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  1. #1

    Dehumidifier location

    I have a four story townhouse (Maryland), 2 zones and no basement. For the past several years the fourth floor is just plain unbearable during the summer months. My HVAC pro says the ac units (I have a gas furnace) are working fine, however it is just hot and humid on that level.

    I tried closing the 3rd floor vents, with no noticeable difference. We added an extra return vent in the hottest room to try and increase the circulation. No help. We added some booster fans to the 4th level vents and that made a marginal difference.

    Finally I got fed up and said "screw the HOA" and installed a window unit in one of the rooms and that of course made a world of difference for that room, though the rest of the level was still muggy.

    I saw this 50 pint dehumidifier at Costco and stuck it in the hallway and noticed it made a big big difference. However the draining in this unit is a pain and the patented delonghi pump system broke after a week.

    I've read getting a whole house system will be more efficient, but my question is where to put it? On the upstairs system where the humidity is the problem, or the downstairs system where it isn't?

    Thoughts?

  2. #2
    Join Date
    Jun 2003
    Location
    Madison, WI/Cape Coral, FL
    Posts
    6,064
    Quote Originally Posted by WhiskerBiscuit View Post
    I have a four story townhouse (Maryland), 2 zones and no basement. For the past several years the fourth floor is just plain unbearable during the summer months. My HVAC pro says the ac units (I have a gas furnace) are working fine, however it is just hot and humid on that lev

    I've read getting a whole house system will be more efficient, but my question is where to put it? On the upstairs system where the humidity is the problem, or the downstairs system where it isn't?

    Thoughts?
    Check out the info on the Ultra-Aire 70H located near the air handler servcing the problem area. Ideally draw air from the open area and supply the dehu output to the supply side of the a/c. Locate the dehumidistat in the open area. Drain the dehu to the a/c moisture drain.
    Keep us posted on the results.
    Regards TB
    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
    That sounds like a great plan. Unfortunately the ac unit is in a closet and there isn't much room. We might have to put the dehumidifier in the attic, though two return vents are close to the spot in question.

  4. #4
    HVAC pro just left, and I showed him TB's post.

    He said he doesn't do a lot of dehumidifiers, because he generally doesn't recommend them because a properly working AC unit should control the humidity. He thinks my 2 ton unit (1 of 2) just might not be strong enough to handle the humidity, but he also considered the fact that since this is the 4th floor and I have over 60% humidity that a dehu might be the prudent choice because the AC unit is 8 years old and it cools the lower level just fine.

    He's going to write up a quote to hang the dehu from the rafters, install an emergency drip pan below that and take the input from the return vent in the ceiling in the hallway where the humidity is the worst, run the condensation to the ac pvc. I'm not sure where we want to put the humidistat. The logical choice would be the same hallway, but being a townhouse the wiring may be a PITA. Worse case scenario is we put it in the laundry room, whose door we usually keep open all the time.

  5. #5
    Join Date
    Aug 2012
    Location
    North Dakota
    Posts
    502
    well the longer the run time of the a\c the better it will work to dehumidify the area as such if the system is under sized or correctly sized it will dehumidify at an acceptable rate and leave the occupants comfortable, a stronger or bigger a\c will make your issue worse! and the post sounds a little confusing do you have one or two a\c systems? as a zoned system would would be one a\c and there may be issues with said zoning system if isolating the third floor didnt make any real changes that may be problematic ?

  6. #6
    Join Date
    Jun 2003
    Location
    Madison, WI/Cape Coral, FL
    Posts
    6,064
    Quote Originally Posted by WhiskerBiscuit View Post
    HVAC pro just left, and I showed him TB's post.

    He said he doesn't do a lot of dehumidifiers, because he generally doesn't recommend them because a properly working AC unit should control the humidity. He thinks my 2 ton unit (1 of 2) just might not be strong enough to handle the humidity, but he also considered the fact that since this is the 4th floor and I have over 60% humidity that a dehu might be the prudent choice because the AC unit is 8 years old and it cools the lower level just fine.

