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HVAC Forums => HVAC Help => Topic started by: Halton on September 18, 2018, 09:17:11 AM

Title: Thermostat Wiring
Post by: Halton on September 18, 2018, 09:17:11 AM
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Hello..... trying to install a new Honeywell Lyric T5 Thermostat

It requires a "C" wire ..... or use of the "G" wire work-around as per instructions

But current set-up seems a little odd..... see attached wiring diagram

As shown..... existing wire to Thermostat is 4 conductor

Any help on how to proceed is much appreciated....  ;)


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(http://i65.photobucket.com/albums/h235/T_Bone_1962/Furnace%20Wiring.jpg) (http://s65.photobucket.com/user/T_Bone_1962/media/Furnace%20Wiring.jpg.html)


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Title: Re: Thermostat Wiring
Post by: Admin on September 18, 2018, 09:20:17 AM
Just remove the G wire from the thermostat and connect it to the C terminal on the new thermostat.  Then remove the G wire from the furnace and connect it to the C terminal with the other wire going to the AC.

The Y wire from the thermostat should not go directly to the AC.  It should go to the Y terminal in the furnace, then go to the AC, otherwise the furnace fan may not start on a call for cooling.  You should end up with 2 wires on the furnace C terminal and 2 wires on the furnace Y terminal.
Title: Re: Thermostat Wiring
Post by: Halton on September 18, 2018, 07:53:15 PM
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ok perfect..... I think I got it now.....  :)

It should look like this in the end...... correct? .......  see new diagram

Wire colours changed for clarity


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(http://i65.photobucket.com/albums/h235/T_Bone_1962/Furnace%20Wiring%202.jpg) (http://s65.photobucket.com/user/T_Bone_1962/media/Furnace%20Wiring%202.jpg.html)


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Title: Re: Thermostat Wiring
Post by: Admin on September 18, 2018, 07:54:38 PM
Perfect!