I've posted bits and pieces of this whole experiment and now I'm about done with the thing so I'll post the whole saga more or less from square one. There are a few minor things I'm going to change here and there, but for the most part, the design is what it will be.
The project started with the need to control the fermentation temperature of two 12.2-gallon B3 conicals. The easiest way by far is to put the whole thing in a fridge with a temperature control, but I just don't have room for another fridge, yet alone two and I'm also thinking a third fermenter may be in the future. The cooling option available from B3 was too expensive in my opinion, so I needed another solution.
My first plan was to create a small cold room with two individual compartments and put the fermenters in there. I really don't have the space for that either, so I needed to come up with a solution to hold temp in each fermenter individually and with a compact source.
A glycol jacket and chiller seemed like the ideal solution, but at $1100 for the smallest one I was obviously going to have to figure out how to make one. I already bought a 6,000BTU window A/C unit to cool the cold room, so I decided to use it. I was inspired by an article I found online about building your own reef aquarium chiller from window A/C parts. I didn't want to compromise the sealed system since I didn't want to vent the refrigerant (illegal) and I couldn't re-charge the system. I decided to carefully bend the evaporator under the unit and set it on top of an ice chest full of coolant and put two pumps in the coolant bath. A temp controller would individually operate each pump and the coolant bath would be controlled by a third.
This worked pretty well but was very difficult to get to the pumps. The other problem was I couldn't be careful enough bending the lines and I kinked the suction line. The unit still worked, but ran warm.
The initial bucket test:
The kinked line:
The original design with A/C on top of ice chest
This unit worked as is for two brewing sessions but the kink failed on the third and sent my vanilla porter up to 85* (it's not drinkable). Now that the refrigerant was gone anyway, I decided to experiment with R134a as it is readily available anywhere including my grocery store. I cut the evaporator off, cut out the cap tube and rearranged everything so that I could sit the A/C unit next to the ice chest to get inside it. I rerouted all the copper lines and brazed new ones in place. I sourced some service fittings and brazed them on:
I bought a venturi vacuum pump and a set of A/C gauges from Harbor Freight Tools for less than $50 for both. Once I had everything sealed back up, I tried evacuating the system, but it wouldn't hold vacuum at all. I pressurized the system and found that my brazing job of the service ports to the tubing was lousy and I had to fill in some material. All my tube-tube connections were great, but those ports are a b**ch! After three tries, I had a system that would hold vacuum. I added the R134A and within seconds the unit was cooling! I was able to drop the coolant bath to 24* within about 1:45 while charging the system at the same time.
To control the pumps, I didn't want to spend the money on several Ranco controllers, so I decided to use cheap digital thermostats and A/C contactors (24VAC relays) Thanks to John for figuring out which one on the market was easy to convert.
I added a 24VAC transformer and a contactor for each pump. They work very well.
The blue connects are the pump load wires and the red ones are the control voltage from the thermostat
Here is the completed unit
The whole setup with both fermenters
The control panel. I happen to be fermenting two ales right now
How the heat is removed from the fermetner
Overall this was a very cool project. I can keep ther fermenters at almost any tempature I want and within 2*. I've brought the beer down to 35* just to see if I could.
A few things though:
1) Electricty is very dangerous. If you don't understand it, leave it alone. I will be moving the connections into a waterproof box now that I know it all works.
2) It is illeagal to vent refrigerant into the atmosphere.
3) Refrigerant can cause bad frostbite burns.
4) R22 and R134a are NOT compatible refrigerants. Do not mix any refrigerants.