Navien NHB-055, Service Manual

Page: 110 / 147

110 NHB Service Manual Version 1.0
Check method
Fault Possible Causes Check method
Defective sensor
Defective temperature
sensor connector
Check if the temperature sensor is open and if the connector is connected
properly.
Temperature sensor
Check the resistance of the temperature sensor. (Defective if it is 30kΩ or higher)
●
Replace the temperature sensor if the resistance value is abnormal.
(refer to page 67)
●
Check the temperature displayed on the front panel.
(refer to page 38)
Possible Issues
Defective PCB If the issues continue despite checking the items above, replace the PCB.
<Heat exchanger input temperature sensor / connector>
Check if the hot water temperature sensor is open (Error type : MΩ Open)