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Wiring in a new thermostat

My t-stat went bad on my HVAC unit so I bought a new one. Problem is, the two t-stats don't have the same letters where you wire it coding what it controls. I don't know if there are "typicals" when wiring a t-stat eg red is common white is cooling transformer etc. If there is a universal way that's cool and that would help greatly. If not then I would need to know how to distinguish what each wire is ran to then I can look at the owners book to see how to wire it in. Thanks in advance for your help.

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On the usual 24v gas heat and cool system, the red is the 24v, or power from the transformer, the white is the heat, the green is the fan (the ON setting on the thermostat not the auto) and the cool is either yellow or blue. You can connect the red to rh or rc, if the new thermostat has this, just put a jumper wire between them. If your new thermostat has a c and o connections, you may have the wrong type.

Posted on Jan 16, 2008


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