Heat Pump and Droop?

Discussion in 'HVAC Heating & Cooling' started by themp, Feb 8, 2020.

  1. themp

    themp Member

    Feb 5, 2008
    Raleigh, North Carolina
    Daughter and son-in-law bought a 100 year old house(2000sf) in Richmond, VA. It was flipped. Has no insulation in the walls or floors, they did insulate the attic. Windows replaced on 3 sides and the front windows were not because they are architecturally what makes the house appealing. They could be storm windowed. The house has a basement(not heated or air conditioned) that was encapsulated, and then a first and second floor. There are a pair of Rheem heat pumps(14 SEER, 2 Tons) for the first and second floor. Basic Honeywell thermostat that is programmable.

    We visited last week and one night the temperature went down to 26F and the Aux heat strips were running continuously. They keep both floors at 68 degrees. They do have a new baby in the house. I have never dealt with a heat pump and my first thought was to drop the temperature on the first floor at night and do the same on the second floor during the day. But in doing internet searches it seems it is best to keep the temperature constant so as not to cause the heat strips to come on. I also thought of dropping the temperature 3 degrees and then bringing it back up to 68 one hour at a time to minimize the heat strips. But, then I ran across a discussion of heat pumps and droop. Meaning you can set a droop temperature and also an up stage timer for Aux heat. Here is how it is described in the smart Honeywell T10 thermostat:

    "The T10 only uses droop for control of the aux heat on systems with a heat pump and either electric heat strips or a gas/oil furnace as backup heat. In these cases the droop setting locks out the aux heat unless the droop condition or upstage timer setting allows the aux heat to run. When electric strips are used as the aux heat, a "Comfort" setting is typically used instead of a droop setting. This is configured by the installer."

    The question is would a smart thermostat with the ability to set droop and up state timer for Aux heat help them save some money? Or would the house just be to uncomfortable by forcing the Aux heat off? Finally, I did also see that a lock out sensor could be put outside and force the Aux heat to not engage when the temperature was above 35F. Again, because the house losses heat so quickly, without Aux heat strips it would be uncomfortable.
  2. WorthFlorida

    WorthFlorida The wife is still training me.

    Oct 28, 2009
    Orlando, Florida
    With digital and programable thermostats, aux heat can be turned off in the settings menu so only the heat pump is called for, but as you stated the home will be cold and uncomfortable.

    In this two floor home, set the temperatures so both heat pumps are running most of the time during a call for heat. HP mode is far less costly and electric heat strips. Since the home cannot have maintain temperature during sever cold weather with the heat pumps and the electric strips. The electric strips can be changed out to a higher wattage. Most are 5kw or 10kw. There are 20 kilowatt units but it may require upgrade the power source. It’s not the end of the world when having to heat with electric. Electric clothes dryers are usually 5 kilowatts or less.
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