205Error - Navien NCB-180 Service Manual

Check method
Fault Possible Causes
Abnormal flow of
110E
intake air supply /
Exhaust blockage
Condensate drain
Condensate drain error
error
Deformed or clogged
Defective air
supply/exhaust
Exhaust gas flows in
flue
through the supply

5.2.11 205Error

Error conditions and Check Items
Error
E205
Heat exchanger
If an error (open: 14°F (-10°C) or lower) in the heat exchanger input temperature sensor is detected, the system
output
displays the 421E error on the front panel. If this occurs, the boiler initiates shutdown.
temperature
sensor open
1. Check if the heat exchanger output temperature sensor connector is wet due to any reason, including
leakage.
Check items
2. Replace the defected heat exchanger output temperature sensor.
3. Replace the controller.
100 NCB Service Manual
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:


exhaust

2. Replace the old PCB with the latest version.
Exhaust air is blocked due to condensate drain error.



1. Check the exterior of the flue for damage and obstructions.
flue
2. Check if rainwater is collected due to vertical installation of the air intake pipe.
If the exhaust gas enters into the air supply pipe, abnormal combustion may cause
E110.
pipe 
Is the inlet thermistor
normal?
Yes
Check connector
(#7 and #8 of CN 13)
Check method
Air supply / exhaust vent for any blockages.
Blocked condensate drain
If the air pressure sensor hose is broken or clogged.
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.
Check the installation of the flue.
Description
NO
Replace outlet thermistor
Resistance between #7 and #8 of CN13 is from
0.437kΩ to 176kΩ at normal condition.
(see page 56 for Wiring Diagram)
Before measuring resistance of the thermistor,
detach the connector from the PCB.
Version 1.0