path","signs":"Primary air fan not running or restricted.","check":"Confirm the primary air source runs and its path is clear.","component":"combustion-fan","mechanism":"blocked-air-path"},{"cause":"Primary air switch setpoint or sensing line","signs":"Air present but switch does not make.","check":"Measure the differential at the switch and compare with its setpoint.","component":"air-switch","mechanism":"switch-drift"}],"distinguish":["F16 is the optional second (primary) air switch; F14 is the main combustion air switch. F17 is the primary switch showing air when it should not."],"evidence":["Subset","Which air switches are fitted","Differential at the primary switch"],"related":["F14"],"title":"Fireye NX6100 F16: Primary Air Pressure Not Proven","description":"Fireye NX6100 F16 means the optional second (primary) air pressure switch did not prove air. How it differs from F14 and what to check.","sources":[{"title":"NX6100 Integrated Burner Controller Commissioning Manual","publisher":"Fireye","docId":"NEX-6101","revision":"2025-02-21, Commissioning Manual 1.4, Section 5 issue 1pt4D","url":"https://www.fireye.com/downloads/NEX-6101-NX6100_Series_Integrated_Burner_Controller_English_2025-21-02.pdf","section":"Section 5, 1.5 List of Fault Code Numbers: F16","page":"5-4"}],"review":{"status":"extracted","checks":["No step asks the reader to bypass, jumper or disable a flame safeguard, limit or interlock.","Electrical and fuel-train checks are framed for qualified personnel only.","F16, its display text and subsets match section 5 of NEX-6101 for the installed firmware."]},"updatedAt":"2026-10-26","url":"https://induqt.ai/troubleshoot/boilers/fireye/nx6100/f16"},{"kind":"fault","family":"boilers","manufacturerSlug":"fireye","modelSlug":"nx6100","controller":"Fireye NX6100 integrated burner controller (Nexus)","firmware":"Commissioning Manual 1.4 (Section 5 issue 1pt4D)","severity":"lockout","code":"F30","name":"Gas Proof of Closure fault","meaning":"F30 means the proof-of-closure (POC) signal from the gas main valve 2 did not behave correctly: the controller could not confirm the valve was closed when it should be, or the signal did not change as the valve moved. The subset is the burner status at the fault.","operatingStates":["Before start-up, when valves must be proven closed","At shutdown, when the valve should return closed"],"subsets":[{"value":"Burner status number","meaning":"Where in the sequence the POC signal was wrong"}],"functions":["valve-proving"],"relatedComponents":["main-fuel-valves"],"causes":[{"cause":"Valve not closing fully or slowly","signs":"Fault at shutdown or just before start.","check":"Have the valve actuator and seat inspected; time the closing stroke.","component":"main-fuel-valves","mechanism":"valve-seat-leak"},{"cause":"POC switch adjustment or wiring","signs":"Valve closes but the signal does not change.","check":"Check the POC switch and its wiring to the controller input.","component":"main-fuel-valves","mechanism":"switch-drift"}],"distinguish":["F30 is gas valve proof of closure; F31 is the oil valve equivalent. F42 is the gas leak test."],"evidence":["Subset","Valve and POC switch model","Valve closing time"],"related":["F42"],"title":"Fireye NX6100 F30: Gas Valve Proof of Closure Fault","description":"Fireye NX6100 F30 means the gas (main 2) valve proof-of-closure signal did not respond correctly. Valve, POC switch and wiring checks.","sources":[{"title":"NX6100 Integrated Burner Controller Commissioning Manual","publisher":"Fireye","docId":"NEX-6101","revision":"2025-02-21, Commissioning Manual 1.4, Section 5 issue 1pt4D","url":"https://www.fireye.com/downloads/NEX-6101-NX6100_Series_Integrated_Burner_Controller_English_2025-21-02.pdf","section":"Section 5, 1.5 List of Fault Code Numbers: F30","page":"5-6"}],"review":{"status":"extracted","checks":["No step asks the reader to bypass, jumper or disable a flame safeguard, limit or interlock.","Electrical and fuel-train checks are framed for qualified personnel only.","F30, its display text and subsets match section 5 of NEX-6101 for the installed firmware."]},"updatedAt":"2026-10-26","url":"https://induqt.ai/troubleshoot/boilers/fireye/nx6100/f30"},{"kind":"fault","family":"boilers","manufacturerSlug":"fireye","modelSlug":"nx6100","controller":"Fireye NX6100 integrated burner controller (Nexus)","firmware":"Commissioning Manual 1.4 (Section 5 issue 1pt4D)","severity":"lockout","code":"F43","name":"Gas pressure limit exceeded, or sensor fault","meaning":"F43 means the controller’s own gas pressure sensor reads outside the operating limits set for the burner, or the sensor stopped responding. The subset separates low pressure, high pressure and sensor faults.","operatingStates":["Any status where gas pressure is supervised, typically from pilot ignition through modulation"],"subsets":[{"value":"1","meaning":"Pressure too low"},{"value":"2","meaning":"Pressure too high"},{"value":"10","meaning":"Gas pressure sensor not responding correctly"},{"value":"255","meaning":"CANbus connection fault"}],"functions":["fuel-delivery"],"relatedComponents":["fuel-supply","comms-network"],"causes":[{"cause":"Supply pressure low (subset 1)","signs":"At high fire or when other users start; utility or plant supply issue.","check":"Check supply pressure upstream of the burner regulator; the manual’s first instruction is to check the gas supply pressure.","component":"fuel-supply","mechanism":"supply-pressure-droop"},{"cause":"Regulator lock-up or creep (subset 2)","signs":"High pressure at light-off or after shutdown.","check":"Have the regulator inspected for lock-up and creep.","component":"fuel-supply","mechanism":"regulator-drift"},{"cause":"Sensor or CANbus (subset 10 or 255)","signs":"Reading jumps or is missing.","check":"Check the sensor and its CANbus wiring.","component":"comms-network","mechanism":"network-fault"}],"distinguish":["F43 is the controller’s analog gas pressure limit; a discrete low or high gas pressure switch usually shows as an external alarm (F01–F09, F12, F13) depending on wiring."],"evidence":["Subset","Gas pressure trend around the trip","Supply pressure upstream of the regulator"],"related":["F10","F42"],"title":"Fireye NX6100 F43: Gas Pressure Limit or Sensor Fault","description":"Fireye NX6100 F43 means the measured gas pressure is outside its operating limits or the gas pressure sensor failed. Subsets 1, 2, 10 and 255 explained.","sources":[{"title":"NX6100 Integrated Burner Controller Commissioning Manual","publisher":"Fireye","docId":"NEX-6101","revision":"2025-02-21, Commissioning Manual 1.4, Section 5 issue 1pt4D","url":"https://www.fireye.com/downloads/NEX-6101-NX6100_Series_Integrated_Burner_Controller_English_2025-21-02.pdf","section":"Section 5, 1.5 List of Fault Code Numbers: F43","page":"5-9"}],"review":{"status":"extracted","checks":["No step asks the reader to bypass, jumper or disable a flame safeguard, limit or interlock.","Electrical and fuel-train checks are framed for qualified personnel only.","F43, its display text and subsets match section 5 of NEX-6101 for the installed firmware."]},"updatedAt":"2026-10-26","url":"https://induqt.ai/troubleshoot/boilers/fireye/nx6100/f43"},{"kind":"signature","family":"boilers","review":{"status":"extracted","checks":["No step asks the reader to bypass, jumper or disable a flame safeguard, limit or interlock.","Electrical and fuel-train checks are framed for qualified personnel only.","Each variant’s “what moves first” description matches field experience on packaged boilers.","Illustrations are clearly labelled as simulated."]},"updatedAt":"2026-10-26","slug":"flame-loss","title":"Boiler Flame Loss: Failure Signature and Trends","description":"How a boiler flame loss looks in trend data: which signal moves first for fuel, air, detection and ratio problems, and the fault codes it shows up as.","headline":"Flame loss while firing: the failure signature","summary":"A flame loss while firing ends the same way every time: the flame signal drops below the control’s threshold and the burner locks out. What differs is what moved first. Looking at the minutes before the trip, in the order the signals changed, usually separates a fuel problem from an air, ratio or detection problem faster than any single alarm.","whereItShows":["Honeywell 7800 fault 17 (Main Flame Fail) or 19 (Main Flame Ign.)","Fireye Nexus F10 with subset x15 or x16 (lost at low fire hold or modulation)","A flame-failure alarm on the boiler HMI or DCS, often followed by low steam pressure"],"signals":[{"signal":"flame-signal","behaviour":"Falls to zero at the trip. A slow decline over days or weeks before the first trip points to detection; a sudden drop from a normal value means the flame really went out or the signal path broke."},{"signal":"gas-pressure","behaviour":"If it sags in the seconds before the flame signal drops, the fuel supply is the lead suspect."},{"signal":"firing-rate","behaviour":"A trip that follows a step in firing rate points to the fuel/air curve or supply capacity at that rate."},{"signal":"air-damper-position","behaviour":"A damper that moves without a matching fuel valve move suggests linkage slip or a servo fault."},{"signal":"flue-oxygen","behaviour":"A jump in O2 just before the trip suggests a lean flame blow-off; low O2 with CO suggests a rich, unstable flame."},{"signal":"air-pressure","behaviour":"If air pressure falls first, follow the combustion airflow signature instead."}],"causes":[{"cause":"Detection decay","signs":"Flame signal drifts down over days or weeks; on the day of the trip, fuel, air and firing rate are steady.","check":"Clean the scanner sight path and confirm sighting at low and high fire; compare the flame signal with the control’s documented minimum.","component":"flame-scanner","mechanism":"lens-fouling"},{"cause":"Fuel pressure sag","signs":"Gas (or oil) pressure dips first, often as the burner ramps up or another user starts; the flame signal collapses within seconds.","check":"Trend burner fuel pressure through a ramp to high fire; check regulator response and supply capacity.","component":"fuel-supply","mechanism":"supply-pressure-droop"},{"cause":"Ratio upset at a firing-rate change","signs":"Trip follows a firing-rate step; O2 swings before the flame signal falls.","check":"Combustion-test at the firing rate where trips happen; check linkages and servo positions against the commissioned curve.","component":"air-damper","mechanism":"air-fuel-ratio-drift"},{"cause":"Signal-path noise","signs":"Short drop-outs of the flame signal with no change in fuel, air or firing rate, sometimes coinciding with motor starts.","check":"Check scanner cable routing, screens and terminations.","component":"flame-scanner","mechanism":"signal-noise"}],"sequence":[{"step":"Line up the trip","text":"Export flame signal, fuel pressure, firing rate, damper position and O2 for 10 minutes either side of the trip, at the fastest sample rate available."