window units increase humidity

[johndeerefarmer]

Over the last few years I have bought three new window units and all three increase the humidity instead of decrease it.
I can turn on the A/C in the bedroom and go to bed and it's cooler but the humidity is way higher than what I had when I went to bed.
I have tried under sizing the unit so it runs more but that makes no difference. I put a 5k BTU in a 600 sq ft area and it did the same thing.
My last experiment I ran it in DRY mode and it still increased the humidity from 41% to 48% over night.

I notice that these new units don't let the condensate drip out the bottom like the older units. I understand this is to increase the efficiency? Can I add a drain hole and will the humidity decrease like it's supposed to?

Thanks

[pecmsg]

There not adding humidity it’s just they leak air so bad !

[pecmsg]

There not adding humidity it’s just they leak air so bad !

What’s wrong with 48%RH?

[johndeerefarmer]

There not adding humidity it’s just they leak air so bad !

If that's the case then why do my two older Whirlpool 2 1/4 ton window units in my shop not increase the humidity? and they both just pour the water out the drain holes while the new ones don't.

[R600a]

Did they lower the temperature? Post before and after temperature and humidity so we can see if the window unit has removed moisture or not. Relative humidity is relative. It varies with temperature if the water content stays the same.

[VTP99]

Modern window shakers have what's called a slinger fan.

[vstech]

Many ac units use the condensate to increase the cooling efficiency of the unit. Anytime cooling occurs, humidity is removed from the space, but if the unit cools more than it removes, it will raise the relative humidity number… water is removed from the space, but the dew point shifts, and the percentage of moisture the air temp can hold increases.

[vstech]

Modern window shakers have what's called a slinger fan.

Iirc, ALL window shakers have them…

[ammoniadog]

Pretty sure the condensate has nothing to do with anything. I think the condensate is slung onto the condenser coil, so it ultimately still goes outside, you just don't see it dripping anymore. Someone please correct me if I'm wrong.

I agree with pecmsg, in that it's probably air leaks that are allowing the humidity to come in. When a room is cooler than the area around it, the air in it shrinks a little bit, causing a slight negative pressure scenario where it will be trying to suck in air from wherever it can. Also, the laws of thermodynamics state that high humidity is naturally attracted to areas of low humidity, so that also might be working against you at the same time as the room being in a vacuum.

You seem to be on the right track when you are trying to undersize the unit to get it to run more. Your statement that the humidity raises overnight indicates that it still might be oversized, at least it is overnight when you don't need as much cooling. When it shuts off, that's when the humidity raises. Not the air conditioner's fault.

There could also be something else going on to increase the humidity as well. Are you sleeping in this room and exhaling moisture all night long?

[johndeerefarmer]

Did they lower the temperature? Post before and after temperature and humidity so we can see if the window unit has removed moisture or not. Relative humidity is relative. It varies with temperature if the water content stays the same.

Temp goes lower, humidity increases. I stuck a digital thermometer in the bedroom last week. Here are a couple readings
5:12pm 73.4 degrees 41%
6:16 pm 69.2 degrees 43% humidity
I didn't record the temp the next morning but I think around 67 but humidity was 48%.

[johndeerefarmer]

Pretty sure the condensate has nothing to do with anything. I think the condensate is slung onto the condenser coil, so it ultimately still goes outside, you just don't see it dripping anymore. Someone please correct me if I'm wrong.

I agree with pecmsg, in that it's probably air leaks that are allowing the humidity to come in. When a room is cooler than the area around it, the air in it shrinks a little bit, causing a slight negative pressure scenario where it will be trying to suck in air from wherever it can. Also, the laws of thermodynamics state that high humidity is naturally attracted to areas of low humidity, so that also might be working against you at the same time as the room being in a vacuum.

You seem to be on the right track when you are trying to undersize the unit to get it to run more. Your statement that the humidity raises overnight indicates that it still might be oversized, at least it is overnight when you don't need as much cooling. When it shuts off, that's when the humidity raises. Not the air conditioner's fault.

There could also be something else going on to increase the humidity as well. Are you sleeping in this room and exhaling moisture all night long?

I have thought about the moisture from our breath and have left the bedroom door open- but no difference that I can tell. Thanks

[VTP99]

Iirc, ALL window shakers have them…

Yes all newer ones after DOE made changes.

[R600a]

Temp goes lower, humidity increases. I stuck a digital thermometer in the bedroom last week. Here are a couple readings
5:12pm 73.4 degrees 41%
6:16 pm 69.2 degrees 43% humidity
I didn't record the temp the next morning but I think around 67 but humidity was 48%.

Using some guesses for the elevation 2.12 grains of water per pound of dry air was removed while cooling the air from 73.4°f @ 41% humidity to 67°f @ 48% humidity. The 48% humidity air is actually drier.

