Page 1 of 2 12 LastLast
Results 1 to 13 of 19
  1. #1
    Join Date
    Mar 2002
    Posts
    41
    Bought 28 year old house. Replaced windows, wiring, HVAC ( including duct work )and insulation. Converted screened in porch into 4 seasons room with separate gas pack HVAC. Air tight crawl space ( double 6 mill vinyl dirt floor covering, foam insulation outer walls ) underneath with duct supply and return.After 1 month occupation, humidity 68-71% throughout house. What options for correcting do I ( and installer ) have? Thanks, guys---------Patrick

  2. #2
    Join Date
    Mar 2004
    Location
    SE Michigan
    Posts
    18,223
    Make sure the duct in the crawl space is ceiled and insulated. Did you have a load calc. done on the home? If not , the a/c may be oversized. It may be cooling the temp. down but not removing the humidity like it should. Does the ac short cycle? What size home? what tonnage is the ac? Model and serial? Outdoor temp? indoor temp-wet bulb? Suction temp? subcooling?
    To put the world in order, we must first put the nation in order; to put the nation in order, we must put the family in order; to put the family in order, we must cultivate our personal life; and to cultivate our personal life, we must first set our hearts right.
    -- Confucius

  3. #3
    Join Date
    Jun 2004
    Location
    Earth, 20th century, North America, Texas. HVAC tech in late 70s.
    Posts
    290
    Your options could be:
    1) Buy a dehumidifier, probably least expensive option.
    2) Have your installer install a TXV (Thermostatic Expansion Valve) at your evaporator to improve latent heat removal (might slow down the blower speed a little bit as well if possible).
    3) Install a "whole-house" dehumidifier. This is probably most expensive option.

    Read these articles for info http://www.contractingbusiness.com/n...sarticleid/550

    or look at the Q/A for hunidity control from this site
    http://www.centralcityair.com


  4. #4
    Join Date
    Aug 2002
    Location
    Office and warehouse in both Crystal River & New Port Richey ,FL
    Posts
    18,836
    Sounds like all the thermal improvements you made,reduced the size A/C system needed,if you replaced with the original size ,now you are likely oversized.

    If your contrator knew of all the improvements,maybe he can help you now.Oversized systemed= high humidity indoors.

  5. #5
    Join Date
    Mar 2002
    Posts
    41
    Thanks,fellas, for your prompt response.
    The current indoor readings: 72.3 degrees, 71% humidity. Outdoor readings: 84% humidity, 77 degrees.
    If its oversized, who has responsibility for corrections?
    Do you replace the current HVAC for lesser ton units?
    If a whloe house dehumidifier is preferred, who foots the bill?
    Can I insist the units be relaced for smaller ones (or is that being too much of an a$$ hole )? .
    The installer thinks the units are short cycling ( I've not noticed ) and adjusting the fan speed will do the trick. Is that reasonable ?
    By the way, fans set on continuous, no moisture on walls or windows yet.
    Thanks again--------Patrick

  6. #6
    Join Date
    Aug 2002
    Location
    Office and warehouse in both Crystal River & New Port Richey ,FL
    Posts
    18,836
    Fan should be set on auto,fan on ,will add humidity,from the wet coil and pan,on the off cycle.

    Who should pay?Depends, as I said,did they know about all the thermal improvements or not?If they did,then they should have some part in correcting the problem.

    Many of the ideas already stated ,will help,hard to say from here if that will be enough.

    Another trick is run a 4" duct ,with a damper, from the supply to the return duct(near the grille),this will improve dehumidification,just as a bypass damper does in a zoning system.

  7. #7
    Join Date
    Mar 2002
    Posts
    41
    Thanks, Dash. FYI- About 2000 sq. ft. house. Three ton Split system for most of house ( one story ) and 2 ton gas pak for 4 seasons room and portion of kitchen.

  8. #8
    Join Date
    Jun 2004
    Location
    Earth, 20th century, North America, Texas. HVAC tech in late 70s.
    Posts
    290
    If the AC is slightly oversized, you can use the extra BTU to remove latent heat i.e. moisture. Ask the installer to move the blower to the lower speed tab possible (to get lower evap. temp for better moisture removal but still above freezing temp), then adjust the Freon charge to get proper supperheat (i.e. guarantee gas returning to the compressor). This would lower your total system's SEER but better in humidity removal. If you can afford, install the TXV since this regulates the freon flow to the evap. best under various heat loads (day vs. night) and prolongs the life of the compressor (well worth it long term).

    Other thought, 72F @ 71 RF, the dew point is about 62F, the evap. should be able to remove a bit of moisture. If your evap drain line puts out decent amount of water, it is doing its job, maybe your house is not well insulated from moisture infiltration from outside or there are moisture generation sources within the house (bath room not ventilated ...). If there is not much water dripping from the AC drain line, then take those suggested measures.

    [Edited by espock on 06-22-2004 at 02:57 PM]

  9. #9
    if you fail to get it lower...downsize the coil to a 2 ton with a 3 ton txv...smaller coil will remove 50% more humidity and still give you three tons of cooling...been downsizing in houston for 18 years so i know this will work

  10. #10
    Join Date
    Mar 2002
    Posts
    41

    Wink

    You guys are the best! Thanks---------------Patrick

  11. #11
    Join Date
    Mar 2002
    Posts
    41

    high indoor humidity

    One other question and I'll quit aggravating you folks. What's a TXV?

  12. #12
    Join Date
    Aug 2003
    Location
    Fort Worth, TX
    Posts
    11,376
    TXV = thermostatic expansion valve. It is a much more accurate metering device for the evaporator in that it maintains a consistent coil temperature over a wider range of operating conditions. A piston, also known as a fixed orifice or flow rater, meters the same amount of refrigerant regardless of conditions. Sometimes this amount is perfect, other times, such as during high or low loads, it's too much or too little, respectively.

    A TXV can contribute to long compressor life, along with proper maintenance.

  13. #13
    Join Date
    Jun 2001
    Location
    Moore, Oklahoma, United States
    Posts
    4,505
    Originally posted by airman1
    if you fail to get it lower...downsize the coil to a 2 ton with a 3 ton txv...smaller coil will remove 50% more humidity and still give you three tons of cooling...been downsizing in houston for 18 years so i know this will work
    Airman, does this increase or decrease DeltaT provided CFM remains constant?

Page 1 of 2 12 LastLast

Posting Permissions

  • You may not post new threads
  • You may not post replies
  • You may not post attachments
  • You may not edit your posts
  •  
Comfortech Show Promo Image

Related Forums

Plumbing Talks | Contractor Magazine
Forums | Electrical Construction & Maintenance (EC&M) Magazine
Comfortech365 Virtual Event