Navien CH-180 Service manual - page 91
89
The surface temperature rises due to defective heat
exchanger.
Replace the heat exchanger.
If the trouble continues despite the checking of above
items, replace the PCB.
disconnected.> Abnormal thermistor No circultion Other trouble Abnormal space heating supply thermistor The heat exchanger is clogged. heat exchanger overheated Defective PCB This trouble occurs if the heating supply thermistor senses the temperature lower than that of the actual heating water temperature. Replace the heating supply thermistor. 1. Check if the heat exchanger is clogged. Separate supply/return pipe of the heat exchanger, and blow air with mouth to check if the pipe is clogged. If the 16 Error occurs when hot water is used only, check if the DHW heat exchanger is clogged. ©Navien America Inc. 2010 CH series service Manual Version 1.0