},{"step":"Find what moved first","text":"Mark the first signal to leave its normal band before the flame signal dropped."},{"step":"Check the history","text":"Compare the flame signal at the same firing rate over the last weeks; a slow decline is a different problem from a sudden loss."},{"step":"Match to the variant","text":"Use the variants above to choose the first physical check."}],"evidence":["Trend export around the trip (CSV)","Controller fault history with sequence step or subset","Flame signal readings over recent weeks","Recent tuning, fuel or scanner work"],"functions":["flame-supervision","fuel-delivery"],"relatedComponents":["flame-scanner","flame-amplifier","fuel-supply","air-damper","fuel-actuator"],"relatedFaults":[["honeywell","7800-series","17"],["honeywell","7800-series","19"],["fireye","nx6300","F10"],["fireye","nx6100","F10"]],"illustration":{"caption":"Fuel-pressure variant: gas pressure sags as the burner ramps toward high fire; the flame signal collapses seconds later.","event":{"at":8,"label":"Lockout"},"series":[{"signal":"firing-rate","points":[0.35,0.35,0.4,0.5,0.62,0.74,0.84,0.9,0.9,0,0,0]},{"signal":"gas-pressure","points":[0.8,0.8,0.79,0.76,0.7,0.6,0.48,0.38,0.36,0.85,0.86,0.86]},{"signal":"flame-signal","points":[0.75,0.75,0.74,0.74,0.72,0.7,0.66,0.55,0.05,0,0,0]}]},"sources":[{"title":"7800 SERIES Relay Modules: Checkout and Test","publisher":"Honeywell","docId":"65-0229-2","revision":"M.S. Rev. 02-06","url":"https://docuthek.kromschroeder.com/download.php?lang=de&doc=66089","section":"Table 3, Hold and Fault Message Summary: fault 17","page":"10"},{"title":"7800 SERIES Relay Modules: Checkout and Test","publisher":"Honeywell","docId":"65-0229-2","revision":"M.S. Rev. 02-06","url":"https://docuthek.kromschroeder.com/download.php?lang=de&doc=66089","section":"Table 3, Hold and Fault Message Summary: fault 19","page":"10"},{"title":"NX6300 Single Fuel Integrated Burner Control Commissioning Manual","publisher":"Fireye","docId":"NEX-6301","revision":"2025-03-19, Commissioning Manual 1.4, firmware 1.4","url":"https://www.fireye.com/downloads/NEX-6301-NX6300_Commissioning_Manual_English_2025-3-19-Web.pdf","section":"Section 5, 1.5 List of Fault Code Numbers: F10","page":"5-4"},{"title":"NX6100 Integrated Burner Controller Commissioning Manual","publisher":"Fireye","docId":"NEX-6101","revision":"2025-02-21, Commissioning Manual 1.4, Section 5 issue 1pt4D","url":"https://www.fireye.com/downloads/NEX-6101-NX6100_Series_Integrated_Burner_Controller_English_2025-21-02.pdf","section":"Section 5, 1.5 List of Fault Code Numbers: F10","page":"5-4"},{"title":"NFPA 85, Boiler and Combustion Systems Hazards Code","publisher":"National Fire Protection Association"},{"title":"ASME CSD-1, Controls and Safety Devices for Automatically Fired Boilers","publisher":"ASME"}],"url":"https://induqt.ai/troubleshoot/boilers/signatures/flame-loss"},{"kind":"signature","family":"boilers","review":{"status":"extracted","checks":["No step asks the reader to bypass, jumper or disable a flame safeguard, limit or interlock.","Electrical and fuel-train checks are framed for qualified personnel only.","Each variant’s “what moves first” description matches field experience on packaged boilers.","Illustrations are clearly labelled as simulated."]},"updatedAt":"2026-10-26","slug":"combustion-airflow","title":"Boiler Combustion Airflow Fault: Failure Signature","description":"The trend signature of a combustion airflow fault: air pressure margin, fan speed, damper position and O2, and how to tell a fan problem from a switch problem.","headline":"Combustion airflow faults: the failure signature","summary":"The burner control proves combustion air with a pressure switch or sensor. An airflow trip means that proof dropped out, or appeared when it should not. The useful question is whether the air really fell, or the switch saw it wrong: trending air pressure, fan speed and damper position next to the switch state answers it.","whereItShows":["Honeywell 7800 faults 23 and 32 (Airflow Switch) or 13 (Airflow Sw. On)","Fireye Nexus F14 (air pressure not detected) or F15 (detected when it should not be); NX6100 F16 for a second air switch","Repeated purge failures or trips on modulating down to low fire"],"signals":[{"signal":"air-proving","behaviour":"Drops to 0 at the trip. Chatter (rapid 1/0) with steady air pressure points to the switch or its sensing line."},{"signal":"air-pressure","behaviour":"Falls toward the switch setpoint before a genuine loss. A small margin at low fire is the most common cause of intermittent trips."},{"signal":"fan-speed","behaviour":"A drop in speed or a VSD current limit just before the trip points to the fan drive."},{"signal":"air-damper-position","behaviour":"Trips that only happen near minimum damper position suggest the switch margin at low fire."},{"signal":"flue-oxygen","behaviour":"Falls as air is lost; steady O2 during a trip suggests the air did not actually fall."},{"signal":"firing-rate","behaviour":"Shows where in the firing range the trip happened."}],"causes":[{"cause":"Low switch margin at low fire","signs":"Trips when the burner modulates down; air pressure at low fire sits just above the switch setpoint.","check":"Measure the differential at the switch across the firing range and compare with its setpoint and the burner maker’s settings.","component":"air-switch","mechanism":"switch-drift"},{"cause":"Restricted air path","signs":"Air pressure at the same damper position falls slowly over weeks; O2 at low fire trends down.","check":"Inspect the intake, fan wheel, inlet damper and flue for restrictions.","component":"combustion-fan","mechanism":"blocked-air-path"},{"cause":"Fan drive problem","signs":"Fan speed or current changes just before the trip; VSD fault or current-limit events.","check":"Check the fan VSD fault log, ramp settings, belts and motor.","component":"combustion-fan","mechanism":"fan-drive-fault"},{"cause":"Switch or sensing line fault","signs":"Proving signal chatters while air pressure is steady; water in the sensing tube.","check":"Clear and re-route the sensing tube; check switch contacts and wiring.","component":"air-switch","mechanism":"switch-drift"},{"cause":"Air proven with the fan off","signs":"Proving signal is 1 in standby or minutes after shutdown.","check":"Check for a welded contact or jumper, a fan that keeps running, or stack draft through the boiler.","component":"air-switch","mechanism":"contact-welded"}],"sequence":[{"step":"Read the state of the switch","text":"Was air lost when it was needed, or seen when it should not be? The fault code or subset says which."},{"step":"Plot the margin","text":"Trend air pressure (or the differential at the switch) against firing rate. Note the lowest value during normal running."},{"step":"Check the fan","text":"Look at fan speed, current and VSD events in the same window."},{"step":"Compare O2","text":"If O2 did not move at the trip, the air probably did not fall: look at the switch and its tubing."}],"evidence":["Fault code or subset","Air pressure or switch differential across the firing range","Fan VSD status and fault log","Flue O2 trend"],"functions":["air-proving","purge"],"relatedComponents":["air-switch","combustion-fan","air-damper"],"relatedFaults":[["honeywell","7800-series","23"],["honeywell","7800-series","32"],["honeywell","7800-series","13"],["fireye","nx6300","F14"],["fireye","nx6300","F15"],["fireye","nx6100","F16"]],"illustration":{"caption":"Low-margin variant: as the burner modulates down, air pressure falls to the switch setpoint and the proving signal drops out.","event":{"at":8,"label":"Air not proven"},"series":[{"signal":"firing-rate","points":[0.7,0.68,0.6,0.5,0.4,0.3,0.22,0.18,0.15,0,0,0]},{"signal":"air-pressure","points":[0.8,0.79,0.72,0.62,0.52,0.43,0.36,0.32,0.29,0.1,0.1,0.1]},{"signal":"air-proving","points":[1,1,1,1,1,1,1,1,0,0,0,0]}]},"sources":[{"title":"7800 SERIES Relay Modules: Checkout and Test","publisher":"Honeywell","docId":"65-0229-2","revision":"M.S. Rev. 02-06","url":"https://docuthek.kromschroeder.com/download.php?lang=de&doc=66089","section":"Table 3, Hold and Fault Message Summary: fault 23","page":"11"},{"title":"7800 SERIES Relay Modules: Checkout and Test","publisher":"Honeywell","docId":"65-0229-2","revision":"M.S. Rev. 02-06","url":"https://docuthek.kromschroeder.com/download.php?lang=de&doc=66089","section":"Table 3, Hold and Fault Message Summary: fault 32","page":"12"},{"title":"7800 SERIES Relay Modules: Checkout and Test","publisher":"Honeywell","docId":"65-0229-2","revision":"M.S. Rev. 02-06","url":"https://docuthek.kromschroeder.com/download.php?lang=de&doc=66089","section":"Table 3, Hold and Fault Message Summary: fault 13","page":"10"},{"title":"NX6300 Single Fuel Integrated Burner Control Commissioning Manual","publisher":"Fireye","docId":"NEX-6301","revision":"2025-03-19, Commissioning Manual 1.4, firmware 1.4","url":"https://www.fireye.com/downloads/NEX-6301-NX6300_Commissioning_Manual_English_2025-3-19-Web.pdf","section":"Section 5, 1.5 List of Fault Code Numbers: F14, F15","page":"5-4 to 5-5"},{"title":"NX6100 Integrated Burner Controller Commissioning Manual","publisher":"Fireye","docId":"NEX-6101","revision":"2025-02-21, Commissioning Manual 1.4, Section 5 issue 1pt4D","url":"https://www.fireye.com/downloads/NEX-6101-NX6100_Series_Integrated_Burner_Controller_English_2025-21-02.pdf","section":"Section 5, 1.5 List of Fault Code Numbers: F14 to F17","page":"5-4"},{"title":"Steam Tip Sheet #4: Improve Your Boiler’s Combustion Efficiency","publisher":"U.S. Department of Energy, Advanced Manufacturing Office","docId":"DOE/GO-102012-3405","revision":"January 2012","url":"https://www.energy.gov/sites/prod/files/2014/05/f16/steam4_boiler_efficiency.pdf","section":"Excess air; flue gas analysis"}],"url":"https://induqt.ai/troubleshoot/boilers/signatures/combustion-airflow"},{"kind":"signature","family":"boilers","review":{"status":"extracted","checks":["No step asks the reader to bypass, jumper or disable a flame safeguard, limit or interlock.","Electrical and fuel-train checks are framed for qualified personnel only.","Each variant’s “what moves first” description matches field experience on packaged boilers.","Illustrations are clearly labelled as simulated."]