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  1. #1
    Join Date
    Jan 2008
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    Unhappy Fresh Air Intake Freezing/Frosting Up

    I live in Michigan, and recently had a fresh air intake put in that routes to my return duct on my furnace. It was professionally done, and put in to code. "First 10' Insulated." However, the remaining 12 feet, when the outside temperature drops below 20 starts to get condenstation, then below 15-10 range, freezes rock hard.

    I had them put in a shot off damper, and it has a one way valve in the line. My question is, why is it freezing? Is my house constantly pulling in cold air, and if so, why?

    What do I do to fix the problem. The general health of my family, since we put this in has greatly improved.
    Your help would be greatly appreciated.

  2. #2
    Join Date
    Jan 2004
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    Your pulling in fresh air any time any of your exhaust fans run. Bath, range hood, etc.
    Plus, natural exhaust, windows, doors, outer wall recepts, etc.
    So you may have a lot more fresh air coming in then you tought.

    Fesh air intakes should have motorized dampers so they only bring in air when the system is running.
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    How many times must one fix something before it is fixed?

  3. #3
    Join Date
    Jun 2003
    Madison, WI/Cape Coral, FL
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    Ideal to bring fresh air when the home is occupied. Best to have the ability to turn on the fan and open the damper when you walk in the door until you leave. Frost is normal when its very cold outside. You should have insulated the fresh inlet to the point where it connects to the return.
    Stack effect creates enough negative pressure at the rim joist to suck in fresh air all the time.
    Is your home getting enough fresh air during extreme cold? Not enough fresh air is indicated by condensation on the windows. Too much fresh air is indicated by extreme low indoor humidity. Static electricity is signal of excess fresh air. If extremely dry, close the fresh air inlet. Most homes do not get enough fresh air during the warm times of the year, because of the lack of stack effect.
    The sign of adequate fresh air during the time of the year that the outdoor dew point is high indoor humidity. That is unless the a/c or dehumidifier are removing 50-100 lbs. of moisture per day. I have never understood the concept of bringing fresh air in on when the heating/cooling system operates. As opposed to bringing fresh air into the home when the people are in the home. 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 2002
    East Grand Forks, MN
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    It was professionally done,
    It should have been insulated all the way to the point of the RA connection!!!
    Not very professionally done!

    Why was it put in? code or health or too wet!

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