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Professional Homeowner
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Discussion Starter #1
I'm having a small moisture issue. The room has exterior poured concrete walls. No heat going to the room, and it's closed off. It's getting in to winter around here, so temperatures are dropping into the teens and twenties. The exterior walls are covered with 2" pink foam attached to the walls with proper fasteners and fender washers. The ones toward the top (above grade) are actually sweating and dripping down the foam a bit. There's a dehumidifier in the room, but it's empty after 24 hours. There's maybe 1/4 ounce or less of water in the pan. The room is pretty cold with no heat, maybe in the mid 50s? There's a little half moon a couple inches high by 1/2" wide of ice building up on the outside of the dehumidifier, probably where the coil gets close to the housing or something. The dehumidifier seemed to work some earlier this month in the much warmer mechanical room when defrosting a freezer, but didn't get but maybe -12 ounces after 24 hours.

My question(s) is this (are these): obviously, how to get rid of the condensation? I know the obvious solution... Vent the room better. Not going to happen. I need the room able to withstand a potential fire (it's basically a fire resistant room. In the event of a house fire itne flame or excess smoke COULD get in there through a vent). I can put an electric heater in there no problem, but would need to get one. Will the warmer air help the dehumidifier do its thing, or maybe even warm it up enough and maybe dry it out so the condensation no longer collects on the coldest surfaces? Figure my dehumidifier is toast? Maybe not enough moisture in the air for it to work?

Otherwise I might end up needing to put a vent in there, with a heat activated mechanism that will close the vent...
 

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It sounds like the water is freezing on/in the dehumidifier, and the temp is probably at or below 32F, otherwise the ice would melt...

A heater would probably help, setup to get the room just above freezing (or rather, so ground level is just about freezing).
 

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never too old to learn
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I’ve experienced the same issue in my basement and it was due to air temperatures. From an article online: “Typically dehumidifiers are designed to operate at temperatures above 65°F degrees. If the temperature drops to 65°F degrees or below, a regular dehumidifier will let water freeze on the condenser coils.”

I worked with a man who used salt as a dehumidifier- plenty of articles on that as well. Those little hanging bags like DampRid use this ‘technology.’
 

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As the air gets colder it is capable of holding more moisture but has already been said a dehumidifier does not work well in those colder temps. Here is a link to several solutions. https://dengarden.com/cleaning/Ways-to-Dehumidify-Your-Greenhouse-andor-Home-Environment
One other note- aside from doing the room, I would also put a product like DampRid in the gun safe to make sure it is dry inside. I use it in one of my safes and it's certainly worth it for what little effort is required to keep it dry. You can also regenerate the stuff on a baking sheet in the oven.
MikeC
 

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You didn't mention what the humidity % actually is, but I assume it's very high. I'm also assuming you have a concrete floor; if it were dirt, a dehumidifier would have to really work hard. Even with concrete, if a proper moisture barrier was not put under it and you are in a place where there is a lot of moisture, some will get through the concrete.

My experience with dehumidifiers is that they will work OK if the temp is 50 F or above. It sounds like your dehumidifier is not working properly.

Over the past 20 years, I have gone thru a half dozen dehumidifiers. Most were the very expensive kind and none of them lasted long. (Don't understand this; fridges last 20 years or more with no problems and a dehumidifier is not that different.) The one I'm running now is a 70 pint Frigidaire that cost less than 25% of the cost of four expensive units (over $1k) that died. It's been running a year now so it may be on its last legs, but I won't know until next spring since it has little to do in the winter months.
Gerald
 

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Professional Homeowner
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Discussion Starter #6
We
You didn't mention what the humidity % actually is, but I assume it's very high. I'm also assuming you have a concrete floor; if it were dirt, a dehumidifier would have to really work hard. Even with concrete, if a proper moisture barrier was not put under it and you are in a place where there is a lot of moisture, some will get through the concrete.

My experience with dehumidifiers is that they will work OK if the temp is 50 F or above. It sounds like your dehumidifier is not working properly.

Over the past 20 years, I have gone thru a half dozen dehumidifiers. Most were the very expensive kind and none of them lasted long. (Don't understand this; fridges last 20 years or more with no problems and a dehumidifier is not that different.) The one I'm running now is a 70 pint Frigidaire that cost less than 25% of the cost of four expensive units (over $1k) that died. It's been running a year now so it may be on its last legs, but I won't know until next spring since it has little to do in the winter months.
Gerald
ll, by that token I guess the $20 for this one we bought at a yard sale 6 years back for $20 probably doesn’t owe us anything. I dumped it many times over the years, once a day in the summer months. Previous owners of our home never ever ran one, and it really wasn’t bad in that basement. I put a fan down there and it helped. There’s only a couple places with condensation, but not much more in the bucket. My dad has 2 more known good dehumidifiers, so maybe I’ll hi jack one of his for awhile. Otherwise, I guess it’ll be a heater added to it.
 

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I have an expensive April Aire dehumidifier in the 1200 cu/ft crawl space at our seasonal place. Without it, the humidity can go as high as 90%. When the unit is running I can easily keep it at 55%, The machine has an automatic defrost mode if the coils build up frost. Like other types of dehumidifiers, it will not run if the ambient temperature is below 50°.
 

