Honeywell TH8321wf1001 wiring to Nest Thermostat

Old 06-11-22, 04:56 AM
Thread Starter
Join Date: Jun 2022
Posts: 1
Received 0 Votes on 0 Posts
Honeywell TH8321wf1001 wiring to Nest Thermostat

Trying to wire my new Nest thermostat where the old Honeywell thermostat once was. First picture was the previous state wiring. 2nd picture is new wiring. Not sure what to do with the black and orange wires (which I now just have taped up).

Currently I have:
Yellow to Y
Blue to C
White to W
Green to G
Red to R
Black to ?
Orange to ?



Last edited by PJmax; 06-11-22 at 10:13 AM. Reason: resized pics
Old 06-11-22, 10:17 AM
PJmax's Avatar
Group Moderator
Join Date: Oct 2012
Location: Jersey
Posts: 70,167
Received 2,977 Votes on 2,686 Posts
Welcome to the forums.

No idea why there were two wires on C. That should not be.
U1 is a switch controlled by the thermostat.
You have lost the function of whatever was connected to the orange wire.
Could be a humidifier or vent.
Yes... tape off orange and black.

What is your system.... heat pump.... gas/electric furnace.... split A/C ?
It makes a difference as the thermostat may need to be reprogrammed for your system.

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