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Thread: new HVAC under performing

  1. #1
    Join Date
    Jun 2022
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    new HVAC under performing

    I just hired someone to install a new Trane XV18 in south Florida and its not performing like it should be. I am going in circles with the HVAC company as the best I can get is 80 degrees inside when its 98 outside. I suspect the problem is related to attic ventilation or insulation issues. The home was built in 2003. The air handler is inside the home and the main trunk line is in the attic above the insulation. The home is just under 2,000 sqft minus the garage space. The city inspector thinks the attic is warmer than it should be but everything else is up-to-code with the install. No leaks or anything. I suspect the problem is related to the attic which brings me to the following questions:

    1. Do I need more insulation?
    Currently it has about 8-10 inches of white blown-in fiberglass. If adding more, should I remove the current? For example is blowing new insulation on top of 20 year old settled insulation a bad idea? Also should I go with fiberglass or cellulose?

    How high should the insulation be? Would adding more insulation be ineffective if its not covering the flex tubes for the main trunk or the return lines crossing the bedrooms? I measured the temps w/ a FLIR camera on the return lines while standing inside the home and they are 10 degrees warmer than the home. My thought is cool air is circulating through the hot attic space which is bad.

    2. Do I need more ventilation?
    The soffit vents have baffles that were knocked around during the last hurricane. Insulation was unknowingly blown around and completely uncovering one of the bedroom ceilings. There are 3 ridge vents on the roof. Attic fan options dont seem viable and I dont have a gable. Although I am considering just pointing an attic fan at the ridge vents. Thoughts?

    3. What else could be the problem?
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  2. #2
    Join Date
    Aug 2009
    Beatrice, NE
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    In the bottom picture it looks like you have some windwashed insulation, IE a strong wind blew the insulation off the ceiling deck so you have exposed sheetrock.

    At the same time I do not see any vent troughs, styrofoam channels that keep the insulation from blocking the opening form the soffit to the attic.

    Seems to me the place to start would be to get someone versed in attic ventilation to correct deficiencies there, then add insulation if needed.

    Another option would be to spray foam the underside of the roof sealing it so it becomes line part of the conditioned space so the attic insulation and duct insulation is not as critical.

  3. #3
    Join Date
    Nov 2004
    SW FL
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    ___________ + INFILTRATION

    ONE must KNOW ALL the parts. ____________

    I would start with COMMISSIONING AND identify the perfomance for various XV18 operation modes.

    https://www.en %2011.pdf
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    Designer Dan __ It's Not Rocket Science, But It is SCIENCE with Some Art. _ _ KEEP IT SIMPLE & SINCERE ___ __ ___ __ Define the Building Envelope & Perform a Detailed Load Calc: It's ALL About Windows & Make-up Air Requirements. Know Your Equipment Capabilities

  4. #4
    Join Date
    Mar 2013
    East Concord, NY
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    What was in there before? Did it perform OK? What changed? Was the entire system removed and replaced?

    What is behind all that wood in the first picture? We can sort of see 2 insulated boxes....with something in between? Better pictures of the actual install would be helpful. The flex doesnt impress me much.
    Nest is POO!!

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