218Error - Navien NCB-180 Service Manual

5.2.12 218Error

Error conditions and Check Items
Error
E218
Heat exchanger
If an error (open: 14°F (-10°C) or lower) in the heat exchanger input temperature sensor is detected, the system
input
displays the 421E error on the front panel. If this occurs, the boiler initiates shutdown.
temperature
sensor open
1. Check if the heat exchanger input temperature sensor connector is wet due to any reason, including
leakage.
Check items
2. Replace the defected heat exchanger input temperature sensor.
3. Replace the controller.
102 NCB Service Manual
Is the inlet thermistor
normal?
Yes
Check connector
(#3 and #4 of CN 13)
Description
NO
Replace inlet thermistor
Resistance between #3 and #4 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