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Nest thermostat

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zepfan
zepfan Member Posts: 397
in Thermostats and Controls
Will a nest thermostat control a duel fuel system? Heat Pump with oil furnace as back up. Normally I would use a Honeywell TH8321wf with a wired outdoor sensor. The customer has an existing Nest thermostat that is about five years old, that currently controls an ac unit, and oil furnace. The customer would like to keep the Nest, and have a heat pump installed, and demo the ac unit. I didn't know if Nest had the algorithm that would use the outdoor temp over wi fi, to determine when the heat pump runs or the oil furnace. Any assistance would be much appreciated. Thanks to all

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  • EdTheHeaterMan
    EdTheHeaterMan Member Posts: 7,864
    edited May 2022
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    I don't think so. Nest tech support will probably not be any help. Their Tech support basically follows a script, then says to call a NEST PRO if they can't solve it over the phone.

    If the * terminal (a terminal that is able to be programmed for different functions) on the Nest does not have a provision in the technical documents available online, then it probably won't do it.

    Edward Young Retired

    After you make that expensive repair and you still have the same problem, What will you check next?

  • EdTheHeaterMan
    EdTheHeaterMan Member Posts: 7,864
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    After thinking about installing a Nest Thermostat, I remember that all you need to do is connect the proper wires to the proper terminals. Once that is complete, you go thru an initial programing setup. Based on what wires are connected, the thermostat asks if it connected to a heat pump. Then it asks if there are more than one stage, what the second stage is. I cant remember if the second stage for heat can be Electric, or Gas/Oil, or Other. If that option is in the programing, then you can. It all depends on the options within the Nest. You won't know until you connect and try to program it. I don't know of any online places to answer that question. Perhaps another poster will know

    Edward Young Retired

    After you make that expensive repair and you still have the same problem, What will you check next?

    zepfan
  • HVACNUT
    HVACNUT Member Posts: 5,841
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    In theory it should work. 
    I've installed many client supplied Nests and haven't really gone past the wiring, testing, and connecting to their network, but during setup on some, you enter the zip code and it in turn gives the client the local temperature. 
    So using O for the reversing valve on the heat pump, and W1 for the boiler, they must have have a way to stage according to outdoor temperature. 
    If not, then🏒
    zepfan

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