5.2.12 218Error
Error conditions and Check Items
Heat exchanger
input
temperature
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 input temperature sensor connector is wet due to any reason, including
leakage.
2.
Replace the defected heat exchanger input temperature sensor.
3.
Replace the controller.
normal?
Resistance between #3 and #4 of CN13 is from
0.437k
Ω
to 176k
Ω
at normal condition.
56 for Wiring Diagram)
(#3 and #4 of CN 13)
Before measuring resistance of the thermistor,
detach the connector from the PCB.
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