Navien NCB-180, Service Manual

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4.9.14 Circulation Pump
Part Check Point
Function
1. Pump operates when using internal or external hot water circulation.
2. Internal circulation will minimize the effect of temperature fluctuations and external circulation
delivers hot water to fixtures quickly resulting in water conservation.
Failure Event
Unable to detect or measure water flow rate when the pump is called to operate.
Effects
1. The boiler freezes.
2. Temperature fluctuations when the boiler is set to internal recirculation.
3. Hot water is not quickly available at fixtures when the boiler is set to external recirculation.
Error Code
-
Diagnostic
1. Visual inspection: Check the circulation pump connection wire.
2. * Check for blocked/clogged water filter.
3. Voltage check: Check range of voltage shown below.
Color/Number of wires
YELLOW-WHITE

ON : AC 96 ~138 V

OFF : 0V
<Circulation Pump> <Air Vent>