Freeze Protection Heaters - A.O. Smith T-M50 ASME Service Manual

10-13. Freeze protection heaters

Unit Part #
Function
Failure event
Effects on the water
heater if heater fails
Error codes when hears
fails
Diagnostic
Color/Number of wires
water
The heater has four types of the heaters in it. All of them for protecting of the heat exchanger,
the water pipes, the water inlet and the water outlet.
Pipe heater (#408 / EKN86)
#408
#425
AOS Part #
#426
#441
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.
White -White 90 to 110 VAC (during freeze protection operation)
Heater 502 (#425 / EX001)
T-M50 / T-M50 ASME Service manual
EKN86
EX001
EX002
EKN67
N/A
For the outlet (#441 / EKN67)
28
CONFIDENTIAL
Ver. 1.05
Checkpoint
Outlet Heater
Heater (#426 / EX002)
L