6 Wire Thermostat Wiring Diagram Guide

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

2nd Stage Heat Pump
Heat pumps with Aux heat
Single stage Furnace with 2nd stage air conditioner
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

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.

Wire	Function
R	Power
Rc	R+Rc joined by Jumper or Slider Tab
Y	Compressor contactor
C	24VAC common
0/B	Changeover valve
G	Fan relay
W2	Auxiliary heat

Nest thermostat 6 wire thermostat wiring diagram

2nd Stage Furnace with 1st stage air conditioner

Terminal Designation	Function
Y1	Compressor Relay (Stage 1)
G	Fan Relay
W1	Heat Relay (Stage 1)
W2/AUX	Heat Relay (Stage 2)
C	24VAC Common Wire
Rh	24VAC power from heating transformer

2nd Stage Heat Pump

Terminal Designation	Function
Y1	Compressor Relay
Y2	Compressor Relay ( stage 2)
G	Fan Relay
O/B	Heat pump changeover valve
Rc	24 VAC power from cooling transformer
C	24VAC common wire.

1st Stage furnace with 2nd stage air conditioner

Terminal designation	Function
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)

Terminal Designation	Function
Y1	Compressor Relay (Stage 1)
G	Fan Relay
O/B	Changeover Valve
Rc	24VAC power from cooling transformer
Aux	Auxiliary Heat Relay
C	Common Wire

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.