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#186108 - 04/17/09 07:51 AM HVAC Thermostat wire color code
Bill39 Offline

Registered: 11/28/01
Posts: 77
Loc: Indianapolis, IN, USA
I know the NEC doesn't do color codes but is there an accepted (traditional) color code for HVAC thermostat wiring?


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#186109 - 04/17/09 08:10 AM Re: HVAC Thermostat wire color code [Re: Bill39]
ghost307 Offline

Registered: 05/09/05
Posts: 883
Loc: Chicago Illinois USA
I don't know what it is, but every thermostat I've wired has little letters next to the screws for the black, yellow, green, red wires. If that's cast right into the plastic, it must be following some color code standard somewhere.

#186110 - 04/17/09 08:37 AM Re: HVAC Thermostat wire color code [Re: ghost307]
renosteinke Offline
Cat Servant

Registered: 01/22/05
Posts: 5305
Loc: Blue Collar Country
Well, let's see ...
The red seems to always be the 'power in.'

Saturday - I've edited the daylights out of my post, because it was simply ... wrong.

Edited by renosteinke (04/18/09 07:55 PM)

#186112 - 04/17/09 10:16 AM Re: HVAC Thermostat wire color code [Re: renosteinke]
EV607797 Offline

Registered: 10/25/06
Posts: 756
Loc: Fredericksburg, VA, USA
I've always seen:

24V common: Red
Heat: White
Cool: Yellow
Fan: Green
Blue: Second heat stage
Orange: LED for aux. heat
Brown: LED for emerg. heat

"But the guy at Home Depot said it would work."

#186120 - 04/18/09 01:35 PM Re: HVAC Thermostat wire color code [Re: Bill39]
klein man Offline
New Member

Registered: 03/27/02
Posts: 6
Loc: York, Nebraska
Here, Im an HVAC Controls Tech. This is a complete diagram for different systems. Ive added Gas, Electric furnaces and heat pumps. I can add water source HP's if desired.

(R) Red - Power
(W1) White- Heat
(W2) Blue- Second Stage Heat
(Y1) Yellow First State Compressor
(Y2) Jumpered (Board Controls Second Stage Compressor)
(O) Orange- Reversing Valve (Heat Pump Only)
(B or X) Depeneding on Manufacture will be Common (Heat Pump Only)
(Brown and Pink) Outdoor Stat (Heat Pump Only)
(G) Green - Blower Relay

Aux Heat for heat pumps no longer is hooked up, the fuel master does it for the unit.

I could add a lot more, but start with these

Edited by klein man (04/18/09 01:40 PM)

#186137 - 04/21/09 11:03 AM Re: HVAC Thermostat wire color code [Re: klein man]
SteveFehr Offline

Registered: 03/19/05
Posts: 1192
Loc: Chesapeake, VA
As klein man pointed out, there's common practice but no real standard so it unfortunately varies from brand to brand. Google is your friend, and will answer your questions for your particular unit smile


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