thermostat wiring - Contractor Talk - Professional Construction and Remodeling Forum

zooter7878 · 04-04-2005, 09:43 PM

I'm trying to install a new thermostat in a home. It controlls both heating and AC. I'm having trouble getting the wiring correct. There's a black wire that I'm not sure of. If I connect it to the RC connection the fan won't shut off in the test program of the thermostat. Do I have to jump R and RC? Very confused. Anyone got the correct way to wire it?

**Teetorbilt** · 04-04-2005, 10:38 PM

Doc will be along, hang tight.

HVAC Doc · 04-05-2005, 06:28 AM

Quote:

Originally Posted by zooter7878

I'm trying to install a new thermostat in a home. It controlls both heating and AC. I'm having trouble getting the wiring correct. There's a black wire that I'm not sure of. If I connect it to the RC connection the fan won't shut off in the test program of the thermostat. Do I have to jump R and RC? Very confused. Anyone got the correct way to wire it?

How many wires do you have total? What is the model of the thermostat? Where was the black wire hooked at on the old stat? We can get you back up and running with just a little more info.

zooter7878 · 04-06-2005, 08:37 PM

Quote:

Originally Posted by HVAC Doc

How many wires do you have total? What is the model of the thermostat? Where was the black wire hooked at on the old stat? We can get you back up and running with just a little more info.

7 wires
Honeywell T8600D

The black wire was hooked to the X connection on the old thermostat. Thank you for any help.

HVAC Doc · 04-06-2005, 09:05 PM

Quote:

Originally Posted by zooter7878

7 wires
Honeywell T8600D

The black wire was hooked to the X connection on the old thermostat. Thank you for any help.

What was the Brand and model of old stat then we can tell you what X should hook to on your T8600D.

Edit: Got to looking at HW contractors site and if you have a single transformer system (one mounted in furnace typically) then all X was normally was a common. You can verify this by looking in your furnace/airhandler and seeing what the black wire hooks to inside. If all it was was a common, according to Honeywells Techlit, you should be able to eliminate that and just jumper your R/RC terminals and it work ok.

NickTech · 04-07-2005, 08:09 PM

http://hbctechlit.honeywell.com/tech...0s/60-2246.pdf

check out page 4. what was the old t-stat model?

zooter7878 · 04-10-2005, 08:17 AM

Quote:

Originally Posted by HVAC Doc

What was the Brand and model of old stat then we can tell you what X should hook to on your T8600D.

Edit: Got to looking at HW contractors site and if you have a single transformer system (one mounted in furnace typically) then all X was normally was a common. You can verify this by looking in your furnace/airhandler and seeing what the black wire hooks to inside. If all it was was a common, according to Honeywells Techlit, you should be able to eliminate that and just jumper your R/RC terminals and it work ok.

Thanks for the help.