Air Circulation for Natural Gas Furnace

Discussion in 'Home Repair' started by MD, Aug 16, 2006.

  1. MD

    MD Guest

    I have a small 1000 sq. ft. house with a basement in Southwestern
    Ohio. The basement has about an 8" diameter hole (covered by a flap)
    in it that a handyman said was for air circulation for the Gas Furnace
    that I have in the basement. Do I really need outside air from this
    hole to run the furnace? Also, if the hole does serve the furnace, is
    there a way I can work around it and get the air from somewhere else?
    It seems very wasteful to me to have an open hole in a basement during
    Ohio winters, and I would like to block the hole. Thanks,

    MD
     
    MD, Aug 16, 2006
    #1
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  2. MD

    m Ransley Guest

    If your house is fairly new with very tight construction and tyvek and
    your furnace vents through a chimney it is possible you could not draft
    when the dryer and motorised vents such as bath vent are on. If so test
    it, but it is most likely unessesary
     
    m Ransley, Aug 16, 2006
    #2
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  3. MD

    hallerb Guest

    at least run pipe from holew to furnace/

    rather than a handyman a HVAC pro is the person to ask when getting the
    furnace serviced before fall...
     
    hallerb, Aug 16, 2006
    #3
  4. If it is properly installed, it is not wasteful, but saving you money.

    You want to bring in combustion air from the outside. You don't want to
    burn up the air you just paid to heat, then suck in more cold air through
    cracks around windows and doors and have to reheat it again.

    If you look at how your furnace works, you may get a better understanding of
    this. There is a heat exchanger that has the flame on one side, the inside
    air circulating on the other side. The air feeds the flame, then is carried
    up the flue along with any exhaust gases, carbon monoxide, etc, all stuff
    you don't want to breath. Meantime, the heat exchange is sort of a hot
    metal box and the inside air passes over it, gets warmed, and goes
    throughout the house.
     
    Edwin Pawlowski, Aug 16, 2006
    #4
  5. MD

    MD Guest

    In response to Edwin I would state that I can understand the
    theory, but it just seems like such a big opening is overkill. It
    seems like there should be a more cost effective way of getting fresh
    air into the basement. I would note that I previously lived in a house
    with a gas furnace in a basement that was sealed and that the furnace
    ran with no problems. Right now it seems as if on a cold winter day,
    the furnace would be running continuously, and I would be wasting a
    substantial amount of heat. Thanks to everyone for their
    contributions.

    MD
     
    MD, Aug 16, 2006
    #5
  6. MD

    Old Fangled Guest

    Absolutely required. This is air that serves as combustion air for the
    furnace -- drawing it from inside your house leaves you at serious risk of
    furnace fires, CO/CO2 poisoning, or even explosions.
    The air has to come from the outside of your house. Think of it this way
    -- all of that cold air drawn in through the pipe is immediately sent right
    back outside again (up the chimney). The cold air hasn't contributed to
    any cooling of your house.
    Buy a higher efficiency furnace -- they still draw combustion air from
    outside, but they extract almost all of the waste heat going up the
    chimney.
     
    Old Fangled, Aug 17, 2006
    #6
  7. You use words like "seems like" Unless you know for sure, it is speculation
    on your part. More information would help. It is not a question of running
    with "no problems", it is question of using outdoor air for combustion, not
    the heated indoor air. That combustion air must come from someplace, even
    if you don't see it. Perhaps a vent in the old house would have cut your
    heating bill by 20%.

    Where is the hole in relation to the furnace? What is the area of the stack
    and heat exchanger intake? What is the air requirements for combustion air
    in cfm? What is the Btu input of the furnace? A possible improvement may
    be to duct the intake closer to the heater intake if the area around the
    heater is not sealed off. .

    FWIW, the boiler in a warehouse building that I operate has a motorized
    damper to allow fresh air in. The opening is about 60" x 48". Yes, you
    want to wear a jacket in the boiler room when it is running, but the rest of
    the building is nice and warm, very efficiently.

    Evidently, you don't understand the theory or you would not think you are
    wasting a substantial amount of heat with the furnace running. The purpose
    of the vent is to AVOID wasting the heated air, instead, using the outdoor
    air for combustion. .
     
    Edwin Pawlowski, Aug 17, 2006
    #7
  8. MD

    Decilj Guest

    Thanks for your very detailed and helpful response. I will look into
    the issues you raised.

    MD
     
    Decilj, Aug 19, 2006
    #8
  9. MD

    bowgus Guest

    Does your gas furnace have a chimney (or is it a high efficiency with
    intake/output with PVC). If you have a chimney, the air for combustion
    has to come from somewhere, hence maybe the simple flap idea. An
    enclosed furnace room with outside air into that would be better.

    However ... up here with a tighly sealed house and high efficiency
    heating, the air in a house can get mighty stale in winter without some
    sort of air exchange arrangement. So it could be that simple flap
    arrangement is serving 2 purposes ... combustion air and fresh air into
    the house ... and maybe that's what the handyman meant by air
    circulation.
     
    bowgus, Aug 19, 2006
    #9
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