T-M50 / T-M50 ASME Service Manual
Ver. 1.05
78
CONFIDENTIAL
Automatic firing system
Activation conditions will depend on the on whether or it is a direct-vent installation. Gas and electrical
power are required for this feature to operate.
T-M50 direct-vent installation:
After 2 minutes have elapsed since the T-M50 direct-vent’s previous firing operation, the computer
will continually check the temperatures of the inlet and output thermistors (the output thermistor is
the one that checks the temperature of the water immediately leaving the heat exchanger, not the
water leaving the T-M50 direct-vent, which is mixed with water from the bypass valve). The
automatic firing system will not activate at all unless these 2 minutes have elapsed.
When the computer checks for these temperatures, the freeze protection firing system will activate if:
T
in
<
39°F and T
out
<
50°F OR T
out
<
39°F
where T
in
is the temperature of inlet thermistor and T
out
is the temperature of the output thermistor.
To sum it up in a chart:
Case 2 minutes have elapsed
since prior operation?
Inlet
thermistor
temperature
Output thermistor
temperature
Will
automatic
firing be activated?
1
No
Any
Any
NO
2
Yes
Above 39°F
Any
NO
3
Yes
Any
Above 50°F
NO
4
Yes
39°F and below
50°F and below
YES
5
Yes
Any
39°F and below
YES
