Wiring – Adding C wire for wireless thermostat

hvacthermostatthermostat-c-wirewiring

I'm trying to install a new wireless thermostat but my old setup only uses 2 wires; one white and one red. On the side of my furnace there is this transformer mounted.

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There are four cables on the other side of the transformer; white, black, blue and yellow.

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The white cable going to the thermostat is tied in with the blue cable from the transformer. Would I able to use any of the other cables from my transformer as my connection for the C wire? Any help would or tips would be appreciated. Let me know if you need any additional information. Thank you
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Best Answer

Blue and yellow are 0v and 24v, since blue is fed to the stat, the yellow is 0v for the "C" connection.

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