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  1. #1
    Join Date
    Jul 2008
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    Need Advice- Oversized System & Bad Installation

    I would greatly appreciate any advice from the forum on this. I bought a 2,800 sq ft house that was gutted, remodeled, and had an addition that doubled the house size (single story ranch). All new sheet rock, ceilings, insulation, windows, siding, plumbing, electrical, roof, and HVAC system. The builder used an HVAC contractor that never did a Manual J calc, and installed two 3-ton Goodman 16 Seer heat pump split systems with the condensers right next to the master bedroom window. I've been in the house for four months, now in middle of the hot South Carolina summer. I hired a third party, qualified HVAC contractor to give me a detailed report of the many installation deficiencies (too ugly and numerous to list) and he told me that the system is way oversized for the house.

    I bought HVAC-Calc and ran the Manual J calcs myself with great care. As an engineer and competent software user, I am confident that the software is giving me accurate results. Using this, HVAC-Calc specifies a 2.5 ton system for the Living Space zone, and a 1.5 ton system for the Bedroom zone (with conservative inputs for the infiltration, insulation, shading, windows, etc). The contractor installed a 3 ton system for the Living Space zone and another 3 ton system for the Bedroom zone. The BR zone system is double what it needs to be.

    I'm aware of the problems with having an oversized system, but the sad fact is that it is so common for HVAC contractors to oversize systems - how much of a case do I need to show negligence in order to force my builder to correct the problem and replace the system with the right sized units? When I told my builder and another Goodman contractor about the problems their first response was "it should be the right size units according to your home's square footage and using a rule of 1 ton per 500 sq ft."

    I would appreciate any helpful advice. Thanks in advance!

  2. #2
    Join Date
    Jul 2008
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    Quote Originally Posted by rb282 View Post
    When I told my builder and another Goodman contractor about the problems their first response was "it should be the right size units according to your home's square footage and using a rule of 1 ton per 500 sq ft."
    Dun dun dun.

    I shudder when I think of what other problems and spotty construction practices are scattered around your house. Seems to me "remodeled" more often than not usually means "we covered up everything bad with lots of paint and thick knock-down texture."

    I'm not really familiar with how you go back after builders for this kind of thing. But was there ever an agreement or contact outlining what you were getting? That would be a place to start. Otherwise, if you just bought the place "as-is" I doubt there is much you can do. Sounds like you've found one decent contractor though. Good luck. =\

  3. #3
    Join Date
    Jun 2003
    Madison, WI/Cape Coral, FL
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    Get what you can out of the builder. After you exhaust that, Adding a whole house dehumidifier will control the indoor humidity regardless the size of the a/c. I have done that many times. All a/cs end-up over-sized during low/no cooling load. If you getting adequate fresh air during the low cooling conditions, all homes end up humid after a week. Adding 50-90 lbs./day of supplemental dehumidification keeps the entire home <50%RH. Most homes need 50-75 cfm of fresh air to purge indoor pollutants. During the winter the stack effect added to wind provides this fresh air. During the summer no stack effect and winds are intermitant. Regards TB
    Bear Rules: Keep our home <50% RH summer, controls mites/mold and very comfortable.
    Provide 60-100 cfm of fresh air when occupied to purge indoor pollutants and keep window dry during cold weather. T-stat setup/setback +8 hrs. saves energy
    Use +Merv 10 air filter. -Don't forget the "Golden Rule"

  4. #4
    Join Date
    Jan 2004
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    Take some humudity readings and record them.
    Then have your lawyer send the builder a letter with a copy of the load calc, and your humidity readings.
    Your lawyer will know how to word it.
    You'll get a better response then.
    Contractor locator map


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

  5. #5
    Join Date
    Apr 2007
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    Lawyers are a lot more expensive than HVAC guys

    My rule is never sue anyone if its less than $10,000.
    I've eaten some bad stuff from contractors, but I'm convinced
    that's the smart thing to do.

    I'm sure you can have a smaller unit put in your bedroom
    area for a lot less than $10,000.

    I think you have a particularly hard case to make that the unit
    is oversized. Now if it was dangerous that might be another
    story. I've had dangerous.

    If this is the only issue you have I'd suggest forget sueing.

    However if you just discovered the whole house is built on
    quicksand and is going to subside its another story.

    Don't feed the lawyers!

    If you are really mad at the contractor you could threaten him
    with some bad publicity. I've had some success with this route.

  6. #6
    Join Date
    Aug 2005
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    I think Teddy Bear nailed this issue. The biggest problem from oversizing results in high humidity leading to mold and other health related issues. Take the $10,000 lawyer money and get a good contractor to install a whole house dehumidifier and feed yourself instead of the lawyer.

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