Honeywell Wi-Fi Thermostat - Need "C" Wire

Reply

  #1  
Old 12-22-14, 12:05 PM
J
Member
Thread Starter
Join Date: Feb 2009
Location: USA
Posts: 14
Received 0 Votes on 0 Posts
Honeywell Wi-Fi Thermostat - Need "C" Wire

Hi All,

A common issue, I am sure. I am trying to install a newly purchased Honeywell Model RTH6580WF Wi-Fi thermostat. I have W R Y & G installed at my old thermostat, and now need a "C" wire.

My furnace is a Lennox G20Q3/4E-100-1, and on the control board, I have terminals labeled W R Y T G.

On page #16 of the installation manual (URL below), I see the terminals labeled both W R Y T G as well as W R Y C G.
http://www.lennox.com/pdfs/installat...ox_G20_IOM.pdf

Can someone "in the know" please verify for me that the "C" wire of the new thermostat should be connected to the "T" terminal on the control board of the furnace.

Also, can I use 24AWG Cat-5 (Ethernet) wiring (I have lots of 4-pair wire lying around) to go from the control board of the furnace to the thermostat?

Many thanks!

Name:  photo 1.jpg
Views: 559
Size:  37.4 KB
Name:  Pages from Lennox_G20_IOM-page-001.jpg
Views: 617
Size:  48.8 KB
 

Last edited by Johnnyboy; 12-22-14 at 01:11 PM.
Sponsored Links
  #2  
Old 12-22-14, 01:05 PM
firedawgsatx's Avatar
Member
Join Date: Jul 2013
Location: USA
Posts: 1,727
Received 0 Votes on 0 Posts
There should be two wires going outside to the a/c condenser. One wire will be connected to the Y terminal on the terminal strip and the other one will be connected to the common wire (which is what you are looking for) terminal. From the photo you posted it looks like it is probably the T terminal. If you trace that wire on the T terminal to see if it goes outside to the a/c condenser that is the terminal you will connect your C wire for the thermostat you want to install.

I would not recommend using the 24AWG wire for the thermostat. While it would probably work, it is not rated for that application. It would be much better to run an 18AWG wire. On page 15 (#6 under Electrical) of the installation guide you linked it states to use 18AWG or larger for thermostat connections.

Make sure to turn off power to furnace before making wiring connections.
 
Reply
Posting Rules
You may not post new threads
You may not post replies
You may not post attachments
You may not edit your posts

BB code is On
Smilies are On
[IMG] code is On
HTML code is Off
Trackbacks are Off
Pingbacks are Off
Refbacks are Off


Thread Tools
Search this Thread
 
Ask a Question
Question Title:
Description:
Your question will be posted in: