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  1. #1
    Join Date
    Aug 2009
    Posts
    54

    Help! New system...indoor unit sweating.

    I just had a new heat pump system installed today, and I noticed the (blower) end of the air handler/blower unit is sweating on the outside. I figure this can't be good. Here's my configuration:

    1150 ft2
    Indoor unit (Rheem RHPL-HM2421) is located in the crawlspace.
    Outdoor unit (Rheem RPRL024JEC 2ton)
    Thermostat (Rheem 305)
    20x20 return, 16" supply duct from box to Clean Effects EAC
    All new metal ducts (progressively sized) with 8 register drops

    It's been running for 5 hours now....the house is feeling great, cooling down nicely and the humidity has pulled down to only 45% inside the house. Btw, this unit (both inside and outside) is freaking QUIET!! I thought my old system was quiet, but this one is unbelievable.

    The crawlspace is pretty humid (70 degF at 86% humidity). The poly moisture barrier is old and not in great shape....the installers disrupted it around the install area as well, and it's really musty down there right now. I picked up some 6 mil poly a while ago and will try to get a new barrier down by the weekend.

    Question 1:
    So are the crawlspace conditions causing the sweating, or is it something in the system or setup? I only noticed it sweating on the far end, away from the supply end. Any help is appreciated, I just want to arm myself with some knowledge before I call up the installer tomorrow.

    Question 2:
    Also, I am running one of the really thin glass 1" filters (20x20) in the return, in from of the Clean Effects....this is at the recommendation of the contractor. He said the static pressure looked good, and as long as I stay really on top of the 1" filter that I will be fine and it will help save the first filter in the Clean Effects. Thoughts?

    Thanks.

  2. #2
    Join Date
    Jul 2009
    Location
    S.E.,PA
    Posts
    99
    Is the duct work sweating or the air handler sweating. Is the duct work insulated in the unconditioned space?
    Even a blind squirrel can find a nut every now and then.

  3. #3
    Join Date
    Aug 2008
    Location
    Georgia
    Posts
    45
    At the conditions you said the attic is 70 degrees and 86% RH the dewpoint is 65.6 degrees. If there is any metal below 65.6 degrees it will condense just like a soda/beer can. Have your contractor check the insulation and seal where ever possible. With such a high dewpoint in the unconditioned space a sealed/insulated airhandler and ductwork is a must.

  4. #4
    Join Date
    Aug 2009
    Posts
    54
    The ductwork is all insulated.

    The unit is in the crawlspace, not the attic. But either way, it is what it is I guess. I would have thought that the unit was insulated inside, but maybe not(?). I'll call the installer tomorrow and see what I can get them to do about insulating the unit. What you say makes sense, as it is not sweating upstream from the coil....just on the end with the blower.

    Another question:
    Should I look at getting a crawlspace dehumidifier? I installed a vent fan about a month ago along with a remote hygrometer so that I could monitor the temps and humidity levels under the house. The fan helps during the (dry) day, but at night or if raining I need to turn it off to keep humidity levels from going even higher. It has been ranging from high 70's% to mid 90's%, depending on conditions.

    Any suggestions on dehumidifier brands/models?

  5. #5
    Join Date
    Jul 2008
    Location
    Rochester NY
    Posts
    4,649
    Probably.

    But if you do, don't expect to dehumidify the great outdoors with it. You might want to consider spray foaming your crawl walls to prevent moist air from infiltrating and reduce your energy use.
    Which makes more sense to you?
    CONSERVATION - turning your thermostat back and being uncomfortable. Maybe saving 5-10%
    ENERGY EFFICIENCY - leaving your thermostat where everyone is comfortable. Saving 30-70%

    DO THE NUMBERS! Step on a HOMESCALE.
    What is comfort? Well, it AIN'T just TEMPERATURE!

    Energy Obese? An audit is the next step - go to BPI.org, or RESNET, and find an auditor near you.

  6. #6
    Join Date
    Jul 2008
    Location
    Alabama
    Posts
    658
    My advice would be to throw that fan and hygrometer in the trash...seriously.

    No matter what the temp or humidity it is under the house is.......when it comes on it will draw more moisture under there.....the concept is a good idea but when you stop to think about what is taking place it doesn't seem to be as good.

    1.) lay down new barrier and be sure to let the poly overlap and go up the walls and pillars about 6".

    2.) close foundation vents.....plywood, ductboard, etc...and silicone the cracks.

    3.) last of all go buy a good(quiality) dehumidifier and put it under the house to remove the moisture....be sure to rig the drain where you dont have to go under the house 10 times a day to empty the bucket.

    most if not all dehumidifiers will have a fitting on the back you pop off and hook a hose to to let it drain(to the outside)


    good luck
    You're only as good as your customer will allow you to be.........If they want junk, sell them junk, but make your junk look neat!!!

  7. #7
    Join Date
    Aug 2009
    Posts
    54
    Quote Originally Posted by superd77 View Post
    My advice would be to throw that fan and hygrometer in the trash...seriously.

    No matter what the temp or humidity it is under the house is.......when it comes on it will draw more moisture under there.....the concept is a good idea but when you stop to think about what is taking place it doesn't seem to be as good.

    1.) lay down new barrier and be sure to let the poly overlap and go up the walls and pillars about 6".

    2.) close foundation vents.....plywood, ductboard, etc...and silicone the cracks.

    3.) last of all go buy a good(quiality) dehumidifier and put it under the house to remove the moisture....be sure to rig the drain where you dont have to go under the house 10 times a day to empty the bucket.

    most if not all dehumidifiers will have a fitting on the back you pop off and hook a hose to to let it drain(to the outside)


    good luck
    Why would you ever recommend throwing the hygrometer away? I can see an argument for eliminating the vent fan, but ignoring a humidity problem (by pitching the hygrometer) won't solve anything. I like to know what I'm dealing with.

    I'm with you on the other suggestions of sealing the space, a dehumidifier, and fixing the damaged barrier though.

    So on the subject of dehumidifiers....is there a particular brand or model you recommend? It's my understanding that regular dehumidifiers won't functgion properly in crawl spaces when the temps drop down. The flip-side isssue is that designated 'crawl space' dehumidifiers are expensive as hell. So, is there anything that funcgtions and won't break the bank?

  8. #8
    Join Date
    Jun 2003
    Location
    Madison, WI/Cape Coral, FL
    Posts
    6,070
    Quote Originally Posted by DaveH2 View Post
    The ductwork is all insulated.

    The unit is in the crawlspace, not the attic. But either way, it is what it is I guess. I would have thought that the unit was insulated inside, but maybe not(?). I'll call the installer tomorrow and see what I can get them to do about insulating the unit. What you say makes sense, as it is not sweating upstream from the coil....just on the end with the blower.

    Another question:
    Should I look at getting a crawlspace dehumidifier? I installed a vent fan about a month ago along with a remote hygrometer so that I could monitor the temps and humidity levels under the house. The fan helps during the (dry) day, but at night or if raining I need to turn it off to keep humidity levels from going even higher. It has been ranging from high 70's% to mid 90's%, depending on conditions.

    Any suggestions on dehumidifier brands/models?
    Get a good plastic barrier down, close the outside vents, and good a better than residiential dehumidifier, like Santa Fe Compact with a drain or condensate pump. Keep the space dry enough to avoid condensation on the a/c. Remote Hygrometer is good. The other poster was refering to the dehumidistat on the fan.
    The perfect retro to a home is fresh air ventilation and whole house humidity control with a whole house ventilating dehumidifier like the Ultra-Aire 65H or 90H. This will take care of controlling %RH throughout including the crawlspace plus providing minimal fresh air ventilation when the home is occupied. The dehu does not dehumidify unless the a/c operation inadequate like during wet cool weather. This more money but the ultimate in comfort and IAQ.
    Regards TB
    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"

  9. #9
    Join Date
    Mar 2007
    Location
    Myrtle Beach, SC
    Posts
    2,919
    Follow this link for crawl-space sealing instructions.


    http://contractingbusiness.com/mag/cb_imp_7253/
    Remember, Air Conditioning begins with AIR.

  10. #10
    Join Date
    Jun 2003
    Location
    Madison, WI/Cape Coral, FL
    Posts
    6,070
    Quote Originally Posted by DaveH2 View Post
    So on the subject of dehumidifiers....is there a particular brand or model you recommend? It's my understanding that regular dehumidifiers won't functgion properly in crawl spaces when the temps drop down. The flip-side isssue is that designated 'crawl space' dehumidifiers are expensive as hell. So, is there anything that funcgtions and won't break the bank?
    After you get your crawlspace organised, plastic down and outside vents closed, you have a short basement with basement problems. You also have minimal fresh air in the conditioned spaces that you occupy. The following data and discussion gets to the ultimate solution to the problem. You may not be able to afford it currently but move in that direction.
    This is the shoulder season with little or no cooling load (1:40 this week). Yet the outdoor fresh air dew points are high enougn to cause moisture problems in a home that is getting adequate fresh air to purge indoor pollutants and renew oxygen. This the data from a home with minimal fresh air (60 cfm of fresh air 14 hours) and 2 occupants half days. I am testing a 65 pint whole house ventilating dehu (Ultra-Aire 65H) ability to maintain reasonable %RH in the home/basement while limited to 14 hours of dehu operation to minimize operating cost. Next week, will operate dehu 24 hours/day while limiting fresh air to 14 hours.
    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"

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