Navien NCB-24LSWE, Service Manual

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90 NCB Service Manual Version 1.0
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 if faulty.
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.