New wifi thermostat install?


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Old 07-10-14, 03:15 PM
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New wifi thermostat install?

I have a Honeywell RTH6580WF to replace an old mercury thermostat. The old one has four wires attached to it, Y, W, G, R in their respective places. There was also a Blue wire that was not attached. I'm assuming I can use this as the C wire to draw power, but in looking at the circuit board on our system I'm at a loss of where to actually do this. The pics I'm attaching look like someone just did a real number on it, but I'm hoping someone can help. My best guess is to use the existing blue wire that is just wound around the brown part and put it onto the COM on the circuit board. BUT there is already a red wire there that when I trace is runs into the ceiling and disappears. I would appreciate ANY help!Name:  IMG_3271.jpg
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Old 07-10-14, 03:24 PM
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Yes, land the B wire on the 24v com. Looks like some one ran 24v to some thing else, Door bell?
 
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Old 07-10-14, 03:26 PM
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We think it runs outside to the compressor or condenser or fan. Is it okay to have them both in the com?
 

Last edited by nook82; 07-10-14 at 03:29 PM. Reason: Wrong word
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Old 07-10-14, 04:23 PM
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Yes it is normal to see two wires on Y and two wires on C.



Color codes vary.
 
 

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