Originally Posted by Kmcogar
I guess I'll keep a little space for maneuverability. Let's say 32 inches tall and 16 inches wide on the inside.
Ok, so let's say it's a 16"x16"x32" chamber.
I'd suggest insulating it at least 2" thick, giving about an R value of 9. This will depend on the type of insulation you use.
The other thing we need to know is what temps you plan on running it at, and the ambient temp around the chamber. I'll do two different cases, one where the difference in temperature won't exceed 15 degrees (which should be the case most of the time if you're fermenting ales) and a case where the temperature difference will be about 45 degrees (in case you want to brew lagers or cold crash). With these values we can figure out the amount of BTU's necessary, which will hopefully be less than 150.
Case 1 ; Temp difference = 15 degrees:
Q = (1/R value) (A) (Change in T)
A = Inner surface Area
16 in = 1.33 ft
32 in = 2.66 ft
A = (1.33ft * 2.66ft * 4) + (1.33ft * 1.33ft * 2)
A = 17.7 sqft + 3.5 sqft
A = 21.2
Q = (1/9) (21.2) (15)
Q = 35.3
So your fridge should be plenty powerful enough to handle a chamber of that size for ales.
Case 2 ; Temp difference = 45 degrees:
Q = (1/R) (A) (Temp difference)
Q = (1/9) (21.2) (45)
Q = 106
So your fridge should be able to handle lager fermentation.
You can also solve for the largest you can make the fridge if you make A your unknown variable, and set Q between 100 and 150. I'd do it, but I really need to know what your temperature differences will be.
Hopefully this was helpful.