use of "C" (common) wire in digital thermostat


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Old 12-29-08, 05:54 PM
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use of "C" (common) wire in digital thermostat

I bought a new programmable thermostat yesterday and hooked it up without any problem, works great. In reading the documentation, it says that if I use the 'C' wire, that the thermostat can utilize a remote control that came with the unit. The 'C' wire also powers the display panel and only utilizes the batteries if the power is off (power outage).
I'd like to utilize the 'C' wire; however, I'm not sure how to do it. Calling a repair company will cost at least $75-100. I am a computer network specialist so I figure if someone helps me I can certainly do this.
The wires I connected to the thermostat are R G Y W RC. There are other wires in the bundle that aren't used (ie: blue, orange, black, etc).
They terminate on a circuit board on my Lennox C26-31FC-1 system on their respective color screw-downs. There is a 'C' screw-down with a wire attached but it's not a color that is in the bundle terminating at the thermostat.
If someone can possibly help me with this, I could easily send a digital picture of the circuit board where the wires terminate.
Would it be as easy as using any one of the unused wires in that bundle (say the orange one) and connecting it the the 'C' connector on the thermostat and then the 'C' screw-down on the circuit board?
 
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Old 12-29-08, 07:04 PM
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Yes, it is that easy. I recommend that you use the blue because orange and black are often used with heat pump systems.

BTW, the wire now on the C terminal of your system is going to the condensing (outside) unit of your air conditioning.
 
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Old 12-29-08, 07:11 PM
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So I just add the blue wire on top of the wire that's already connected on the board, then use the other end of the blue wire at the thermostat and connect to the 'C' terminal?
Really? I was just joking about it being that easy

I was wondering where the existing wire was going to because I tried to follow it, assuming it would follow the thick bundle of wires, but obviously not!

Thanks!!!!
 
 

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