On 04/26/2017 9:48 PM, DoN. Nichols wrote:
....

But he was looking for something mechanical -- or with a minimum
of electrical, so something like what I pointed to, with a couple of
relays, could do it -- with minimal battery backup. And the learning
curve, with all of the options which can be set in the controllers, may
be a problem.
....

Don't know why didn't think of it before, just a thermistor in the
control circuit...hadn't thought of it before then, but the HVAC
contractor when we installed the geothermal loop added it to prevent
backup resistance heating elements from coming on until outside temp was
~25F...worked just spiffy keen.

Until, of course, we went to sell the house and the buyer's inspector
couldn't figure why it wouldn't turn on and claimed needed fixing and
I'd forgotten about it being there by then...

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