Problems related to residential installations.
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I have a Ruud and a Rheem system that I am adding new thermostats to. The Ruud was very easy to add the C wire to. I just found the blue wire on each end, connected it to the C terminal and I was done. On the Rheem, I am not sure as to which terminal I am supposed to use. When looking at the diagram, it goes as - C - C - X - R - Y - G - W. I thought originally that the X wire was the answer, but when I tapped into that wire, it did not work. Also, the diagram shows that the brown wire is supposed to be plugged into the second C terminal, but when I opened it, the brown was plugged into the first C (the first one on the right). Could anyone give me direction as to how to proceed? Any help would be greatly appreciated!!
If you post a model number it would be helpful. The C (common) you want is the C that is directly connected to one leg of the transformer... the R being the other leg. Usually, and I say usually, the C is also connected to the furnace chassis. So to find the right C, check the AC voltage between the R and each C. The one that gives you 24 volts, AC should work. Also check for continuity between each C and the furnace chassis. The one with continuity should be the right C. Lastly check continuity between both C terminals... they may already be connected and there are 2 for convenience.