},"updatedAt":"2026-10-26","slug":"feedwater-instability","title":"Boiler Feedwater and Drum Level Instability: Signature","description":"How feedwater and drum level instability looks in trends: shrink and swell, feed supply shortfall, a hunting level loop and a bad level sensor, and how to tell them apart.","headline":"Feedwater and drum level instability: the failure signature","summary":"Low-water cut-offs and high-level alarms are safety events, but the cause is usually visible minutes earlier in the relationship between steam flow, feedwater flow and level. A level that dips when steam demand jumps behaves differently from a level that falls because feedwater cannot keep up, and both differ from a level transmitter that is simply wrong.","whereItShows":["Low-water alarm or low-water cut-off trip","High-level alarm, carryover or wet steam complaints","Feedwater valve hunting or pump cycling"],"signals":[{"signal":"drum-level","behaviour":"The symptom. Note whether it swings around setpoint, drifts away from it, or jumps."},{"signal":"steam-flow","behaviour":"A level swing that starts with a steam-flow step is shrink and swell; the level control must ride through it."},{"signal":"feedwater-flow","behaviour":"If feedwater flow is at its maximum while level falls, supply is the limit; if it oscillates with level, the loop is the problem."},{"signal":"steam-pressure","behaviour":"A sudden pressure drop makes level swell briefly, then shrink: a common cause of nuisance level alarms."},{"signal":"firing-rate","behaviour":"Large firing-rate changes have the same effect on level as pressure changes."}],"causes":[{"cause":"Shrink and swell on load changes","signs":"Level rises briefly when steam demand jumps, then falls below setpoint; feedwater responds late.","check":"Review the level control strategy. The DOE sourcebook notes that two- and three-element control (adding steam flow and feedwater flow) handles abrupt load changes better than level-only control.","component":"feedwater-system","mechanism":"control-loop-tuning"},{"cause":"Feedwater supply shortfall","signs":"Feedwater valve near fully open and flow flat while level falls; deaerator level or feed pump pressure low.","check":"Check feed pump discharge pressure, deaerator level and valve capacity during the event.","component":"feedwater-system","mechanism":"feed-supply-shortfall"},{"cause":"Hunting level loop","signs":"Level and feedwater flow oscillate together at steady load.","check":"Have the level loop tuned; check the feedwater valve for stiction.","component":"feedwater-system","mechanism":"control-loop-tuning"},{"cause":"Level measurement fault","signs":"Transmitter disagrees with the gauge glass, or the level jumps with no change in flows.","check":"Compare with the gauge glass and blow down the level column per site procedure.","component":"feedwater-system","mechanism":"sensor-failure"}],"sequence":[{"step":"Plot the three flows","text":"Trend level, steam flow and feedwater flow together for the event."},{"step":"Find the trigger","text":"Did steam flow or pressure step first, or did feedwater flow stop following demand?"},{"step":"Check the measurement","text":"Confirm the transmitter against the gauge glass before tuning anything."},{"step":"Act on the right part","text":"Supply problem: pump, deaerator, valve. Control problem: strategy and tuning. Measurement problem: level column and transmitter."}],"evidence":["Trend of drum level, steam flow and feedwater flow","Level control type (single, two or three element)","Feed pump and deaerator data","Gauge glass vs transmitter readings"],"functions":["limit-supervision"],"relatedComponents":["feedwater-system","limit-string"],"relatedFaults":[],"illustration":{"caption":"Shrink-and-swell variant: steam flow steps up, level swells briefly then falls below setpoint before feedwater catches up.","event":{"at":3,"label":"Demand step"},"series":[{"signal":"steam-flow","points":[0.4,0.4,0.4,0.75,0.78,0.78,0.78,0.78,0.78,0.78,0.78,0.78]},{"signal":"drum-level","points":[0.5,0.5,0.5,0.66,0.6,0.42,0.3,0.28,0.35,0.44,0.49,0.5]},{"signal":"feedwater-flow","points":[0.4,0.4,0.4,0.38,0.45,0.6,0.78,0.9,0.88,0.82,0.78,0.78]}]},"sources":[{"title":"Improving Steam System Performance: A Sourcebook for Industry, Second Edition","publisher":"U.S. Department of Energy, Advanced Manufacturing Office","docId":"DOE/GO-102012-3423","revision":"Second Edition, 2012","url":"https://www.energy.gov/sites/prod/files/2014/05/f15/steamsourcebook.pdf","section":"Section 1, Generation: water-level control; boiler feedwater system","page":"7"},{"title":"ASME CSD-1, Controls and Safety Devices for Automatically Fired Boilers","publisher":"ASME"}],"url":"https://induqt.ai/troubleshoot/boilers/signatures/feedwater-instability"},{"kind":"signature","family":"boilers","review":{"status":"extracted","checks":["No step asks the reader to bypass, jumper or disable a flame safeguard, limit or interlock.","Electrical and fuel-train checks are framed for qualified personnel only.","Each variant’s “what moves first” description matches field experience on packaged boilers.","Illustrations are clearly labelled as simulated."]},"updatedAt":"2026-10-26","slug":"steam-pressure-drop","title":"Steam Pressure Drop: Boiler Failure Signature","description":"Why boiler steam pressure drops, read from trends: demand above capacity, a control loop that does not fire up, fuel limits at high fire, burner trips and lost heat transfer.","headline":"Steam pressure drop: the failure signature","summary":"The steam-pressure control raises the firing rate when pressure falls below setpoint. A pressure drop therefore means either the burner did not fire up, or firing up was not enough. Putting steam pressure, steam flow and firing rate on one chart separates the two in a few minutes.","whereItShows":["Low steam pressure alarm at the boiler or header","Process complaints of slow heat-up or low steam","Boiler held at high fire for long periods"],"signals":[{"signal":"steam-pressure","behaviour":"The symptom. Note how fast it falls and whether it recovers."},{"signal":"steam-flow","behaviour":"Rising steam flow during the drop means demand rose; flat flow means the boiler is not delivering."},{"signal":"firing-rate","behaviour":"At 100% during the drop: capacity or heat transfer. Not rising: control, a low-fire hold or manual mode."},{"signal":"gas-pressure","behaviour":"Low fuel pressure at high fire caps the real firing rate even when the control asks for more."},{"signal":"burner-status","behaviour":"A lockout or recycle at the start of the drop means the pressure loss is a consequence of a trip."},{"signal":"stack-temperature","behaviour":"Rising over months at the same load points to fouled heating surfaces limiting output."}],"causes":[{"cause":"Demand above firing capacity","signs":"Steam flow rises above its normal peak; firing rate pinned at 100%; pressure recovers when demand falls.","check":"Compare peak steam flow with the boiler rating; stagger large loads or bring another boiler online.","component":"fuel-actuator"},{"cause":"Burner does not fire up","signs":"Pressure falls but firing rate stays low or modulates down; modulation in manual or a low-fire hold active.","check":"Check setpoint, modulation band, manual/auto mode and any hold inputs; compare the controller’s pressure reading with a local gauge.","component":"pressure-sensor","mechanism":"control-loop-tuning"},{"cause":"Fuel limited at high fire","signs":"Firing rate at 100% but fuel pressure sags at high fire; steam flow below rating.","check":"Trend fuel pressure at high fire against the burner’s required pressure.","component":"fuel-supply","mechanism":"supply-pressure-droop"},{"cause":"Burner trip or short cycling","signs":"Burner status shows a lockout or frequent recycles at the start of the drop.","check":"Read the fault history and follow the flame-loss or airflow signature.","component":"burner-controller"},{"cause":"Lost heat transfer","signs":"Stack temperature higher than it used to be at the same firing rate; maximum output has fallen over months.","check":"Trend stack temperature at a fixed firing rate and O2; inspect tubes at the next shutdown. DOE notes that scale can reduce steam output if the firing rate cannot be raised to compensate.","component":"heating-surfaces","mechanism":"surface-fouling"}],"sequence":[{"step":"Overlay three signals","text":"Steam pressure, steam flow and firing rate on one chart, for the drop and a normal day."},{"step":"Ask whether it fired up","text":"If the firing rate did not rise, look at control. If it was already at 100%, look at capacity, fuel and heat transfer."},{"step":"Rule out a trip","text":"Check burner status and the fault history for a lockout at the start of the drop."},{"step":"Look at the long trend","text":"Compare stack temperature and maximum output with months ago."}],"evidence":["Trend of steam pressure, steam flow and firing rate","Fuel pressure at high fire","Burner fault history","Stack temperature history"],"functions":["positioning","fuel-delivery","combustion-monitoring"],"relatedComponents":["pressure-sensor","fuel-supply","fuel-actuator","heating-surfaces","burner-controller"],"relatedFaults":[["fireye","nx6300","F41"],["fireye","nx6100","F43"]],"illustration":{"caption":"Capacity variant: steam demand rises, the firing rate reaches 100% and stays there, and pressure still sags until demand falls.","event":{"at":3,"label":"Demand rises"},"series":[{"signal":"steam-flow","points":[0.5,0.5,0.52,0.8,0.9,0.92,0.92,0.9,0.88,0.6,0.55,0.52]},{"signal":"firing-rate","points":[0.55,0.55,0.56,0.8,1,1,1,1,1,0.8,0.62,0.58]},{"signal":"steam-pressure","points":[0.7,0.7,0.7,0.66,0.58,0.5,0.45,0.43,0.42,0.55,0.66,0.7]}]},"sources":[{"title":"Improving Steam System Performance: A Sourcebook for Industry, Second Edition","publisher":"U.S. Department of Energy, Advanced Manufacturing Office","docId":"DOE/GO-102012-3423","revision":"Second Edition, 2012","url":"https://www.energy.gov/sites/prod/files/2014/05/f15/steamsourcebook.pdf","section":"Section 1, Generation: steam-pressure control; steam flow meter","page":"7"},{"title":"Steam Tip Sheet #7: Clean Firetube Boiler Waterside Heat Transfer Surfaces","publisher":"U.S. Department of Energy, Advanced Manufacturing Office","docId":"DOE/GO-102012-3597","revision":"April 2012","url":"https://www.energy.gov/sites/prod/files/2014/05/f16/steam7_surfaces.pdf","section":"Steam production and firing rate"},{"title":"NX6300 Single Fuel Integrated Burner Control Commissioning Manual","publisher":"Fireye","docId":"NEX-6301","revision":"2025-03-19, Commissioning Manual 1.4, firmware 1.4","url":"https://www.fireye.com/downloads/NEX-6301-NX6300_Commissioning_Manual_English_2025-3-19-Web.pdf","section":"Section 5, 1.5 List of Fault Code Numbers: F41","page":"5-8"},{"title":"NX6100 Integrated Burner Controller Commissioning Manual","publisher":"Fireye","docId":"NEX-6101","revision":"2025-02-21, Commissioning Manual 1.4, Section 5 issue 1pt4D","url":"https://www.fireye.com/downloads/NEX-6101-NX6100_Series_Integrated_Burner_Controller_English_2025-21-02.pdf","section":"Section 5, 1.5 List of Fault Code Numbers: F41, F43","page":"5-8 to 5-9"}],"url":"https://induqt.ai/troubleshoot/boilers/signatures/steam-pressure-drop"},{"kind":"signature","family":"boilers","review":{"status":"extracted","checks":["No step asks the reader to bypass, jumper or disable a flame safeguard, limit or interlock.","Electrical and fuel-train checks are framed for qualified personnel only.","Each variant’s “what moves first” description matches field experience on packaged boilers.","Illustrations are clearly labelled as simulated."]