Navien NCB-150E Service Manual page 88

Check method
Failure mode
Defective circulation
Defective 3-way valve
The heating strainer is
The main heat or
Abnormal circulation the hot water heat
exchanger is clogged.
Valve closed
Cause
When check the circulation pump, the circulation pump and fan run continuously in the
error condition,
In the status not occurred error, set PCB DIP S/W #1 on and.
pump
1. Check power supply to the circulation pump(AC 120V)
2. Replace the PCB if power is not supplied
Check for proper operation of the 3-way valve while the unit is in DHW mode.
If there is no change in temperature,
1. Red + Black (AC 120V) : Heating
2. Blue + Black (AC 120V) : Hot water
3. Defective 3-way valve if power is normally supplied
4. Defective PCB if power is not supplied
1. Check if the strainer is clogged with debris
2. Check the cause of debris if the strainer is clogged(Aluminum distributor oxidized
clogged
steel, etc.)
1. Separate the inlet/outlet pipe from the main heat exchanger, and blow air through
the heat exchanger to check if the pipe is clogged.
2. If the Error 001 only occurs when the DHW is used, check if the hot water heat
exchanger is clogged.
<Check if the hot water heat exchanger is clogged>
Check heating inlet/outlet valve and heating manifold piping.
At least one vlave on the heating manifold must always be open.
Check method
Troubleshooting 87