AC unit in a closed space?

Hey All-

We're getting ready to move and it looks like the new place has a sweet little storage room. Can't tell from the floor plan, but it looks like a really deep walk-in closet. Probably big enough to store/age beer and ferment a few carboys worth of ales.

Just wondering what would happen if I get a cheap window a/c unit (maybe 5k btu?) and put it in there on a chair or something. Would it even work considering the unit wouldn't be venting outside and instead back into the same room?

Alternatively, I've seen the evaporator coolers (swamp coolers) but I'm not sure how much they drop temp, plus I'd hate to get mold/rot from a closed humid room. I've also seen the "portable" ac units, but they're prohibitively expensive.

Any thoughts?

Heh, I tried explaining this to my wife one time. If you place an a/c unit in a closed room and do not let it vent outside the area being cooled, you will end up with no net gain. The heat that you are removing from the air is simply being exhausted back into the air. You cannot create or destroy energy, the heat energy is not being destroyed, it is simply being converted and exhausted, in this case, back into the room you are trying to cool.

How do those upright, portable units work? Are they vented to a window as well?

the_bird said:

How do those upright, portable units work? Are they vented to a window as well?

Click to expand...

Yes. They have a vent tube to feed to a window.

'k, that makes sense. Always wondered how they disobeyed the laws of thermodynamics!

Does a window unit need to vent outside, or for example, can I frame out a space in the basement and have the ac unit going through the wall venting into the remainder of the basement?

You'll probably have to deal with a lot of humidity in the rest of the basement, at the very least.

Yeah, I was kinda worried about that. Don't need any extra moisture in the basement...HA!

Tell me about it! I'm doing all I can to keep the relative humidity reasonably low and consistent for the lumber and the grain I've got stored down there. It's a damn losing battle!

Actually, a freestanding window ac unit left to run in a closed space will raise the temp. It will turn electrical energy into heat via the compressor and fan motor.

The portable units do have a large flexible duct that blows the exhaust out "somewhere" and that does require an extra fan inside. You can install a window unit on an inside wall but keep in mind that it will heat up the backside area and also drip condensate out of the unit.

So this storage area is nowhere near an outside wall?

We were talking about this the other day...

My walk-in is set up with the AC unit venting into my basement

https://www.homebrewtalk.com/showthread.php?t=74485

.. the fan on the unit is wired to blow 24/7/365 and the condenser is wired to a thermostat to kick on to maintain temp only. You HAVE TO seal the everloving crap out of it with a vapor barrier or you WILL get moisture and your coils will freeze up. Mine is sealed up like crazy and doesn't get any moisture except when I open the door but even that is enough to put a light frost on the coils... . which is why the fan runs 24/7, as soon as the condenser shuts down, the fan auto-defrosts the unit.

Mine's been running non-stop for about a year now... holding dead perfect 38 degrees in the cooler. (I know I know... that's pretty cold for beer)

Bobby_M said:

So this storage area is nowhere near an outside wall?

Click to expand...

Well....the house will be in military housing. Can't really make permanent mods, and I gotta protect the room from mold.

I really hope there's just a vent in there, that'd solve most of my problems. I can't upload the PDF of the plans; it's too big. Basically, the room appears to be in an "L" shape, roughly 20-30 sq ft. As far as I can tell, there's no way to vent any hot air except out the only entry door to the closet, and that'd be mighty unattractive. Maybe I could vent under the door with a flattened duct? It could swing out as you enter. So would the condensate collect in the ducting?

Sorry to sound like such a HVAC newb...I guess I kinda already understood the negative efficiency due to radiated heat, but I wondered if there were some way around it.

If you have a room that size, the only thing I could think to do is to do what I did... build a stand alone... for lact of a better term... big wooden box.

It wouldn't be permanent, especially if you knew ahead of time you would have to break it down at some point and you could mount an AC unit on the side like I did.

If the unit is insulated well, has a decent vapor barrier and is sealed at tight as possible, you won't get heat or condensation off of the unit. I don't.

My cooler is in a smaller storage area of my basement and I don't notice that area any warmer at all (if the cooler is insulated really well, the AC unit won't need to suck 'heat' out of the cooler that often).

Because it's sealed, there's no moisture produced and no condensation. I have a small plastic cup on the floor to catch the once-in-a-blue moon drip but it's been bone-dry for months.

The condensation happens when warmer air hits the really cold coils, INSIDE the cooler. You'll get a tiny bit of frost and then when it defrosts, the water is pushed out the back of the unit... and you see the unit drip. So if you have the front of the unit in an area with no moisture and the back stuck out into super muggy hot humid air... you won't get any condensation... it's how wet the air being cooled is that produces the condesation.