A.O. Smith T-D2-IN, Service Manual

Page: 67 / 78

T-D2-IN / T-D2-OS Service Manual
Ver. 1.00
67
CONFIDENTIAL
To sum it up in a chart:
Case 5 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 37°F Any NO
3 Yes Any Above 50°F NO
4 Yes 37°F and below 50°F and below YES
5 Yes Any 37°F and below YES
T-D2-OS installation:
After 25 minutes have elapsed since the T-D2-IN or T-D2-OS’s previous firing operation, the computer
will continually check the temperatures of the inlet and output thermistors. The automatic firing
system will not activate at all unless these 25 minutes have elapsed.
When the computer checks for these temperatures, the freeze protection firing system will activate if:
T
in
<
37°F and T
out
<
50°F OR T
out
<
37°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 25 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 37°F Any NO
3 Yes Any Above 50°F NO
4 Yes 37°F and below 50°F and below YES
5 Yes Any 37°F and below YES