Fireye NX6100 (Nexus) fault F16: Second (primary) air pressure not detected
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.
Diagnose this with AI
Try Free Boiler Diagnostic Upload a keypad photo, the fault history or a parameter export from your Fireye NX6100 (Nexus). InduQT compares the evidence and suggests the next useful checks.
When it happens
- Status 07 onwards, wherever primary air must be proven
Reading the subset
| Subset | What it tells you |
|---|---|
| Burner status number | Where in the sequence primary air was not proven |
Where it sits in the burner
Supervised function: Combustion air proving.
| Component | Signals to look at | How it fails |
|---|---|---|
| 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 |
| 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 |
Likely causes and checks
1Primary air fan or path
- Points to it
- Primary air fan not running or restricted.
- Check
- Confirm the primary air source runs and its path is clear.
2Primary air switch setpoint or sensing line
- Points to it
- Air present but switch does not make.
- Check
- Measure the differential at the switch and compare with its setpoint.
Telling it apart
- 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 to collect
- Subset
- Which air switches are fitted
- Differential at the primary switch
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.