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  1. #1
    Join Date
    Jun 2018
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    2
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    Data on AC Dehumidifying Effectiveness

    Hi,

    First time lurker, first time poster. My AC unit was on the fritz, recently recharged with R410A, purchased a dehumidifier in the meantime. I found that I have a Trane XL15I and the paired XV80 has the Comfort-R feature which is apparently supposed to dehumidify by adjusting fan speed during startup, starting slow for 1 minute, speeding up for 7.5 minutes, then going full blast.

    But! I couldn't find any data on the actual effectiveness of either the Trane or simply dehumidifying by adjusting fan speed, or how much AC units dehumidify in general. I found this forum by finding a post about the theoretical amount one can dehumidify but Google wouldn't give me anything on real numbers (e.g., reduces humidity levels from x% to y% or by z%), it's been mostly anecdotal claims. I know there are several different variables that would go into the calcs but either a legit study or ballpark figures would be helpful.

    Anyone have any data to back the dehumidifying claims? Also, I'm assuming it would be cheaper to live in a colder, more humid house maybe with a fan running, than a warmer, less humid house with the dehumidifier running and generating heat but any data on that would be helpful. Honestly though, I'd probably live at the same temp, would just want it drier...

    Thanks,
    Kevin

  2. #2
    Join Date
    Jun 2003
    Location
    Madison, WI/Cape Coral, FL
    Posts
    9,768
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    The amount of air flowing through the cooling coil controls the amount of moisture removed by the cooling coil. My past experience says to operate the blow at an air that removes enough moisture to make the home a little on the dry side after a long cooling run all of the time, not just when to damp. After a couple hours of cooling, your home should be <50%RH. As the heat of the day subsides and the a/c cycles, the total moisture removed declines. Unfortunately, the latent cooling load remains steady. By midnight, no sensible cooling load yet the latent load remains steady. Slow the fan or turn it off, your a/c will not remove significant moisture without significant sensible cooling load.
    I am attaching the specs from a 5 ton a/c showing the different amounts of moisture removal at the different air flow rates.
    Get your a/c adjusted for 30^F split between room temperature and the cooling coil temperature. A good a/c tech can do this for you.
    Than add a good whole house dehumidifier like the Ultra-Aire sized and connect properly for a home that will maintain temperature and %RH you set it for.
    If you need more info, ask the question.
    ULtra-Aire is site sponsor and is the grand daddy of the whole house dehumidifiers.
    Regards Teddy Bear

    Name:  sensiblelatent btus per hour.JPG
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    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
    Join Date
    Jun 2018
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    2
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    Thread Starter
    Thank you Teddy Bear! Sorry for the belated thanks, I was expecting an email notification from the site that there was a reply.

    I figured there would be more information out there since there are obviously very knowledgeable experts out there, a little industry-terminology goes a long way. Due to space limitations, my house setup won't allow for a legit dehumidifier, only a portable one that expels heat in whatever room it's in. I'll play around with it when the weather heats up - the last heat-spell I had temps in the mid-80s and 85% humidity and the dehumidifier consistently got it down to around 50-55% during the day, in that room at least (plenty of ventilation from that room to the living areas). However, that was when the ac unit didn't have enough refrigerant so we'll see what happens next week when it's supposed to be consistent summer weather (live in the DC area).

    New home owner, my thermostat is a pretty basic setup so not sure I can do much about fan speed but I'll continue to research. Fascinating subject, I had no idea the complexities involved, from installation to performance to maintenance, and I'm sure a ton of things I don't know about.

    Thanks again!
    Kevin

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