Author Topic: Thermostat Wiring  (Read 324 times)

Offline Halton

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Thermostat Wiring
« 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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Offline Admin

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Re: Thermostat Wiring
« Reply #1 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.

Offline Halton

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Re: Thermostat Wiring
« Reply #2 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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Offline Admin

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Re: Thermostat Wiring
« Reply #3 on: September 18, 2018, 07:54:38 PM »
Perfect!