Help finding C *terminal* inside the furnace


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Old 01-22-15, 07:52 PM
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Help finding C *terminal* inside the furnace

Hello,

I just bought a Honeywell wifi RTH8500 series thermostat and need help finding the "C" wire inside the furnace. I don't have the C wire installed and trying to do the GC bypass configuration that Honeywell and others show how to do on youtube. My problem is my furnace does not have terminals but wires attached via wirecaps. I can figure out most of this Except for the darn C wire inside the furnace. I see r, w and green coming from the circuit board and there is a label attached identifying them. But the label says blue is C but the only other wire I see is gray. Maybe it was blue at one time but it's going to the frame, so I am guessing this is ground. Should the C terminal/wire come from the circuit board or is it a ground wire?


I am not sure if this is normal or not but I have 2 transformers on this system:

1 near the circuit board that does say 24 volts. And another mounted on the wall near the furnace. It has two wires - 1 that connects the gray/blue wire that goes to ground near the circuit board. the other goes to the yellow wire going directly to the thermostat . Last weekend I measured the output across this transformer and got about 20 volts.

My furnace has no label on it but an AC repair guy told me the name once. I can't remember but I think it starts with a G. It is old original with the house which was built in Nov , 1980 if that helps.

So I guess what I am asking is C normally a ground wire ??

Thanks!
 
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Old 01-22-15, 08:14 PM
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Goodman

Yes, C is ground.
 
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Old 01-22-15, 08:35 PM
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Thank you. It doesn't look difficult to run a new 5 wire cable through the wall. I may do that instead of the cg setup. Just needed to know what the C wire actually was.

And now that you said the name, Goodman is what he told me.
Thanks again!
 
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Old 01-24-15, 09:02 PM
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The new wire install went fine and everything is a go. It was actually more difficult to get the wifi going(they have an issue with WPA security) than installing the new wire. But all go now. thanks..off to ask some general ac questions.
 
 

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