Navien NCB300-28K, Service Manual

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64 Troubleshooting
5.2.3 Error 004
Error Conditions and Checklist
Error Description
E004
False-flame detection
1. Pre ignition false-flame
2. If a flame signal is detected continuously for 3 sec before combustion (stand-by,
pre-purge, pre-ignition), a false-flame error 004E (automatically cleared) is displayed
on the front panel. The system performs a continuous post-purge and starts the
circulation pump.
3. Post purge false-flame
4. If a flame signal is detected continuously for 3 sec when the system performs post-
purge after the gas supply closes, a false-flame error 004E (automatically cleared) is
displayed on the front panel. The system performs a continuous post-purge and starts
the circulation pump.
Checklist
1. Check for gas leaks and defective seals on the main gas valve.
2. Check if a spark of sufficient intensity is discharged by the electrode.
3. Check if gas is supplied within the correct pressure range.
4. Check the PCB and replace it if faulty.
Is there burner flame when
there is no ignition?
External noise interference
Clean or replace the flame rod
Check the current #1 at CONK1: 1-20 μA.
(See page 35 for Wiring Diagram.)
No
Yes
Testing method
Error Cause Testing method
Flame before/
after combustion
Main gas valve leak
If flame occurs before ignition or if gas continues to burn after combustion stops,
replace the flame rod.
Error before/after
combustion
Electrode level of
discharge
Spark discharges from electrode to flame sensor at ignition.
●
Replace or correct the position of the flame rod.
Gas valve
Gas may leak from the main gas valve if the gas supply pressure exceeds the boiler
specifications.
●
Check the supply pressure: NG: 17-25 mbar, LP: 25-35 mbar.
●
If gas pressure is too high, notify the gas supplier and if necessary, replace the gas
valve.
●
If there is a gas leak, close the gas supply valve and repair the unit before using the
system.
Other faults PCB fault If the error condition continues after checking these items, replace the PCB.