Wiring Nest (3-rd gen) for 1-stage heat pump and 2-stage gas furnace system with a single W wire

[Powel]

Hello,

I was wondering what the wiring should be for a single stage heat pump and a two stage gas furnace.

The Nest Pro Installation Guide shows this situation with two heating wires, W1 and W2, My system

has only one heating wire, W, it's a Goodman GMCV96100* furnace.

The manual claims that the circuit board delegates whether stage 1 or stage 2 is engaged.

So my question would be which terminal on the thermostat should I use, W1 or W2?

W2 is labeled in the Pro Guide as W2/AUX Heat Relay (Stage 2) / Auxiliary Heat Relay.

Would connecting this W wire to W2 terminal make sense?

[Patrick_Caezza]

@Powel 

Can you post a picture of the original thermostat's wiring here?

[Powel]

@Patrick_Caezza

This is how the thermostat is wired

[Powel]

@Patrick_Caezza

I thought that perhaps wiring at the furnace would complete the picture.

[Powel]

@Patrick_Caezza

I found this in the troubleshooting section of the Pro Installer Guide.

Could this be the answer to my question?

[Patrick_Caezza]

@Powel 

You have a discrepancy between the Nest wiring and the furnace wiring. I don't see the orange wire connected anywhere in the furnace.

Do you happen to have a picture of the old thermostat's wiring?

Based on the furnace wiring the Nest should be wired like this,

Yellow - Y to Y1

White - W to W1

Green - G to G

Blue - C to C

Red - R to Rc

[Powel]

@Patrick_Caezza

Life is so much easier when you're not color blind.

Not that I see the world black& white but I don't pick up differences like that easily.

Believe it or not, this is a new installation, so no I don't have a picture of the old thermostat wiring.

Also, there's a black wire that is connected at the furnace board, but not anywhere else, so I'm guessing I could get rid of it altogether.

Many thanks for the thorough inspection!

[Patrick_Caezza]

@Powel 

I wouldn't make any changes to the furnace unless you know exactly where that wire goes.

[Powel]

@Patrick_Caezza

The black wire does not go anywhere. It's attached to the board on one end and wrapped around the entire cable on the other end. It's superfluous.

[Patrick_Caezza]

@Powel 

Remove it if you want.

[Powel]

@Patrick_Caezza 

The orange wire, that is missing on the circuit board terminals, goes straight from a non-communicating single stage heat pump

[Patrick_Caezza]

@Powel 

Ahhhh

That makes more sense.

Then I would suggest this wiring.

Yellow - Y to Y1

White - W to W2/AUX (set as Aux heat)

Green - G to G

Blue - C to C

Red - R to Rc

[Powel]

@Patrick_Caezza 

Thank you, I will do just that!