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  1. #14
    Join Date
    Jun 2003
    Location
    Madison, WI/Cape Coral, FL
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    9,768
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    Quote Originally Posted by BaldLoonie View Post
    The comments that it should be on high for cool are dead wrong. A GOOD tech would take a static pressure reading and use the blower performance chart that came with the unit to set the CFM for no more than 400 CFM per ton. If you want more dehumidification, you want 350 CFM per ton. That looks like an X13 motor so there are 4 speeds plus constant fan on low. Someone should set the blower speeds correctly and see what happens. Do NOT run the blower constantly.
    This is good advice. You need an a/c coil temperature about 30^F below the return air temperature, the temperature in the home. 75^F, 50%RH, which is a 55^F dew point. When the outdoor dew point is +60^F, nothing to de with outdoor %RH, you need dehumidification in the home. First a cold coil a/c, next extended sensible cooling load. Like 4-6 hours per day to remove 4-8 lbs. per hour of moisture removal per hour.
    The fan should be in the "auto" mode.
    During hours of low/no sensible cooling and high outdoor point, supplemental dehumidification will be needed. In addition when the space is occupied, add 1-3 lbs. of moisture load.
    If you want good air indoor air quality, you need a fresh air change in 4-5 hours when the home is occupied.
    During cool damp weather, conventional a/c is unable to remove moisture without over cooling the home. Overcooling the home results in higher indoor %RH and the need for additional supplemental dehumidification.
    At the extreme over-cooling leads to mold growing on the damp cold side the drywall and on the damp side of ducts. Sensitive occupants will affected.
    You would do better to allow the home to warm when unoccupied which allows the condensation evaporates and dryout the materials. This interrupts mold growth.
    A properly setup a/c will dryout the home during a 1-2 cool down.
    Finally, to deal with wet cool weather, you will need an adequately sized whole house dehumidifier to get you <50%RH during low/no sensible cooling loads and high outdoor dew points.
    You had a record rainy period in TX. The homes with a ideal setup a/c and whole house dehumidifiers maintain 50%RH during all of this.
    You can not count of weather.
    Keep us posted. Ma be hot dry weather will returns to TX. Watch the outdoor dew point, not the %RH.
    Regards Teddy Bear
    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"

  2. #15
    Join Date
    May 2016
    Posts
    7
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    Thread Starter
    This setting did the trick. I think it disables outside air from entering. Ventilation Type=NONE


  3. #16
    Join Date
    Jul 2010
    Location
    napping on the couch
    Posts
    13,488
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    Did they set the fan to run continually thinking that more airflow over the filter is better? This will raise the humidity level in the house.

    Or, did they do a good job sealing the ductwork when they swapped out the filter assembly. Is it possible there is an air leak pulling humid air from wherever the air handler is?
    “Free men do not ask permission to bear arms.”
    -Possibly said by Thomas Jefferson(but true even if he didn't)


    “What one generation tolerates, the next generation will embrace.”
    ― Definitely said by John Wesley

  4. #17
    Join Date
    Jun 2003
    Location
    Madison, WI/Cape Coral, FL
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    Fresh air is way over rated. Indoor pollutants are not that bad, right. During calm weather natural infiltration declines, pollutants build, and oxygen declines. This fan "on" verses fan "off" is a biggy.
    Seriously, during peak cooling loads, an a/c with correct blower speed will remove remove the moisture from occupants and adequate fresh air ventilation. Measure the supply air temperature/%RH, calculate the dew point, should be 5^F below what you want in the space. 75^F, 50%RH, is a 55^F dew point. The a/c supply should be <50^F to maintain 50%RH..
    When you home is occupied, a fresh air change in 4-5 is a must if you value your health, long term.
    When the sun goes down or on a rainy day, the a/c does not run much. Therefore no moisture removal, therefore no humidity control.
    If the dew points outside are plus 60^F, you are breathing, how do any of you expect to maintain low %RH.
    Am I missing something?
    Keep posted on how humidity control can work when a/c loads are low and outdoor dew points are high for a couple days.
    Regards Teddy Bear
    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"

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