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Smart Thermostat Wiring Help

  • Last Updated:
  • Aug 29th, 2021 5:40 pm
[OP]
Newbie
Mar 9, 2016
48 posts
15 upvotes

Smart Thermostat Wiring Help

I just moved to a new house and I am trying to install a smart thermostat, but I am going crazy trying to get it to work. When I match the existing wiring to what is shown on the old thermostat, the ac no longer works.

I opened the furnace to see how it was wired and it got me even more confused with how many wires there are. Hoping someone here can help me out, otherwise, I might have to call a HVAC person.

Thanks
Images
  • existing.jpg
  • furnace1.jpg
  • furnace2.jpg
  • new.jpg
5 replies
Deal Addict
Mar 29, 2015
1999 posts
154 upvotes
Wood Bridge
Looks like you also have a HRV you forgot to mention to us about. This complicates the install. I'm no expert. But waiting for other experts to chime in. You also have a two stage furnace.
Thanks
Deal Expert
Aug 2, 2004
36194 posts
9452 upvotes
East Gwillimbury
Hard to tell from that picture, but can you verify that you have 5 wires going to the thermostat? My guess is that you are probably missing the C wire

… I can see the white wire attached to the C position, but I don’t know if that is coming from the furnace
Penalty Box
Jun 24, 2015
7222 posts
2254 upvotes
0 downvotes
Something does not look right, the previous owner may have wired it up incorrectly or did some patch work to try to bring more wires to the thermostat. Is there really a HRV installed like the previous poster mentioned or just the wires roughed in? the furnace has the W2 terminal for 2 stage heat but its not hooked up at the furnace but a wire is present at the thermostat, This worries me. what else did they wire up wrong?
Say NO to the WAR!
PEACE is the answer!
[OP]
Newbie
Mar 9, 2016
48 posts
15 upvotes
Hard to tell from that picture, but can you verify that you have 5 wires going to the thermostat? My guess is that you are probably missing the C wire

… I can see the white wire attached to the C position, but I don’t know if that is coming from the furnace
Yeah, when I took off the old thermostat it looks like there is 2 bundles of wires and each bundle has 4 wires
Something does not look right, the previous owner may have wired it up incorrectly or did some patch work to try to bring more wires to the thermostat. Is there really a HRV installed like the previous poster mentioned or just the wires roughed in? the furnace has the W2 terminal for 2 stage heat but its not hooked up at the furnace but a wire is present at the thermostat, This worries me. what else did they wire up wrong?
Yeah, I think they must have had a smart thermostat before because those stickers were already on the wires. Yes, I do have an HRV system, but that has it's own controls on the first floor.

This house has two furnaces, one for the first floor and this one for the second floor. The first floor one was simple as it only had four wires and that one I was able to switch over no problem.
Deal Addict
Mar 29, 2015
1999 posts
154 upvotes
Wood Bridge
2 furnaces? Wow how big is your house?

Imagine having 2 smart thermostats wow that's asking for trouble
Thanks

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