Navien NFC-175, Service Manual

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80 NFC Service Manual
Version 1.0
5.2.3 004Error
Error occurrence conditions and check items
Error Description
E004
False-flame detection
1. Pre ignition false-flame
If a flame signal is detected continuously for 3 seconds before combustion (stand-by, pre-
purge, pre-ignition), a false-flame error 004E (automatically cleared) is displayed on the
front panel and the system performs continuous post-purge and operates the pump.
2. Post purge false-flame
If a flame signal is detected continuously for 3 seconds when the system performs post-
purge as fuel supply is stopped, a false-flame error 004E (automatically cleared) is displayed
on the front panel and the system performs continuous post-purge and operates the
pump.
Check items
1. Check if gas leaks due to defective seals on the main gas valve.
2. Check if proper spark is discharged from the electrode.
3. Check if gas is supplied within the proper pressure range.
4. Check the PCB and replace if defective.
Is the flame detected in
the burner when there is
no ignition?
External noise current
Clean or replace flame rod
Check the current #2 of CNI1: Over 3-4 μA
(See page 50-51 for Wiring Diagram.)
No
Yes
Check method
Failure mode Cause Check method
Flame before / after
combustion
Leakage from main gas
valve
Replace the gas valve if flame occurs before combustion or if there is remaining
flame after combustion is stopped.
Error before / after
combustion
Discharge of electricity
from electrode
Spark discharges from electrode to flame sensor at ignition.
●
Replace or correct location of flame detecting rod.
Gas valve
Gas may leak as the main gas valve is pushed by the gas supply over the standard
pressure.
●
Check the supply pressure: NG: 3.5” - 10.5” W.C, LP: 8” - 13.5”W.C
●
If the gas pressure is too high, notify the gas supplier about the issue, 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 trouble Defective PCB If the issue continues despite the checking of items above, replace the PCB.