oil burning furnace

I need to hook up a C wire to power a wi-Fi thermostat. I have an extra unused blue wire, but I don't know what to hook it up to at the furnace. I don't have the traditional wiring R W RC G Y C on the furnace. I did locate a 24V transformer coming out, but I'm not sure if I can hook the blue wire (C) to the red hot wire which is already carrying a red wire to the thermostat RH terminal.

1 Answer 1


The gray (grey) wire coming off the transformer is the C wire. You can make your connection down near the transformer, or up where the A/C condensing unit wiring connects.

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