Freeze Protection Heaters - A.O. Smith Water Heater 520 Direct Vent Indoor Service Manual

10-17. Freeze protection heaters

Unit Part #
Function
Failure events
Effects on the water
heater if heater fails
Error codes when
heaters fails
Diagnostic
Color/Number of wires
3 array heater (#454 / 319143-116)
Pipe heater
(#426 / 319143-089)
For heat exchanger
Heater
#405
#415
#426 AOS Part #
#453
#454
Prevents the heat exchanger, water valves, and water pipes within the water
heater from freezing. The heaters are but one of the freeze protection
devices in the water heater.
Open circuit failure: Ceramic heaters do not receive the voltage needed to
heat up.
Ceramic heaters do not activate, allowing water contained in the heat
exchanger to freeze up, possibly causing the heat exchanger to burst.
1. Visual inspection: connection/breakage of wires and the condition of the
heaters.
2. Check: whether those are in the normal range as shown in the following
table.
Black - Black 90 to 110 VAC (during freeze protection operation)
Flat Heater (#453 / 319143-115)
520 Indoor / 520 Outdoor Service Manual
319143-068
319143-078
319143-089
319143-115
319143-116
N/A
For the outlet pipe
(#415 / 319143-078)
35
CONFIDENTIAL
Ver. 1.00
Checkpoint B1
Heater (#405 / 319143-068)