},"updatedAt":"2026-10-26","slug":"high-stack-temperature","title":"High Boiler Stack Temperature: Failure Signature","description":"What a rising boiler stack temperature means: fireside soot, waterside scale or excess air. How to read stack temperature with firing rate and O2, with DOE references.","headline":"High stack temperature: the failure signature","summary":"Stack temperature is the cheapest efficiency indicator a boiler has. Read on its own it is ambiguous, because it rises with firing rate. Read at a fixed firing rate and flue O2, a slow rise points to fouled heating surfaces, while a rise that comes with high O2 points to excess air. DOE’s steam tip sheets recommend exactly this trend.","whereItShows":["Stack or flue temperature high alarm (Fireye Nexus L59 where an O2 interface is fitted)","Rising fuel use for the same steam output","Visible smoke or soot at the stack"],"signals":[{"signal":"stack-temperature","behaviour":"The symptom. Compare at the same firing rate, not at different loads."},{"signal":"firing-rate","behaviour":"Use it to pick comparable periods."},{"signal":"flue-oxygen","behaviour":"High O2 with high stack temperature means excess air; normal O2 with rising stack temperature means heat transfer is falling."},{"signal":"steam-pressure","behaviour":"Higher operating pressure raises water temperature and therefore stack temperature; check it has not changed."},{"signal":"steam-flow","behaviour":"Steam output per unit of fuel falls as efficiency drops."}],"causes":[{"cause":"Waterside scale","signs":"Stack temperature creeps up over weeks or months at constant firing rate and O2.","check":"Trend stack temperature at a constant firing rate and excess O2, as DOE Tip Sheet #7 recommends; inspect tubes at shutdown and review water treatment.","component":"heating-surfaces","mechanism":"surface-fouling"},{"cause":"Fireside soot","signs":"Rise follows a period of low O2, smoky combustion or oil firing.","check":"Inspect and clean fireside surfaces; correct the combustion setting that produced the soot.","component":"heating-surfaces","mechanism":"surface-fouling"},{"cause":"Excess air","signs":"O2 higher than the commissioned value; stack temperature and fuel use up together.","check":"Have a combustion analysis done and the burner retuned. DOE Tip Sheet #4 gives the rule of thumb of about 1% efficiency for each 15% reduction in excess air or 40°F reduction in stack temperature.","component":"air-damper","mechanism":"air-fuel-ratio-drift"},{"cause":"Step change after maintenance","signs":"Stack temperature jumped after work on the boiler, at the same firing rate and O2.","check":"Confirm baffles, turbulators, seals and any economizer bypass were restored as designed.","component":"heating-surfaces"}],"sequence":[{"step":"Pick comparable points","text":"Select periods at the same firing rate and steam pressure, months apart."},{"step":"Check O2 first","text":"If O2 rose, the cause is combustion air; if O2 is steady, look at heat transfer."},{"step":"Look at the shape","text":"Slow creep suggests fouling; a step change suggests a mechanical or tuning change."},{"step":"Plan the check","text":"Combustion analysis now; tube inspection at the next shutdown."}],"evidence":["Stack temperature, firing rate and O2 trend over months","Last combustion analysis report","Water treatment records","Maintenance history"],"functions":["combustion-monitoring"],"relatedComponents":["heating-surfaces","flue-analyser","air-damper"],"relatedFaults":[],"illustration":{"caption":"Fouling variant: over months, stack temperature creeps up while firing rate and O2 stay the same.","series":[{"signal":"firing-rate","points":[0.6,0.6,0.6,0.6,0.6,0.6,0.6,0.6,0.6,0.6,0.6,0.6]},{"signal":"flue-oxygen","points":[0.4,0.41,0.4,0.4,0.39,0.4,0.41,0.4,0.4,0.4,0.41,0.4]},{"signal":"stack-temperature","points":[0.4,0.42,0.44,0.47,0.5,0.53,0.57,0.6,0.64,0.67,0.71,0.75]}]},"sources":[{"title":"Steam Tip Sheet #7: Clean Firetube Boiler Waterside Heat Transfer Surfaces","publisher":"U.S. Department of Energy, Advanced Manufacturing Office","docId":"DOE/GO-102012-3597","revision":"April 2012","url":"https://www.energy.gov/sites/prod/files/2014/05/f16/steam7_surfaces.pdf","section":"Monitor flue gas temperature"},{"title":"Steam Tip Sheet #4: Improve Your Boiler’s Combustion Efficiency","publisher":"U.S. Department of Energy, Advanced Manufacturing Office","docId":"DOE/GO-102012-3405","revision":"January 2012","url":"https://www.energy.gov/sites/prod/files/2014/05/f16/steam4_boiler_efficiency.pdf","section":"Excess air; stack temperature and flue gas oxygen as indicators"},{"title":"Improving Steam System Performance: A Sourcebook for Industry, Second Edition","publisher":"U.S. Department of Energy, Advanced Manufacturing Office","docId":"DOE/GO-102012-3423","revision":"Second Edition, 2012","url":"https://www.energy.gov/sites/prod/files/2014/05/f15/steamsourcebook.pdf","section":"Section 1, Generation: economizers","page":"6"},{"title":"NX6300 Single Fuel Integrated Burner Control Commissioning Manual","publisher":"Fireye","docId":"NEX-6301","revision":"2025-03-19, Commissioning Manual 1.4, firmware 1.4","url":"https://www.fireye.com/downloads/NEX-6301-NX6300_Commissioning_Manual_English_2025-3-19-Web.pdf","section":"Section 5, 1.5 List of Fault Code Numbers: L58, L59","page":"5-10"}],"url":"https://induqt.ai/troubleshoot/boilers/signatures/high-stack-temperature"},{"kind":"symptom","family":"boilers","slug":"flame-failure","title":"Industrial Boiler Flame Failure: Causes and Diagnosis","description":"Why a burner control declares flame failure, how the stage of the trip narrows the cause, and the evidence that separates fuel, air, ignition and flame-detection problems.","headline":"Industrial boiler flame failure: causes and diagnostic sequence","summary":"A flame failure means the burner control did not see a proven flame when it required one: during the pilot or ignition trial, during the main-flame trial, or while firing. The control shuts the fuel valves and normally locks out. The stage at which it happened is the most useful single clue.","whereItShows":["A lockout message on the burner control or its display module, usually naming the sequence stage.","A flame-failure alarm on the boiler HMI or plant DCS, often followed by low steam pressure alarms.","A drop of the flame signal reading to zero in the control’s diagnostics."],"causes":[{"cause":"Ignition not established","signs":"Failure only during the pilot or ignition trial; no flame signal at all during the trial.","check":"Observe the igniter spark and pilot through the sight glass during a trial; check ignition transformer output and electrode condition and gap per the burner manual."},{"cause":"Fuel supply pressure drops at light-off","signs":"Failure on the main-flame trial, or when other gas users start; low gas-pressure switch events near the trip.","check":"Record gas pressure at the burner train during a light-off; compare with the burner’s required inlet pressure."},{"cause":"Air/fuel ratio wrong at low fire","signs":"Unstable or lifting flame at light-off; trips after a combustion tune or linkage work.","check":"Have the burner combustion-tested at low fire; check damper and fuel-valve linkage for slip."},{"cause":"Flame detector cannot see the flame","signs":"Flame visible but the control reports a weak or zero flame signal; signal has been drifting down over weeks.","check":"Compare the flame signal with the control’s documented minimum; inspect and clean the scanner lens or flame rod and check its sighting."},{"cause":"Flame lost during firing","signs":"Trips while running, often at load changes or high fire.","check":"Trend fuel pressure, air flow and firing rate around the trip; look for a pressure dip or damper movement just before it."}],"sequence":[{"step":"Read the lockout before resetting","text":"Photograph the control display or fault history. Note the stage (pilot trial, main trial, run) and the flame signal value if shown."},{"step":"Place the trip in the sequence","text":"Ignition-trial failures point to ignition, pilot fuel or detection; main-trial failures to the main fuel train and light-off air; running failures to fuel stability, air or detection."},{"step":"Check what changed","text":"Recent maintenance, tuning, fuel supply work, weather and load changes often line up with the first trip."},{"step":"Gather data around the trip","text":"Fuel pressure, air flow or damper position, firing rate and flame signal for the minutes before and after."},{"step":"Test one cause at a time","text":"Use the checks above in order of likelihood, and record what you find so the next trip can be compared."