T-M50 / T-M50 ASME Service manual
Ver. 1.05
34
CONFIDENTIAL
10-19. Freeze protection thermostat
Unit Part #
#140
AOS Part #
EM286
Checkpoint
N/A
Function
Temperature detecting device which prevents the pipes within the water
heater from freezing. When this device detects temperatures below 36.5˚F
(2.5˚C) inside the water heater, power is supplied to the electric heaters to
prevent the water heater from freezing.
Failure event
1. ON-failure (Always senses freezing temperatures, regardless of actual
temperature).
2. OFF-failure (Never senses freezing temperatures).
Effects on the water
heater if the freeze
protection
thermostat
fails
1. The freeze protection heaters will always be ON, causing heat damage to
components inside the water heater.
2. The freeze protection heaters will never be able to turn on, even under
freezing temperatures, causing freeze damage to the water heater.
Error codes when the
freeze
protection
thermostat fails
N/A
Diagnostic
1. Visual inspection: connection/breakage of wires and/or the body has been
broken.
2. Check resistance and voltage: proper range of values shown below.
Color/Number of wires
Black - Black
(itself)
ON mode: 90 to 110 VAC and less than 1 Ω
OFF mode: less than 1 VAC and more than 1 MΩ
Activation and deactivation temperature of the T-M50’s freeze protection system
ON mode: 36.5˚F (+6.3˚F -2.7˚F) 2.5˚C (+3.5˚C -1.0˚C)
OFF mode: above 46.4˚F
above 8 ˚C
7 / 8 " ( 2 2 .2 m m )
1
-
3
/
8
"
(
3
3
.5
m
m
)
1 / 4 " ( 5 .7 m m )
