A.O. Smith RPV series Installation Instructions And Use & Care Manual page 20

Display
E14 4-Chamber models only:
Outlet thermistor open (TH-4).
E20 Inlet thermistor shorted.
E21
Shorted
thermistor.
E22 2-Chamber models:
TH-2 thermistor is shorted.
4-Chamber models:
TH-3 thermistor is shorted.
E23 4-Chamber models only:
TH-2 thermistor is shorted.
E24 4-Chamber models only:
TH-4 thermistor is shorted.
E51 Communica ons Failure. The
& user interface has lost connec on
E52 with the control board.
20 • Electric Tankless Water Heater
Description
1.
2.
3.
4.
5.
2- and
4-Chamber
models:
TH-1 shorted.
Point-of-use
models:
T-Out shorted.
Replace the temperature sensor that is listed in the le -hand column.
See "Thermistor (Temperature Sensor) Replacement" on page 25.
Turn off power to the water heater. Contact Technical Support.
Action / Solution
Turn off power to the water heater.
Check the connec ons of the thermistor in ques on.
Disconnect the thermistor, then reconnect it.
Turn on power to the water heater.
Does the error code reoccur? If yes, turn off power and replace the
thermistor that is listed in the le -hand column. See "Thermistor
(Temperature Sensor) Replacement" on page 25.