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  1. #1
    Join Date
    Feb 2005

    HVAC in new house - NOT WORKING

    Well, it does work downstairs but not upstairs. the system runs 24/7 and the temperature hovers around the low 80s when the outside temperature is in the 90s. The filters are clean and the system has been pressure washed to remove any dirt.

    The house, located in s.e. pa, has a geothermal system with the airhandlers for the 2nd floor in the attic. the units themselves are in an insulated "room" in the attic. on a recent inspection, the hvac contractor found that the coil on the airhandler had "iced up". one thing that the hvac guys did is to SLOW DOWN the fan speed so that the air flowed across the coil more slowly (i think i have this right). The duct work in the attic is insulated with foam insulation.

    the HVAC contractor, a good guy, is trying to figure out a fix for this. the steps he recommends:

    1. change the attic insulation to R-38 from R-30. The sizing of the system was made assuming R-38 but the wrong insulation was put in the attic by the builder.

    2. add an attic fan to move some of the very hot (130 degrees+ on days when the o/s temp is in the 90s) out of the attic. the roof has roof vents but the upper ones are not at the very peak of the roof, they are down the roof by about 20% of the roof (in other words, off about 20% from the top of the roof).

    my questions:

    a. do insulation changes often make a dramatic change in the efficiency of the system?

    b. i am reluctant to put another hole in my roof or add another mechanical system that could fail in terms of an attic fan of some sort. is such a device likely to reduce the high temperature that much and should i truly be concerned about having another mechanical device?

    c. i am not on any sort of witch hunt but i do want this system to work well. if i wanted to seek a thoughtful, unbiased opinion and evaluation of the system, where would i go? an energy consultant? another hvac person? i worry that my hvac people (like i said, i like them and they are good people and i believe competent) may not be able to step back and evaluate the system with a critical eye.

    thank you all for your input.

  2. #2
    Join Date
    Dec 2002
    Rochester, MN
    The guy who is working on the unit is from the company who installed this?

    Is this his first install of Geo system?

    How many Ton is this system upstairs, and is it Geo system for the lower level?

    Slowing down the blower is not going to stop the ice up.. COuld be low on charge.

  3. #3
    Join Date
    Feb 2005
    same guy did install who is working on it now, not his first.

    they checked the coolant level and adjusted it a small amount (i think they said they had too much).

    i dont know the unit size differences - will check.

  4. #4
    Join Date
    Aug 2003
    Fort Worth, TX
    Always better off to reduce heat gain to an attic than stick a fan up there in a desparate attempt to blow out heat that waltzed right through the roof decking and into the attic. That is...consider installing radiant barrier. A cooler attic translates to a cooler house. If ducts are in the attic, and sounds like yours are, a cooler attic also gives a capacity increase to your a/c system, without changing any equipment.

  5. #5
    Join Date
    Dec 2006
    Middle Tennessee


    Quote Originally Posted by mayguy View Post
    Slowing down the blower is not going to stop the ice up.
    not only will that not stop the ice up it will make it worse!


  6. #6
    Join Date
    Jan 2007
    Minneapolis, MN
    What is the air flow through the AC coil? What is the delivered BTU? Are there duct leaks? What is the CFM to the rooms? Was the system commissioned or did they just turn it on? What is the temp rise through the supply ducts? Need more information. R 30 to R 38 will help but minimally. Roof cooler has a bigger affect on attic temps.

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