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Nest compatibility with new HVAC

fox13az
Community Member

2 weeks ago

We had a new HVAC system installed and we are having issues the HVAC techs can't seem to fix.  

We have had a Next 3rd generation that worked great with our old system (1 stage heating, 1 stage cooling).

Our new American Standard Gold system has 2 stage heating and a 2 stage cooling unit. The A/C unit is their new 454B refrigerant multispeed (not a variable speed A/C unit) which supposedly should be hooked up the same as a regular 2 speed (2 stage) A/C unit.

Does the 3rd Generation Nest work when a 2 stage heating and 2 stage A/C are both installed?

If so what is the correct hookup, wire colors and terminals for this?  According to the diagram on the Nest app the way it is wired is:

  •  Y1 yellow on cool,
  •  W1 white on heat,
  •  G green is fan,
  •  C blue is 24V common, and
  •  Rc red is power.

Is 5 wires enough to for the thermostat to differentiate two separate stages on heat and two stages on cool?

Any help would be appreciated!

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1 REPLY 1

GeremiG
Community Specialist
Community Specialist

2 weeks ago - last edited 2 weeks ago

Hi @fox13az!

 

Thank you for posting in the community. I'm sorry to hear that your new HVAC system with your Nest Learning Thermostat (3rd gen) is experiencing issues that the HVAC techs haven't been able to pinpoint. I'm happy to help you!

Let's address your questions about your Nest 3rd Generation Thermostat and your new American Standard Gold 2-stage heating and 2-stage cooling system:

  • Does the 3rd Generation Nest work when a 2-stage heating and 2-stage A/C are both installed? Yes, the Nest 3rd Generation Learning Thermostat is designed to be compatible with multi-stage HVAC systems, including those with 2-stage heating and 2-stage cooling.
  • Are 5 wires enough for the thermostat to differentiate two separate stages on heat and two stages on cool? No, the five wires you've listed (Y1, W1, G, C, and Rc) are typically not enough for a thermostat to independently differentiate and control both two-stage heating and two-stage cooling. This means you would usually need at least 7 wires (Y1, Y2, W1, W2, G, C, and Rc/Rh) to have independent control of all stages.

For a true 2-stage heating and 2-stage cooling system, you would typically need additional wires to control the second stages. The standard connections are:

Y1: First-stage cooling
Y2: Second-stage cooling
W1: First-stage heating
W2: Second-stage heating
G: Fan
C: Common
Rc: 24V Power 

If you have any questions or need additional help, please don't hesitate to let us know.

 

Best regards,
Geremi

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