Author Topic: Installing smart thermostat with no "c" wire  (Read 1704 times)

Offline Sport

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Installing smart thermostat with no "c" wire
« on: July 04, 2017, 12:50:22 PM »
Anyone have experience switching a "g" to "c"?
My old thermostat doesnt have a "c" wire.  Honeywell recommends switching the "g" to the "c". In order to do that I need to move the wire in the ac untit that is currently in the "g" terminal to the "c" terminal. The problem I'm having is there is already 2 wires connected to the "c" terminal.

Offline ElectricCPR

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Re: Installing smart thermostat with no "c" wire
« Reply #1 on: July 04, 2017, 04:12:19 PM »
Your "g" wire is the "c"
G stands for ground which is a Common wire or Neutral wire in thermostats

Offline ElectricCPR

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Re: Installing smart thermostat with no "c" wire
« Reply #2 on: July 04, 2017, 04:44:39 PM »
And about the 2 wires on "c" in which picture because I don't see what you're referring to

Offline Sport

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Re: Installing smart thermostat with no "c" wire
« Reply #3 on: July 04, 2017, 09:22:16 PM »
And about the 2 wires on "c" in which picture because I don't see what you're referring to
In the 2nd picture  (the one of the unit) top left terminal is the "c" terminal. There is a red wire running into it.

Offline Sport

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Re: Installing smart thermostat with no "c" wire
« Reply #4 on: July 04, 2017, 09:23:30 PM »
Your "g" wire is the "c"
G stands for ground which is a Common wire or Neutral wire in thermostats
But in my new, smart, thermostat I need to wire it as a "c". Which means it needs ti change at the unti also.

Offline ElectricCPR

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Re: Installing smart thermostat with no "c" wire
« Reply #5 on: July 04, 2017, 09:42:50 PM »
I have 3 questions.
 1. Who put the "G" sticker on?
 2. Can I get a clear second picture so I can see what it says.
 3. Do you have a continuity and/or multi-meter

Offline Sport

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Re: Installing smart thermostat with no "c" wire
« Reply #6 on: July 04, 2017, 09:56:22 PM »


I have 3 questions.
 1. Who put the "G" sticker on?
 2. Can I get a clear second picture so I can see what it says.
 3. Do you have a continuity and/or multi-meter

1. I put those stickers on, by matching to the terminals that they are in of the current thermostat.
2. Going to bw difficult, whoever installed my unit wasnt the brightest and put the panel on the far side of the unit. I would need to climb over the unit which is in a tight crawlspace. I can tell you what each terminal is labeled if thay helps: top left - "c" top right "r", bottom middle "g".
3. Sorry dont know what those are.


Offline ElectricCPR

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Re: Installing smart thermostat with no "c" wire
« Reply #7 on: July 04, 2017, 10:27:11 PM »
My guess is "G" is your common wire. To confirm this trace the wire I circled in the picture and let me know if it connects to the metal box or to green or bare wire in the box.

Offline ElectricCPR

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Re: Installing smart thermostat with no "c" wire
« Reply #8 on: July 04, 2017, 10:28:00 PM »
Just be careful you may want to shut the power

Offline somefield

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Re: Installing smart thermostat with no "c" wire
« Reply #9 on: July 05, 2017, 10:53:57 AM »
Anyone have experience switching a "g" to "c"?
My old thermostat doesnt have a "c" wire.  Honeywell recommends switching the "g" to the "c". In order to do that I need to move the wire in the ac untit that is currently in the "g" terminal to the "c" terminal. The problem I'm having is there is already 2 wires connected to the "c" terminal.

Supco offers an "Add a wire module". Allows you to wire a 5 wire stat using 4 wires. Sells on Amazon for around $10. Simple and easy install. G'Luck!

Offline aygart

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Re: Installing smart thermostat with no "c" wire
« Reply #10 on: July 05, 2017, 12:15:35 PM »
Supco offers an "Add a wire module". Allows you to wire a 5 wire stat using 4 wires. Sells on Amazon for around $10. Simple and easy install. G'Luck!
This already has 5 wires.
Just because things turned out a certain way doesn't mean you were right.

Offline ElectricCPR

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Re: Installing smart thermostat with no "c" wire
« Reply #11 on: July 05, 2017, 12:24:14 PM »
Listen g is c

Offline Sport

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Re: Installing smart thermostat with no "c" wire
« Reply #12 on: July 05, 2017, 12:26:48 PM »
Listen g is c
What do you mean by that, I can just attach that wire to the "c" terminal in the new thermostat?

Offline as2

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Re: Installing smart thermostat with no "c" wire
« Reply #13 on: July 05, 2017, 12:55:23 PM »
What do you mean by that, I can just attach that wire to the "c" terminal in the new thermostat?
Correct.
Memories last forever, make them while you can.

Offline menachem

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Re: Installing smart thermostat with no "c" wire
« Reply #14 on: July 05, 2017, 01:27:37 PM »
Wow! quite amazing.
Hopefully we won't have any posts of pics from a plumbing issue  ;D