window units increase humidity instead of decrease it?
Four or five years ago I stuck a 5k btu air conditioner in our back bedroom. The plan was to run this unit at night and let the main tstat be set higher. The problem was the humidity would increase over night in the room to the point that it felt clammy in the room. The room is 12 x12. I thought maybe the unit was too large so I left the door open- no difference. I then put the unit in our 16 x20′ living area and it did the same thing. I gave up and took the unit out.
Last week I tried it again. This time I got a 8k unit and put it in our 12×16′ bedroom with the same exact results. During the day the central unit keeps the humidity in the bedroom in the low 50’s and if I run it on 75 at night it will be upper 40’s humidity in this bedroom. (hygrometer has been checked for accuracy). However if I use the window unit in the bedroom the same thing happens. The humidity goes up to near 65%.
I have tried running the fan on constant. Also tried running it on low speed. Neither made a difference.
I have two larger 2 1/4 ton window units in our two shops and neither do this?
Any thoughts? I wonder if the the fan throwing the water up on the condensor causes this? Both units are designed this way.
Thanks
Replies
For your 144 sq. ft. room you should have about 20 BTU's per square foot, or 2880 BTU's, plus 600 for each occupant. So assuming two people, this rule of thumb would suggest a 4000 BTU unit, plus other BTU additions for ceiling height, and other adjustments. Therefore, your 5000 BTU window unit is in the ballpark for your cooling.
Since your evening setpoint for the window unit is 75 degrees F, I would imagine that the unit doesn't have to work very hard or long to reach that temperature, depending on your climate, and the head start provided by the central air. The clammy feeling, I would guess, is due to a situation where the unit can cool the air quickly, but shuts off before the room is dehumidified. Opening the door to the bedroom would exacerbate the situation, as warmer air from outside the room would also be introducing additional water vapor in the air.
Try running the 5000 BTU unit at a setpoints less than 75 degrees F, maybe 72 or 73 degrees F, and the door closed, to see if you get a better result.
I leave the central unit on 75 not the window unit. The window unit was set as low as it would go and still muggy. Since the humidity in the rest of the house was lower than the bedroom, opening the door should help not hurt..
Just to cover all bases, the window unit is mounted with the proper tilt to the outside, correct? Could the drains be clogged? Are the 5k and 8k the same brand bought from the same place or totally different? Could they be blowing in humid outside air?
5k was a LG unit bought about 3 years ago. New unit is 8k LG unit. These new units don't have drain holes. The fan is designed to throw the water up on to the condenser. Supposed to make it more efficient...
I think the water is thrown on the condenser and then makes it's way inside. I am tempted to drill a drain hole and let it drain and see if it makes a difference.
The new unit has a DRY mode. Runs the compressor at a lower speed to force it to run longer to pull more moisture out of the air... It doesn't help!!!
Call their tech support, see what they have to say about it. I'd be interested to know too in case I ever need to buy another window AC.
I would have expected the DRY mode to help, but only if you are trying to cool and dehumidify the air in the room, and not the whole house.
Your central air system can keep up with both the cooling and dehumidifying, so I'm guessing that your central air system has significant dehumidifying capability, which uses a lot of electricity, which is why you're trying to use window units at night. I'm also guessing that you live in a hot, humid climate...
Yea, live in Texas. Temps in 90's and humidity is high.
To keep the humidity below 55% using the central unit I had to slow the fan speed down and I run it lower than I like. If I run it on 77 during the day I can keep it around 52-54%
Troubleshooter,
Maybe the solution is to move north!!! :) We don't have the combined heat and humidity in NY's Mid-Hudson Valley. For the past several days, my window air conditioners have been turned off and the windows opened...
I have an LG unit as well, and I'm wondering if you have the lever set to bring in fresh air from outside. That could be introducing moisture into the room. I keep mine closed and have had good results - one 12k window unit cools and dehumidifies my entire leaky 1950s ranch most of the summer. We run a portable dehumidifier when we don't need cooling, and occasionally to supplement the AC for drying. I'm in NY's Hudson Valley and temps aren't usually all that high, but humidity sure is.
Think this is the answer right here: https://diy.stackexchange.com/questions/29111/why-does-my-window-air-conditioner-cool-but-not-dehumidify
In a nutshell: The window AC doesn't dehumidify that much. The humidity measurement is relative. Temperature goes down, water content in air stays about the same, relative humidity goes up. Your central air unit removes more moisture so you don't get the same problem.
“[Deleted]”