Navien NP-180 Service Manual page 103

Check method
Error
Defective heat
exchanger
Heat exchanger
over-heated
Defective
overheat
Defective
Other trouble
©Navien America Inc. 2010
Cause
1. The error occurs due to high exhaust gas temperature caused by
the defective heat exchanger.
2. The error occurs due to high temperature due to the heat leaked
from the heat exchanger.
3. Replace the heat exchanger.
Defective contact point of the exhaust gas overheat controller (149 )
Check connection of the overheat controller.
Remove the PCB and check, with a tester, the resistance
PCB
(M Ω defect).
< Check the overheat controller >
If the trouble continues despite the checking of above items,
replace the PCB.
PCB
101
NR/NP series service Manual
Check method
Version 2.0