Navien NP-180 Service Manual page 95

Check method
Error type
The main heat
exchanger is
clogged.
Thudding
noise caused
by circulation
error
Defective
overheat
Defective
safety device
The temperature
Defective
fuse is discon-
safety device
©Navien America Inc. 2010
Cause
Separate inlet/outlet pipe of the main heat exchanger, and blow air
with mouth to check if the pipe is clogged.
<Check if the main heat exchanger is clogged.>
Check if the contact point of the overheat PCB is defective.
Use a tester to see if the resistance is normal (0 Ω) or abnormal (∞).
PCB
<Overheat controller>
Check, with a tester, if the temperature fuse is disconnected.
If the fuse is disconnected, replace the part and check the
nected.
cause of overheating.
NR/NP series service Manual
Check method
<Check if the overheat controller wire is disconnected.>
93
Version 2.0