Results 1 to 6 of 6
  1. #1
    Join Date
    Feb 2019
    Posts
    7
    Post Likes

    Low Humidity when Running AC

    Hello AOP,

    I previously posted an HVAC question and was very pleased with the support and direction on this forum, so I figured I'll post my current predicament.

    When my AC runs my humidity within my house becomes very low. I realize HVAC systems naturally lower humidity through their running process, but the dry air is starting to become a problem. My wife is having nose bleeds, and the effects are compounded after sleeping (most uninterrupted time in the house). We have bought a humidifier for our master bedroom in an attempt to alleviate the sleeping problem. The humidifier unit has a sensor (no idea the reliability) that reads 30-something % when we first turn it on for the night.

    I know the easy "let me google this" answer is to get a humidifier. I got that, and it works kinda ok for our master. Our house though is 2300sqft, and I don't feel like getting several humidifier units for each room is the right solution (unless it actually is).

    My question is... is there any way to increase the humidity in my house? Any adjustments to my HVAC unit I can make? Any add-ons to my HVAC unit that will make the air more humid?

    I live in SE Florida, and having too dry a house is not the typical problem. In the past I have had to get dehumidifiers for several apartments and houses. My very naive guess (polite corrections always welcome) is that since our house is fitted with hurricane impact windows that any ventilation or "breathing" the house is supposed to do has been stifled, resulting in inadequate air exchange and also inadequate humidity.

    All suggestions are welcome. Thank you for past help and thank you for your future responses.

  2. #2
    Join Date
    Jun 2003
    Location
    Madison, WI/Cape Coral, FL
    Posts
    9,765
    Post Likes
    What a great problem to have! What is the %RH in your during the and evenings? And on rainy days? Some are sensitive to <55%RH. Get a temp/%RH meter from Amazon or local hardware stores.
    60%RH is about as high as you can go without have biologicals growing in in your home. Dust mites need =60%RH and mold slightly higher.
    Short term set the t-stat to "on" for recirculation of air during a/c off cycle.
    Adding a small amount of fresh filtered air is also important to purge indoor pollutants and renew oxygen. Most suggest a fresh air change in 4-5 hours. Out side air in your area is high humidity during 3 seasons of the year. This easy done by adding a 6" fresh air inlet from outside connected to the return of your a/c. After fresh air and "on" a/c blower,and you need more humidity, your a/c air flow can be can be increased.
    Let us hear about you current %RH during times of the and weather systems.
    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
    Join Date
    Feb 2019
    Posts
    7
    Post Likes
    Thread Starter
    Hi teddy bear!

    Thank you so much for your response and my apologies for it taking so long for me to get back to you. Had some other house issues to take care of, and then got the sensor and was waiting for some readings. I wasn't as precise with my data collection as I would like, but I can give a decent sample of indoor RH%:

    Over several days (about 2 readings a day, and then 1 because I was distracted) I got:
    43% (evening) very rainy
    38% (morning), 44% (evening) raining
    42% (morning), 38% (evening) raining
    35% (evening)
    37% (evening)
    35% (evening)
    .... now comes a generalization from memory.... the next several days had readings between 36%-44% with A LOT of rain occurring (sorry for missing specifics).

    I also noticed (kinda by accident) that one day we ran the AC on fan only the whole day. We were out of the house most of the day and didn't notice until I came in hot and wondered why I wasn't getting cooled down. During that time the RH% was reading ~56%. I turned the AC on and within an hour or two it dropped to 38%.

    It feels like this is too low a RH%. My wife is suffering a lot, and while I feel it less, I do feel it. Hurts to breath some times. Probably over conditioned to always breathing wet air.

    I'm intrigued by your mention of a 6" fresh air inlet. I have never heard of that. Would that cause the house to feel hotter since it's bringing in the hot summer air? Or is that just a trade off I'll have to make? Sort of an interesting one, since if it might make the house hotter, then the AC will run longer, therefore causing more humidity to be extracted, needing more fresh air.... and the cycle continues. If I mention such a thing to my local AC company will they understand (standard procedure?)?

    I really appreciate the feedback and am open to other suggestions. If the RH% levels aren't too low, what else could be the problem? Would it be worth getting an air quality report (if such a thing exists), or is the most likely culprit the low humidity?

    Thanks a ton.

  4. #4
    Join Date
    Mar 2018
    Location
    Chico, Ca #StateofJefferson
    Posts
    1,864
    Post Likes
    At what temp do you keep the house during the day and night? Have you tried turning the temp up a few degrees? This will raise your humidity with less runtime, and see if you start feeling better

  5. #5
    Join Date
    Jul 2010
    Location
    nebraska
    Posts
    2,810
    Post Likes
    If possible get your blower speed increased. That will make the AC pull a little less moisture out of the air.

  6. #6
    Join Date
    Jun 2003
    Location
    Madison, WI/Cape Coral, FL
    Posts
    9,765
    Post Likes
    A restrive air filter, low refrigerant charge, and low air floor all could contribute to this unique problem.
    Fresh air from 6" inlet connected to your air handler will not bring large quantities of fresh air. All thing considered, you are not getting much fresh air.
    Using your Temp/%RH meter, measure the room temp/%RH and at the a/c supply closest to the a/c. This will tell us how the a/c is working.
    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"

Tags for this Thread

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