}],"evidence":["Photo of the lockout message and fault history","Burner control make and model","Flame detector type (UV, infrared or flame rod)","Gas or oil pressure and firing-rate trend around the trip","Recent maintenance or tuning"],"relatedLinks":[{"href":"/troubleshoot/boilers/faults/burner-lockout-during-ignition","label":"Burner lockout during ignition"},{"href":"/blog/burner-lockout-vs-flame-failure","label":"Burner lockout vs. flame failure"},{"href":"/troubleshoot/boilers","label":"Boiler & burner troubleshooting"}],"sources":[{"title":"NFPA 85, Boiler and Combustion Systems Hazards Code","publisher":"National Fire Protection Association"},{"title":"ASME CSD-1, Controls and Safety Devices for Automatically Fired Boilers","publisher":"ASME"}],"review":{"status":"extracted","checks":["No step asks the reader to bypass, jumper or disable a flame safeguard, limit or interlock.","Electrical and fuel-train checks are framed for qualified personnel only.","Cause list and checks reflect common packaged-boiler practice."]},"updatedAt":"2026-10-26","url":"https://induqt.ai/troubleshoot/boilers/faults/flame-failure"},{"kind":"symptom","family":"boilers","slug":"burner-lockout-during-ignition","title":"Boiler Burner Lockout During Ignition: What to Check","description":"A burner that locks out during the ignition trial usually has an ignition, pilot fuel, air or flame-detection problem. How to tell which, and what evidence to collect.","headline":"Boiler burner lockout during ignition","summary":"When a burner locks out during the ignition (pilot) trial, the control did not prove flame within its fixed trial time. Because the main fuel valves have not opened yet, the cause is almost always in the ignition system, the pilot fuel supply, the light-off air flow or the flame detector.","whereItShows":["A lockout naming the pilot or ignition trial stage (abbreviations such as PTFI are common).","Repeated failed starts at the same point of the sequence."],"causes":[{"cause":"No or weak spark","signs":"No ignition noise or visible spark during the trial.","check":"Inspect the electrode, insulator and gap; check the ignition transformer and its lead, following the burner manual."},{"cause":"Pilot gas not reaching the burner","signs":"Spark present but no pilot flame; pilot regulator or valve recently serviced.","check":"Check pilot gas pressure during the trial and confirm the pilot valve opens."},{"cause":"Too much or too little light-off air","signs":"Pilot lights briefly then blows out, or lights poorly after damper work.","check":"Check the low-fire damper position and linkage against the commissioning settings."},{"cause":"Detector does not see the pilot","signs":"Pilot is visible but the flame signal stays below the control’s minimum.","check":"Clean and re-sight the scanner, or check the flame rod position and grounding."}],"sequence":[{"step":"Confirm the stage","text":"Make sure the lockout is during the ignition or pilot trial, not the main-flame trial."},{"step":"Watch one start","text":"With a qualified technician, observe a start through the sight glass: spark, pilot flame and the flame signal reading."},{"step":"Split the problem","text":"No spark: ignition. Spark but no flame: pilot fuel or air. Flame but no signal: detection."},{"step":"Record and compare","text":"Note pressures and the flame signal so the next attempt can be compared after each change."}],"evidence":["Photo of the lockout message","Control and scanner model","Pilot gas pressure reading","Flame signal value during a trial"],"relatedLinks":[{"href":"/troubleshoot/boilers/faults/flame-failure","label":"Boiler flame failure: causes and diagnosis"},{"href":"/tools/free-boiler-diagnostic","label":"Free boiler diagnostic"}],"sources":[{"title":"NFPA 85, Boiler and Combustion Systems Hazards Code","publisher":"National Fire Protection Association"},{"title":"ASME CSD-1, Controls and Safety Devices for Automatically Fired Boilers","publisher":"ASME"}],"review":{"status":"extracted","checks":["No step asks the reader to bypass, jumper or disable a flame safeguard, limit or interlock.","Electrical and fuel-train checks are framed for qualified personnel only."]},"updatedAt":"2026-10-26","url":"https://induqt.ai/troubleshoot/boilers/faults/burner-lockout-during-ignition"},{"kind":"equipment","family":"vfd","manufacturer":"ABB","manufacturerSlug":"abb","model":"ACS580","modelSlug":"acs580","firmware":"Standard control program ASCDX 2.05","title":"ABB ACS580 Fault Codes: Troubleshooting Guide","description":"How the ABB ACS580 general-purpose drive reports faults, where to find the fault log, and what the most searched fault codes (2310, 3210, 3220) mean, with manual references.","summary":"The ACS580 is ABB’s general-purpose low-voltage AC drive. Faults are four-digit hexadecimal codes; warnings start with A. The drive keeps a time-stamped event log, so the first step in any diagnosis is to read which fault tripped and what was logged around it.","faultReporting":["Active faults and the fault and event log are on the panel under Menu > Diagnostics.","Parameter group 04 Warnings and faults shows the tripping fault (04.01), other active faults (04.02–04.03), the latest stored faults (04.11–04.13) and the latest warning (04.16).","The event log keeps the last 8 fault recordings and the last 10 warnings or pure events, each time-stamped. A fault reset is logged as event 64FF.","Auxiliary codes, where a fault has them, are in the event details on the panel and in the event list in Drive composer."],"evidence":["Photo of the panel showing the fault code","Event log (Menu > Diagnostics) or a Drive composer export","Drive type code and firmware version","Motor rating plate and group 99 motor data","What the machine was doing at the trip"],"codeIndex":[{"code":"2310","name":"Overcurrent"},{"code":"3210","name":"DC link overvoltage"},{"code":"3220","name":"DC link undervoltage"},{"code":"A3A2","name":"DC link undervoltage (warning, drive stopped)"}],"sources":[{"title":"ACS580 standard control program Firmware manual","publisher":"ABB","docId":"3AXD50000016097","revision":"Rev E (2018-02-15), firmware ASCDX 2.05","url":"https://www.ghv.de/files/elektrische-antriebstechnik/frequenzumrichter/acs580/downloads/dokumentationen/en_acs580_firmware_ghv.pdf","section":"Fault tracing: Warning/fault history","page":"408–409"},{"title":"ACS580 standard control program Firmware manual (current revision)","publisher":"ABB","docId":"3AXD50000016097","revision":"Rev H (2022-02-28)","url":"https://library.e.abb.com/public/052c19b4002f45cf908d536363a39bb4/ASCD2216x_en.pdf"}],"review":{"status":"extracted","checks":["Facts were taken from Rev E (firmware 2.05) via an ABB distributor copy; confirm each code, cause and parameter number against Rev H and the firmware actually installed.","Electrical checks are framed for qualified personnel, with isolation and capacitor discharge per the drive manual.","Insulation testing is only suggested with the motor disconnected from the drive."]},"updatedAt":"2026-10-26","url":"https://induqt.ai/troubleshoot/vfd/abb/acs580"},{"kind":"fault","family":"vfd","manufacturerSlug":"abb","modelSlug":"acs580","controller":"ABB ACS580 drive","code":"2310","name":"Overcurrent","severity":"fault","title":"ABB ACS580 Fault 2310 (Overcurrent): Causes and Checks","description":"ACS580 fault 2310 means output current exceeded the drive’s internal limit. The causes ABB lists, the parameters to check, and how to read the trip from the event log.","meaning":"The drive measured output current above its internal fault limit and tripped. ABB notes that the same fault can also be caused by an earth fault or by a lost supply phase, not only by a genuinely high load current.","operatingStates":["At start or during acceleration (ramp too short for the load)","On a sudden load increase or a jam","Immediately at start when the motor or its cable is faulty"],"causes":[{"cause":"Load too heavy or acceleration too fast","signs":"Trips during the ramp; fewer trips with a lighter load or a longer ramp.","check":"Check the motor load and the acceleration times in group 23 (speed ramp), 26 (torque) or 28 (frequency)."},{"cause":"Wrong scaling","signs":"Trips after commissioning or a parameter change.","check":"Check scaling parameters 46.01, 46.02 and 46.03."},{"cause":"Motor data wrong","signs":"Drive replaced or motor changed recently.","check":"Compare the motor data in group 99 with the motor rating plate."},{"cause":"Motor, cable or connection fault","signs":"Trips instantly at start, even with little load.","check":"Check the motor and motor cable, including phasing and the star/delta connection."},{"cause":"Equipment switching in the motor cable","signs":"Trips coincide with a contactor operating between drive and motor.","check":"Check for contactors opening or closing in the motor cable while the drive runs."},{"cause":"Capacitors or surge absorbers on the motor side","signs":"Power-factor capacitors or surge absorbers are fitted in the motor cable.","check":"Check for and remove power-factor capacitors or surge absorbers from the motor cable."},{"cause":"Earth fault","signs":"Trips persist with the load removed.","check":"Measure the insulation resistance of the motor and cable, with the motor disconnected from the drive."}],"distinguish":["If the trip happens partway through a start, ramp time and load are the first suspects; if it happens the instant the drive starts, look at the motor, cable and connections.","Because ABB lists an earth fault and a lost supply phase as possible triggers, an insulation test and a check of the supply are worthwhile even when the load looks normal."],"evidence":["Event log entry for 2310 with its time stamp","Acceleration time and ramp settings","Group 99 motor data and the motor rating plate","Whether a contactor, capacitors or surge absorbers sit in the motor cable","Insulation test results"],"parameters":[{"id":"23.xx / 26.xx / 28.xx","name":"Acceleration times (speed, torque, frequency ramps)","note":"Too short a ramp for the load’s inertia is a common trigger."},{"id":"46.01–46.03","name":"Speed, frequency and torque scaling","note":"Wrong scaling is listed by ABB as a cause."},{"id":"99.xx","name":"Motor data","note":"Must match the motor rating plate."},{"id":"31.12","name":"Autoreset selection (bit 0: overcurrent)","note":"Can reset overcurrent automatically; only enable once the cause is understood."}],"related":["3210","3220"],"sources":[{"title":"ACS580 standard control program Firmware manual","publisher":"ABB","docId":"3AXD50000016097","revision":"Rev E (2018-02-15), firmware ASCDX 2.05","url":"https://www.ghv.de/files/elektrische-antriebstechnik/frequenzumrichter/acs580/downloads/dokumentationen/en_acs580_firmware_ghv.pdf","section":"Fault tracing: Fault messages","page":"420"},{"title":"ACS580 standard control program Firmware manual (current revision)","publisher":"ABB","docId":"3AXD50000016097","revision":"Rev H (2022-02-28)","url":"https://library.e.abb.com/public/052c19b4002f45cf908d536363a39bb4/ASCD2216x_en.pdf"}],"review":{"status":"extracted","checks":["Facts were taken from Rev E (firmware 2.05) via an ABB distributor copy; confirm each code, cause and parameter number against Rev H and the firmware actually installed.","Electrical checks are framed for qualified personnel, with isolation and capacitor discharge per the drive manual.","Insulation testing is only suggested with the motor disconnected from the drive."]