Fireye NX6300 (Nexus) fault F10: Flame Failure
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.
Diagnose this with AI
Try Free Boiler Diagnostic Upload a keypad photo, the fault history or a parameter export from your Fireye NX6300 (Nexus). InduQT compares the evidence and suggests the next useful checks.
When it happens
- 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
Reading the subset
| Subset | What it tells you |
|---|---|
| 1xx | Flame 1 (the first flame input); the last two digits are the burner status number |
| 2xx | Flame 2 (the second flame input) |
| x11, x12 | Pilot ignition (safety time t4) or pilot ignition interval (t5): flame never proven or pilot lost |
| x13, x14 | Main ignition (t6) or waiting for main flame (t7): lost at the change from pilot to main flame |
| x15 | Moving to low fire or low fire hold (t8) |
| x16 | Modulation: lost while firing |
Where it sits in the burner
Supervised functions: Flame supervision, Ignition and pilot, Main fuel delivery.
| Component | Signals to look at | How it fails |
|---|---|---|
| Flame scanner (UV / IR) | Flame signal | Dirty or fogged scanner sight path; Scanner no longer sighted on the flame root; Detector or amplifier ageing; Electrical noise on signal wiring |
| Flame amplifier / flame input | Flame signal | Wrong detector, amplifier or configuration; Detector or amplifier ageing; Electrical noise on signal wiring |
| Ignition transformer and electrode | Ignition output | Igniter electrode wear or wrong gap; Ignition transformer or lead failure |
| Pilot gas train | Pilot valve output, Pilot gas pressure | Regulator out of adjustment or sticking; Fuel supply pressure droop; Fuel valve not opening fully |
| Fuel supply and regulator | Main gas pressure, Oil pressure | Fuel supply pressure droop; Regulator out of adjustment or sticking |
| Air damper, actuator and linkage | Air damper position, Firing rate | Air/fuel ratio drift; Damper or valve linkage slip; Actuator or feedback fault |
Likely causes and checks
1No pilot flame at ignition (subset x11–x12)
- Points to it
- 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.
2Pilot gas pressure or regulator (subset x11–x12)
- Points to it
- Spark present, pilot weak or absent.
- Check
- Read pilot gas pressure during the trial and confirm the pilot valve opens.
3Main flame does not take over (subset x13–x14)
- Points to it
- 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.
4Flame lost while firing (subset x15–x16)
- Points to it
- 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.
5Flame present but not seen
- Points to it
- 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.
Telling it apart
- 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 to collect
- 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
Work on fuel trains, burners, pressure vessels and electrical equipment must be done by qualified personnel following the manufacturer’s documentation and local codes. Never bypass a safety device or interlock.