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Thread: Nest Wiring Guidances HP with LP Backup furnace

  1. #1
    Junior Member

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    Nest Wiring Guidances HP with LP Backup furnace

    I just bought a house that has a Heil DC90 heat pump with a LP furnace. The previous owners still had an White-Rogers analogy (with mercury) style thermostat. When wiring up the Nest there have been question's about how to handle the LP furnace. In the White-Roger Thermostat, the white wire "W" (indicated by the Furnace control board) was plugged into an "E" Terminal however you could see on the circuit that it was jumped back to the heat function as well. Now moving to the Nest it seems I need to either put it in W1, W2/Aux, or *. Currently I have it setup in W1 and have the Nest configured in dual fuel mode indicating that W1 is the LP furnace. Then in the Nest App I get an option for at what outside temperature it should use LP furnace over the heat pump. Is that that correct setup, or is their a better option? I have attached I pic of my original thermostat's wiring configuration.
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  2. #2
    HVAC Thermostat Specialist

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    Nest is a poor choice for those with heat pumps. Staging doesn't work correctly. It's a known issue on Nest.

  3. #3
    Junior Member

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    Quote Originally Posted by Servicetech View Post
    Nest is a poor choice for those with heat pumps. Staging doesn't work correctly. It's a known issue on Nest.
    It's true the nest it isn't the best when it comes to heat pumps but anything has to be better then my originally mercury thermostats, or just digital thermostat. So thanks for you post but it doesn't help.

  4. #4
    HVAC Thermostat Specialist

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    http://support.nest.com/article/What-is-Pro-Setup


  5. #5
    HVAC Thermostat Specialist

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    Does your system have a DF kit installed? Is there a outdoor mechanical thermostat that switches from HP to LP?
    A quality DF thermostat will allow you to select run time of heat pump before switching LP. It will also have HP and LP lockout settings when used with an outdoor temp sensor.

  6. #6
    Junior Member

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    Quote Originally Posted by Servicetech View Post
    Does your system have a DF kit installed? Is there a outdoor mechanical thermostat that switches from HP to LP?
    A quality DF thermostat will allow you to select run time of heat pump before switching LP. It will also have HP and LP lockout settings when used with an outdoor temp sensor.
    I just bought this house and the hp is about 15 yrs old , home built in 1999. So I'm not sure. Is there something obvious to look for?

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