T-K3 Service Manual
Ver. 1.05
60
CONFI DENTIAL
12-16. Freeze protection system
There are tw o features to the T-K3’s freeze protection system: the automatic firing system and
the ceramic heating blocks. The automatic firing system allow s the T-K3 to briefly fire on for
about 4 seconds and the ceramic heating blocks w ill heat up w hatever portion of the heat
exchanger the blocks are strapped to. The firing system mainly focuses on providing freeze
protection around the heat exchanger drum. The three heating blocks focus on protecting the
inlet and outlet piping inside the T-K3, as w ell as the front drum pipe. The conditions to activate
either feature are different from each other. How ever, the tw o features are not mut ually
exclusive, because they focus on different areas of the T-K3. As long as each particular
feature’s activation requirements are met, it is possible for both f eatures to operate at the same
time.
Automatic firing system
Activation conditions w ill depend on the on w hether or it is an indoor / direct-vent or outdoor
installation. Gas and electrical pow er are required for this feature to operate.
Indoor / direct-vent installation:
After 5 minutes have elapsed since the T-K3’s previous firing operation, the computer w ill
continually check the temperatures of the inlet and outlet ther mistors (the outlet ther mistor is the
one that checks the temperature of the w ater immediately leaving the heat exchanger, not the
water leaving the T-K3, w hich is mixed w ith w ater from the bypass valve). The automatic firing
system w ill not activate at all un less these 5 minutes have elapsed.
When the comput er checks for these temperatures, the freeze protection firing system w ill
activate if:
T
in
≤ 39°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 outlet ther mistor.
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