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Thread: High humidity

  1. #1
    Join Date
    Sep 2003
    Location
    Ocean County, N.J.
    Posts
    484
    Went on an A/C service call today. The homeowner wanted to get a head start on a problem she's had since the equipment was installed 3 years ago. She claimed since the first day of her new install in the summer time her home experiences 65 to 70 percent humidity, and she just doesn't want to do another summer like that. 1900 sq. ft. home in central N.J. Condensor is Lennox HS27 030 4P, furnace is Lennox G60UH 36B 090 05 and coil is Lennox CH33 44/48 2F. Mismatched equipment? Condensor too small for coil? She claimed she just didn't have this problem with the old equipment, and she bought a matched system as recommended to her by her HVAC service company. I'm just doing a little research before I offer her a recommendation.

  2. #2
    Join Date
    Feb 2006
    Location
    USA
    Posts
    4,381
    is the fan speed set to high ? earlier in my young career before i learned technical stuff i worked for this outfit in central jersey that used 99% lennox & that set every furnace on high speed for cooling no matter what & they always used higher fan drives than needed as they claimed too much air flow is never bad .. disregarding the fact they may overshoot temp & not properly remove humidity ... dunno if this is your answer but its something

    [Edited by hvac wiz 33 on 03-15-2006 at 06:37 PM]

  3. #3
    Join Date
    Aug 2002
    Posts
    1,647
    Jack,

    I agree with the Wiz that the fan may be blowing too much air.. Get the fan chart from lennox and test the TESP and set the fan speed correctly for the A/c unit size..

    Also, you might want to check the piston size required for that unit and check and make sure they have the correct piston installed.. Might be too large of piston in there also..

    Goodluck, Let us know how it turns out.
    J

  4. #4
    Join Date
    May 2000
    Location
    Indianapolis, IN, USA
    Posts
    34,189
    Tell her not to run the fan all the time, let it cycle. Amazing how much more humid the house is with constant fan in humid weather.

    I'm not real up on Lennox numbers, looks like that coil is ARI rated with the HS27-030 but with a TXV kit which would help on latent in moderate weather.

  5. #5
    Join Date
    Jun 2003
    Location
    Madison, WI/Cape Coral, FL
    Posts
    6,451
    Agree with above. Is there a crawlspace without plastic on the earth? Also open vents on the crawlspace allow lots of high moisture air into the space. Duct air leaks into unconditioned space sucks outside air into the house(seal ducts). Slowing the air flow of the AH as much as possible and getting air distribution while not freezing the coil or condensing moisture on the ducts/grills is preferred. This maxs the latent removal. For humidity control with no/low cooling loads, a supplemental eff. dehumidier are the ultimate in humidity control(Santa Fe/Ultra-Aire). With an over-sized a/c or turn off the a/c and have <50%RH. Easy to during the shoulder seasons to have <50%RH. It's that time of year. TB

  6. #6
    Join Date
    Sep 2003
    Location
    Ocean County, N.J.
    Posts
    484
    Thanks for all your replies. The thing is they've lived in the home for 20 years. They've set the stat the same for 20 years: same temps winter and summer, fan on auto. For the first 17 years they never had a problem. They were comfortable and satisfied. About 3 years ago their system was low on refrigerant and the service tech. told them he could perform a leak check, but given the age of the equipment it might wise to consider a system replacement. Well, they bought a matched Lennox system: cond., furn., and coil from an autherized Lennox dealer. The system was what was recommended to them. They would have bought whatever the company "suggested". Since day one they were disappointed, and found their home uncomfortable. Same house, same duct work, same people, different equipment. After 3 years of unsatisfactorily going back and forth with the installing company they decided to go to another company, the one I work for, and get it resolved. It's about 45 degrees here now, so we won't be going back till it warms up. I was just looking for a head start. I'll post the results after we go back.

  7. #7
    Join Date
    Apr 2004
    Posts
    7,680
    Heres the heads up, check the humidity for yourself, do a total capacity check on the system and a then a sensible check. Verify the ductwork isnt leaking (may have been moved when new system was installed and not sealed). Check the airflow and properly set it. Far too many installers assume that heating speed should be on low and cooling should be on high or do not even mess with fan speeds when they install it.

    Also the old system may also have been oversized and just not performing to full capacity, a new system installed of the same size may be working properly bu just oversized. Just because the duct is common with the old one has no bearing on how it operates.

  8. #8
    Join Date
    Mar 2005
    Location
    burlington county n.j.
    Posts
    9,744
    unit to coil match is the highest seer match for that unit. fan speed is likely culprit.

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