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btu sizing

daniel ( doctors heating & cooling)
daniel ( doctors heating & cooling) Member Posts: 24
in THE MAIN WALL
i know for central air the rule of thumb is 1 ton per 700sq.ft. what is the easiest and most correct way for determining btu size for furnaces.
thanks for this & all previous help!!

DANIEL

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Comments

  • Mark Wolff_2
    Mark Wolff_2 Member Posts: 77
    btu sizing

    Depending on your area, the tightness of your home, the overall climate, etc. The rate can be between 30 and 45 btu per square foot. The worst I have seen is just under 60 btu a square foot. It's not really the appropriate method, but it gives some guidance.
  • Brad White_144
    Brad White_144 Member Posts: 17
    Rules of Thumb

    What Mark Wolff wrote is pretty much my experience for a range of homes in a "low single-digit F." design area.

    The "60 BTUH per SF" is indeed too common and is found in uninsulated older frame houses. Sometimes this creeps up to 75 BTUH/SF if there is a lot of glass or leakage. Rather makes the case for air sealing and insulation, doesn't it?

    But it needs to be said: These are Check Figures only! They are used for preliminary ballpark estimates to get a rough idea of appliance size, but are not a substitute for a thorough heat loss calculation. Then these check figures corroborate what you have calculated (sanity check) and if your neighbors tolerate you, bragging rights for having lower numbers :)
  • [Deleted User]
    [Deleted User] Posts: 0
    Rules of Dumb...

    Can't take credit for coming up with that term. Can't remember who it was that did either, but Thanks for the use.

    There is NO substitute for doing a heat loss correctly. If you don't know how, or want to learn how, ask.

    Rules of dumb generally end up grossly over sizing the equipment, and that does absolutely NO ONE any good.

    JMHO

    ME
  • daniel ( doctors heating & cooling)
    daniel ( doctors heating & cooling) Member Posts: 24


    your rule of dumb comment? is that refering to the 1 ton for every 700 sq.ft a/c sizing i was taught? if so learn me on that as well as proper heat loss calc. thanks so much, all you guys are a godsend to us newbees!!!

    Daniel

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