Need advice on central AC unit(s)
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  1. #1
    Join Date
    Oct 2011
    Posts
    3

    Need advice on central AC unit(s)

    Hi,

    I have a 1 1/2 story house being built and need some advice on the AC. The house is 2400 sf with only a gameroom (340sf) upstairs that open to the 1st floor. The ceiling is 18" all around most of the house. I have a choice to choose between the following options:

    1. 1 16 Seers Unit Dual Zone
    Carrier 16seers 5 tons 2stage (I'm waiting for them model number)

    2. 1 Large and 1 small 14 seers units.
    Small unit: Carrier ca16na024 2tons
    Large unit: Carrier ca16na048 4tons
    More info can be found here: http://www.xpedio.carrier.com/idc/gr...a16na-01pd.pdf


    Any opinions or recomendation is much appreciated.

    Thank you in advance!

  2. #2
    Join Date
    May 2000
    Location
    Indianapolis, IN, USA
    Posts
    33,884
    Where are you? How well is this joint being built?

    5 tons seems a lot for new construction of that size unless you are in a very hot climate. If you really need that much, how are they insulating the place?

    Sure don't need 2 tons for the game room of 340 sq ft. A 1 ton mini split might be the way to go up there.

    Then a reasonably sized unit for the 2400 sq ft. Again, unless super hot or an extra lot of windows, 4 tons for 2400 sq ft seems big for new place.

  3. #3
    Join Date
    Oct 2011
    Posts
    3

    Frown

    I'm in North Texas which is extremely hot here.
    The house is not big, but has a big open space with 18" ceiling. I do have a lot of big windows around the house.
    It has radiant barrier and the following insulation:
    1. R-3 Insulated sheathing on all Exterior Walls
    2. R-13 wall insulation
    3. R-22 batt insulation on sloped ceilings
    4. R-30 blown insulation on flat ceilings
    5. Poly-sealed foam base plates
    6. Poly-sealed foam wire and plumbing holes from attic
    7. Gasket seal at all Exterior wall base plates

    Thanks for the reply!

  4. #4
    Join Date
    Feb 2009
    Location
    Portland OR
    Posts
    1,941
    With a small pace like that why not something like a Mitsubishi ductless mini split if it's an open game room. They are up to 26 SEER and would be the most comfortable with a separate system downstairs. However a second system means more maintenance, repair bills and the like. If the upstairs area was larger I might suggest something different or if there are multiple rooms upstairs.
    Check out my YouTube channel - http://www.youtube.com/user/skyheating1 We have customer testimonials, product reviews and more!
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  5. #5
    Join Date
    Jun 2005
    Location
    SW Wisconsin
    Posts
    4,847
    Quote Originally Posted by rustedteg View Post
    I'm in North Texas which is extremely hot here.
    The house is not big, but has a big open space with 18" ceiling. I do have a lot of big windows around the house.
    It has radiant barrier and the following insulation:
    1. R-3 Insulated sheathing on all Exterior Walls
    2. R-13 wall insulation
    3. R-22 batt insulation on sloped ceilings
    4. R-30 blown insulation on flat ceilings
    5. Poly-sealed foam base plates
    6. Poly-sealed foam wire and plumbing holes from attic
    7. Gasket seal at all Exterior wall base plates
    Thanks for the reply!
    I agree with the pro posts, use a separate ductless on the only room upstairs.

    The other area looks well insulated, & depending on where the Return Air & Supply Air are located, in the cooling mode you could take advantage of stratification with the cold air at the occupant level.

    You can absolutely design your home to be super efficient, & then do a manual J, S, D & T to optimize the cooling mode equipment, duct system design & sizing.

    You could take nearly all the guesswork out of the equation.
    Who knows what size cooling equipment you need, but I'm betting it won't be 5-Ton!


    The 18' foot ceiling allows the heating mode air > to effectively heat where you aren't located.

    Where you are located, the cooling mode may be most important to design for.

  6. #6
    Join Date
    Oct 2011
    Posts
    3
    Quote Originally Posted by udarrell View Post
    I agree with the pro posts, use a separate ductless on the only room upstairs.

    The other area looks well insulated, & depending on where the Return Air & Supply Air are located, in the cooling mode you could take advantage of stratification with the cold air at the occupant level.

    You can absolutely design your home to be super efficient, & then do a manual J, S, D & T to optimize the cooling mode equipment, duct system design & sizing.

    You could take nearly all the guesswork out of the equation.
    Who knows what size cooling equipment you need, but I'm betting it won't be 5-Ton!


    The 18' foot ceiling allows the heating mode air > to effectively heat where you aren't located.

    Where you are located, the cooling mode may be most important to design for.
    It get pretty cold here too.
    I will check with them regarding the ductless. But I think that are the only 2 options they gave me.
    I think I might be going with the 2 seperate units. I believe the 4-tons is more than enough to cool my whole house. The smaller unit is most likely going to be backup.
    Is there a big diff. in saving between 16seers vs 14seers?

    Thank you all for you replies.

  7. #7
    Join Date
    Jun 2005
    Location
    SW Wisconsin
    Posts
    4,847
    Is there a big diff. in saving between 16seers vs 14seers?
    I personally believe optimizing RA filter areas & airflow factors, plus using a more efficient indoor DC blower motor may be more efficient ways to to invest the difference in 14 to 16-SEER unit prices.(?)

    I am sure others have many varying opinions concerning your question.

    You do have a long cooling season, however, a lot of it is at higher temps & not in the lower temp areas where SEER might become a little more of a factor.

    Perhaps some realistic thorough testing, on identical homes side by side with the same orientation, etc., using 14 & 16 SEER condenser's ought to be performed.

    The question is whether the price differential would result in enough increased savings...?

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