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  1. #1

    Level of humidity to expect in home

    I read in USA Today that a comfortable humidity level is anywhere between 35% to 50% relative humidity inside the home.

    I just had a Trane 15i 3.5 ton installed with a 5 ton Trane air handler (dip switched to run at 3.5 tons.)

    The system has run for a day and the humidity level in the house here in Orlando is 63% without opening doors/windows/taking showers for 12 hours.

    Is this within normal operating specs or should a well fitted unit do better?

  2. #2
    Join Date
    May 2006
    Location
    Tampa, FL
    Posts
    81
    Typical indoor summer relative humidity levels in Florida are around 55%. The 63% in your home seems high. Why do you have a 5-ton air handler with a 3.5 ton condensing unit? The larger coil is affecting the humidity removal of your system as it is not getting cold enough.

    Another issued could be how well your house is sealed up. Is it a newer home or an older home?

  3. #3
    Join Date
    Jun 2005
    Location
    SW Wisconsin
    Posts
    4,481

    Tremendous Number of Factors Involved

    There are a lot of factors involved in how fast or how low the system can bring down the humidity.

    Outdoor humidity level & air infiltration rate; amount of moisture in everything in your home that has to be given up before humidity can level to systems latent capacity.

    The number of things that can compromise latent heat removal are too numerous for my typing difficulties to list here. I'll leave it to those with good fingers, instead of eraser ends of two pencils! I have several in-depth I-pages on this subject - click udarrell above - Darrell
    Last edited by udarrell; 05-20-2009 at 10:21 AM. Reason: have I-pages on this subject

  4. #4
    Join Date
    Jun 2003
    Location
    Madison, WI/Cape Coral, FL
    Posts
    6,071
    I attached a pdf of Orlando weather for may 10-20 2008. A/c should be able to maintain <50% during the day with +90^F days on 5/ 8-10. So on hot days the a/c should be setup to remove significant amounts of moisture. During days like the 5/19-20 with cool weather, the a/c will not operate enough to remove significant moisture. Expect the moisture level to rise high levels depending on the number of occupants, the outside moisture, and the amount of a/c operation. Your home has moisture from the occupants, infiltration and ventilation fresh air. Your home should have air change every 4-5 hours as minimum to purge indoor pollutants and renew oxygen. Many are using a whole house dehumidifier to provide ideal humidity and even fresh air in tight homes. Whole house dehumidifiers are capable of maintain <50%RH throughout the home during wet cool weather without any a/c operation by removing 50-150 lbs. of moisture per day. Raising the indoor t-stat temps without concern about maintaining <50%RH saves energy.
    Regards TB
    Attached Images Attached Images
    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"

  5. #5
    Join Date
    Jan 2004
    Location
    Lancaster PA
    Posts
    66,821
    If its a VS air handler. Ask your contractor to enable Comfort r.
    And or, set the blower to 350 CFM per ton.
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    How many times must one fix something before it is fixed?

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