Page 1 of 2 12 LastLast
Results 1 to 13 of 20
  1. #1
    Join Date
    Mar 2020
    Posts
    3
    Post Likes

    High humidity with AC

    My daughter just bought her first home (1400 sq ft) nearby us in Texas. The HVAC is Carrier heat pump model # FB4CNP030. The home was visited prior to purchase in January and Feb and we did not notice a humidity issue (it was below 50% when I saw the house the first time). We also were in and out of the house after closing prior to move in when it was still Texas "winter."

    She moved in early March when it was cool, but it warmed up the next day so that the system was switched to cool (Fan Auto) and the system had no problem keeping the house to temperature. However, the humidity went up to 72% by that evening. We kept it much cooler than comfortable and got it to drop into the mid 60s.

    We called the contractor (everything in a 1 yr warranty period, parts and labor), a tech came out checked everything and noted only that the refrigerant was a little low and topped it off. He told her to give it a few days.

    The humidity stayed through the weekend until a cool front came through, the heat got turned on and humidity eventually dropped to the high 50% range. When it warmed up yesterday, the AC was turned back on, the humidity went back to the upper 60s in a short time and the house was muggy again.

    Tech visit #2 happened this afternoon. He told my daughter that all diagnostics checked out and the system was just not running long enough. He set the thermostat to 68 saw it drop from 67% to 66% and said she just needed to run it cold for a few days. He said that once it got even warmer outside it would run longer and the humidity should improve.

    You should not have to freeze in the warm Texas spring and fall to keep the humidity level in the house below 70% and cross your fingers that it get into the 90s soon. I've never lived in a place this humid in Texas that had an HVAC so I know this is not right.

    Any advice and guidance would be appreciated.

    Mitch

  2. #2
    Join Date
    Aug 2002
    Location
    Southold, NY
    Posts
    27,164
    Post Likes
    Is this a new construction house?

  3. #3
    Join Date
    Jan 2014
    Location
    New England
    Posts
    6,724
    Post Likes
    That number you gave was the Air Handler number, do you have the model number of the OD unit? Found low on charge and topped it off? How did he do that by pressure only or checking and or adjusting the subcooling/superheat?

    A load calculation was done to determine actual size needed?

    Did you register your equipment, as manufacturers warranty decreases significantly if never registered.

    “ everything in a 1 yr warranty period, parts and labor “

    You should have at the minimum a 5 year compressor and parts warranty not one year on parts. If your system got registered you should have a 10 year compressor and parts warranty. Certainly a one year labor warranty is typical on new equipment.

  4. #4
    Join Date
    Nov 2004
    Location
    SW FL
    Posts
    9,969
    Post Likes
    Quote Originally Posted by HumidinTexas View Post

    My daughter just bought her first home (1400 sq ft) nearby us in Texas.

    The HVAC is Carrier heat pump model # FB4CNP030.

    The home was visited prior to purchase in January and Feb and
    we did not notice a humidity issue (it was below 50% when I saw the house the first time).

    We also were in and out of the house after closing prior to move in when it was still Texas "winter."

    She moved in early March when it was cool,
    but it warmed up the next day so that the system was switched to cool (Fan Auto)
    and the system had no problem keeping the house to temperature.

    However, the humidity went up to 72% by that evening.

    We kept it much cooler than comfortable and got it to drop into the mid 60s.

    Any advice and guidance would be appreciated.

    Mitch
    ZIP _ _ _ _ _

    What is the Manufacturer and model number of the Hygrometer?

    How old is the instrument ?
    Hygrometers are generally not very accurate after a number of years.
    ___________

    Is the overcooling actually the Root Cause of the Relative Humidity increase?

