Navien NCB-700-2S+/42K Service Manual page 67

Testing methods
Error type
Circulation errors
Other faults
66 Troubleshooting
Cause
The circulation pump and fan run continuously in the error condition.
Circulation pump fault
1. Check the power supply to the circulation pump (AC 230 V).
2. Replace the PCB if power is not available at the pump.
Check that the 3-way valve is operating correctly in DHW mode.
If there is no temperature change in temperature;
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3-way valve fault
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1. Check if the strainer is obstructed by debris.
Heating strainer is
2. Identify the type of debris caught in the strainer (aluminium, oxidised
obstructed
1. Disconnect the inlet and outlet pipes from the main heat exchanger. Blow
Heating or DHW heat
exchanger is obstructed.
2. If E001 occurs in DHW, check if the DHW heat exchanger is obstructed.
Check the heating inlet and outlet valves and the heating manifold pipes.
Valve closed
At least one valve on the heating manifold must always be open.
Sudden temperature increases due to PCB DIP switch setting errors or
exceeding maximum settings.
Model settings
PCB faults If the error condition remains after checking these items, replace the PCB.
Testing method
RED + WHITE (AC 230 V): Heating
RED + PURPLE (AC 230 V): Hot water
3-way valve is faulty if the voltage is normal.
PCB fault is the voltage is not available at the 3-way valve.
steel, etc.) to help identify the cause of the obstruction.
air through the heat exchanger to check if the pipes are obstructed.
Model
NCB700-2S+/42K
NCB700-3S/54K
DIP Switch Settings
3 4
OFF ON
ON ON