A.O. Smith CAWH 8-455-6, Installation, User And Service Manual

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11.1.2 Displayed errors
Note
For the coding of the connections, refer to the Electrical wiring diagram.
Note
Contact your service and maintenance engineer if the error persists.
Note
Each error has a code and a description.
Display shows Error code Cause Measure
Relay error 786 Water temperature is sensed to be
rising when there is no water heat-
ing Recycle electrical power to heater. Re-
place main control board.
Upper sensor er-
ror 787 Upper tank temperature sensor is
not functioning. Replace upper tank temperature sensor.
Mid-upper sensor
error 788 Mid-upper tank temperature sensor
is not functioning. Replace mid-upper tank temperature sen-
sor.
Mid-lower sensor
error 789 Mid-lower tank temperature sensor
is not functioning. Replace mid-lower tank temperature sen-
sor.
Lower sensor er-
ror 78A Lower tank temperature sensor is
not functioning. Replace lower tank temperature sensor.
Low voltage error 78B Power supply voltage is too low. Check the power supply to the unit and
make sure it is higher than 198 VAC.
Higerror voltage
error 78C Power supply voltage is too high. Check the power supply to the unit and
make sure it is lower than 252 VAC.
Dry fire protec-
tion 78D Not enough water in tank. Fill unit completely with water. Open a
nearby hot water faucet to permit air in
the system to escape. Close the hot water
faucet when water starts to flow without
air interruptions.
Discharge over
temperature er-
ror 78E Heat pump discharge temperature is
too high. Contact a qualified installer or service
agency for repair. Refer to phone number
listed on the technical support label loca-
ted on the unit.
Discharge sensor
error 78F Heat pump discharge temperature
sensor is not functioning. Contact a qualified installer or service
agency for repair. Refer to phone number
listed on the technical support label loca-
ted on the unit.
Coil sensor error 790 Coil temperature sensor is not func-
tioning. Contact a qualified installer or service
agency for repair. Refer to phone number
listed on the technical support label loca-
ted on the unit.
Ambient sensor
error 791 Ambient temperature sensor is not
functioning. Contact a qualified installer or service
agency for repair. Refer to phone number
listed on the technical support label loca-
ted on the unit.
Suction sensor
error 792 Heat pump suction sensor is not
functioning. Contact a qualified installer or service
agency for repair. Refer to phone number
listed on the technical support label loca-
ted on the unit.
Low pressure 793 Heat pump low pressure switch is
open. Contact a qualified installer or service
agency for repair. Refer to phone number
listed on the technical support label loca-
ted on the unit.
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EN