Window A/C Fermentation Chamber in basement

Is anyone using a window A/C unit to cool a fermentation chamber in their basement without venting out a window well? A new 5000BTU unit can be had for around $100 and I think would provide more cooling power plus built-in air circulation versus a small refrigerator.

I am worried about the noise level and the amount of heat exhausted by the unit into the basement if not vented outside via a window. A condensation collection system would also be needed (i.e a bucket )

I can understand your concern for it making too much noise but I would not worry too much about it causing a lot of heat in other parts of the basement. Essentially all you will be doing is removing the heat from the relatively small space in your chamber outside in the basement. This can't be a ton of thermal mass and it will spread throughout the rest of the basement. The AC unit will throw off some heat as well but again not too much in my opinion. Just my 2 cents.

The term heat exhaust was misleading. I am concerned about how much the heat the A/C unit would generate during operation. I know little about refrigeration principles but I do know air blown off from my central A/C compressor outside is pretty warm. To make something cold, the heat must be shed somewhere else.

rcrabb22 said:

The term heat exhaust was misleading. I am concerned about how much the heat the A/C unit would generate during operation. I know little about refrigeration principles but I do know air blown off from my central A/C compressor outside is pretty warm. To make something cold, the heat must be shed somewhere else.

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That was his point. The heat your AC puts out is only the heat it removes from the cold side, plus a little bit from the electricity that operates it. Assuming you're not pushing the temperature inside the box too low or are otherwise not wasting the work of the AC, the amount of heat it will put off is probably not enough to worry about.

An AC is a heat engine run in reverse. Go here and look at the heat engine diagram, but reverse the direction of the arrows.

Think about it this way. Let's say your chamber is 2x2x3, or 12 cu ft, and your basement is 22x34x8, or 5984 cu ft. Then the thermal mass of the air in your basement is (5984/12=) 498.6 times as much as your chamber (and this doesn't include the thermal mass of anything that's in you basement, which in total is probably much higher that the air anyway).

Bottom line, if you want the AC to cool the air in the chamber by 20 degrees, the increase in temp in your basement is several hundred times less (assuming perfect efficiency). I don't notice any significant increase in temp in my basement from my AC.

You can also think about it this way...

If you put a new refrigerator in your basement, would you be worried about it overheating the basement? The mechanism by which an AC generates cold air is the same as a refrigerator.

Thanks, I'm feeling better about the heat. I was comparing a central AC unit to a much smaller window unit. My bad.

I guess my only concern now is how loud the unit would be. I have a dehumidifier running down there now and that is not that bad. Given half the A/C unit would be in a insulated box I wonder if noise level would be similar?

what's the worry with the noise?

rcrabb22 said:

Thanks, I'm feeling better about the heat. I was comparing a central AC unit to a much smaller window unit. My bad.

I guess my only concern now is how loud the unit would be. I have a dehumidifier running down there now and that is not that bad. Given half the A/C unit would be in a insulated box I wonder if noise level would be similar?

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I think the noise issue could only be answered by you. I know to get to my basement there are no doors and therefore no way to really keep the sound from traveling up into the living room etc. So this completely depends on the setup of your house. I would say the size of AC unit that you are talking about would be equivalent to a box fan running on medium as far as sound intensity and pitch.

JKoravos said:

what's the worry with the noise?

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I work from home a few days a week and my office "space" is in the basement too. I can learn to tune it out but I join conference calls on speakerphone. A headset mic picks up background noise as well.

I work from home as well, is your headset/mic noise canceling? I know with mine I can't hear people outside my door.

I appreciate the advice. I am going to pick up the A/C unit and give it a go to sample the noise level. If it is acceptable, I'll go forward with the project. I'll post pictures as I progress.

Remember, with a temp controller, the AC unit won't be running continuously, only once in a while. Especially if you've insulated your fermentation chamber well.

I'm doin' it with a 12k btu unit. So far, so good. Check out my discussion and pics here.

I've had a little 5k BTU unit running constantly to chill a DIY walk-in for almost two years now. The fan never shuts off and the compressor is wired to a thermostat that regulates the temp in the walk-in. I did it that way because it was a simple way to avoid freeze-ups on the AC unit. I keep my walk-in at 38 degrees so it is pretty cold.

If i get any frost build up on the coils inside the walk-in while the compressor is on, it defrosts almost instantly once the compressor kicks off and the fan stays on. There are better ways to handle this but I was lazy and the tiny fan on the unit probably runs me about $3 a month to run so I went with it.

I vent into my basement and there is no noticible "heat" coming off of that unit at all. It is also behind a closed door and you can't hear the unit at all in the bar area.

The best peice of advice I can give is use vapor barrier the crap out of your build as condensation can be a nightmare.

I use my bedroom. Its small and I ferment in there. I crank it during the day when I am at work and turn it off when I go to sleep. I can keep beer around 67* f with this method.

It would hardly work (run the compressor) at all in a little box.

$98 unit new.