Fireye NX6300 (Nexus) fault F42: Valve prove (leak) test fault
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.
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 03–09: the leak test runs in parallel with the start-up sequence
Reading the subset
| Subset | What it tells you |
|---|---|
| Valve prove status number | The step of the leak test that failed; the manual’s valve proving section lists the steps |
Where it sits in the burner
Supervised function: Valve proving and proof of closure.
| Component | Signals to look at | How it fails |
|---|---|---|
| Main safety shutoff valves | Main fuel valve output, Valve proof of closure | Valve seat leakage or slow closing; Fuel valve not opening fully; Welded, jumpered or miswired contact |
| Fuel supply and regulator | Main gas pressure, Oil pressure | Fuel supply pressure droop; Regulator out of adjustment or sticking |
Likely causes and checks
1Upstream or downstream valve seat leaking
- Points to it
- 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.
2Supply pressure low or unstable
- Points to it
- Fails intermittently, often when other users are on.
- Check
- Check supply pressure during the test against the nominal pressure set in the controller.
3Test parameters wrong
- Points to it
- 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).
Telling it apart
- F42 is the controller’s own leak test. A separate proof-of-closure fault (NX6100 F30) is a valve-position switch problem.
Evidence to collect
- Subset (valve prove status)
- Gas supply pressure during the test
- Valve train make and model
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.