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New Heat Pump Install Help

Hi there,

Apologize in advance if I should be using another forum.

I had a new Trane XR15 heat pump installed a few days ago.
With this install, I also had them put in an Ecobee thermostat.

I'm hoping someone could help me figure out the threshold (and correct settings) for aux heat transfer to use my heat pump as often as possible.

The sticker on the outdoor unit reads:
Trane XR15
Model: 4TWR5042H1000AB

Based on similar posts/models and assumptions, I have:
Aux Savings Optimization: Maximum
Aux Heat Max Outdoor Temperature: 25
Compressor Min Outdoor Temperature: 20

Thank you for any help!


  • Hot_water_fan
    Hot_water_fan Member Posts: 1,651
    What's your heat loss and how does it compare to the Trane's capacity vs. temperature?
  • Jamie Hall
    Jamie Hall Member Posts: 22,212
    Your settings are probably about as good as you're going to get -- but @Hot_water_fan has a very relevant question...
    Br. Jamie, osb
    Building superintendent/caretaker, 7200 sq. ft. historic house museum with dependencies in New England
  • junkfroggy
    junkfroggy Member Posts: 4
    To be honest, I'm not really sure. 

    I feel like I'm mainly hoping to find company numbers as to what conditions the XR15 will run efficiently with as a heat pump. 

    If anything, that would be a starting point and I can always dial it in either direction to find a good middle ground for value and performance. 
  • Hot_water_fan
    Hot_water_fan Member Posts: 1,651
    edited August 2021
    Thanks Jamie. The reason I ask is that if the output is high enough relative to heat loss at your lowest temperatures, you could switch the backup heat manually at the panel (if it’s like a day or two per year). If not, I’d set the minimum compressor outdoor temperature as low as it’ll go. There’s really no downside to running the compressor, as it’s usually (just in case there’s one heat pump out there that is the exception) more efficient than the strips at every temperature. This only applies if your backup is electric. If backup is a gas furnace/something else, let us know
    HVACNUT Member Posts: 5,490
    Not being overly familiar with that model heat pump, or the Ecobee, I typically program stage 2 to energize when the temperature drops 2°F from the stage 1 setpoint. 
    What is your auxiliary heat, electric resistance, or something else?
    HVACNUT Member Posts: 5,490
    Hot_water_fan said: If not, I’d set the minimum compressor outdoor temperature as low as it’ll go. 
    Is that something that's specific to the Ecobee?
  • junkfroggy
    junkfroggy Member Posts: 4
    I can't believe I forgot to mention what kind of auxiliary heat I have. 

    Sorry about that. 

    I'm using a propane furnace as my auxiliary heat source. Until now, I've only had that as all of my heat. 

    Gets expensive so I installed a heat pump in hopes that I'd be able to save a few bucks. 

    I just want to make sure I don't damage the heat pump or cause issues by running it all the time. 
    My understanding was also that I should run it down to where it becomes less efficient and then switch heat sources. 
    EBEBRATT-Ed Member Posts: 14,593

    You can play with the setting to see what works best but I would change over around 25 deg. Below that a HP starts having to defrost
  • junkfroggy
    junkfroggy Member Posts: 4
    So you'd do:
    Aux Heat Max Outdoor Temperature: 30
    Compressor Min Outdoor Temperature: 25

    Or something else?

  • ratio
    ratio Member Posts: 3,555
    Plot the $/BTU of both the furnace and the heat pump. The gas furnace will be a line, but the HP will be a curve. They'll intersect at one point—one's cheaper above that point, the other below. Then, find the outdoor temperature where the heat loss of your house corresponds to that point. That's where you want to switch fuels.