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  1. #1

    Downstairs Gas, Upstairs Heat Pump

    What am I doing wrong? Thanks for any help.

    Location: South Carolina. Normally 50* in winter, occasionally 30* on cold nights.
    House: 3200 sqft, 2 story. Dual system. Registers and thermostats are both upstairs and down, and are near the stairwell.
    Upstairs: heat pump, large A/C unit
    Downstairs: Gas heat, small A/C unit

    In summer, everything works well. Upstairs gets a little hotter despite having the larger A/C unit (larger sqft upstairs with FROG, and heat rises), but generally acceptable.

    During winter, I set the downstairs to 67* to run gas heat and set upstairs to 62* so it is basically off. Upstairs thermostat reads 68* because of heat drifting up stairs. Some heat comes through floor, but not enough on cold nights. If I turn on upstairs fan to circulate the gas heat drifting up the stairs, the bedroom (62*) and bathroom (58*) still stay very cold.

    What do I need to do? Should I turn down the gas downstairs and run the heat pump upstairs more? Should I even run gas given the relatively mild winters? Should I tailor based on the outside temps or night vs. day? Thanks.

  2. #2
    Join Date
    Dec 2001
    Ocean Pines, MD
    Where is the thermostat upstairs?

  3. #3
    Join Date
    Mar 2006
    The South

    You are expecting too much.

    Why have a second floor system and not operate it?

    Put thermostat on 67-68 degrees and see how comfort level changes. If your air handler has var speed blower, then set stat with fan on.

    You also should have an insulation pro to perform an audit of second floor and make suggestions for improvement.

    Ductwork system for second floor system should be inspected as to insulation, size of supply lines to rooms with hot/cold spots, and adequate return for second floor.

    If you are looking for a quick and inexpensive fix, I doubt you will find one.


  4. #4
    Quote Originally Posted by Stamas View Post
    Where is the thermostat upstairs?
    Upstairs: Thermostat is on landing right across from stairwell. Register is about 3 feet down the hall from the thermostat. Staircase is split with landing. Walk up the stairs and you will walk right into the thermostat.

    Downstairs: Thermostat is on wall right across from stairwell. Register is directly above.


  5. #5
    Quote Originally Posted by tigerdunes View Post
    Why have a second floor system and not operate it?

    Put thermostat on 67-68 degrees and see how comfort level changes. If your air handler has var speed blower, then set stat with fan on.
    If I set both units to 68, the upstairs would effectively never run. The upstairs thermostat normally reads about 1* higher than downstairs (even when upstairs is off), because the heat drifts up.

    What I don't get is why running the fan (without heat pump, since upstairs hall by register is already warm) isn't pulling warm air from the hallway and circulating it to the rooms.

    Ductwork was recently inspected and resealed, as were the units (during late summer for A/C).

    I'm wondering if I should set upstairs heat pump to constant 68, and then set gas downstairs to 68 during day and 65 at night so that at night the upstairs heat pump will kick on and I'm not heating unused space downstairs.

  6. #6
    Join Date
    Jul 2004
    You have a 2-zone system that you're complaining operates as a 1-zone system. Have you ever verified that the two thermostats are reading the same temperature? If the are, I'd first suspect a leaky house. The reason I say that is that despite warm air rising, for each molecule of air that moves upstairs, one matching molecule must move to a new location. In a tight house, that would be toward the downstairs but in a loose house, that's right outdoors. As that molecule moves outdoors, another molecule must move into the home from outdoors and that molecule is colder and needs to be warmed. This is referred to as 'stack effect' and is a major source of energy losses. A blower door test would need to be done to verify the leak rate of the home.

    You can also turn down the 1st floor setting and turn up the 2nd floor setting. This should allow you to maintain the upstairs at a slightly warmer temperature than the downstairs and eliminate the stack effect between the 1st and 2nd floors (the warmer air will already be upstairs). This won't improve your energy use but it may help clear up your concerns as to which unit is doing the heating. I'd recommend you compare the operating costs of the HP versus the gas furnace and favor that which is of lower cost.
    If YOU want change, YOU have to first change.

    If you are waiting for the 'other guy' to change first, just remember, you're the 'other guy's' other guy. To continue to expect real change when you keep acting the same way as always, is folly. Won't happen. Real change will only happen when a majority of the people change the way they vote!

  7. #7
    Join Date
    Jan 2009
    Keokuk, IA
    Sounds like a lot of air leaks driving air movement upstairs. The 2nd common problem is that the wonderful modern open concept floor plans (ie builders save money on fewer walls) make for nice unobstructed convective airflow, expecially with a nice open, single section stairwell.

    As mentioned, try leaving the fan to "ON" for the upstairs unit. Downstairs, make sure registers on the perimeter of the hosue are fully open and you might partially close any near the stairwell.

    FOr air leaks, the most common are leaks are pupular recessed lights, bath fans and then any other ceiling fixture or penetration. Seal them up air tight if you can.

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