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  1. #1
    Join Date
    Oct 2010
    Location
    Anderson, South Carolina, United States
    Posts
    7,468

    Customer with high humidity

    My company installed a broan 3.5 ton heat pump in one of our customers houses just over 3 years ago. Performed a load calc and came out to around 45k btu for cooling so we installed the 3.5. it has worked fine with no complaints until about a week ago he called and said the humidity is really high, his salt shaker won't work, doors are getting stuck, and it's uncomfortable at 75F. So I go over and as soon as I walk in it feels sticky. I check rh and it ranges from 77-85 in his house. 85 being directly above where the air handler is in crawl space. So I go under and the ah is sweating but duct and insulation are dry. About a 4' radius around the ah the ground is damp but not soaked. The rh in crawlspace ranges from 87-92. Everywhere else other than around ah the ground and structure is dry. I checked unit blower speed (ECM) and verified it was set up correct with installation manual. Went outside gauged and checked superheat and sub cool (can't remember what readings were but matched with charging chart. I am going back tomorrow and doing a blower door test to see if we can get to what's causing the high rh all of a sudden. I checked all plumbing and water heater to see if that was the problem and found no signs of water to explain it. It has been cooler low to mid 70s at night and low to mid 80s during day with lots of rain and high humidity, 70-90% for the past week and a half. Any suggestions to look for when I go tomorrow. I hope I overlooked something and it's a plumbing problem but this is a good long time customer and I really need to get it resolved for them.

  2. #2
    Join Date
    Oct 2010
    Location
    Anderson, South Carolina, United States
    Posts
    7,468
    Quote Originally Posted by jtrammel View Post
    My company installed a broan 3.5 ton heat pump in one of our customers houses just over 3 years ago. Performed a load calc and came out to around 45k btu for cooling so we installed the 3.5. it has worked fine with no complaints until about a week ago he called and said the humidity is really high, his salt shaker won't work, doors are getting stuck, and it's uncomfortable at 75F. So I go over and as soon as I walk in it feels sticky. I check rh and it ranges from 77-85 in his house. 85 being directly above where the air handler is in crawl space. So I go under and the ah is sweating but duct and insulation are dry. About a 4' radius around the ah the ground is damp but not soaked. The rh in crawlspace ranges from 87-92. Everywhere else other than around ah the ground and structure is dry. I checked unit blower speed (ECM) and verified it was set up correct with installation manual. Went outside gauged and checked superheat and sub cool (can't remember what readings were but matched with charging chart. I am going back tomorrow and doing a blower door test to see if we can get to what's causing the high rh all of a sudden. I checked all plumbing and water heater to see if that was the problem and found no signs of water to explain it. It has been cooler low to mid 70s at night and low to mid 80s during day with lots of rain and high humidity, 70-90% for the past week and a half. Any suggestions to look for when I go tomorrow. I hope I overlooked something and it's a plumbing problem but this is a good long time customer and I really need to get it resolved for them.
    Oops I meant to post this in tech to tech residential

  3. #3
    Join Date
    Sep 2008
    Location
    Western PA
    Posts
    25,765
    Quote Originally Posted by jtrammel View Post
    Oops I meant to post this in tech to tech residential
    Done.

    Moved to tech to tech residential.

  4. #4
    Join Date
    May 2000
    Location
    Indianapolis, IN, USA
    Posts
    34,310
    How cool does he keep it? You say it is uncomfortable under 75? I have Tappan, same as Broan. We've had an extremely steamy few days but the house has stayed pretty comfy. I did turn my dehumidify on demand on and set it to 55% and it sometimes does climb above that so the blower slows down. We've had outside humidity in the 90% range overnight and last weekend, tended to be all day with rain.

    I'm on a crawl, have heavy plastic down taped at joints. Have a dehumidifier down there. Furnace is in garage, supply in crawl, return in attic. No leakage. Tight house.

    Hopefully they aren't running the fan constantly. That can add 10 points to the RH%. Got the blower set below 400 CFM/ton?

  5. #5
    Join Date
    May 2005
    Location
    South
    Posts
    580
    I guess you checked the drain pan and line?

  6. #6
    Join Date
    Jun 2001
    Location
    Moore, Oklahoma, United States
    Posts
    4,376
    What indoor and outdoor temps did you use for manual J? When you had a design day did the system run nonstop?

  7. #7
    Join Date
    Aug 2012
    Posts
    2,675
    Did you check to see if the electric heat strips were powered?

  8. #8
    Join Date
    Oct 2010
    Location
    Anderson, South Carolina, United States
    Posts
    7,468
    He keeps it set at 75 and it is uncomfortable. Temp is 75 but humidity is in 80s. It's raining pretty hard here today do not going to do blower door today. Checked drain working fine. Blower set for 1380 cfm. I don't think fan speed is problem, the humidity has to be coming from somewhere to be that high. Used 92 summer and 23 winter for manual j. Yes, unit runs non stop when above 90f outdoor ambient. The crawlspace has plastic down, cheap thin plastic but the ground doesn't seen to be where the humidity is coming from. Didn't check strips but it's putting out 56f air with 75 return so I'm sure they aren't running

  9. #9
    Join Date
    Dec 2008
    Location
    Ontario Canada
    Posts
    548
    Quote Originally Posted by toocoolforschool View Post
    Did you check to see if the electric heat strips were powered?
    That would drive the humidity down

  10. #10
    Join Date
    Dec 2004
    Location
    Grand Rapids, MI
    Posts
    619
    I know this does not help, but 3 years with no issues = "something has changed" ie: more family visiting for showers and cooking, extras rain and high water table, fan on "on" ????? Any type of remolding ? Changed the gaslog fireplace to wood burning ? Added a deck ? Removed the gutters ?
    We had a job that need the IAQ t-stat to run the blower slower, really helped.
    luck dan

  11. #11
    Join Date
    Sep 2004
    Location
    Phoenix, Arizona
    Posts
    90
    Slower blower speed to 350 cfm per ton and check to make sure your condensate it trapped proper, vent after the trap and is draining. Water being held back can also keep the levels up. I also agree that something has changed since install. Also check refrigerant charge. Water should be flowing out the condensate drain at that humidity level.

  12. #12
    Join Date
    May 2000
    Location
    Indianapolis, IN, USA
    Posts
    34,310
    What's the air handler?

  13. #13
    Join Date
    Oct 2010
    Location
    Anderson, South Carolina, United States
    Posts
    7,468
    Im not 100% sure but I think it's a b4vmx36 air handler. Drain is trapped correctly and drains like a water faucet when ac is running. I agree something has changed I went by there today and it had been raining all morning and the sun had just poked out so humidity outside was around 95% and so was crawlspace. The ac was not running and homeowner was not there so no access to inside. I crawled the entire house looking for evidence of water, no luck except for a 4' radius around air handler is damp but not soaked, I assume from the a/h sweating. Duct and insulation not sweating but air handler still had drops of water on sides and bottom from sweating the last cycle it ran before I got there

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