Navien NPE-180A Service Manual page 90

Check method
Fault Possible Causes
Defective overheat
Defective safety device
Defective hot water
Temperature sensor
output temperature
error
Check if the contact point of the overheat controller is defective.
controller
Use a multimeter to see if the resistance is normal (0.3Ω) or abnormal (∞).
●
Overheat controller
1. If the hot water temperature is sensed lower than it actually is due to a defective
sensor, check if the deviation of temperature is large due to a defective
temperature sensor.
Check the output temperature displayed on the front panel.
●
sensor
2. Measure the temperature sensor resistance, and determine if the sensor is
defective.
Check method
Check if the overheat controller wire is
disconnected ( Normal 0.3Ω )
Troubleshooting 89