Navien NCB-150E Service Manual page 118

Check method
Fault
Water is not Cold water valve is closed
Refilled
Defective auto feeder
Water supply
Water flow over
through the condensed
water hose.
Defective heat exchanger Water leaks through the condensed water hose due to a defective heat exchanger.
Frequent 351E
Possible Causes
Turn on cold water tap and check if the valve works or is frozen.
or frozen
1. Check the auto feeder valve filter if water is not refilled.
2. Check the power supply (DC 24V).
valve
Replace the auto feeder valve if power is supplied normally.
●
3. Replace the PCB if power is not supplied.
<Check if the filter is clogged with debris>
Drain valve open Check the drain valve under the left of the main heat exchanger.
<Check if the filter is clogged with debris>
Frequent water filling can occur due to leakage of pipe. Check the leakage on the
Pipe leaks
pipe connector and distributor.
Check method
Troubleshooting 117