},"updatedAt":"2026-10-26","url":"https://induqt.ai/troubleshoot/vfd/abb/acs580/2310"},{"kind":"fault","family":"vfd","manufacturerSlug":"abb","modelSlug":"acs580","controller":"ABB ACS580 drive","code":"3210","name":"DC link overvoltage","severity":"fault","title":"ABB ACS580 Fault 3210 (DC Link Overvoltage): Causes","description":"ACS580 fault 3210 means the intermediate DC voltage went too high, usually from braking a high-inertia load or supply overvoltage. ABB’s checks and the 30.30 overvoltage control setting.","meaning":"The drive’s intermediate-circuit (DC link) voltage rose too high and the drive tripped. This usually happens when the motor regenerates energy while slowing down, or when the supply voltage itself is too high.","operatingStates":["During deceleration or stopping, especially with high-inertia loads","With an overhauling load that drives the motor","At any time if the supply has static or transient overvoltage"],"causes":[{"cause":"Overvoltage control switched off","signs":"Trips on stops; 30.30 is disabled.","check":"Check that 30.30 Overvoltage control is on. ABB notes it must be disabled when a brake chopper and resistor or a regenerative supply is fitted."},{"cause":"Deceleration too fast","signs":"Trips only on fast stops or large speed reductions.","check":"Check the deceleration time; use coast-to-stop where the application allows."},{"cause":"Brake chopper or resistor not working, or wrongly sized","signs":"A resistor is fitted but trips continue.","check":"Check the brake chopper and resistor, and that the resistor is dimensioned correctly with resistance within the allowed range."},{"cause":"Supply voltage too high","signs":"Trips even on gentle stops or at standstill.","check":"Check that the supply voltage matches the drive’s nominal input and look for static or transient overvoltage on the supply."}],"distinguish":["Trips on deceleration point to regenerated energy (ramp, overvoltage control, braking); trips while running steadily or stopped point to the supply.","If the process needs fast stops of a heavy load, ABB’s listed fix is a brake chopper and resistor."],"evidence":["Event log entry for 3210 and what the drive was doing","Deceleration time and stop mode","Setting of 30.30","Whether a brake chopper and resistor are fitted, and the resistor value","Measured supply voltage"],"parameters":[{"id":"30.30","name":"Overvoltage control","note":"Reduces braking torque to hold the DC voltage down; disable when a brake chopper and resistor or a regenerative supply is used."},{"id":"23.xx","name":"Deceleration times","note":"Longer deceleration returns energy more slowly."},{"id":"31.12","name":"Autoreset selection (bit 1: overvoltage)","note":"Can reset overvoltage automatically; only once the cause is understood."}],"related":["2310","3220"],"sources":[{"title":"ACS580 standard control program Firmware manual","publisher":"ABB","docId":"3AXD50000016097","revision":"Rev E (2018-02-15), firmware ASCDX 2.05","url":"https://www.ghv.de/files/elektrische-antriebstechnik/frequenzumrichter/acs580/downloads/dokumentationen/en_acs580_firmware_ghv.pdf","section":"Fault tracing: Fault messages; Parameters 30.30","page":"421, ~258"},{"title":"ACS580 standard control program Firmware manual (current revision)","publisher":"ABB","docId":"3AXD50000016097","revision":"Rev H (2022-02-28)","url":"https://library.e.abb.com/public/052c19b4002f45cf908d536363a39bb4/ASCD2216x_en.pdf"}],"review":{"status":"extracted","checks":["Facts were taken from Rev E (firmware 2.05) via an ABB distributor copy; confirm each code, cause and parameter number against Rev H and the firmware actually installed.","Electrical checks are framed for qualified personnel, with isolation and capacitor discharge per the drive manual.","Insulation testing is only suggested with the motor disconnected from the drive."]},"updatedAt":"2026-10-26","url":"https://induqt.ai/troubleshoot/vfd/abb/acs580/3210"},{"kind":"fault","family":"vfd","manufacturerSlug":"abb","modelSlug":"acs580","controller":"ABB ACS580 drive","code":"3220","name":"DC link undervoltage","severity":"fault","title":"ABB ACS580 Fault 3220 (DC Link Undervoltage): Causes","description":"ACS580 fault 3220 means the DC link voltage dropped too low, usually from a missing supply phase or blown fuse. How it relates to warning A3A2, undervoltage control and automatic restart.","meaning":"The drive’s DC link voltage fell too low and the drive tripped. ABB lists a missing supply phase, a blown fuse or a fault in the rectifier bridge as the causes. When the drive is stopped, the same condition shows as warning A3A2 instead of a fault.","operatingStates":["During supply dips or interruptions","After a fuse blows or a supply phase is lost","At the end of an automatic-restart window if the supply has not returned"],"causes":[{"cause":"Missing supply phase or blown fuse","signs":"Trip coincides with a supply event; other equipment on the same supply also reacts.","check":"Check the supply cabling, fuses and switchgear."},{"cause":"Supply interruption longer than the ride-through","signs":"Trips after short power dips; automatic restart enabled but the dip lasted too long.","check":"Compare the length of the dip with 21.18 Auto restart time (up to 10 s), and check whether 30.31 Undervoltage control is enabled."},{"cause":"Rectifier bridge fault","signs":"Supply and fuses are healthy but the fault repeats.","check":"Refer to ABB service; the rectifier is inside the drive."}],"distinguish":["Fault 3220 trips the drive; warning A3A2 is the same low-voltage condition reported while the drive is stopped (ABB’s action: check the supply voltage and the 95.01 Supply voltage setting).","With automatic restart, the undervoltage fault is held back for up to 21.18 seconds and a warning is shown; the drive trips on 3220 only if the DC voltage is still too low when that time runs out."],"evidence":["Event log entries for 3220 and A3A2 with time stamps","Plant supply events or power-quality records at the same time","Fuse and switchgear condition","Settings of 30.31, 21.18 and 95.01"],"parameters":[{"id":"30.31","name":"Undervoltage control","note":"Lowers motor torque so the load inertia keeps the DC link charged during a supply loss."},{"id":"21.18","name":"Auto restart time","note":"Allows restart after a supply loss of up to 10 s; the fault is held back during this time."},{"id":"95.01","name":"Supply voltage","note":"Should match the actual supply; checked for warning A3A2."},{"id":"31.12","name":"Autoreset selection (bit 2: undervoltage)","note":"Can reset undervoltage automatically."}],"related":["3210","2310"],"sources":[{"title":"ACS580 standard control program Firmware manual","publisher":"ABB","docId":"3AXD50000016097","revision":"Rev E (2018-02-15), firmware ASCDX 2.05","url":"https://www.ghv.de/files/elektrische-antriebstechnik/frequenzumrichter/acs580/downloads/dokumentationen/en_acs580_firmware_ghv.pdf","section":"Fault tracing: Fault and Warning messages; Program features: Automatic restart","page":"410, 421, 139"},{"title":"ACS580 standard control program Firmware manual (current revision)","publisher":"ABB","docId":"3AXD50000016097","revision":"Rev H (2022-02-28)","url":"https://library.e.abb.com/public/052c19b4002f45cf908d536363a39bb4/ASCD2216x_en.pdf"}],"review":{"status":"extracted","checks":["Facts were taken from Rev E (firmware 2.05) via an ABB distributor copy; confirm each code, cause and parameter number against Rev H and the firmware actually installed.","Electrical checks are framed for qualified personnel, with isolation and capacitor discharge per the drive manual.","Insulation testing is only suggested with the motor disconnected from the drive."]},"updatedAt":"2026-10-26","url":"https://induqt.ai/troubleshoot/vfd/abb/acs580/3220"},{"kind":"symptom","family":"vfd","slug":"trips-on-acceleration","title":"VFD Trips on Acceleration: Causes and Diagnosis","description":"Why a variable-frequency drive trips while ramping up, usually on overcurrent, and how to separate ramp settings, mechanical load and motor or cable faults.","headline":"VFD trips on acceleration","summary":"A drive that trips while ramping up is almost always reporting overcurrent (or current limit). The motor is drawing more current than the drive allows: because the ramp asks for more torque than the load can take, because the load is stuck, or because of a fault in the motor or its cable.","whereItShows":["An overcurrent or current-limit fault during start or speed increase","Trips that disappear when the acceleration time is lengthened"],"causes":[{"cause":"Acceleration ramp too short for the inertia","signs":"Trips only during fast starts; fans and centrifuges are typical.","check":"Compare the acceleration time setting with the load’s inertia; trial a longer ramp and watch peak current."},{"cause":"Mechanical load or brake not released","signs":"Trips immediately at start; motor barely turns.","check":"Confirm the brake releases and the driven machine turns freely."},{"cause":"Motor data or control mode wrong","signs":"Trips after a drive replacement or parameter change.","check":"Check motor nameplate data in the drive and that the motor identification run was done if the drive requires it."},{"cause":"Motor or cable insulation fault","signs":"Instant trip at start even unloaded; may alternate with ground-fault trips.","check":"Insulation-test the motor and cable with the motor disconnected from the drive."}],"sequence":[{"step":"Read the fault and its log","text":"Note the fault code and, if the drive stores them, the current, frequency and DC voltage at the trip."},{"step":"When in the ramp?","text":"Instantly at start points to motor, cable or brake; partway through the ramp points to ramp time or load inertia."},{"step":"Compare with the load","text":"Was the machine heavily loaded, cold or recently serviced?"},{"step":"Change one setting","text":"If mechanics and wiring are healthy, lengthen the ramp in steps and compare peak current."