    Thermostat set-point: ___ 'F
    ___________ _ _ ODT ___'F Dew Point ___ 'F

    ___________ 78'F __ _ _. % R.H.
    ___________ 76'F __ _ _.
    ___________ 74'F __ _ _.
    ___________ 72'F __ _ _.

    heat on _____ 74'F __ 58% ? ODT: 48'F ?
    Designer Dan
    It's Not Rocket Science, But It is SCIENCE with "Some Art". ___ ___ K EEP I T S IMPLE & S INCERE

    Define the Building Envelope and Perform a Detailed Load Calc: It's ALL About Windows and Make-up Air Requirements. Know Your Equipment Capabilities

  5. #5
    Join Date
    Jun 2003
    Location
    Madison, WI/Cape Coral, FL
    Posts
    9,765
    Post Likes
    What is the outdoor dew point? We are having the same problem in SW FL. The outdoor dew point is 68-70^F with a high of 84^F during the day and 70^F low at night.
    The a/c runs a couple hours during the day but only short cycles during the evening.
    Two-three occupants in the home and a fresh air change in 4-5 hours, 80 cfm of fresh air. Three occupants and 80 cfm of fresh air at 68^F dew point plus occcupants works out to 2-3 lbs. of dehumidification needed per hour will maintain 50%RH. Wonder what the problem is with little or no a/c run time?
    We need 30-40 lbs of moisture removed per day if we are going to get near 50%RH.
    Any ideas???
    Must be something wrong with a/c?
    A 3 ton a.c removes 10 lbs. of moisture per hour of steady operation when setup ideally.
    I bet the a/c is not setup ideally plus it is not running enough to remove the 30 lbs. of moisture per day.
    Here is an ideal, add a small whole house dehumidifier to removes moisture without over-cooling the home??
    Or just live with problem until it gets hot enough to make the a/c run more.
    I installed a small whole house dehumidifier and had my a/c setup to remove more moisture during long cooling runs.
    Keep us posted.
    Regards Teddy Bear
    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"

  6. #6
    Join Date
    Mar 2020
    Posts
    3
    Post Likes
    Thread Starter
    Thanks everyone for the quick responses.

    Yes, this is a new construction. Carrier with registration is 10 year warranty but with the new build it comes with 100% warranty in first year with the builder/contractors.

    OD(?) Model # The outside AC condenser unit model # is CH14NB024-A

    My wife was there when first tech visit and I asked her to ask the tech if the system was load tested and he said yes. Online reading suggests improperly sized unit is the most likely culprit in most high humidity situations. Should the contractor retain the results of a load test?

    The inside humidity numbers I am quoting are from the thermostat unit. The tech's hygrometer unit was within 1% of the thermostat.

    I just asked my daughter to start recording throughout the day. I am hesitant to spend $ on a dehumidifier at this point and get it resolved within this 1 year period.

    Outside temp 90, 34% humidity (according to weather app), so that is dew point of 58F.
    Thermostat is set at 71, temp at 71, in house humidity 65%. From what I have been reading this should be at max ~50% humidity when it is this warm outside.

    Thanks again,
    Mitch

  7. #7
    Join Date
    Aug 2002
    Location
    Southold, NY
    Posts
    27,164
    Post Likes
    So the builder and his sub sized and installed the equipment.

    It will cast you but get a independent start up and commissioning report to dispute what the contractor has done. You probably wont get satisfaction from the installing contractor, his loyalty is with the contractor that supply him with jobs.

    Most jobs we see are Oversized equipment on undersized ducts.

  8. #8
    Join Date
    Jan 2014
    Location
    New England
    Posts
    6,724
    Post Likes
    “My wife was there when first tech visit and I asked her to ask the tech if the system was load tested and he said yes. Should the contractor retain the results of a load test.”

    There shouldn’t be a issue for the Contractor to leave a copy with the equipment ( startup guide/commissioning report ) or even if you wanted to see it. They are suppose to leave the installation guide of the ID and OD unit with the equipment. Many don’t.

    Your Air Handler says it comes with a TXV as the metering device. The OD unit electrical data plate says what the subcooling number should be, according to the install guide. The install guide shows the Installing Contractor how to dial in the field refrigerant charge. They should have checked your static pressure also set the CFM to your residence. Others things they could have checked was the motors and compressor amprege draws. Of course they could fudge numbers as most homeowners don’t understand what they should be. I suppose if it does not affect the labor warranty from this company, may want to consider what pecmsg suggested, getting a independent start up and commissioning report.

    BTW your system is a AHRI match, listed at 14 SEER, 11.5 EER, 8.20 HSPF 22,200 total cooling BTU on paper.

