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09-27-2011, 07:24 PM   #1
newdamage1
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 Fermenterator, how big can I go?

hiya folks, I just picked up a 2.8cuft mini-fridge, and I would like to convert it to a dual chamber/zone fermenter. I'm looking at storage for 2 six gallon carboys per zone.
The long term intention is to have and ale & lager side, Plus, enough room on the lager side for a few corny kegs down the road.

The question is, how large an area do you think I can go with this type of unit (Emerson cr282b)? The space I'm looking to use is 26"w X 48"h X 36"t.

Ive seen people chill some pretty big area with a A/C window unit, so I'm guessing this will work, just figured I'd run it by you fine folks.

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09-27-2011, 07:36 PM   #2
DrDarwin
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The calculation I used to size my fermentation chamber was (Surface Area * Temp-Differential)/(R-Value) = BTUs

Figure out what kinds of temperature's you're going to see where you're going to locate the chamber, and then find out how many BTUs of cooling you're going to need to keep it cool. To simplify, you may want to just assume that the whole chamber will be maintaining lager temps. Throw all of your variables into a spreadsheet with your max needed height, and play with the length and width of the chamber until you think you've found a reasonable BTU output for your minifridge. Keep in mind that you're not going to want to max the little guy out, and that there will be some inefficiencies in your chamber.

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09-27-2011, 07:42 PM   #3
aomagman78
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Based on no calculations...that seems like a lot to ask out of the little guy. You can probably pull it off with lots of insulation, but you can probably expect a big temperature swing if you throw in a new 'warm' carboy.

DrDarwin - what units do you use for the calculation? in^2 or ft^2?

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09-27-2011, 07:46 PM   #4
DrDarwin
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R vales are (1h*Ft^2*degF)/BTU - so if you're working in inches you'll need to convert one or the other.

Edit: I should say that I left out the /h part of the BTU answer since the BTU rating of a condenser should be time dependent as well (i.e. technically you are looking at XXX BTU/h cooling capacity vs. BTU/h needed).

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09-27-2011, 08:15 PM   #5
newdamage1
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Is there anyway to figure out the BTU's from wattage or high or low pressure info? I've been over their manual and website, no spec info at all (heck I just called their help line, no dice)

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09-27-2011, 08:19 PM   #6
DrDarwin
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I remember seeing conversions for watts to BTU/h way back when. I think it was something like 1 watt = 3.4 BTU/h. I wouldn't take my word outright on that one though.

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09-27-2011, 09:16 PM   #7
newdamage1
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It says the power supply is 90watts, not sure if that's the info we need. Assuming that's correct, it's only 306BTU, that doesn't sound like much, the old crusty window shaker in the garage is 5k btu! (well, maybe 2.5k Its pretty beat-up.) I have a call into their tech folks, hopefully they can get back to me with a real number.

In the mean time, lets speculate.

My box looks to be 7824 inches SQ, so with your formula,
7824*40/30=10432

if that's right, I'm not even close on BTU's.

That doesn't seem right, should it be: 7824/12*40/30=869?

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Last edited by newdamage1; 09-27-2011 at 09:42 PM. Reason: 1+1=3.1459

09-27-2011, 09:50 PM   #8
horseinmay
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Quote:
 Originally Posted by newdamage1 It says the power supply is 90watts, not sure if that's the info we need. Assuming that's correct, it's only 306BTU, that doesn't sound like much, the old crusty window shaker in the garage is 5k btu! (well, maybe 2.5k Its pretty beat-up.) I have a call into their tech folks, hopefully they can get back to me with a real number. In the mean time, lets speculate. My box looks to be 7824 inches SQ, so with your formula, 7824*40/30=10432 if that's right, I'm not even close on BTU's. That doesn't seem right, should it be: 7824/12*40/30=869?
If you are using the /12 to convert to square feet, then you need another 12 in there. There are 144 square inches in a square foot. If this is the case, then 7824/144*40/30=72.44. You should have plenty. Don't forget that if it's well insulated, once it's cold, it will stay cold, so you only need the compressor to come on and give it a little boost every now and again.
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Last edited by horseinmay; 09-27-2011 at 09:51 PM. Reason: clarity

09-27-2011, 10:50 PM   #9
david_42
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The 3.4 ratio is for heating. Cooling is a different story and 6-8 x watts will put you in the ballpark.

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09-28-2011, 03:49 AM   #10
day_trippr
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Aww...from the topic title I thought someone was going to build a truly epic size fermenter...

Cheers!

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