}],"evidence":["Keypad photo of the fault","Drive model and firmware","Fault log values at the trip","Acceleration time and current limit settings","Description of the driven load"],"relatedLinks":[{"href":"/blog/vfd-fault-codes-explained","label":"VFD fault codes explained"},{"href":"/tools/free-vfd-diagnostic","label":"Free drive diagnostic"}],"sources":[{"title":"Drive firmware manuals (overcurrent and current-limit sections) for the specific model","publisher":"Drive manufacturers"}],"review":{"status":"extracted","checks":["Electrical checks are framed for qualified personnel, with isolation and capacitor discharge per the drive manual.","Insulation testing is only suggested with the motor disconnected from the drive."]},"updatedAt":"2026-10-26","url":"https://induqt.ai/troubleshoot/vfd/faults/trips-on-acceleration"},{"kind":"symptom","family":"vfd","slug":"overvoltage-during-deceleration","title":"VFD Overvoltage During Deceleration: Causes and Fixes","description":"Why a drive trips on DC bus overvoltage while slowing down, and how deceleration time, the overvoltage controller and braking resistors affect it.","headline":"VFD overvoltage during deceleration","summary":"When a motor is slowed faster than the load would coast, it acts as a generator and pushes energy back into the drive’s DC bus. If the drive cannot absorb or dissipate that energy, the DC bus voltage rises until it trips on overvoltage.","whereItShows":["A DC bus (DC link) overvoltage fault during stops or speed reductions","Trips more often with heavy, high-inertia loads"],"causes":[{"cause":"Deceleration time too short","signs":"Trips only on fast stops or large speed changes.","check":"Lengthen the deceleration time and compare the DC bus voltage at the end of the ramp."},{"cause":"Overvoltage control disabled","signs":"The drive’s automatic overvoltage controller is switched off in parameters.","check":"Check whether the overvoltage controller is enabled, unless a braking chopper is fitted and the manual says to disable it."},{"cause":"Braking resistor or chopper not working","signs":"Resistor fitted but stays cold; chopper fault or disabled in parameters.","check":"Verify the resistor value and wiring and that braking is enabled, following the drive manual."},{"cause":"High supply voltage","signs":"Trips even on gentle stops; supply measured near the top of tolerance.","check":"Measure the incoming line voltage and compare with the drive’s rating."}],"sequence":[{"step":"Confirm the moment","text":"Check the fault log: was the drive decelerating when it tripped?"},{"step":"Look at the load","text":"High inertia or overhauling loads regenerate the most energy."},{"step":"Check settings","text":"Deceleration time, overvoltage control and braking settings."},{"step":"Decide on braking","text":"If the process needs fast stops, size a braking resistor or regenerative unit per the manufacturer."}],"evidence":["Fault log with DC bus voltage at the trip","Deceleration time and braking settings","Whether a braking resistor is fitted","Incoming supply voltage"],"relatedLinks":[{"href":"/blog/vfd-fault-codes-explained","label":"VFD fault codes explained"},{"href":"/tools/free-vfd-diagnostic","label":"Free drive diagnostic"}],"sources":[{"title":"Drive firmware manuals (DC link overvoltage sections) for the specific model","publisher":"Drive manufacturers"}],"review":{"status":"extracted","checks":["Electrical checks are framed for qualified personnel, with isolation and capacitor discharge per the drive manual.","Insulation testing is only suggested with the motor disconnected from the drive."]},"updatedAt":"2026-10-26","url":"https://induqt.ai/troubleshoot/vfd/faults/overvoltage-during-deceleration"}],"graph":{"functions":{"limit-supervision":{"name":"Limit and interlock supervision","text":"Operating and safety limits, the running interlock string and low-water protection must be closed before and during firing."},"air-proving":{"name":"Combustion air proving","text":"The control proves combustion air is present when the fan runs, and absent when it should be off."},"purge":{"name":"Purge","text":"The fan and dampers drive to purge position for a timed purge before every light-off."},"ignition":{"name":"Ignition and pilot","text":"Spark and pilot fuel must produce a flame the detector can prove within the pilot trial time."},"flame-supervision":{"name":"Flame supervision","text":"The flame detector and amplifier must see flame when it should exist and none when it should not."},"fuel-delivery":{"name":"Main fuel delivery","text":"The fuel train must deliver stable pressure through the safety shutoff valves across the firing range."},"valve-proving":{"name":"Valve proving and proof of closure","text":"Safety shutoff valves are proven closed before start, and on gas systems may be leak tested."},"positioning":{"name":"Firing-rate positioning","text":"Air damper, fuel valve and fan speed follow the commissioned fuel/air curve, proven by position switches or servo feedback."},"controller-integrity":{"name":"Controller self-checks","text":"The control checks its own relays, memory, inputs, supply and communications, and locks out if any check fails."},"steam-temperature-control":{"name":"Steam temperature control","text":"On superheated-steam boilers, desuperheater spray trims main steam temperature to its setpoint as firing and load change."},"combustion-monitoring":{"name":"Combustion monitoring","text":"Flue oxygen, CO and stack temperature are monitored against limits, often with trim of the fuel/air ratio."}},"components":{"flame-scanner":{"name":"Flame scanner (UV / IR)","functions":["flame-supervision"],"signals":["flame-signal"],"mechanisms":["lens-fouling","sighting-shift","detector-ageing","signal-noise"]},"flame-rod":{"name":"Flame rod","functions":["flame-supervision"],"signals":["flame-signal"],"mechanisms":["flame-rod-grounding","sighting-shift"]},"flame-amplifier":{"name":"Flame amplifier / flame input","functions":["flame-supervision"],"signals":["flame-signal"],"mechanisms":["amplifier-mismatch","detector-ageing","signal-noise"]},"igniter":{"name":"Ignition transformer and electrode","functions":["ignition"],"signals":["ignition-output"],"mechanisms":["electrode-wear","transformer-failure"]},"pilot-train":{"name":"Pilot gas train","functions":["ignition"],"signals":["pilot-valve","pilot-gas-pressure"],"mechanisms":["regulator-drift","valve-not-opening","supply-pressure-droop"]},"main-fuel-valves":{"name":"Main safety shutoff valves","functions":["fuel-delivery","valve-proving"],"signals":["main-valve","proof-of-closure"],"mechanisms":["valve-not-opening","valve-seat-leak","contact-welded"]},"fuel-supply":{"name":"Fuel supply and regulator","functions":["fuel-delivery"],"signals":["gas-pressure","oil-pressure"],"mechanisms":["supply-pressure-droop","regulator-drift"]},"combustion-fan":{"name":"Combustion air fan (FD / ID)","functions":["air-proving","purge"],"signals":["fan-run","fan-speed","air-pressure","fan-current","fan-vibration"],"mechanisms":["blocked-air-path","fan-drive-fault","bearing-wear"]},"air-switch":{"name":"Combustion air proving switch","functions":["air-proving"],"signals":["air-proving","air-pressure"],"mechanisms":["switch-drift","contact-welded","blocked-air-path"]},"air-damper":{"name":"Air damper, actuator and linkage","functions":["positioning","purge"],"signals":["air-damper-position","firing-rate"],"mechanisms":["linkage-slip","actuator-feedback-fault","air-fuel-ratio-drift"]},"fuel-actuator":{"name":"Fuel valve actuator and linkage","functions":["positioning","fuel-delivery"],"signals":["fuel-valve-position","firing-rate"],"mechanisms":["linkage-slip","actuator-feedback-fault","air-fuel-ratio-drift"]},"position-switches":{"name":"Low fire and high fire position switches","functions":["positioning","purge"],"signals":["low-fire-switch","high-fire-switch"],"mechanisms":["switch-drift","linkage-slip","contact-welded"]},"limit-string":{"name":"Operating and safety limits","functions":["limit-supervision"],"signals":["running-interlock","steam-pressure","water-temperature","drum-level"],"mechanisms":["limit-trip","switch-drift","contact-welded"]},"pressure-sensor":{"name":"Steam pressure / temperature sensor and control loop","functions":["limit-supervision","positioning"],"signals":["steam-pressure","water-temperature","firing-rate"],"mechanisms":["sensor-failure","control-loop-tuning","network-fault"]},"feedwater-system":{"name":"Feedwater pump, valve and level control","functions":["limit-supervision"],"signals":["drum-level","feedwater-flow","steam-flow"],"mechanisms":["feed-supply-shortfall","control-loop-tuning","sensor-failure","limit-trip"]},"flue-analyser":{"name":"Flue oxygen probe and stack sensor","functions":["combustion-monitoring"],"signals":["flue-oxygen","stack-temperature"],"mechanisms":["sensor-failure","air-fuel-ratio-drift"]},"heating-surfaces":{"name":"Boiler tubes and heating surfaces","functions":["combustion-monitoring"],"signals":["stack-temperature","flue-oxygen","furnace-temperature","steam-pressure","steam-flow"],"mechanisms":["surface-fouling"]},"desuperheater":{"name":"Desuperheater (spray attemperator) and its control loop","functions":["steam-temperature-control"],"signals":["steam-temperature","spray-valve","spray-flow","furnace-temperature"],"mechanisms":["control-loop-tuning","valve-not-opening","sensor-failure"]},"comms-network":{"name":"Controller communication network","functions":["controller-integrity","positioning"],"signals":["burner-status"],"mechanisms":["network-fault","signal-noise"]},"burner-controller":{"name":"Burner management controller","functions":["controller-integrity"],"signals":["burner-status","line-voltage"],"mechanisms":["controller-internal","power-quality","configuration-change","signal-noise"]}},"signals":{"flame-signal":{"name":"Flame signal","kind":"analog","unit":"Vdc, % or µA by controller","aliases":["flame signal","flame strength","flame %","flame current","scanner signal","flm","flame1","flame 1","flame_signal"]},"burner-status":{"name":"Burner sequence state","kind":"state","aliases":["burner status","burner state","sequence step","sequence status","ek30","bms state","burner_status"]},"air-proving":{"name":"Combustion air proving switch","kind":"digital","aliases":["air proving","airflow switch","air flow switch","air pressure switch","aps","caps","combustion air switch"]},"air-pressure":{"name":"Combustion air pressure","kind":"analog","unit":"inWC or mbar","aliases":["air pressure","combustion air pressure","windbox pressure","fan pressure","fan