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Thread: Heat Load Calc.

  1. #14
    Join Date
    Nov 2006
    Location
    Montana
    Posts
    134
    Quote Originally Posted by crash69 View Post
    There was a heat load calc done for permitting just ask him for it. 4 tons is perfect for that sq ft
    Assuming there was no heat loss calc performed, how do you know that 4 tons is what this house needs. You don't even know where the house is located other than in Kentucky. In my area, this could be a 2.5-3 ton house depending on construction, orientation, windows...well, you know...or do you?

  2. #15
    Join Date
    Jan 2004
    Location
    Lancaster PA
    Posts
    67,875
    Around here, 1700 sq ft 100+ year old drafty house is usually 3.5 tons.

    new construction with a lot of glass, 3 tons.
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  3. #16
    Join Date
    Feb 2008
    Location
    Western NC
    Posts
    2,504
    Quote Originally Posted by shodinjido View Post
    Assuming there was no heat loss calc performed, how do you know that 4 tons is what this house needs. You don't even know where the house is located other than in Kentucky. In my area, this could be a 2.5-3 ton house depending on construction, orientation, windows...well, you know...or do you?
    I think you scared em off. Good work. It was just starting to get interesting

  4. #17
    Join Date
    Nov 2006
    Location
    Montana
    Posts
    134
    Nah. He'll be back....We're the idiots afterall

  5. #18
    Join Date
    Sep 2004
    Posts
    175
    I've decided to do my own calculation, thanks for the help & smarta$$ remarks

  6. #19
    Join Date
    Jan 2004
    Location
    Lancaster PA
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    67,875
    There is seldom a shortage of remarks from us.
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  7. #20
    Join Date
    Mar 2007
    Location
    Connecticut
    Posts
    104
    Quote Originally Posted by jsherhvac View Post
    Is it required by code (in Kentucky specifically)that a contractor perform a heat load calc. on a install, or just good practice. The reason I ask is because I have not done any residential in years. I am looking at buying a new house 1750 sq ft w/ 4ton heat pump. Seems a little big to me. Any input or a place where I could go and read those type of codes on the net would be greatly appreciated.
    All the National codes require load calculations. If your jurisdiction uses a national code, then yes. With that said, what matters - and has been posted here ad-nauseum, is YOU need to do a professioinal Manual J load calculation regardless of what the builder submitted or says his/her mechanic did.

    That size Heat Pump they may have been chosen may be because of the heating load. Who knows? Is it a two-stage unit to help compensate for oversizing in the cooling? Is it zoned?

    New construction is running around 17 to 22 BTU's per square foot for heating loads, so your heat loss is probably around 35,000 BTU's (just a statistical guess). Your heat gains will range from 700 to 1200 square feet per ton, so I'd say you need around 2 tons of cooling in a house that size if it has Low-E glass and is reasonably tight.

    Again if you want to know for sure (well if you want to make sure it will work), do the Manual J, and to be really accurate, have a Blower Door test done to measure actual building infiltration and put the results of this back into the Manual J calculations.

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