Navien NCB-24LSWE, Service Manual

Page: 89 / 144

NCB Service Manual 87 Version 1.0
Failure
mode
Cause Check method
Ignition
failure
Ignition gap: 3.5-4.5 mm (1/8”)
No spark from the
electrode
When no discharge is seen at the electrode during ignition:

Remove the electrode and check for cracks in the insulator.

Adjust the gap if discharge is visible.

Ensure that the insulating gasket is fitted between the electrode and burner
casing.

Check the input voltage at the ignition transformer (AC 230 V).

If the voltage is correct, replace the ignition transformer.

If there is no or low voltage at the ignition transformer, replace the PCB.

Check the insulator boots on the spark leads for cracks or holes.
Igniter
Flame rod
Bracket