    He's going to write up a quote to hang the dehu from the rafters, install an emergency drip pan below that and take the input from the return vent in the ceiling in the hallway where the humidity is the worst, run the condensation to the ac pvc. I'm not sure where we want to put the humidistat. The logical choice would be the same hallway, but being a townhouse the wiring may be a PITA. Worse case scenario is we put it in the laundry room, whose door we usually keep open all the time.
    Laundry is a good location if on the same floor. Use the Santa Fe Compact II with a self contained dehumidistat. If possible, discharge the dry through the wall into the hall. For an attic install, use the Ultra-Aire 70H with a remote dehumidistat.
    I agree that a properly sized and setup a/c can maintain <50%RH during medium to high cooling loads. But during low/no cooling loads, the a/c will not run enough to remove the moisture needed to maintain <50%RH.
    Keep us posted.
    Regards TB
    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"

  7. #7
    For an attic install, why discharge the dry air back through the wall instead of sending it back to the AC return?

  8. #8
    Join Date
    Jun 2003
    Location
    Madison, WI/Cape Coral, FL
    Posts
    6,064
    Quote Originally Posted by WhiskerBiscuit View Post
    For an attic install, why discharge the dry air back through the wall instead of sending it back to the AC return?
    Yes or better yet, send it back to the supply side of the a/c for even better distribution of the dry air throughout the home. This would be similar to the Ultra-Aire.
    http://www.ultra-aire.com/pdf/Ultra-...Spec_Sheet.pdf
    Simple, better, and best.
    Regards TB
    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"

  9. #9
    Ok, the quote came in and the cost is somewhat prohibative IMO. The install is more than twice the cost of the dehumidifier just for a ballpark figure.

    Since my laundry room is located on the 4th floor, do any of you see a problem with just having it run from there? Noise might be an issue, but I can have my guy hang it from the ceiling.

  10. #10
    Join Date
    Jun 2003
    Location
    Madison, WI/Cape Coral, FL
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    6,064
    Quote Originally Posted by WhiskerBiscuit View Post
    Ok, the quote came in and the cost is somewhat prohibative IMO. The install is more than twice the cost of the dehumidifier just for a ballpark figure.

    Since my laundry room is located on the 4th floor, do any of you see a problem with just having it run from there? Noise might be an issue, but I can have my guy hang it from the ceiling.
    For a simple install, the utility room is good. Ideally discharge the dry air through the wall to the hall. A 1" undercut of the door will allow house to return to the laundry room/dehumidifier. You can try with the door open. I have done this on a home. You must leave the door open.
    Keep us posted.
    Regards TB
    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"

  11. #11
    I just bought the Santa Fe 2 compact. Considering the laundry is right off the problem area, I'm hoping leaving the door open will allow entropy to do its stuff

  12. #12
    Join Date
    Jun 2003
    Location
    Madison, WI/Cape Coral, FL
    Posts
    6,064
    Quote Originally Posted by WhiskerBiscuit View Post
    I just bought the Santa Fe 2 compact. Considering the laundry is right off the problem area, I'm hoping leaving the door open will allow entropy to do its stuff
    Keep us posted. I did a 2,400 sqft. single story with one. Leaving all of the doors kept the home <50%RH. Register the warranty and get your ^F/%RH monitor to help monitor the far corners of the space.

    Keep us posted.
    Regards TB

    PS Catch the condensate for a couple days to see what it takes to dry the space.
    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"

  13. #13
    I put this in my laundry room on top of the washer and am collecting the water in a trash can. So far so good, though its a bit noisy with the laundry door open. I plan on adding a foam-dampened shelf above the washer and running the drain down the same exhaust used by the washer.

    With the door closed, it's still a little noisy, but acceptable enough. The door has about a 3/4 inch gap at the bottom. My concern with the door closed is that this room will get the lion's share of the dehumidification benefit. I'd like to avoid putting this unit into the attic for cost/convenience reasons. I'm considering ordering the vent kit for the Santa Fe which will give me more options, some of which are getting a contractor to:

    • Vent the exhaust into the attic from laundry room
    • Vent the exhaust into hall (install new vent)
    • Vent the exhaust into ducting used by return


    If I were to do any of the above, would the 3/4 inch gap be enough to pull air in from the floor of the hallway? I could also use any of the options above and vent the input from the hall, though the location for #2 above would have to located away from the input.

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