Columbia Furnace and Honeywell Thermostat Wiring


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Old 10-23-14, 04:14 PM
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Columbia Furnace and Honeywell Thermostat Wiring

So my wife got a new wifi thermostat and I went to hook it up, and I can tell this is gonna be trouble.

The house is 40+ years old, has an oil burner furnace, and an AC unit outside.
Will someone tell me if this is wired up correctly currently, and what my options are for hooking up this new thermostat.

Thermostat side I have 5 wires > that go to terminals on the furnace side
W > T on furnace
RH > T on furnace
RC >R on furnace
G > G on furnace
Y/Y1 > to black wire from control box from power company to control peak usage.

Then a red wire comes back from the control box and is connected to a white wire that goes to the AC unit, a red wire from the AC unit goes to the C terminal on the Furnace, and there is a Green wire unused from the AC unit.

Its all kinda sloppy and looks like crap, Im half tempted to rip everything out and start over

The new thermostat (Honeywell RET97E5D) standard wiring is expecting G,W,C,Y,R (C to supply power to the thermostat, and I dont have a spare wire in the bundle to use to power it with) I read about using the G wire, but it didnt make sense to me with how mine is wired...

I have a few pics to help









 
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Old 10-23-14, 04:38 PM
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Post approved....

Pros will be with you shortly... welcome to the forums....
 
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Old 10-24-14, 07:41 AM
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Welcome to the forums!! The best solution to get a wire to the C terminal at your thermostat is to run a new wire. If that is not possible due to obstacles or difficulty in doing so, you can use the G wire as follows:

Move the wire from G to C at the thermostat and the furnace
Place a jumper wire from Y to G at the furnace
At the furnace you should end up with 3 wires on Y, 2 wires on C, 1 wire on W, and 1 wire on G if you have a single stage condenser.
 
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Old 10-24-14, 01:45 PM
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Thanks.

Forgive my ignorance, but are the y and c wires from the condenser the two wires I have coming from AC unit outside? And what would happen to the two wires going to the T terminals on the furnace?

I am leaning more towards running new wires any way though, and replacing whats there. I currently have 5 wires, I know i need at least 1 more for the C wire. Is 8 conductor the most I would likely ever need? I would rather not have to do this again in the future.
 
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Old 10-24-14, 02:16 PM
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Yes, the Y and C wires are the two wires that go outside to the a/c condenser.
I have attached a diagram that should get you wired up if you want to use the G wire as a C wire.
It is always better to run a cable with more wires than you require for future upgrades. Eight conductors should be enough for most applications.
 
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