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  1. #1
    Join Date
    Aug 2010
    Posts
    11

    Sizing Two stage AC & three stage furnace

    I've had two contractors do calcs and tell me that the heat gain is about 28,700 for my house.
    They have each recommended a single stage and an option of a two Stage unit.
    The single stage size both say should be a 2.5 ton and two stage a 3 ton (don't come in half sizes).
    I am concerned with the three ton as I have that size now and it is very poor at taking humidity out as it runs for 5 or 6 minutes at a time.
    Can you safely oversize a two stage by a half ton or a ton and still get good dehumidification?
    I'm not sure what capacity a bryant runs at (Model 187B)
    1,650 sq ft ranch in up state NY, I run the AC A lot due to allergies so I'm leaning toward the two stage.
    Honestly I have the same question for the furnace.
    Calcs show right about 60,000 btu.
    One contractor is recomnding the three stage Bryant (Model 355CAV) at 60,000 BTU input and the other is saying to go with the 80,000 and it will run in 1 & 2nd stage most of the time making it more comfortable and cheaper.

    Any help would be appreciated.
    Last edited by jlvs13440; 08-11-2010 at 05:53 PM. Reason: Correcting AC Heat gain Number

  2. #2
    Join Date
    May 2000
    Location
    Colorado flatland native
    Posts
    15,067
    If your heatgain is that small, why not use a 2 stage 2 ton? 24,000 btu on high stage, les on low for the other 85% of the summer. Very good humidity control. I live in the Colorado Plains, my heat gain called for 4 ton, [3000 sq ft] I used a 3 ton 2 stage and am very happy!
    My doctor gave me six months to live, but when I couldn't pay the bill he gave me six months more.
    Walter Matthau

  3. #3
    Join Date
    Aug 2010
    Posts
    11

    Correcting BTU Calc to 28,700

    The contractors calcs were both about 28,700 for heat gain.
    (Not 23,000 & 26,000).

  4. #4
    Join Date
    May 2001
    Location
    Bennington, Vermont U.S.A.
    Posts
    13,864
    Up here in the NE you need a lot of horse power (tonage or capacity) to get rid of humidity. Once you get the moisture removed from your home than you can coast on less capacity.

    If it were me I would not be concerned with the 2 stage 3 ton system.

    As far as heat is concerned-- the more stages the better. Has anyone on suggested varible speed?

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