[kdean1]

Over the last few years I have bought three new window units and all three increase the humidity instead of decrease it.
I can turn on the A/C in the bedroom and go to bed and it's cooler but the humidity is way higher than what I had when I went to bed.
I have tried under sizing the unit so it runs more but that makes no difference. I put a 5k BTU in a 600 sq ft area and it did the same thing.
My last experiment I ran it in DRY mode and it still increased the humidity from 41% to 48% over night.

I notice that these new units don't let the condensate drip out the bottom like the older units. I understand this is to increase the efficiency? Can I add a drain hole and will the humidity decrease like it's supposed to?

Thanks

Your hypothesis is intriguing. Please elaborate on the source of the oxygen and hydrogen that the unit uses to make water. Perhaps this technology could be used in arid regions.

[R600a]

Yes all newer ones after DOE made changes.

Darn it I was just going to ask what the department of transportation has to do with window units but you fixed it.

[johndeerefarmer]

Using some guesses for the elevation 2.12 grains of water per pound of dry air was removed while cooling the air from 73.4°f @ 41% humidity to 67°f @ 48% humidity. The 48% humidity air is actually drier.

Thanks. It sure doesn't feel like it. Elevation is 8500 ft in southern Colorado. Here's my situation. We have a vacation home there. The master bedroom has a 12x8' sunroom attached with (single pane windows all around) and there are two french doors into the bedroom. The temp in the house can get up to near 80 in July and August. We like to sleep cool. Since it's a semi desert climate most of the summer months we can open the windows in the sunroom and aim a box fan toward the bedroom. Once it starts to get dark it cools off fast. July and August are monsoon season so it rains most afternoons and some in the evenings, so we can't leave the windows open. I put the window unit in the sunroom and am trying to cool the sunroom and bedroom. Since the sunroom has single pane windows its usually at least 10 degrees hotter than the bedroom so the window unit runs more. I blow that cold air into the bedroom with the fan. Once night comes and it starts to cool off, the sunroom gets cool quick so the window unit shuts off. Even though it's on 62 the bedroom will never get that cool.

[ammoniadog]

I have thought about the moisture from our breath and have left the bedroom door open- but no difference that I can tell. Thanks

Is the house negative for other reasons than just the air conditioner? Do you have a bathroom or kitchen exhaust fan running all night long, or a clothes drier? All of these things constantly trying to suck air from inside of the house and force it outside can also cause excessive humidity problems.

One more thing, I think some air conditioners might have a fresh air damper built into them. Either manual or electronic. Does your window shaker have a setting for "recirculate" that you can turn on and off?

[VTP99]

Darn it I was just going to ask what the department of transportation has to do with window units but you fixed it.

And for my next trick ....

[R600a]

Thanks. It sure doesn't feel like it. Elevation is 8500 ft in southern Colorado. Here's my situation. We have a vacation home there. The master bedroom has a 12x8' sunroom attached with (single pane windows all around) and there are two french doors into the bedroom. The temp in the house can get up to near 80 in July and August. We like to sleep cool. Since it's a semi desert climate most of the summer months we can open the windows in the sunroom and aim a box fan toward the bedroom. Once it starts to get dark it cools off fast. July and August are monsoon season so it rains most afternoons and some in the evenings, so we can't leave the windows open. I put the window unit in the sunroom and am trying to cool the sunroom and bedroom. Since the sunroom has single pane windows its usually at least 10 degrees hotter than the bedroom so the window unit runs more. I blow that cold air into the bedroom with the fan. Once night comes and it starts to cool off, the sunroom gets cool quick so the window unit shuts off. Even though it's on 62 the bedroom will never get that cool.

It's going to be hard for a window unit to remove enough moisture at night with people in the room and the night cooling off. Personally 48% humidity is perfect for me but I understand a person used to the desert would be used to lower.
I'd recommend a dehumidifier. Even a cheap portable will make a big difference.

[johndeerefarmer]

Is the house negative for other reasons than just the air conditioner? Do you have a bathroom or kitchen exhaust fan running all night long, or a clothes drier? All of these things constantly trying to suck air from inside of the house and force it outside can also cause excessive humidity problems.

One more thing, I think some air conditioners might have a fresh air damper built into them. Either manual or electronic. Does your window shaker have a setting for "recirculate" that you can turn on and off?

No fans running at night besides the box fan and ceiling fan in the bedroom. The humidity in the rest of the house stays fairly constant at 48% at least over the week that we were there. No settings for recirculate and no damper doors that you can open to let outside air in. Both of the last two window units have this dry mode that is supposed to remove humidity and cool somewhat. That setting works better than regular max cool as the reading that I posted were in Dry mode not max cool. In that mode the humidity feels like 60-65%- feels clammy.