Flow Sensor - Navien NPE-180A Service Manual

4.11.11 Flow Sensor

Part
Function To detect water flow in GPM (Gallons Per Minute) for steady hot water temperatures.
1. Unable to detect or measure water flow rate.
Failure Event
2. Damage to and/or water leakage from the water flow sensor.
Effects Ignition sequence does not start.
Error Code E439
1. Visual inspection: Connection and/or breakage of wires.
Diagnostic
2. Visual Inspection: Check for damage and/or scale formation on sensor.
68 NPE Service Manual
Check Point
Version 2.21