Installing Honeywell Wifi Thermostat - G wire to C terminal
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Installing Honeywell Wifi Thermostat - G wire to C terminal
Hi everyone, I dont know much about HVAC's and would really appreciate some help. I am trying to install a new Honeywell Thermostat in our apartment that has centralized AC. My old thermostat had a G wire and no C wire and the Honeywell manual said to put the G wire into the C terminal. Then, also move the G wire to the C terminal on the cooling and heating unit's board and put a jumper cable on the Y and G terminal as well.
I'm not surr what to do because I dont see any letters on the overhead unit as seen on the picture. How can I install the thermostat correctly? Thank you in advance.
I'm not surr what to do because I dont see any letters on the overhead unit as seen on the picture. How can I install the thermostat correctly? Thank you in advance.


#2
Welcome to the forums.
We keep one topic in one thread so your other post in the second thread is gone.
We need to know what that is there. That is not a standard split A/C system.
We need to know it's make and model number.
or we need the make and model of the old thermostat and what color wire was on each terminal.
We keep one topic in one thread so your other post in the second thread is gone.
We need to know what that is there. That is not a standard split A/C system.
We need to know it's make and model number.
or we need the make and model of the old thermostat and what color wire was on each terminal.
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I will try to find out the make and model of the ac unit from the management company but the thermostat present now is White & Rodgers 1F78. Here is a photo of it. Pls note there are 2 wires in Y terminal.



#5
White & Rodgers 1F78-??? . That's a partial model number.
DO NOT rush to install the new stat. There are questions here yet.
Your stat is currently wired in a heat pump format. It may not be a heat pump but it is using the O (heat pump) terminal.
I see....
G = green
W = white
Rh + Rc = red
Y = ? color
Is Y jumpered to O ?
DO NOT rush to install the new stat. There are questions here yet.
Your stat is currently wired in a heat pump format. It may not be a heat pump but it is using the O (heat pump) terminal.
I see....
G = green
W = white
Rh + Rc = red
Y = ? color
Is Y jumpered to O ?
#11
Ok....great.
You do have a heat pump system with no back up electric heat.
You must live in a fairly warm area to not have back up/emergency heat.
G = green
Rh + Rc = red
Y = yellow
O = white
We're almost there. We need to locate the C. You've posted two pictures of the wiring.
Can you spread the wiring out and take a few more pictures ?
The C is there I just need to ID it.
You do have a heat pump system with no back up electric heat.
You must live in a fairly warm area to not have back up/emergency heat.
G = green
Rh + Rc = red
Y = yellow
O = white
We're almost there. We need to locate the C. You've posted two pictures of the wiring.
Can you spread the wiring out and take a few more pictures ?
The C is there I just need to ID it.
#13
I need a picture of the wiring at your A/C end where the blower is. I can't ID the colors.
BUT.... this is good. Look at your cable..... you have a spare blue wire. That will be C.
Try to trim your wires so there isn't so much bare wire. If that shorts you'll lose your system.
BUT.... this is good. Look at your cable..... you have a spare blue wire. That will be C.
Try to trim your wires so there isn't so much bare wire. If that shorts you'll lose your system.
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Ok. So I should use the Heat Pump Terminals of the New Thermostat?
What should I do about the Jumper Cable in Y and W on the old jumper since there is no W Terminal on the Heat Pump Set of Terminals on the new thermostat.
What should I do about the Jumper Cable in Y and W on the old jumper since there is no W Terminal on the Heat Pump Set of Terminals on the new thermostat.

#16

Sorry.... I can SEE the colors. Too much paint.
Is that the thermostat cable ?
Is the the spare blue wire wrapped around there ?
Look at the A/C comp cable. What colors are connected in it ?
I'll give you the wiring as soon as I see it.
#18
Acetone would probably work.
You don't see any wiring diagram posted there... do you ?
I think I Id'ed the cables correctly. The stat one should have the same colors as at the thermostat.
The other cable should be going to the A/C condensor. That's the one we need the colors.
There should be a yellow, red, white and the C wire.
What large wire colors do you have coming down from the unit ?
In the picture I see yellow, blue, brown.
You don't see any wiring diagram posted there... do you ?
I think I Id'ed the cables correctly. The stat one should have the same colors as at the thermostat.
The other cable should be going to the A/C condensor. That's the one we need the colors.
There should be a yellow, red, white and the C wire.
What large wire colors do you have coming down from the unit ?
In the picture I see yellow, blue, brown.
#21
Ok.... I think we're set.
Connect the spare blue wire at the back of the stat to C.
In the picture.... the blue wire in the A/C cond. cable is C.
So that means you need to unwrap the spare blue wire from the stat cable and connect it to the blue wire. You will probably have a connection of 3 blue wires there.
Connect the spare blue wire at the back of the stat to C.
In the picture.... the blue wire in the A/C cond. cable is C.
So that means you need to unwrap the spare blue wire from the stat cable and connect it to the blue wire. You will probably have a connection of 3 blue wires there.

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Thanks So much Pete!
Last, I see a Jumper in Y and W on my opd thermostat. If I use the letters for Heat Pump on my new thermostat, there is no terminal for W. only the Conventional Row has that letter. How do I go about that?
Last, I see a Jumper in Y and W on my opd thermostat. If I use the letters for Heat Pump on my new thermostat, there is no terminal for W. only the Conventional Row has that letter. How do I go about that?

#23
You will use the heat pump connections.
G = green
R + Rc = red
Y = yellow
O/B = white
C =blue
No Y to W jumper needed.
G = green
R + Rc = red
Y = yellow
O/B = white
C =blue
No Y to W jumper needed.
