6 Wire Thermostat Wiring Diagram Guide 

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Are you planning to install a new thermostat or upgrade your existing one to a new one with 6 wires? If you  are wondering what wires go on where on a 6 wire thermostat, then this is a perfect guide for you. In this guide, we’ll walk you through the process of wiring a 6 wire thermostat step by step.

What systems use 6 wire thermostat wiring?

There are a few systems that can use the 6 (or more) wire thermostat wiring, these include

  1. 2nd Stage Heat Pump
  2. Heat pumps with Aux heat
  3. Single stage Furnace with  2nd  stage air conditioner
  4. 2nd Stage Furnace with Single stage air conditioner

But you would also have other systems not mentioned above that use the 6 wire thermostat configuration. One of the  important things to note is that to successfully wire your thermostat, you’ll need to know the thermostat wiring color code code and the type of system you have.

Remember  to take a picture of your thermostat  of the current wiring on your old thermostat and don’t forget to put the label sticker on each wire taken off the old thermostat

Read also: How to wire a Honeywell thermostat Full Guide

Common thermostat wire colors and functions

The thermostat wiring color code is not universal and may vary depending on the region and the type of HVAC system you have. However, in the United States, the most common color code used for thermostat wiring is as follows:

R (Red) – Power supply for the thermostat. Connects to the R terminal on the thermostat and provides 24VAC power from the transformer.

W (White) – Heating. Connects to the W terminal on the thermostat and controls the 1st stage heating heating system.

Y (Yellow) – Cooling. Connects to the Y terminal on the thermostat and controls the cooling system.

G (Green) – Fan. Connects to the G terminal on the thermostat and controls the HVAC fan.

C (Blue) – Common. This wire is used to provide a common return path for the 24VAC power, enabling the thermostat to draw power without relying solely on the batteries.

 Not all thermostats require a C wire, but many modern smart thermostats do.

AUX – For Auxiliary heat. Auxiliary heat  helps heat your home more quickly or to help heat your home when it’s too cold outside for your heat pump to efficiently heat.

O/B (Orange) – Changeover valve for heat pumps (used to switch between heating and cooling modes on heat pump systems that do not use a separate O wire).


W2 (White or other color) – Second stage heating. This controls second stage heating if you have a furnace with 2 stage heating. And if you have a heat pump with auxiliary heat, , W2 is  used for controlling  auxiliary heat.

Read: 7 Wire honeywell thermostat wiring diagram

Honeywell 6 Wire Thermostat Wiring Diagram

As I mentioned earlier, a 6-wire thermostat wiring can include a heat pump with auxiliary heat as shown in the chart below. Be sure to wire the W/ W2 terminal  into the  W2.

WireFunction
RPower
Rc R+Rc joined by Jumper or Slider Tab
YCompressor contactor
C24VAC common 
0/BChangeover valve
GFan relay
W2Auxiliary heat

Nest thermostat 6 wire thermostat wiring diagram

2nd Stage Furnace with 1st stage air conditioner

stage 2 furnace stage 1 ac

Terminal DesignationFunction
Y1  Compressor Relay (Stage 1)
GFan Relay
W1Heat Relay (Stage 1)
W2/AUXHeat Relay (Stage 2) 
C  24VAC Common Wire
Rh24VAC power from heating transformer

2nd Stage Heat Pump

2nd stage heat pump
Terminal DesignationFunction
Y1Compressor Relay
Y2Compressor Relay ( stage 2)
GFan Relay
O/B Heat pump changeover valve
Rc24 VAC power from cooling transformer
C24VAC common wire.

1st Stage furnace with 2nd stage air conditioner

stage 1 furnace stage 2 ac
Terminal designationFunction
Y1  Compressor Relay (Stage 1)
Y2 Compressor Relay (Stage 2), 2nd-speed fan
W1  Heat Relay (Stage 1)
C  24VAC Common Wire
Rh 24VAC power from heating transformer
G  Fan Relay*

1st  Stage Heat Pump with Aux Heat (6 wire)

heat pump with
Terminal DesignationFunction
Y1Compressor Relay (Stage 1)
GFan Relay
O/BChangeover Valve
Rc24VAC power from cooling transformer
AuxAuxiliary Heat Relay
CCommon Wire

Read also: How to wire a Nest thermostat

Final thoughts

That is all there is to wiring a 6 wire thermostat. Remember, before you remove the thermostat wires from the current thermostat to label them or take a picture so that you  will easily know where to put what.

I hope you have managed  to wire your thermostat after going throught this guide. Thanks for reading.

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