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  1. #1
    Join Date
    Nov 2007
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    Default Down Regulating furnace?

    We are having a new heating and cooling system installed for the 2nd and third floor of our home. The current furnace was sized for the 1st and second floor. A HVAC person recommended "down regulating" our current furnace in order to continue to use it. Does this work, or should we get a new furnace that would be sized for only the first floor?
    Also any experience with wall mounted electric panel heaters?

  2. #2
    Join Date
    Feb 2008
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    550

    Default Re: Down Regulating furnace?

    Tes:

    Downsizing of heating units is done quite often---could you provide more info as to how old the unit is, is this forced hot water heat, or forced hot air, oil-fired, or gas-fired; and the age of the furnace/boiler.

    Could you check the name tag on the heating unit to determine its output; name of furnace/boiler & model #.

    What is the total square footage of the 1st floor, total square footage of all windows & sliding glass doors.

    If the heating tech recommended it be done, it's probably a good idea.

  3. #3
    Join Date
    Jan 2010
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    163

    Default Re: Down Regulating furnace?

    It sounds like he's recommending keeping the existing furnace, but reducing its input--that is, its BTU input.

    This can be done by installing smaller orifices to the burners so that what was once, say, an 80k BTU furnace, now becomes a 60k BTU furnace.

    This is commonly done, and is a good idea since you are decreasing the load that the furnace formerly had. The fan speed for the blower can also be reduced if needed to more nearly match the new BTU output.

  4. #4
    Join Date
    Nov 2007
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    5

    Default Re: Down Regulating furnace?

    Quote Originally Posted by NashuaTech View Post
    Tes:

    Downsizing of heating units is done quite often---could you provide more info as to how old the unit is, is this forced hot water heat, or forced hot air, oil-fired, or gas-fired; and the age of the furnace/boiler.

    Could you check the name tag on the heating unit to determine its output; name of furnace/boiler & model #.

    What is the total square footage of the 1st floor, total square footage of all windows & sliding glass doors.

    If the heating tech recommended it be done, it's probably a good idea.
    It is a Trane XB TUE1c 80k BTU gas furnace. It was installed about 3 years ago. 80% efficency. The space it serves is likely 2000-2400 sq feet. But I was told the furnace was specifically sized for the two floors. We are planning on adding a second unit to heat the unheated 3rd floor and to also serve the second floor. So, the space heated by the furnace, may be cut in half.

    Any exerience with electric heating panels that go on walls?

    Thanks

  5. #5
    Join Date
    Feb 2008
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    550

    Default Re: Down Regulating furnace?

    Tes:

    The only accurate way of determining how closely sized the original furnace is to the 1st floor is to do a comprehensive, computer-driven HEAT LOSS CALCULATION.

    If the Trane XB80 furnace is still rated at 80,000 btu/hr, it would depend on what the heat loss estimate is for the first floor alone.

    This would depend on a lot of factors, such as total square footage, total square footage of windows, glass doors if any, your geographical location, exterior wall composition & insulation, etc.,etc.

    The 1st floor heat loss may be 80k, or considerably less, depending on the factors stated.

    Electric panels are often installed only when there is no other option, due to the normally high cost of electrical service---electric heat is often the most costly way of heating a home if your local rate is above 10 cents/kwh---they have some emergency use in the event the gas furnace breaks down for something other than a power outage.
    Last edited by NashuaTech; 01-13-2010 at 11:03 PM.

  6. #6
    Join Date
    Jan 2010
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    163

    Default Re: Down Regulating furnace?

    Although what NashuaTech says about doing a load calc as the only way to know the heating needs of the space is true, there are practical limits to this in your case:

    Since you are reducing the area served by the existing furnace by half or more, and do not plan on replacing the furnace, even if a load calc showed it to be two or three times as big as needed, you would still end up just de-rating, or down-regulating. And there are limits as to how much de-rating can be done with the existing unit.

    It will be cheaper and easier to do a trial-and-error de-rating. Let your furnace guy de-rate according to his best guess with the understanding that if more is needed later, he can come back and tweak it further.

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