two heating systems off of 1 thermostat?

Discussion in 'HVAC Heating & Cooling' started by g_eakin, Nov 17, 2008.

  1. g_eakin

    g_eakin New Member

    Nov 15, 2008
    I have a geothermal system run off of a thermostat. Also I have a Alaska coal furnace run off of a thermostat. The two heating systems are fighting. I’m told that I can put a relay on the Y1 wire and turn on the coal furnace when the geothermal thermostat calls for heat. Can someone tell me about this relay?

  2. jadnashua

    jadnashua Retired Defense Industry Engineer xxx

    Sep 2, 2004
    Retired Systems engineer for defense industry.
    New England
    A thermostat is basically a temperature controlled switch. To turn on a heating device, all you need is to connect the two thermostat wires together. A simple single-pole 24vac relay will be fine. Basically, connect the relay with the two leads of the thermostat from one heating system you want to control on the common and normally open sides fo the relay, and the coil wires connected to the common and output of the thermostat from the other. Then, when one system's thermostat turns on, it will energize the relay, emulating the thermostat of the other furnace.

    If you search on isolation relay, you should get some examples.
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  4. g_eakin

    g_eakin New Member

    Nov 15, 2008
    Thanks Jim,

    >> ... search on isolation relay ...

    Now I see. I do electronics for a living instead of electricity or heating/cooling. The terminology was the source of my confusion.

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