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  1. #1
    Join Date
    Dec 2019
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    System ignoring min compressor temp

    I have a Carrier heat pump system with Ruud electric aux heat furnace. This is our first winter in this house, so we are just now dipping into the colder temps here in Montreal.

    To save on the electric bill, I just recently installed an Ecobee 3 lite thermostat. I have noticed that when outdoor temps drop below 0 deg C, when the thermostat is requesting heat, the heat pump will not turn on and only aux heat comes on. This is pretty inefficient, and the system takes hours to heat the house from 19 C overnight to 21 C for the morning temp setting.

    I checked the setting a few days ago, and lowered the “compressor min outdoor temp” to -15 C. Still, the heat pump will not come on. Yesterday we had a relatively “warm” day of 10C, and the heat pump was running (with fantastic heat output from the registers), so i know the heat pump functions fine. Today is cold again, and no heat pump anymore.

    So, why is the system ignoring the ecobee min compressor outdoor temp setting?

  2. #2
    Join Date
    May 2000
    Location
    Indianapolis, IN, USA
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    The default setting is 35F to shut off the compressor which I agree is nuts. But we've always had then work when we lower the temp. Might give Ecobee a ring and see what they think.

  3. #3
    Join Date
    Dec 2019
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    Thread Starter
    It was doing the same thing with the Carrier brand non-programmable thermostat before. So I’m wondering if there is some secondary temperature sensor that is limiting it from turning on. Is this possible? Or is the thermostat the ultimate “master controller” and there is no secondary controller further down the 24V wiring chain that could be preventing the signal from going to the heat pump outside.

  4. #4
    Join Date
    May 2000
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    Indianapolis, IN, USA
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    The Ecobee should be the controller but someone might have put a manual thermostat outside.

  5. #5
    Join Date
    Jan 2004
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    PA
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    Quote Originally Posted by BaldLoonie View Post
    The Ecobee should be the controller but someone might have put a manual thermostat outside.
    Yep, sounds like there's a Stat in the heat pump locking it out.
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  6. #6
    Join Date
    Dec 2019
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    Thread Starter
    Quote Originally Posted by beenthere View Post
    Yep, sounds like there's a Stat in the heat pump locking it out.
    Ok thanks!

    Talked to Ecobee support yesterday (a cold day with highs around -7C), and even with connected the R wire straight to the Y wire at the thermostat, the heat pump refused to turn on.

    It’s a (relatively) warm day again here today with temps above freezing, and the heat pump is back to running again (and putting out way more heat from the registers than just aux heat).

    Do you think it’s worth calling out a tech to remove the Stat, or is this normal to have the heat pump locked out below 0C?
    Last edited by HydroTesla; 12-13-2019 at 02:57 PM. Reason: Formatting

  7. #7
    Join Date
    Jan 2004
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    PA
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    Call a tech out and have them remove or disable the outside thermostat.
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    How many times must one fix something before it is fixed?

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