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  1. #1
    Join Date
    Jun 2017
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    3
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    Ultra-aire 98h install question

    Hi folks, trying to get my rh down in my house. With the AC running I'm still between 60-70 RH. Decided to purchase the 98h. I'm planning my install in my basement and want to make sure I purchase all necessary supplies.

    Unfortunately there is no viable option to install a dedicated return for the dehu.
    My plan is to tap into the return and supply plenums and hang the unit adjacent to the air handler. Install option in the middle of page 12 of the manual for reference.

    My goal is to have the air handler NOT required to run with the dehu running. I understand I need a 10" round backdraft damper in the duct prior to feeding the supply.

    My question surrounds the "check damper" between the return duct feeding the dehu and the air handler. Should this be a motorized damper such as the Honeywell ZD10X20TZ? Is there a way to wire it so that it is normally closed? And opens when the air handler fan kicks in?

    Or is there a different type of damper I should use? The plenum is 10x20.

    The dehu will be controlled by an ecobee4.
    My plan is to add a fresh air duct with motorized damper wired to a wemo switch/and relay. This will be phase two of the project, want to get the humidity in the house down first.

    Thanks in advance!

  2. #2
    Join Date
    Jun 2003
    Location
    Madison, WI/Cape Coral, FL
    Posts
    8,277
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    Quote Originally Posted by trip1050 View Post
    Hi folks, trying to get my rh down in my house. With the AC running I'm still between 60-70 RH. Decided to purchase the 98h. I'm planning my install in my basement and want to make sure I purchase all necessary supplies.

    Unfortunately there is no viable option to install a dedicated return for the dehu.
    My plan is to tap into the return and supply plenums and hang the unit adjacent to the air handler. Install option in the middle of page 12 of the manual for reference.

    My goal is to have the air handler NOT required to run with the dehu running. I understand I need a 10" round backdraft damper in the duct prior to feeding the supply.

    My question surrounds the "check damper" between the return duct feeding the dehu and the air handler. Should this be a motorized damper such as the Honeywell ZD10X20TZ? Is there a way to wire it so that it is normally closed? And opens when the air handler fan kicks in?

    Or is there a different type of damper I should use? The plenum is 10x20.

    The dehu will be controlled by an ecobee4.
    My plan is to add a fresh air duct with motorized damper wired to a wemo switch/and relay. This will be phase two of the project, want to get the humidity in the house down first.

    Thanks in advance!
    Thanks for the chance to serve. I am concerned about your comment about "60-70%RH" while cooling. Any time your a/c operates for an hour or more steady, your a/c should be able to get to the target %RH. 50%RH is a good target. During long cooling runs, a properly setup a/c should remove enough moisture to dry the home. If not, check the supply air temperature/%RH for <50^F dew point. It is important to efficient humidity control during high cooling loads. Usually the blower is moving too much air through the cooling coil and must be slowed to allow a colder coil temperature. A colder a/c coil removes more moisture like 3 lbs. of moisture per ton. You will still need the dehumidifier for low/no cooling runs and high outdoor dew points to remove 2-4 lbs. of moisture per hour.

    Back to your install questions. Is the basement open to the main floor of the home? If yes, suggest connecting the return of the dehumidifier to the return of the a/c. Blow the dry air from the dehumidifier to the basement developed area. This avoids any check dampers or need to operate the a/c blower while dehumidifier runs. This also focuses the drying of the dehumidifier to the basement which is much cooler. Even a 1" basement door under cut may be enough of a basement to the mainfloor return to the open part of the home.
    I would start by checking the a/c for proper setup and operating the dehumidifier just on the basement while monitoring the %RH in both spaces. The basement will drop to <50%RH with significant impact on the mainfloor. Next connect the return of the dehumidifier to the a/c return. Pressurizing the basement with air from the mainfloor that will infiltrate the main floor through basement door undercut and other leaks. The dry air from the dehumidifier will find its way back to the a/c duct system. This will get you the air movement for humidity control and fresh air circulation.

    Also avoid blowing the dry air from the dehumidifier into the a/c return. The warm dry air from the dehumidifier decreases the moisture removed by the a/c when both operate.
    This was the original method of install the dehumidifiers for years. I do this in my own basement home. Basements are usually too cool.
    Give me feed back on the temp/%RH supply/return of your a/c. Where is this home?
    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"

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