Have you tried contacting Pentair (1-800-831-7133)?
I figure there has to be some kind of a device to connect between a typical timer/fireman switch and the thermostat board.
*** Don't try the following at home ***
It seems like a transformer to step the voltage down and then a low voltage relay should do the trick. But this is normally where someone jumps in with why didn't you just buy X instead of doing that? Actually you'd want to change the voltage to DC to reduce the chances of inducing a current in the low voltage line due to magnetic fields. I'd still be somewhat concerned that voltage spikes could be sent when the relay is tripped.
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