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Thread: Whole House Dehumidifier at NJ Beach House

  1. #1
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    Whole House Dehumidifier at NJ Beach House

    Hoping you guys can help me. We built a new home in Brigantine NJ, just across the street from the bay. The house is three stories and the first floor is on a concrete slab with cinder block walls. 50% of the first floor is finished space with tile floors, drywall and two returns and three supply registers on the ceiling. The first floor HVAC also services the complete second floor. The half of the first floor and complete second floor total about 2,000 sq/ft of finished living space. The third floor has a dedicated system in the attic and seems to be under control and comfortable without the need for supplemental dehumidification.

    As you would expect, being close to the water and given the the NJ shore is notorious for high humidity the lower level can reach 70-80% humidity levels and we have had to clean up some mold due to the excess moisture issue. The Rheem HVAC systems seem to be oversized and really don’t do enough to control humidity, especially during the late spring and early fall when air temps are 60-70 degrees and humidity levels outside are 90-100%. The house is new and built very tight in my opinion. When you open the doors or windows you can see my digital humidistats located on each floor jump up due to humid outside air flowing into the home.

    Two weeks ago we had our mechanical contractor install an AprilAire 1850 WHD and it’s connected to an AprilAire 8910 humidistat which is located in the first floor finished space, where humidity levels are highest. The techs ducted the system return to supply.

    While the system seems to be working somewhat (humidity levels on the first floor have reduced from 76% to 54%, after two weeks of constant running and connected to the air handler fan which runs with the WHD, the WHD can’t seem to reach the set point of 50% and also seems to work less effective when we turn on the air conditioner.

    Our contractor is going to send over his tech this week to test the static pressure as AprilAire ONLY recommends a return to supply duct configuration when the static pressure does not exceed .6 w.c. Also, when running the WHD along with the air conditioner we hear a surging sound coming from the AC compressor. We don’t hear the surging if we temporarily turn off the AprilAire unit.

    I am not sure if the ducting needs to be changed to return to return as AprilAire recommends or if the return/supply registers on the first floor just don’t have enough flow to reach set point and to be that effective? I will say the our second floor is also serviced by the same duct work/dehumidifer and the humidity levels on that floor have reduced from 55% to about 40% with the set point set to 50% down on the first floor. The regular thermostat is located on the second floor so as to get better reading for heating and cooling needs.

    I have been sitting up reading this forum every night searching for an answer and finally decided to sign up and ask the experts for some help.

    Thank you in advance for any insight and feedback.

  2. #2
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    Two issues. Is your a/c doing what it is designed to do? During high continuous cooling load, does the a/c remove enough moisture to get below 50%RH. In other words, your a/c should remove about 3 lbs. of moisture per ton per hour. This is much more than your dehumidifier. This requires proper setup which some contractors do not understand. It depends on the a/c coil temperature and the supplied temp/%RH/^F dew point. You want 75^F, <50%RH,<55^F dew point in your living area. The a/c must supply <50^F dew point air. That is the first issue. Make sure the a/c is doing its part.
    Adding a dehumidifier to an a/c system that unable to remove considerable moisture with a 55^F return dew point is a lazy a/c and you will need a very large dehumidifier. You sized the dehumidifier to assist the a/c and together they will remove +10 lbs. of moisture per hour.
    Next comes the ducting. At .6" WG, your dehumidifier is struggling. Might try measuring the amount of moisture your a/c and dehumidifier remove together and separately. Mush better if you had an independent return from the open part of the home and supply to the a/c supply. Stop operating your fan when you dehumidify during the a/c off cycle.
    Ideally your a/c setup right should maintain 50%RH during high cooling loads and the dehumidifier starts assisting as the a/c starts to short cycle during low cooling loads.
    Avoid the return to dehu to return ducting. It is the poorest way of ducting. This is many because the fan must run whenever the dehu runs and the warm dry air from the dehu reduces the amount of moisture that the a/c removes.
    Hope this helps, come back with the issues from your contractor or yourself.
    In a few years when your dehu quits, get an Ultra-Aire. I respect you and your contractor for tacking this thorny moisture problem. Most green grass climate homes are on the edge of mold and dust mite problems.
    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"

  3. #3
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    Apr 2021
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    Confused

    Dear Original Poster (OP):

    I wonder if you ever able to resolve this issue? And might you have a suggestion for a contractor that solved it?

    I am 100 feet from the sand in Ocean County NJ and have the same exact problem you describe. My house is on stilts, brand new, very tight, and the HVAC system + a WHD (added 1 year after the CO was issued) is unable to keep up. Indoor humidity levels exceed 75+% mid summer and the combined HVAC + WHD systems are unable to keep up. I have to keep the AC down to low to mid 60s at night to keep the house "comfortable" for guests, otherwise we are uncomfortable and people cannot sleep. Additionally, I have warped floorboards by July, and they flatten out in the winter.

    At this point, I'm at my wits end and would do anything to solve this problem.

    Thanks,
    Mr. Humidity

  4. #4
    Join Date
    Sep 2002
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    Your AC system is too large and/or not performing correctly.

    Do you have an exhaust/make-up air system installed?

