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  1. #14
    Join Date
    Jul 2012
    Location
    michigan
    Posts
    5
    My other contractor offered putting 5 ton coil on 4 ton ac unit. Does it work or is it a sales gimmick. Also what size filter would I need for 4 ton unit.

  2. #15
    Join Date
    Jun 2005
    Location
    SW Wisconsin
    Posts
    4,967
    Quote Originally Posted by mi2006 View Post
    My other contractor offered putting 5 ton coil on 4 ton ac unit. Does it work or is it a sales gimmick. Also what size filter would I need for 4 ton unit.
    With your load conditions I would stay with a 4-Ton indoor coil, the compressor will be able to pull the pressure & temp down a little better at particular loads which will be helpful for humidity control.

    IMO, the slight gain in SEER is with lab conditions &, would usually be immaterial in your conditions in Detroit.

    However, that is a decision you have to make...

  3. #16
    Join Date
    Jul 2012
    Location
    michigan
    Posts
    5
    Thank you for your advice. Is there a way to calculate by how much the heat load will be reduced if attic insulation goes from R-35 to R-60 for example. Also, should the contractors perfom manual D calculation or is it only done for new construction or remodeling
    Last edited by mi2006; 07-22-2012 at 11:18 AM.

  4. #17
    Join Date
    Nov 2004
    Location
    SW FL
    Posts
    6,271

    Hmm Small

    Quote Originally Posted by mi2006 View Post
    Is there a way to calculate by how much the heat load will be reduced
    if attic insulation goes from R-35 to R-60 for example.
    876 BTU/Hr reduction based on ceiling/attic area of 1,600 square feet

    Q = U * A * dt

    120 T attic
    74 T room
    46 dT
    35 R
    0.0286 U = 1/R
    1600 A
    2102.86 BTU/Hr with R-35
    1226.66 BTU/Hr with R-60

    _876.19 Difference = 0.07 ton
    Designer Dan
    It's Not Rocket Science, But It is SCIENCE with "Some Art". ___ ___ K EEP I T S IMPLE & S INCERE

    Define the Building Envelope and Perform a Detailed Load Calc: It's ALL About Windows and Make-up Air Requirements. Know Your Equipment Capabilities

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