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  1. #11
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    Jul 2009
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    Northeast
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    661

    Default Re: Maximum Effectiveness with a Programmable Thermostat

    Look into an Aprilair whole house humidifier, there not to hard to install and it would be better than a basic humidifier.

  2. #12
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    Default Re: Maximum Effectiveness with a Programmable Thermostat

    There is no magic number limit for setting back a thermostat. No disrepect intended Houston -- but what did your late father-inlaw base that number of 7 on ?
    The lower the delta-T ( the closer the inside temp and outside temp are ) the less heat loss --- the less the heating system has to operate --- the less fuel burned and less electricity used.

    Personally, I set back my thermostat 8 degrees and have experienced a 25% savings on my utility bill.

    The determining factors are how low a temperature is comfortable and at which point is the dew point for the Relative Humidty ( RH ) creates condensation issues.

    There's plenty of creditable information available --- just google and check the reputable sources and you will see the facts.
    "" an ounce of perception -- a pound of obscure "
    - Rush

  3. #13
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    Dec 2010
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    Houston Texas
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    Default Re: Maximum Effectiveness with a Programmable Thermostat

    The 7F temperature swing was told to me by an engineer with PE&G who worked for the company for 40 years. He wasn't one to settle unless he tested everything himself. Unless you install an 'hours run' meter on your heater, its somewhat difficult to guage how much energy usage occurs. There are too many external variables; wind, temperature, humidity are the big 3, but the heater is either running or it is not. (most being single stage) When properly sized, a heater is supposed to run nearly all the time on the coldest of cold days one normally experiences. From that one can see that a larger heater would run less but be less efficient considering the energy expended to get the heater up to speed and then when the heater turns itself off. The heat inside the heater after running isn't used for heating the house. Yes, the larger heater would run less, but the overall expense would be greater. If larger heaters were more effecient, then we would all have huge hunkering heaters that ran for 3 seconds a day.

    Since we know that a properly sized heater will run nearly all the time, then turning it off - or the temperature down very far - has the effect of making it run longer when turned back on to bring the house back to temperature. All the time the heater is off, the heat is leaving the house, the furniture, the walls, the fish tank, everthing in the house. When the heater is turned back on, the air is the first to come to temperature, but the objects in the house take much longer to come up to temperature. Depending on the run time, the objects may never come to temperature and remain closer to the lower thermostat temp setting. These cooler objects act against the heater every time the heater is turned back on. They make the heater cycle more often (or run longer) than it would if the objects were already at the desired temperature. The mass of those objects are a huge heat sink. By maintaining a more constant temperature, that of a 7 swing or so, that thermal mass is put to use by moderating the ambient air temperature, and making the heater work less or needing a smaller heater (both use less energy).

    Think about your refridgerator- everyone knows a fully packed or very empty fridge takes more energy to run. The fully packed fridge has more thermal mass to keep things cool, but air flow is very restricted. An empty fridge looses its thermal mass when the door is opened and the cold air drops out onto the kitchen floor.

    An 8F swing might very well be perfect for your heater & home.
    Last edited by HoustonRemodeler; 12-21-2011 at 01:16 AM.

  4. #14
    Join Date
    May 2009
    Location
    Elyria, Oh.
    Posts
    236

    Default Re: Maximum Effectiveness with a Programmable Thermostat

    Heat loss is pure physics. There is no 7 or 8 degrees or any other temperature that is the best temperature. The 2nd law of thermodynamics states that heat always flows from a warm body to a cooler one, never in the opposite direction.

    When the temperature of the air mass surrounding a building is colder than the air in the building then heat will flow from the building to the air surrounding it. The greater the difference between the two the faster the heat loss.

    Anytime you decrease the difference between the two you reduce the heat loss. The only way we humans can do this is to turn the temperature down in our houses and other buildings bacause we can't control the outside temperature. The greater amount and time that you turn your own heat down the more money you save. It is just that simple. You can slow heat transfer with insulation but you can never stop it.

    There is also no truth that your furnace works "harder" to to get the building back to the design temperature and therefore negates any savings. Any heating unit whether boiler, forced air, electric or otherwise has a certain BTU capacity and it will only operate at the capacity.

  5. #15
    Join Date
    May 2011
    Posts
    251

    Default Re: Maximum Effectiveness with a Programmable Thermostat

    +1 on the above. The efficiency of the furnace changes little based on how long or frequently it runs. Oversized equipment however, causes the indoor temp to have larger and more frequent swings, this uses more energy.
    1925 Two-Story Stucco Beaux Arts Neoclassical

  6. #16
    Join Date
    May 2011
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    251

    Default Re: Maximum Effectiveness with a Programmable Thermostat

    Quote Originally Posted by HoustonRemodeler View Post
    Think about your refridgerator- everyone knows a fully packed or very empty fridge takes more energy to run. The fully packed fridge has more thermal mass to keep things cool, but air flow is very restricted. An empty fridge looses its thermal mass when the door is opened and the cold air drops out onto the kitchen floor.
    Sort of.... a fridge is less efficient when airflow is restricted. That is true. It's less efficient when empty because with so little mass, the compressor only runs for a short time. Unfortunately, it's not common knowledge that short compressor cycles are less efficient... or that restricted airflow is bad... oherwise people would stop wanting their AC systems oversized. IT can take 5 minutes or longer for a refrigeration system or cooling system to reach peak performance.
    1925 Two-Story Stucco Beaux Arts Neoclassical

  7. #17
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    Aug 2007
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    The Great White North
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    Default Re: Maximum Effectiveness with a Programmable Thermostat

    Houston ----Not debating with you rather having a discussion

    Not to beat this topic to death -- There is no magic number --- the swing can be anywhere from 1 - 10 degrees --- the amount of setback is dependant on each individual home and the occupants.


    I'm not going to micro-analayze and discuss all your points you posted . Though one point needs to be said------
    A furnace is either off or on --- there really isn't much energy loss when the furnace starts up and doesn't have to come* up to speed * --- not like an automobile .

    Simply looking at your utility bill you will see a reduction of fuel consumption which equates to a cost savings.
    "" an ounce of perception -- a pound of obscure "
    - Rush

  8. #18
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    Aug 2007
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    The Great White North
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    Default Re: Maximum Effectiveness with a Programmable Thermostat

    Quote Originally Posted by Mclark View Post
    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?
    Just don't have the humidty level too high otherwise you risk potential condensation which could also lead to mould mildew issues.
    "" an ounce of perception -- a pound of obscure "
    - Rush

  9. #19
    Join Date
    May 2011
    Posts
    251

    Default Re: Maximum Effectiveness with a Programmable Thermostat

    Yes, human comfort is tied directly to humidity levels. Your ability to sweat or determines comfort level as much as temperature. A change in relative humidity of 10% could make the air tempature feel 1-2F warmer or cooler.

    SO yes, humidty will allow you to keep the house cooler which will save energy. But yes, you don't want to have it too humid. 35-40%RH is a good target down to 15F and 20-30% below that.

    Humidity levels is also why oversized AC Systems use more energy. Air conditioners also use more energy when they short cycle.
    1925 Two-Story Stucco Beaux Arts Neoclassical

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