discharge pressure"]},"fan-run":{"name":"Combustion fan running","kind":"digital","aliases":["fan run","blower run","burner motor","fan status","blower status","fan_on"]},"fan-speed":{"name":"Combustion fan speed","kind":"analog","unit":"% or Hz","aliases":["fan speed","blower speed","vsd speed","fan vfd","fan hz"]},"gas-pressure":{"name":"Main gas pressure","kind":"analog","unit":"inWC, psig or mbar","aliases":["gas pressure","main gas pressure","manifold pressure","burner gas pressure","inlet gas pressure","gas_press"]},"pilot-gas-pressure":{"name":"Pilot gas pressure","kind":"analog","unit":"inWC or mbar","aliases":["pilot pressure","pilot gas pressure","pilot gas"]},"oil-pressure":{"name":"Oil pressure","kind":"analog","unit":"psig or bar","aliases":["oil pressure","fuel oil pressure","atomizing pressure"]},"ignition-output":{"name":"Ignition output","kind":"digital","aliases":["ignition","igniter","ignition transformer","spark","ign"]},"pilot-valve":{"name":"Pilot valve output","kind":"digital","aliases":["pilot valve","pv","pilot solenoid"]},"main-valve":{"name":"Main fuel valve output","kind":"digital","aliases":["main valve","mv","main fuel valve","main gas valve","sov","safety shutoff valve"]},"proof-of-closure":{"name":"Valve proof of closure","kind":"digital","aliases":["proof of closure","poc","valve closed switch","pre-ignition interlock","pre ignition interlock","pii"]},"running-interlock":{"name":"Running interlock / limit string","kind":"digital","aliases":["running interlock","limit string","limits","run ilk","lockout interlock","safety limits"]},"firing-rate":{"name":"Firing rate","kind":"analog","unit":"%","aliases":["firing rate","modulation rate","mod rate","burner load","fire rate","output %"]},"air-damper-position":{"name":"Air damper position","kind":"analog","unit":"% or °","aliases":["air damper","damper position","air servo","air actuator","air drive"]},"fuel-valve-position":{"name":"Fuel valve position","kind":"analog","unit":"% or °","aliases":["fuel valve position","gas valve position","fuel servo","fuel actuator","fuel drive","gas butterfly"]},"low-fire-switch":{"name":"Low fire position switch","kind":"digital","aliases":["low fire switch","lfs","low fire proven","low fire start"]},"high-fire-switch":{"name":"High fire (purge) position switch","kind":"digital","aliases":["high fire switch","hfs","purge position","high fire proven"]},"steam-pressure":{"name":"Steam pressure","kind":"analog","unit":"psig or bar","aliases":["steam pressure","header pressure","drum pressure","boiler pressure","steam_press"]},"water-temperature":{"name":"Boiler water temperature","kind":"analog","unit":"°F or °C","aliases":["water temperature","supply temperature","outlet temperature","hot water temp"]},"drum-level":{"name":"Drum / water level","kind":"analog","unit":"% or in","aliases":["drum level","water level","gauge glass","lwco","low water cutoff"]},"steam-flow":{"name":"Steam flow","kind":"analog","unit":"lb/h or kg/h","aliases":["steam flow","steam_flow","steam output","steam load","boiler load","steam rate"]},"feedwater-flow":{"name":"Feedwater flow","kind":"analog","unit":"lb/h, kg/h or gpm","aliases":["feedwater flow","feed water flow","fw flow","feedwater"]},"stack-temperature":{"name":"Stack (flue gas) temperature","kind":"analog","unit":"°F or °C","aliases":["stack temperature","stack temp","flue temperature","flue gas temperature","exhaust temperature","flue temp"]},"flue-oxygen":{"name":"Flue gas oxygen","kind":"analog","unit":"% O2","aliases":["o2","oxygen","flue o2","excess oxygen","stack o2"]},"fan-vibration":{"name":"Fan vibration","kind":"analog","unit":"mm/s or in/s","aliases":["fan vibration","bearing vibration","vibration","fan vib","id fan vibration","fd fan vibration"]},"fan-current":{"name":"Fan motor current","kind":"analog","unit":"A","aliases":["fan current","motor current","fan amps","id fan current","fd fan current","blower amps"]},"furnace-temperature":{"name":"Furnace temperature","kind":"analog","unit":"°F or °C","aliases":["furnace temperature","furnace temp","upper furnace temperature","bed temperature","furnace exit temperature"]},"steam-temperature":{"name":"Main steam temperature","kind":"analog","unit":"°F or °C","aliases":["main steam temperature","steam temperature","superheated steam temperature","sh outlet temperature","steam temp"]},"spray-valve":{"name":"Desuperheater spray valve position","kind":"analog","unit":"%","aliases":["spray valve","desuperheater spray valve","attemperator valve","spray valve position","desuperheater valve"]},"spray-flow":{"name":"Spray water flow","kind":"analog","unit":"t/h or lb/h","aliases":["spray water flow","spray flow","attemperator flow","desuperheater flow"]},"line-voltage":{"name":"Controller supply voltage","kind":"analog","unit":"Vac","aliases":["line voltage","supply voltage","mains","l1","120v","230v"]}},"mechanisms":{"lens-fouling":{"name":"Dirty or fogged scanner sight path","text":"Soot, oil film, condensation or a dirty sight tube cuts the radiation reaching the detector, so the flame signal falls slowly over weeks."},"sighting-shift":{"name":"Scanner no longer sighted on the flame root","text":"The scanner mount, swivel or burner geometry has moved, or the flame shape changed with tuning, so the detector sees the flame only at some firing rates."},"detector-ageing":{"name":"Detector or amplifier ageing","text":"UV tubes and amplifiers lose sensitivity or fail on self-check with age; a UV tube can also fail \"on\" and see flame that is not there."},"flame-rod-grounding":{"name":"Flame rod or burner ground fault","text":"A cracked insulator, a rod touching metal or poor burner grounding stops the rectified flame current from flowing correctly."},"signal-noise":{"name":"Electrical noise on signal wiring","text":"Ignition or power wiring run alongside detector or low-voltage leads couples noise in, producing false flame signals or intermittent input faults."},"amplifier-mismatch":{"name":"Wrong detector, amplifier or configuration","text":"The flame amplifier, detector type, response time or jumpers do not match each other or the application."},"electrode-wear":{"name":"Igniter electrode wear or wrong gap","text":"Eroded tips, carbon tracking, a cracked insulator or a gap outside the burner maker’s setting weakens or misplaces the spark."},"transformer-failure":{"name":"Ignition transformer or lead failure","text":"An open or shorted transformer winding, or a broken high-voltage lead, gives no spark or a weak one."},"supply-pressure-droop":{"name":"Fuel supply pressure droop","text":"Upstream pressure sags when the valves open or other users start, starving the flame during light-off or at high fire."},"regulator-drift":{"name":"Regulator out of adjustment or sticking","text":"A pilot or main regulator delivers the wrong pressure, or responds slowly to the step in flow at light-off."},"valve-not-opening":{"name":"Fuel valve not opening fully","text":"A coil, actuator or wiring fault means a safety shutoff valve opens late, partially or not at all."},"valve-seat-leak":{"name":"Valve seat leakage or slow closing","text":"A safety shutoff valve does not seal or close in time, so a leak test, proof-of-closure or pre-ignition check fails."},"air-fuel-ratio-drift":{"name":"Air/fuel ratio drift","text":"Linkage slip, a changed setpoint curve, fan wear or a fuel change moves the mixture away from the commissioned ratio, making the flame unstable or lifting."},"linkage-slip":{"name":"Damper or valve linkage slip","text":"A loose coupling or set screw lets the damper or fuel valve move differently from the actuator that drives it."},"actuator-feedback-fault":{"name":"Actuator or feedback fault","text":"A servo, feedback potentiometer or end switch no longer reports the true position, or the actuator cannot reach it."},"blocked-air-path":{"name":"Restricted combustion air path","text":"A blocked intake, dirty fan wheel, closed inlet damper or flue restriction reduces the air pressure the fan can make."},"fan-drive-fault":{"name":"Fan motor or drive fault","text":"A tripped overload, slipping belt, failed motor or a fan VSD that is slow to reach speed delays or reduces air flow."},"switch-drift":{"name":"Pressure or position switch out of adjustment","text":"The setpoint has drifted, the sensing tube is blocked or wet, or the contacts are dirty, so the switch makes or breaks at the wrong point."},"contact-welded":{"name":"Welded, jumpered or miswired contact","text":"A switch or relay contact stays closed when it should be open, often from a welded contact, a jumper left in place or a wiring error."},"limit-trip":{"name":"Operating or safety limit open","text":"A pressure, temperature or water-level limit opened because the process went out of range, or the limit device itself failed."},"sensor-failure":{"name":"Transmitter or sensor failure","text":"A transmitter, thermocouple or probe reads out of range, drifts or loses its supply."},"network-fault":{"name":"Communication wiring fault","text":"CANbus or fieldbus cabling, termination, addressing or screening problems interrupt messages between controller, display, servos and sensors."},"power-quality":{"name":"Supply voltage, frequency or grounding problem","text":"Low or noisy supply voltage, wrong phasing or a missing earth upsets the controller’s safety self-checks."},"surface-fouling":{"name":"Fouled heating surfaces","text":"Soot on the fire side or scale on the water side insulates the tubes, so less heat reaches the water: stack temperature and fuel use rise for the same steam output."},"control-loop-tuning":{"name":"Control loop tuning or strategy","text":"A level, pressure or firing-rate loop is too slow, too aggressive or uses too few measurements to ride through load changes."},"feed-supply-shortfall":{"name":"Feedwater supply shortfall","text":"The feed pump, deaerator level or feedwater valve cannot deliver the flow the boiler needs at that moment."},"bearing-wear":{"name":"Bearing wear or misalignment","text":"A worn, poorly lubricated or misaligned bearing raises vibration and temperature long before the machine stops."},"controller-internal":{"name":"Controller internal fault","text":"A self-test, memory or safety-relay check inside the controller failed; the manufacturer usually directs replacement if it repeats."},"configuration-change":{"name":"Configuration or commissioning data changed","text":"Jumpers, option parameters, a profile or a replaced servo no longer match what the controller stored at commissioning."}}}}