Navien NFC-175 Service Manual page 77

Failure mode
No spark from electrode
Ignition failure
Version 1.0
Cause
Igniter
Flame Rod
Ignite gap distance : 3.5~4.5mm (1/8")
When no spark is made from the electrode at ignition:
Remove the electrode and check if there is a crack on the insulator.
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Adjust the gap if there is a discharge of electricity from the metallic part of the burner.
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Ensure that the insulating gasket is installed between the electrode and burner casing.
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Check the input power to the ignition transformer (AC 96 ~ 138 V).
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If there is sufficient power to the ignition transformer, replace the ignition transformer.
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Replace the PCB if there is no power or insufficient power supplied to the ignition
●
transformer.
Check the insulator boots on the spark wires for cracks / holes.
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Check method
Ignition transformer
NFC Service Manual 77