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  1. #1

    Furnace Works But Doesn't Reach Thermostat Temp

    I have an older American Standard furnace w/ heat pump. When the outside temps drop below 30 degrees or so, the room temperature never reaches the temp the thermostat is set to. I know heat pumps only work down to a certain temp before the electric heat takes over.

    Example: If i set the thermostat to 75 the room temp will only reach 73, or if I set the thermostat to 68 the room temp will only reach 66. Obviously this causes the firnace to run non stop. Any thoughts?

  2. #2
    Join Date
    May 2008
    Location
    Missouri
    Posts
    3,543
    You need to have this system looked at by a competent, licensed repair service. We cannot assist with DIY repairs other than recommend checking the air filter etc..Sorry, this site does not allow us to "advise" a DIY attempt.

  3. #3
    Join Date
    Oct 2005
    Location
    Pacific Northwest
    Posts
    2,267
    Quote Originally Posted by macdiesel View Post
    I have an older American Standard furnace w/ heat pump. When the outside temps drop below 30 degrees or so, the room temperature never reaches the temp the thermostat is set to. I know heat pumps only work down to a certain temp before the electric heat takes over.

    Example: If i set the thermostat to 75 the room temp will only reach 73, or if I set the thermostat to 68 the room temp will only reach 66. Obviously this causes the firnace to run non stop. Any thoughts?
    Make sure your outdoor unit is running. If it is running "normally" in those conditions you should be seeing a uniform thin layer of ice build up and a defrost once every 30-60 minutes or so. You should also call a pro and have the system checked.

  4. #4
    Thanks guys. I planned on it, but was curious if it was something simple to check other than the air filter, which is brand new. Thanks again.

  5. #5
    Join Date
    May 2008
    Location
    Missouri
    Posts
    3,543
    I assume you don't have a digital thermostat?

  6. #6
    Yes. I do have a digital thermostat. It is a Smart Tempฎ TX9100E 7 Day Universal Programmable Thermostat.

  7. #7
    Join Date
    Feb 2009
    Location
    Tallahassee, FL
    Posts
    6,051
    Sounds like a refrigerant problem with the heat pump if everything is running but no/low 1st stage heat.

    Let us know what he finds.

  8. #8
    Join Date
    Mar 2005
    Location
    burlington county n.j.
    Posts
    9,748
    sounds like a thermostat wiring problem if you are always 2 deg off setting. indoor fan keeps running to heat house but heat source is cutting out once 2nd stage setpoint is reached....

  9. #9
    Join Date
    May 2000
    Location
    Indianapolis, IN, USA
    Posts
    34,245
    Sounds like a heat pump not heating or coming on like SB said. When the furnace isn't on but the house isn't up to temperature, is the outdoor unit on? If so, feel the copper pipe leading into the house, the big one under the rubber insulation. Is it hot? If no to either, put stat on emergency heat and call a good pro.

  10. #10
    Join Date
    Oct 2006
    Location
    The Beach
    Posts
    718
    Are you sure you have a furnace and not just a heat pump that is running off of the strips. A proper size furnace will heat up your house at the temperture you set it. Call a pro and ask him to fix what ever is wrong.
    Blue Fox

  11. #11
    Join Date
    Nov 2000
    Location
    Eastern PA
    Posts
    68,950
    Excuse me folks, but what it "sounds" like is that the system is set up as a two stage system at the thermostat and that the second stage doesn't kick in until the heat pump can't keep up. Second stage is always lower than first stage, otherwise there would be no difference between the two.

    There may be a calibration in the t-stat to get the differential between 1st and second stage to be less.

    Or, find the balance point in which the heat pump cannot keep up with the heat loss and have a qualified HVAC technician install an outdoor thermostat to switch the heat pump to furnac only when the outdoor temps are a few degrees above the balance point.
    Government is a disease...
    ...masquerading as its own cure…
    Ecclesiastes 10:2 NIV


  12. #12
    This is the Ask Our Pro's forum, and only Pro members that have been vetted by the AOPC may post advise, commentary, or ask questions of the OP here. Please apply to the AOPC today, thank you.

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    Further infractions may result in loss of posting privileges.
    Last edited by beenthere; 01-30-2013 at 05:31 AM. Reason: Non Pro * Member

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