12-14. Freeze protection system
There are two features to the 510 Indoor or 510 Outdoor’s freeze protection system: the automatic firing
system and the ceramic heating blocks. The automatic firing system allows the 510 Indoor or 510
Outdoor to briefly fire on for about 4 seconds and the ceramic heating blocks will heat up whatever
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 510 Indoor or 510 Outdoor, 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 510 Indoor or 510 Outdoor. As long as
each particular feature’s activation requirements are met, it is possible for both features to operate at
the same time.
Automatic firing system
Activation conditions will depend on the on whether or it is an indoor / direct-vent or outdoor
installation. Gas and electrical power are required for this feature to operate.
510 Indoor installation:
After 5 minutes have elapsed since the 510 Indoor or 510 Outdoor’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 510 Indoor or 510 Outdoor, which is mixed with water from the
bypass valve). The automatic firing system will not activate at all unless these 5 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.
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