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  1. #1
    Join Date
    Dec 2007
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    Default Maximum Effectiveness with a Programmable Thermostat

    I live in a 3,500 Square Foot East Lake Victorian that was once a boiler/radiator system. But the house was converted into apartments and they installed two forced air furnace systems (one upstairs and one down). We have programmable thermostats for both and we often wonder if we are setting them too cold in their down period as it takes a while for the house to warm up.

    At night, we have the 2nd floor set at 63 degrees and the 1st floor set at 50. The 1st floor kicks on around 3:30 runs nonstop for over 2 hours to get to 65 degrees. Then the same thing happens at the end of the day when we get home. It has some tech in it that allows it to calculate when it needs to turn on to have the house warm by a particular time, but I am wondering if it running for so long to warm up for such a short period of time is off setting the potential savings of it going down that low in the first place.

    So, how low is too low when it comes to programmable thermostats?

  2. #2
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    Aug 2007
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    Default Re: Maximum Effectiveness with a Programmable Thermostat

    Quote Originally Posted by Mclark View Post
    I live in a 3,500 Square Foot East Lake Victorian that was once a boiler/radiator system. But the house was converted into apartments and they installed two forced air furnace systems (one upstairs and one down). We have programmable thermostats for both and we often wonder if we are setting them too cold in their down period as it takes a while for the house to warm up.

    At night, we have the 2nd floor set at 63 degrees and the 1st floor set at 50. The 1st floor kicks on around 3:30 runs nonstop for over 2 hours to get to 65 degrees. Then the same thing happens at the end of the day when we get home. It has some tech in it that allows it to calculate when it needs to turn on to have the house warm by a particular time, but I am wondering if it running for so long to warm up for such a short period of time is off setting the potential savings of it going down that low in the first place.

    So, how low is too low when it comes to programmable thermostats?
    Not really. The longer the thermostat is set back and the lower the temperature the less frequent the heating system runs = a savings.
    The run time that brings the temp up won't diminish the savings by much.
    Though running non-stop for two hours sounds strange -- unless the up temperature is very high.
    I have my setback at 60 then at 3:30 comes up to 69 -- the furnace runs for maybe 20 minutes.
    At lot depends on how well insulated and air tight the living spaces are.
    "" an ounce of perception -- a pound of obscure "
    - Rush

  3. #3
    Join Date
    Jul 2010
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    SoCal
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    5,084

    Default Re: Maximum Effectiveness with a Programmable Thermostat

    I'm not a fan of programmable thermostats. My tenants used to mess them up, so I replaced them all with simple to use 'hot and cold' cheap thermostats and I've never had any complaint since.

    These simple thermostats still allow you to have your furnace automatically go on when the temp in the room dips below the desired temperature.

  4. #4
    Join Date
    Dec 2010
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    Houston Texas
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    Default Re: Maximum Effectiveness with a Programmable Thermostat

    Its been my experience that a 7 degree swing is the most you want between the high and low temps on the thermostat. I was told this by an engineer with the local utility company whom I have known for decades. After the 7 degree swing, the efficientcy goes down,

    I too have simple thermostats for renters after replacing the fancy ones.

  5. #5
    Join Date
    Jul 2009
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    Default Re: Maximum Effectiveness with a Programmable Thermostat

    Quote Originally Posted by HoustonRemodeler View Post
    Its been my experience that a 7 degree swing is the most you want between the high and low temps on the thermostat. I was told this by an engineer with the local utility company whom I have known for decades. After the 7 degree swing, the efficientcy goes down,

    I too have simple thermostats for renters after replacing the fancy ones.
    I'd have to agree with Houston, it's easier to figure out if your losing, winning or breaking even with oil heat by the nozzle size or how many gallons an hour you use, .5 x 75 would be 1/2 gallon an hour, the 75 is the spray angle or pattern. Then you have to know how many times your furnace comes on in an hour verses how long your furnace stays off when the stat is turned down. Then how long does it run to get to the desired temp. the next morning. It's just Math

  6. #6
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    Jul 2009
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    Default Re: Maximum Effectiveness with a Programmable Thermostat

    Quote Originally Posted by Sten View Post
    I'd have to agree with Houston, it's easier to figure out if your losing, winning or breaking even with oil heat by the nozzle size or how many gallons an hour you use, .5 x 75 would be 1/2 gallon an hour, the 75 is the spray angle or pattern. Then you have to know how many times your furnace comes on in an hour verses how long your furnace stays off when the stat is turned down. Then how long does it run to get to the desired temp. the next morning. It's just Math



    Never thought I'd break 600

  7. #7
    Join Date
    Dec 2007
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    20

    Default Re: Maximum Effectiveness with a Programmable Thermostat

    Quote Originally Posted by HoustonRemodeler View Post
    Its been my experience that a 7 degree swing is the most you want between the high and low temps on the thermostat. I was told this by an engineer with the local utility company whom I have known for decades. After the 7 degree swing, the efficientcy goes down,
    Thank you for the information. I will make changes tonight. I was also told that using a basic humidifier will help make the air feel warmer than it is. Does anyone know if that is true?

  8. #8
    Join Date
    Dec 2010
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    Houston Texas
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    Default Re: Maximum Effectiveness with a Programmable Thermostat

    Yes that is correct. Humid air 'feels' warmer than dry air.

    Just ask the people of Houston and Phoenix

  9. #9
    Join Date
    Dec 2010
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    Houston Texas
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    Default Re: Maximum Effectiveness with a Programmable Thermostat

    One more thought;

    Most folks think if the heater runs full tilt all the time its a bad thing. It usually isn't for a simple reason; if the heater is correctly sized, then on the coldest days it should run about 90-95% of a 24 hour day. Too big a heater and it will cycle less. Too small a heater and it will never turn off and the house will not get to temperature.

  10. #10
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    Northeast
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    Default Re: Maximum Effectiveness with a Programmable Thermostat

    Quote Originally Posted by HoustonRemodeler View Post
    One more thought;

    Most folks think if the heater runs full tilt all the time its a bad thing. It usually isn't for a simple reason; if the heater is correctly sized, then on the coldest days it should run about 90-95% of a 24 hour day. Too big a heater and it will cycle less. Too small a heater and it will never turn off and the house will not get to temperature.

    Of course the heat is going to run most of the time of a 24 hour day. On the coldest day, -5 or whatever, it's going to run as soon as the temp drops to what you have the stat set for and it will maintain that temp. As for 90-95% maybe.

    One more thing with Programmable Stats., if there is people in the house that get up at diff. times, have diff schedules and come home at diff. timmes or are in and out of the house all day your better off just getting a Manual Stat. We have a Braburn and it's not even programed just for that reason.

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