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I am having some difficulty figuring out the correct wiring for my new wifi thermostat. Before I bring out the A/C technician, I was wondering if anyone here might be able to help? Searched other threads and did not see one that applied to my situation...

It is a Honeywell RTH65800WF, watched all of their videos and spoke with their support department and still no luck, so here it goes:

Existing Thermostat Terminals:

  • G - Green Wire,
  • Y - Blue Wire (previous owner wrote a B next to Y label),
  • W - White Wire,
  • RH - Red Wire (with jumper to RC terminal) (previous owner appears to have highlighted the R),
  • B - Empty,
  • O - Empty,
  • RC - Jumper to RH terminal

Existing AHU Terminals:

  • C - Blue Wire,
  • R - Red Wire,
  • G - Green Wire,
  • Y/Y2 - Yellow and Gray Wires (not sure where these lead to , but I think to outside unit),
  • O - Empty,
  • W1 - White Wire,
  • W2 - Empty,
  • Y1 - Empty

New Thermostat Terminals (need to connect to): C, G, Y, W, R

So it appears the C terminal at the Air handling unit (AHU) block is currently connected to the Y terminal at the existing thermostat? Is that possible?

I will attempt to include photos of the AHU and Existing Thermostat terminal blocks:

AHU:

enter image description here

Ex. Thermostat

enter image description here

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Hugh
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1 Answers1

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I've labeled your photo, which should help you understand what's going on.

enter image description here

What you describe as a "blue" wire at the thermostat, you describe as "gray" at the air handler. I can't be sure, since I'm not there, but I think they are one in the same.

If you want to install a fancy new WiFi thermostat, you're going to have to pull an additional wire from the air handler to the thermostat. Once you have that, you'll connect one end to the C terminal of the air handler, and the other end to the C terminal of the thermostat.

Tester101
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