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  1. #1

    Interpreting HVAC-CALC Results

    I am converting my garage into a family room. Trying to figure out whether I can tap into my existing central air or if I need to go with a ductless mini-split.

    Did a HVAC-CALC tonight.

    Existing: 10,000 Gain, 29,000 Loss

    Garage: 6,500 Gain, 13,500 Loss

    Total: 16,500 Gain, 42,500 Loss

    I have a 1.5 ton 10 SEER A/C, and a 40,000 BTU furnace.

    So I am close. But is it too close? Any advice?

    Thanks,

    Chris

  2. #2
    Join Date
    Jun 2007
    Location
    south carolina
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    175
    1.5 ton is 18000 btu's of cooling so if you did your numbers right then it looks good. Although mini splits are nice too.

  3. #3
    Join Date
    Aug 2003
    Location
    Lincoln, Nebraska
    Posts
    1,051
    Depending on the match between the indoor and outdoor unit you may not be getting close to 18000 BTU's. You would need to find out by posting indoor and outdoor model numbers and see if we could tell you. Is your furnace 80%, 90%? I woud say you are really close but it may work.
    Its a good Life!

  4. #4
    Join Date
    Jan 2004
    Location
    Lancaster PA
    Posts
    67,765
    Is that total gain, or sensible gain.
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  5. #5
    Quote Originally Posted by beenthere View Post
    Is that total gain, or sensible gain.
    12.5K Sensible + 4K Latent = 16.5 Total

  6. #6
    Join Date
    Jan 2004
    Location
    Lancaster PA
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    67,765
    If your OD design is 95, and you did your ID design at 70.
    The average 1.5 ton won't have a 12,500 BTU sensible capacity.

    So on those 95 degree days it would lose temp a little.
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  7. #7
    Join Date
    Aug 2004
    Location
    North Richland Hills, Texas
    Posts
    14,914
    In addition to the possibly undersized AC, if your furnace is 80% efficient, you only have 32,000 btu of output, at best.
    If more government is the answer, then it's a really stupid question.

  8. #8
    Quote Originally Posted by m kilgore View Post
    Depending on the match between the indoor and outdoor unit you may not be getting close to 18000 BTU's. You would need to find out by posting indoor and outdoor model numbers and see if we could tell you. Is your furnace 80%, 90%? I woud say you are really close but it may work.
    Armstrong Concept 10
    SCU10A18A-3A
    S/N: 8496B13894

    Contractor told me the 18 in the model # means 1.5 ton. Can someone verify that.

    Armstrong Ultra II 97
    EG6E40DC13-6
    S/N: A18170KMA
    Natural Gas

    Furnance clearly says 40K BTU.

    Thanks for your help,

    Chris

  9. #9
    Join Date
    Jan 2004
    Location
    Lancaster PA
    Posts
    67,765
    Its a nominal 1.5 ton A/C.
    Weather its true capacity is 18,000 BTU's or not, that I can't tell you.
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  10. #10
    Join Date
    May 2007
    Location
    DC Metro Area (MD)
    Posts
    3,369
    Your furnace output won't be 40k btu, as Mark said.

  11. #11
    Join Date
    Aug 2002
    Location
    Office and warehouse in both Crystal River & New Port Richey ,FL
    Posts
    18,836
    Quote Originally Posted by wrldruler View Post
    I am converting my garage into a family room. Trying to figure out whether I can tap into my existing central air or if I need to go with a ductless mini-split.

    Did a HVAC-CALC tonight.

    Existing: 10,000 Gain, 29,000 Loss

    Garage: 6,500 Gain, 13,500 Loss

    Total: 16,500 Gain, 42,500 Loss

    I have a 1.5 ton 10 SEER A/C, and a 40,000 BTU furnace.

    So I am close. But is it too close? Any advice?

    Thanks,

    Chris
    Was the wall between the home and the garage ,treated as an inside wall in both calculations??

    If not the load would be reduced.

  12. #12
    Quote Originally Posted by dash View Post
    Was the wall between the home and the garage ,treated as an inside wall in both calculations??

    If not the load would be reduced.
    I ignored the wall between the garage house. It was not in the calc. Thanks

  13. #13
    Join Date
    Dec 2005
    Location
    Vero Beach, Florida, United States
    Posts
    2,669
    Put the mini split in the garage.

    Yes the 18 in the serial means 1.5 ton. Total capacity sensible and latent. I doubt it has 18k sensible capacity.
    Owner
    All-American Air Conditioning
    Vero Beach, Florida

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