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  1. #1
    Join Date
    May 2018
    Posts
    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
    Join Date
    Jun 2003
    Location
    Madison, WI/Cape Coral, FL
    Posts
    8,349
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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"

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