Thermistor - Navien NHB-055 Service Manual

4.9.3 Thermistor

Part
Function
Failure Event
Effects
Error Code
Diagnostic
Testing/inspection
information
Temp(°F)
32~40
40~50
50~60
60~70
70~80
80~90
90~100
100~110
Version 1.0
Measure Hot water, Cold water, Space heating outlet and inlet temperatures in the boiler.
Unable to properly measure water temperature within the boiler.
1. If any of the thermistors fail, an error code appears before starting operation.
2. If resistance values are off, the boiler will produce temperature fluctuations in hot water.
E047, E205, E218, E278, E279
1. Visual inspection: Check wire connections are secure.
2. Check the resistance of the sensor (Stop operating and lower the temperature before
checking).
Resistance range : Please refer to the table below
Check if the hot water temperature sensor is open (Error type : MΩ Open)
Thermistor(kΩ)
17.9~25.4
14.5~20.3
11.4~16.4
9.4~12.8
7.5~10.4
6~8.2
5.1~6.6
4.1~5.7
Check Point
Wire Color: BLUE-BLUE
Inlet, Outlet
Exhaust Limit Temperature Sensor
Wire Color: BLUE-BLUE
Exhaust Limit Temperature Sensor(kΩ)
113.6~180.7
89.2~139.5
67.5~108.5
51.5~81.1
41.5~61.3
32.2~48.9
26.3~37.6
20.83~30.4
NHB Service Manual 67