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  1. #1
    Join Date
    Apr 2005
    Location
    Arlington, Texas
    Posts
    1
    I am currently contracting a new home to be built. I live in Dallas, Texas and need a little help making sure my A/C is sized properly and also want to upgrade to a better unit.

    I am having a 2975sq ft house built that will have two a/c units installed. I have 16ft ceilings in the foyer and the family room(350sq ft). The standard equipment is a 12seer Amana unit with a 80% AFUE(or something like that). I already know what a/c I am going to upgrade to, 14seer RCE model but am not sure of the model number Air Handler I should chose to go with it. I know I want a variable speed air handler I just don't want to break the bank and I also don't want to chose something that will be of no benifit.

    Which variable speed airhandler goes with this model and also can some tell me which units, sizes in tonage, I should see for the upstairs and downstairs. I have an optional game room that is closed off in the upstairs with about 350sq ft.(included in 2975sq ft)

    I know it is hard to size the units without doing a load factor but I would like a general idea to keep them honest. =)

    Thanks in advance for any help,

    Eric

  2. #2
    6 tons minimum .... 2 3.5 tons if zoned

  3. #3
    Join Date
    Jan 2004
    Location
    Lancaster PA
    Posts
    67,750
    The furnaces are your air handlers.
    Contractor locator map

    How-to-apply-for-Professional

    How many times must one fix something before it is fixed?

  4. #4
    Join Date
    Aug 2003
    Posts
    626
    Find an independant Firm that helps people build energy effecient homes. Call your electric utility or check the EPA Energy star program for your area. The ONLY way to size HVAC is with an accurate Manual J. Everthing else is just BS.

  5. #5
    Join Date
    Apr 2005
    Posts
    2
    i would say from what i hear 5 to 6 tons minimun figure the rule of thumb is 500 sq ft per ton but with 16 ft ceilings forget that get a load calc done. the AMV furnace 95% efficient matches up good with the RCE and in most cases accomplishes 15 seers plus u get the best warrantys on the market. lifetime compressor, and heat exchanger,10 years parts,who else is doing that or the 80% variable speed will also get the 15 seers with the high ceilings i would say variable speed is a good choice. and the RCE is a good unit. very quiet. the RCE will only get 14 seers without a variable speed motor but 14 seers is good too make sure you get the proper matching coil to get the seer you want to accomplish.

    [Edited by rnghvac on 04-22-2005 at 03:37 AM]

  6. #6
    Join Date
    Mar 2004
    Posts
    1,042
    What's important is that the contractor actually does the load calculation and that they guarantee performance. Rules of thumb are a waste of time. You have to know the insulation, the windows, which way the windows face, etc., before you can correctly choose the size of an air conditioner.

    Oversizing is worse than undersizing, especially in a humid climate like Houston. Oversized systems don't dehumidify well at all. If you get variable speed systems, ask the contractor to set it up with a humdistat for on-demand dehumidification.

    The best ways I've seen for a homeowner to make sure that a real load calculation is done are the following:
    -pay $50 for HVAC-Calc and do your own calculations to see if they are reasonably close to agreeing (but this requires some technical savvy)
    -demand to see their load calculation. They may not want to show it to you before they have a signed contract, but after that point, there's no reason they shouldn't show you. You can write a contract based on a size guess, with the condition that they will perform the load calc and show you their work once the contract is signed, and tweak equipment sizes as needed at that point to get it right.

    A furnace over 80% efficiency is a waste of money in Houston. Get a variable speed 80% if you're going to use gas for heat.

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