T-M50 / T-M50 ASME Service Manual
Ver. 1.05
76
CONFIDENTIAL
12-21. Freeze protection system
There are two features to the T-M50’s freeze protection system: the automatic fan motor system and the
ceramic heating blocks. The automatic fan motor system allows the T-M50 to briefly do fan motor
operation and the ceramic heating blocks will heat up whatever portion of the heat exchanger the blocks
are strapped to.
The automatic fan motor mainly focuses on providing freeze protection from the back flow of the
venting. The seven heating blocks focus on protecting the inlet and outlet piping inside the T-M50, as
well as the front drum pipe. The conditions to activate either feature are different from each other.
However, the two features are not mutually exclusive, because they focus on different areas of the
T-M50. As long as each particular feature’s activation requirements are met, it is possible for both
features to operate at the same time
Ceramic heating blocks
The blocks will only activate based on what the freeze protection thermostat senses. The thermostat is
located on the fan motor. Electrical power is required for this feature to operate.
The heating blocks will activate if the thermostat senses a surrounding temperature below 36.5°F.
Once they are on, the heating blocks will only deactivate if surrounding temperatures reach above
46.4°F.
Automatic fan motor system
This feature is for only Indoor installation.
Electrical power is required for this feature to operate.
The computer will continually check the temperatures of the inlet, outlet and mixing
thermistors.
Automatic fan motor will not work if the “Activation of the fan motor freeze protection system”
is disabled. See section12-6.
<Activate condition>
When the computer checks for these temperatures, the Automatic fan motor system will activate if:
T
out
< 41°F AND T
out
< T
in
- 5°F
where T
in
is the temperature of inlet thermistor and T
out
is the temperature of the output thermistor.