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Discussion Starter #8
I’ll need to put a thermometer with a humidity meter on there to see what i’m up against. It might be low 50s in there; who knows... And if the humidity is low maybe it’s a moot point. I just don’t like the idea there may be moisture between the foam and the concrete.

There is plastic moisture barrier under the floor ‘s concrete.
 

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Your difficulty lies in the type of dehumidifier you have. The most common ones work down to around 65℉ and you can find some that work down to around 45℉. Under that and you have to go to a different type of humidifier.

 

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Discussion Starter #10 (Edited)
Your difficulty lies in the type of dehumidifier you have. The most common ones work down to around 65℉ and you can find some that work down to around 45℉. Under that and you have to go to a different type of humidifier.

Great to know! I wondered if there was something like that out there. The price is high, though.

I put a very small (like 5”?) fan on the floor a couple days back. I don’t know if it’s because it’s warmer outside, but the visible condensation is gone. There were maybe 2 cups of water in the pan today when I emptied it.

I went out and bought a cheap $20 electric heater this morning. It felt warmer in there almost immediately. In the 5 minutes it took me to clear out around the heater and empty the dehumidifier, it felt like the air temperature came up 5 degrees. It was warmer in there to begin with though. Probably because of the dehumidifier running for 5-7 days continuously.

I’ll check tomorrow to see how much is in the pan. I should have grabbed a little thermometer / humidity gauge when I was out to see if it’s even necessary to run the dehumidifier. Maybe a medium size fan is all I really need until summer. Then there’s no question that a dehumidifier will be required then.

I figure for the cost of the new dehumidifier I can run that heater for a many years.
 

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As the air gets colder it is capable of holding more moisture...
You got that backwards. Cold air can hold less moisture.

As others said, it is too cold in the room for that dehumidifier. Maybe one with a defrost cycle might work down to a colder temp so long as it is still above freezing.
 

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Contrary to what some have said, cold air holds much less moisture than warm air. Cold air is the primary reason hands and lips get chapped even with feet of snow all around you. It's also the reason your dehumidifier doesn't have anything in the pan since it only works to ~65℉ (which is almost freezing, to me).
Your idea of the small heater is fine, what you really ought to do is when the warmer weather comes back, is to tackle the moisture problems there.
 

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Try setting the dehumidifier on a stool or table, maybe 18" off the floor. I had one that would always freeze up and I had to let it thaw. I cleaned the coils real well as they had collected a lot of dirt and dust over the years. Solved the freezing problem really well. Also, a small box fan that will run very low, just enough to move the air, will help a lot, especially if you can aim it towards the ceiling a bit.
 

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Discussion Starter #14
Try setting the dehumidifier on a stool or table, maybe 18" off the floor. I had one that would always freeze up and I had to let it thaw. I cleaned the coils real well as they had collected a lot of dirt and dust over the years. Solved the freezing problem really well. Also, a small box fan that will run very low, just enough to move the air, will help a lot, especially if you can aim it towards the ceiling a bit.
There might be some merit to this. It's definitely warmer off the floor, since heat rises and there really isn't much air circulation.

That said, i had a lot of success with the heater. I just went down and turned the heater down to low (750 watt setting). The case is starting to thaw out, and the bucket is about 1/4 or 1/3 full after just one day in our "dry" season.

I ended up moving the heater next to the dehumidifier in hopes the dehu's bigger fan will circulat the warm air a little better, and it might thaw out the rest of the frost on the case. I should probably take off the screen and clean out the coils as suggested. That'll be tomorrow's project. Once the dehu is completely defrosted, I'm wondering if the heat from the dehu will be enough to keep the room warm enough for it to properly work, but I'm probably not that lucky.
 

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If your dehumidifier doesn't have a defrost cycle, you could try putting the it on a timer so it runs for a while and stops just long enough to defrost.
 

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Here is another thought, too. After you clean the coils spray a little silicone lube on a cloth or brush and rub it onto the coils Might make the condensed water run off the coils better to prevent freezing. I think the reason for the freezing is the fact that moisture is staying on the coils long enough to freeze. Do you have a sump pump/drain in the room? We've been fortunate to be able to let the unit drain into a hose and not have to worry about emptying it.
 

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There is also a little gizmo called a dehumidifier pump that allows you to move the condensate someplace else. Depending upon which model you get, the head height is around 15-20 feet.

When I first moved into my house, I had major moisture problems in my crawlspace underneath. I'm disabled and it was a royal pain having to get into the crawlspace to empty the tank every day. Used this little pump to direct the condensate outside.
I actually had a stream flowing through the crawlspace when it rained due to cracks and holes in the masonry. Once I eliminated those, the crawlspace remains dry year round even with the 60 inches of rain a year. 1576415277791.png
 

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Discussion Starter #18
The room was built with a dehumidifier in mind. There is plumbing in there that goes to the lift station. At the moment though, I’d rather manually empty it out so I know what it’s doing or not doing. This summer i’ll plumb it to the drain.

The timer and silicone spray are good ideas also... I have both.
 

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You got that backwards. Cold air can hold less moisture.
Yupper, real brain bubble on that. Have no idea how I got to that from thought that was - warm air releases the moisture when if comes into contact with colder surfaces/air. Thanks for clearing that up. Now lets talk about fog cause that is apparently what I was in that morning.:eek:
MikeC
 
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