Fireye NX6300 (Nexus) fault F14: Combustion air pressure not detected
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.
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 07: proving purge positions, after the air pressure prove time t1
- Status 08–16: purge, ignition and firing, where air must stay proven
Reading the subset
| Subset | What it tells you |
|---|---|
| 07 | Air not proven when the air prove time ended, before purge |
| 08 to 16 | Air pressure lost during purge, ignition or firing |
Where it sits in the burner
Supervised functions: Combustion air proving, Purge.
| Component | Signals to look at | How it fails |
|---|---|---|
| Combustion air fan (FD / ID) | Combustion fan running, Combustion fan speed, Combustion air pressure, Fan motor current, Fan vibration | Restricted combustion air path; Fan motor or drive fault; Bearing wear or misalignment |
| Combustion air proving switch | Combustion air proving switch, Combustion air pressure | Pressure or position switch out of adjustment; Restricted combustion air path; Welded, jumpered or miswired contact |
| Air damper, actuator and linkage | Air damper position, Firing rate | Damper or valve linkage slip; Actuator or feedback fault; Air/fuel ratio drift |
Likely causes and checks
1Fan not running or slow (subset 07)
- Points to it
- 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.
2Air path restricted
- Points to it
- Gradual onset; dirty inlet, closed damper, flue restriction.
- Check
- Inspect intake, fan wheel, damper travel and flue.
3Switch setpoint too close to the low-fire differential (subset 15–16)
- Points to it
- Trips at low fire or on modulation down.
- Check
- Measure the differential at the switch across the firing range and compare with its setpoint.
Telling it apart
- F14 is air not proven when required; F15 is air proven when it should not be.
Evidence to collect
- Subset (burner status)
- Fan motor or VSD status at the fault
- Air pressure at the switch at low and high fire
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.