Navien NCB-180, Service Manual

Page: 103 / 149

100 NCB Service Manual Version 1.0
Check method
Fault Possible Causes Check method
110E
Exhaust blockage
Abnormal flow of
intake air supply /
exhaust
1. If 110E occurs intermittently during ignition or combustion, compare the
standard RPM with the current RPM at Min / Max combustion (dip switch 1-
1&1-2). If the current RPM is higher than normal, check the following:

Air supply / exhaust vent for any blockages.

Blocked condensate drain

If the air pressure sensor hose is broken or clogged.
2. Replace the old PCB with the latest version.
Condensate drain
error
Condensate drain error
Exhaust air is blocked due to condensate drain error.

Check if the condensate hose or the siphon is frozen.

Check if the condensate hose is kinked.

Remove bottom of trap and verify it is not blocked.
Defective air
supply/exhaust
flue
Deformed or clogged
flue
1. Check the exterior of the flue for damage and obstructions.
2. Check if rainwater is collected due to vertical installation of the air intake pipe.
Exhaust gas flows in
through the supply
pipe
If the exhaust gas enters into the air supply pipe, abnormal combustion may cause
E110.

Check the installation of the flue.
5.2.11 205Error
Error conditions and Check Items
Error Description
E205
Heat exchanger
output
temperature
sensor open
If an error (open: 14°F (-10°C) or lower) in the heat exchanger input temperature sensor is detected, the system
displays the 421E error on the front panel. If this occurs, the boiler initiates shutdown.
Check items
1. Check if the heat exchanger output temperature sensor connector is wet due to any reason, including
leakage.
2. Replace the defected heat exchanger output temperature sensor.
3. Replace the controller.
Is the inlet thermistor
normal?
Resistance between #7 and #8 of CN13 is from
0.437k
Ω
to 176k
Ω
at normal condition.
(see page 56 for Wiring Diagram)
Check connector
(#7 and #8 of CN 13)
Replace outlet thermistor
Before measuring resistance of the thermistor,
detach the connector from the PCB.
NO
Yes