Sanity check
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Thread: Sanity check

  1. #1
    Join Date
    Sep 2004
    Posts
    5

    Post

    I have a 1 1/2 yr. old house in upstate S.C. The house is a two story with 1/2 finished basement. 3300 s.f. on 1st floor, 1300 sf. on second floor, and 1200 sf. in basement..There are 3 A/C units - (1) 5 ton for main floor and (2) 2 1/2 units for 2nd floor and basement. In the summer the 1st foor runs 55-65% humidity.
    Based on a load study, I have too much capacity and can take the basement unit off line - tie into the 5 ton unit and install ultra -aire APD to service these 2 levels and maintain 45-48% humidity.
    Based on monitoring the humidity levels in the house for the past year there has been a consistent 20% differential between the 1st flr and basement .During cold weather the humidity on 1st floor fell to 28%. To prevent trim cracking,etc. I turned on furn. humidifier to restore 45%. At the same time the basement was at 55-62% and I was running a portable de-humidifier.
    Won't I have the same problem with the APD servicing both floors and the control in the basement????
    Advice--Solutions???

  2. #2
    Join Date
    Nov 2004
    Location
    Chicago, Illinois
    Posts
    17

    humidity

    After reading your post you do not mention what the temperatures are. Also if humidity is critical to you and the desire to maintain 40-45% humidity then your systems are all wrong. Going after humidity rather than comfort cooling and heating represent 2 drastic system designs. To maintain humidity you would need to cool the air and wring moisture out then reheat the air for comfort levels. The operating and installation cost would be unbelievable. An example at a food processing plant the desire was to maintain 20% RH at all times to allow for proper packaging. For a 2000 sq ft room we installed an 80 ton A/C system with an 8 row intertwined coil. The discharge air was 45 degrees. Too cold for people so a 1,000,000 btu boiler and hot water coil were installed to bring discharge air up to 75 degrees.

    As you can see comfort cooling and humidty control are 2 different things.

  3. #3
    Join Date
    Oct 2004
    Posts
    41
    jgbowman, I recommend that you contact the people at Therma-Stor regarding the Ultra-Aire APD that you reference. The people there are extremely helpful and very willing to assist you with your questions. I recently toured the Therma-Stor plant and was highly impressed. Imho, your problem is not unique and could be easily remedied through the use of a ventilating dehumidifier. Because the house is so new, the concrete basement floor is likely contributing to the higher basement humidity. Again, I would talk to the Therma-Stor folks.

  4. #4
    Join Date
    Jun 2003
    Location
    Madison, WI/Cape Coral, FL
    Posts
    6,231
    Originally posted by jgbowman
    I have a 1 1/2 yr. old house in upstate S.C. The house is a two story with 1/2 finished basement. 3300 s.f. on 1st floor, 1300 sf. on second floor, and 1200 sf. in basement..There are 3 A/C units - (1) 5 ton for main floor and (2) 2 1/2 units for 2nd floor and basement. In the summer the 1st foor runs 55-65% humidity.
    Based on a load study, I have too much capacity and can take the basement unit off line - tie into the 5 ton unit and install ultra -aire APD to service these 2 levels and maintain 45-48% humidity.
    Based on monitoring the humidity levels in the house for the past year there has been a consistent 20% differential between the 1st flr and basement .During cold weather the humidity on 1st floor fell to 28%. To prevent trim cracking,etc. I turned on furn. humidifier to restore 45%. At the same time the basement was at 55-62% and I was running a portable de-humidifier.
    Won't I have the same problem with the APD servicing both floors and the control in the basement????
    Advice--Solutions???
    After a recent cold trip to the Carolinas, low of 23^F in Mrytle Beach, I appreciate your problem. Humidify to the point that condensation appears in the corners of the windows. 55%RH in a cold basement is ok unless condensation appears on the coldest surfaces. To correct condensation, warm the cold surfaces with heat or insulation. Dehumidifying during cold weather is the last resort. All earth in crawlspaces must be covered to avoid evaporation which humidifies. Outside air vents should be closed all the time. Ulta-Aire APD will do good job of controlling humidity during warm humid weather. Suggest dehumidification to maintain 50% RH during the summer and avoiding condensation on windows during cold weather.

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