Navien NHB-055 Service Manual page 84

Check method
Failure mode
Abnormal circulation
Other potential issues
84 NHB Service Manual
Cause
When check the circulation pump, the circulation pump and fan run continuously
in the error condition,
Defective circulation
In the status not occurred error
pump(external)
1. Check power supply to the circulation pump(AC 120V)
2. Replace the PCB if power is not supplied
1. Check if the strainer is clogged with debris
The heating strainer is
2. Check the cause of debris if the strainer is clogged (Aluminium distributor
clogged
The main heat exchanger Separate the inlet / outlet pipe from the main heat exchanger, and blow air
is clogged. through the heat exchanger to check if the pipe is clogged.
Check heating inlet / outlet valve and heating manifold piping.
Valve closed
At least one valve on the heating manifold must always be open.
Sudden increase of temperature due to PCB DIP S / W model setting error or max
setting.
Capacity setting
Defective PCB If the trouble continues despite the checking of above items, replace the PCB.
oxidized steel, etc.)
Capacity
55,000 BTU (NHB-055)
80,000 BTU (NHB-080)
110,000 BTU (NHB-110)
150,000 BTU (NHB-150)
Check method
DIP S / W No.
1-5
OFF
ON
OFF
ON
1-6
OFF
OFF
ON
ON
Version 1.0