I needed a fermentation chamber for a Scottish Heavy Ale I'm doing and had a 1.8 cu.ft. mini fridge that the 5 gallon carboy wouldn't quite fit in, so I decided to build a collar for it and add an "eBay Temperature Controller" while I was at it. Below are a few pics and the plans I made for anyone looking to do a similar build.
The collar is 12" deep and increased the capacity from 1.8 to 4 cu.ft., making plenty of room for the 5 gallon and another 3 gallon carboy. Not wanting to make a frame, I decided to make my own insulated structural panels using 1/2" R5 rigid insulation sandwiched between sheets of MDF I cut from a couple 2'x4'x1/4" MDF handy panels since MDF has slightly better insulating qualities. They're bonded to the insulation using Loctite Foam Insulation Adhesive and to each other using Gorilla Wood Glue. I fashioned a top brace connecting the fridge to the collar from a scrap piece of MDF and the base is supported by 3 3/4" pine boards. The outside joints are sealed with black duct tape and the inner joints with duct work foil tape.
Sorry for the mess in the picture, by the way
Along the front I lined the perimeter with a magnetic adhesive strip and covered it with black duct tape. On its own it wouldn't hold much, but with the fridge door's magnetic seal it holds it shut nice and tight.
Afterwards I purchased an STC-1000 temperature controller from eBay for $23.99 with free shipping, a 7"x5"x3" project enclosure, 8-port terminal strip (both from Radio Shack) and used a 12-gauge, 15-amp extension cord I already had. Here's the wiring diagram I made to keep everything straight:
I cannibalized the wiring I needed from the extra length on the extension cord I didn't need and the whole thing came together nicely. I only wired it for cooling, but the 8-port terminal will allow me to add on to it later as I need to:
Yes, the duct tape will be replaced with proper electrical tape very soon, ha-ha.
The temps stay steady and the refrigerator hardly runs at all thanks to the insulated collar and tight seals. I'm very happy with the way it turned out, but going metric will take some getting used to. Happy brewing, everyone!