    Can you collect the AC drain water for a few hours - say from 10:00A to 2:00P - on a warm day? That would be an easy DIY method of diagnosis.

    PHM
    --------


    Quote Originally Posted by MrHumidity View Post
    Dear Original Poster (OP):

    I wonder if you ever able to resolve this issue? And might you have a suggestion for a contractor that solved it?

    I am 100 feet from the sand in Ocean County NJ and have the same exact problem you describe. My house is on stilts, brand new, very tight, and the HVAC system + a WHD (added 1 year after the CO was issued) is unable to keep up. Indoor humidity levels exceed 75+% mid summer and the combined HVAC + WHD systems are unable to keep up. I have to keep the AC down to low to mid 60s at night to keep the house "comfortable" for guests, otherwise we are uncomfortable and people cannot sleep. Additionally, I have warped floorboards by July, and they flatten out in the winter.

    At this point, I'm at my wits end and would do anything to solve this problem.

    Thanks,
    Mr. Humidity
    PHM
    --------
    The conventional view serves to protect us from the painful job of Thinking

  5. #5
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    Quote Originally Posted by MrHumidity View Post
    Dear Original Poster (OP):

    I wonder if you ever able to resolve this issue? And might you have a suggestion for a contractor that solved it?

    I am 100 feet from the sand in Ocean County NJ and have the same exact problem you describe. My house is on stilts, brand new, very tight, and the HVAC system + a WHD (added 1 year after the CO was issued) is unable to keep up. Indoor humidity levels exceed 75+% mid summer and the combined HVAC + WHD systems are unable to keep up. I have to keep the AC down to low to mid 60s at night to keep the house "comfortable" for guests, otherwise we are uncomfortable and people cannot sleep. Additionally, I have warped floorboards by July, and they flatten out in the winter.

    At this point, I'm at my wits end and would do anything to solve this problem.

    Thanks,
    Mr. Humidity
    Keeping the interior of a home below the outdoor dew point causes condensation in the outer shell of home. Green grass climates are +70^F outdoor dew points. much of the mild seasons. Moisture migrates to the innner surfaces of the home and will grow moid while being difficult to keep <50%RH inside.

    A properly setup a/c the removes enough moisture to maintain <50% with indoor temperature 73-75^F. When the home is unoccupied, suggest raising the indoor temperature setting to avoid moisture condensation and migration from outside through the outer surfaces. The wrapped flooring is a classic example. I suspect that you lack a good vapor barrier on the outside of the insulation under the floor. Closed cell foam well sealed may be needed plus avoid over-cooling when outside dew points are high.

    Check you a/c return/supply temp/%RH to comfirm the a/c settup to remove excess moisture during sensible cooling runs. Keeping a home at 75^F, 50%RH, q 55^F dew point, we need a/c supply of less than a 50^F dew point.

    Next you have added a whole house dehumidifier to maintain <50%RH when the a/c is not cooling enough. The installation is critical. Best to have a return from the open part of home to the dehumidifier intake. The supply of dehumidifier should be connect to the a/c supply for circulation throughout the home. Also the dehumidifier should be large enough remove moisture to maintain <50%RH.
    Start with you fan set to "auto".

    Start be telling us the a/c return/supply temperature on a typical cooling day.

    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. Likes MrHumidity liked this post.
  7. #6
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    Apr 2021
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    Dear PHM,

    Thank you for the reply and your suggestions. I will attempt to collect the drain water from the downstairs unit (which services the first and second floors) on a warm day (might be a while here in NJ). The third floor is in a difficult space to get at for a non-professional.

    I suspect you are correct, however. The installer (who installed the HVAC as part of the new house construction) of the HVAC unit and the WHD assured me he reconfirmed his sizing calculations and "could have gone larger". However, given some short cycling on warm days, I suspect that may be the ultimate cause.

    They have "lowered the fan speeds" of the blower on both units to attempt to reduce the humidity, but that didn't work. We decided then to install the WHD (Honeywell TruDRY 120 PPD Whole-House Dehumidification system, in the "B" option Main Return to Main Supply). the house is ~3800 sq. No Makeup Air. Exhaust fans exist in bathrooms and the range hood.

    I also suspect the Honeywell is unable to overcome the static pressure of the blower fan, because in this "B" configuration, the Blower fan is always ON when there is a call for Dehumidification from the WHD, but no AC cooling from the HVAC.

    I would love to be able to get someone in the Ocean County NJ area that can solve this for me.

    Thank you,
    Mr. Humidity.

  8. #7
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    Apr 2021
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    Dear Teddy Bear,

    Thank you for your reply and interest in helping me.

    I will report back when I have a warm enough day in NJ to be able to cool the home.

    I have ordered from Amazon two Humidity meters to attempt to accurately measure the humidity:

    1. Extech 445580 Humidity and Temperature Pen Sized Meter
    2. ERAY Temperature and Humidity Gauge Meter with Backlight Digital Psychrometer Thermometer Hygrometer, Dew Point and Wet Bulb Temperature, Battery Included

    I hope these are accurate enough to make measurements.

    Thank you again.

    Mr Humidity

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