    Here’s a generic commissioning guide. As you have a TXV metering device at the Air Handler they should concentrate on the subcooling portion instead of the piston metering device section.

    https://www.google.com/url?sa=t&rct=...GtreMqRxxNNbzS
    Last edited by Bazooka Joey; 03-25-2020 at 09:14 PM.

  9. #9
    Join Date
    May 2006
    Location
    Philadelphia, PA
    Posts
    2,215
    Post Likes
    Commissioning report would be helpful. What is the temp difference between supply and return air after 10 mins of operation?
    Climate Control Solutions for your Home or Office

    Serving Northeast Philadelphia and Surrounding Areas

  10. #10
    Join Date
    Nov 2004
    Location
    SW FL
    Posts
    9,969
    Post Likes
    Quote Originally Posted by HumidinTexas View Post

    My daughter just bought her first home (1400 sq ft) nearby us in Texas.

    The HVAC is Carrier heat pump model # FB4CNP030.

    The home was visited prior to purchase in January and Feb and we did not notice a humidity issue (it was below 50% when I saw the house the first time). We also were in and out of the house after closing prior to move in when it was still Texas "winter."

    Any advice and guidance would be appreciated.

    Mitch
    I am not familiar with the location "nearby us in TX" .
    ___________________________ DWF ?

    TX = 268,820 sq miles __ a.k.a. NOT Small

    I don't know which sq mile Her House in located in.
    Designer Dan
    It's Not Rocket Science, But It is SCIENCE with "Some Art". ___ ___ K EEP I T S IMPLE & S INCERE

    Define the Building Envelope and Perform a Detailed Load Calc: It's ALL About Windows and Make-up Air Requirements. Know Your Equipment Capabilities

  11. #11
    Join Date
    Jun 2003
    Location
    Madison, WI/Cape Coral, FL
    Posts
    9,765
    Post Likes
    Quote Originally Posted by HumidinTexas View Post
    Thanks everyone for the quick responses.

    Yes, this is a new construction. Carrier with registration is 10 year warranty but with the new build it comes with 100% warranty in first year with the builder/contractors.

    OD(?) Model # The outside AC condenser unit model # is CH14NB024-A



    Outside temp 90, 34% humidity (according to weather app), so that is dew point of 58F.
    Thermostat is set at 71, temp at 71, in house humidity 65%. From what I have been reading this should be at max ~50% humidity when it is this warm outside.

    Thanks again,
    Mitch
    This has become a big enough issue that some big class builders are installing a whole house dehumidifier rather than fight the fact an a/c is unable to remove significant moisture evenings and raining days to maintain the healthy/comfortable 50%RH. They are also including filtered fresh air option to purge the indoor pollutants and renew oxygen in these quality air tight homes.

    I understand why want to try to get the a/c to do the job. Most of us live the problem of no fresh ventilation and occasional high humidity. During peaking sensible cooling loads, a properly setup a/c should be able to maintain <50%RH during the day. Evenings and rainy days are impossible for an a/c to remove the moisture from infiltration/ventilation plus the moisture from the occupants. There is 20-50 lbs. of moisture that must removed from the home when the outdoor dew points are plus 60^F.

    But there is a change taking place in the industry. Most a/c manufactures are now offering a small whole house dehumidifier, most have a fresh air option. Many codes are suggesting the need for supplemental fresh air and dehumidification to avoid mold/dust mites and occasional uncomfortable high humidity.

    Keep us posted.
    Regards Teddy Bear
    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"

  12. #12
    Join Date
    Aug 2002
    Location
    Southold, NY
    Posts
    27,164
    Post Likes
    Once we went from slightly leaking homes (Fiborglass glass) to living in a plastic bag (spray foam) the requirements changed dramatically. Smaller units are a must. Outside air must be brought in mechanically and T B’s going to be busy. “Seperate Dehumidification” are now required .

  13. #13
    Join Date
    Jan 2004
    Location
    PA
    Posts
    78,514
    Post Likes
    Is there a frsh air intake connected to the system. If so, it may be bring in too much outside air, and causing the humidity issue.

    Could also be the blower speed/CFM is set too high.
    Contractor locator map

    How-to-apply-for-Professional

    How many times must one fix something before it is fixed?

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
  •  
Contracting Business
HPAC Engineering
EC&M
CONTRACTOR