Navien NCB300-28K, Service Manual

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84 Troubleshooting
5.3.3 Circuit breaker operation
Error type Cause Check method
Defective sensor
Power supply
The circuit breaker trips immediately as soon as the power cord is plugged in
the receptacle.
Check the sheath of power cord, or if there is short-circuit.
Check the components in order from the power transformer to the PCB.
Defective part assembly
If the circuit breaker operates after repairs check the wiring of each part.
Maintain proper direction when assembling the ignition transformer.
Be careful that wire is not compressed when assembling the main gas valve
Check if the wire is fixed and properly attached on the main side of the heat
exchanger.
Circuit breaker trips
Normal assembly
Short-circuit due to defective assembly Wiring near the heat exchanger
Circuit breaker operates
while the boiler is
running
If circuit breaker trips during the operation of the boiler, check the order of
operation, and replace the concerned part.
e.g., The circuit breaker operates at switchover to burner stage 2 after ignition.
●
Replace the dual venturi.
Remote controller power Check the wire
Check the power supply to the remote controller terminal.
If there is a problem in power supply, check the output voltage of the PCB,
and take the action separately for wiring error and defective PCB, respectively.
If the power supply is normal, replace the remote controller.