My first major project when I joined VHS last year was this keg fridge. I did the woodworking in my friend’s basement shop, but I did most of the electronics and general design here at VHS.
I finally got around to documenting it. I’m glad that for this project I remembered to take lots of photos. It ended up being a pretty drawn-out project!
I exchange 20lbs cylinders at Dan’s, which is convenient for me. Costs about $30 and lasts me the better part of a year. At my cidery we use Praxair or Air Liquid. I’ve always exchanged — never refilled myself.
My current water carbonation process is to fill a corny keg with water and put it in the fridge with the co2 on at 15-20psi. It takes a few days to carbonate like that, or you can do it in 10 minutes if you take the keg out and shake it a couple times to help it dissolve. It’s a function of temperature (colder is better), surface area (bubbles from shaking count!), and pressure. Well, and time I guess.
Very quick carbonation and cooling: liquid and a chunk of dry ice in a 2L bottle. Amount of dry ice to add depends on how much carbonation you want and the amount of void space in the bottle to contain the CO2 expansion. If you want to be safe, use a pressure relief valve. I actually had great results just dropping a cube of dry ice into a bucket with water, ended up with chilled club soda.