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Thread: Thermostat going bad??

  1. #1
    sfarmer is offline New Member
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    Thermostat going bad??

    We have a dual stage heat pump system and is 14 years old. Over the last few weeks the heater has started blowing cooler air. However when I turn the thermostat up 10 degrees, the air becomes warmer.

    Is it the thermostat going out or might it be the heating/ac unit?

    Thanks.

  2. #2
    Hube is offline Journeyman
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    The thermostat is more than likely OK. Its very seldom a thermostat will go bad. When you turn it up 10 degrees its kicking in the Heat Strip stage,(as it should) but the First stage is not working properly.. You will need a TECH to have a look at the heatpump.

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    16x80 is offline Handyman
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    sfarmer

    Welcome to the Home Repair Forum

    FYI! A heat pump unit is an air conditioner in reverse. In temps above 30 deg F your heat pump is the most efficient form of heat, In temps below 30 deg F your heat pump begins to become less efficient in removing the heat from the outside air and putting it into your home.
    As it becomes less efficient the temps coming out of your registers get lower and lower until the thermostat has a greater demand for heat then it kicks in the electric heat banks in your air handler.

    When you move the thermostat up 10 deg you are creating a greater need for heat, the extra demand causes the electric heat banks to kick on.

    What you should do when you heat pump becomes ineffective you should switch the thermostat to emergency heat mode and that will shut off your out door unit and allow the electric heat to run in the air handler.

    16x80


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    sfarmer is offline New Member
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    Thanks for the info. In California, the outside temps are at night are around 40 to 45 degrees right now. What I am thinking is that something might be wrong with the pump itself. When I do turn it up the second stage does kick on.

    Does this mean I need to replace the pump or something that might be able to be repaired.

  5. #5
    hoar is offline New Member
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    Re: suggestion to switch to Emergency heat at 30 F.

    The efficiency of a heat pump decreases as the temperature drops.
    However so does the power required to run it. Mine still puts out 25,000 btus per hour at 20 degrees. Therefore do not shut off compressor by going to Emergency heat.
    However, 25 lbtus is not enough to heat the house. If the temperature of the room drops too far below thermostate setting then auxiliary heat is needed and is supplied by electric coils in furnace. On my thermostat, this is indicated by a light comming on labled aux.
    Air comming from furnace may feel cool but still be supplying heat. This is especially true near end of on cycle. If house is held at desired temperature, then at least part of furnace is working. If you use aux heat a lot, but not all the time, maybe coils are clogged, gass is low, or an actual malfunction. If compressor runs all the time but can't heat house, then aux heat is not comming on. I had a thermostat where the aux light was burned out, but could tell when aux heat was in demand by looking at mercury switches inside thermostat.

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    hoar is offline New Member
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    RE: go to emergency heat when temperature drops below 30 degrees.

    Efficiency does drop with temperature but so does power required to run compressor (outside unit)
    My unit pumps out 25,000 btuh at 20 degress so do not switch to emergency power just because it's cold.

    Air from vent may feel cold expecially at end of cycle but may be supplying heat. If house stays at steady temperature you're ok. Do not place too much stock in numbers on thermostat--adjust it by how house feels.

    25,000 btus is not enough to heat my house. Then aux heat (electric heatere in furnace) kicks in and supplies extra. This cost more then power to run compressor, so keep in normal mode unless something is broken.

    If you use a mostly aux heat, maybe your coils neeed clearning (DIY) or unit needs service.

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