A guide to making holes in fridges


I have a tiny brewery. Everything fits in a three by seven foot space in the cupboard under my basement stairs. I do the actual brewing in the garage or on the patio, but fermenting, washing, bottling, and everything else happens in the cupboard under the stairs. I’ve installed extra lighting, drawers, countertops, peg boards and plumbed in an oversized laundry sink large enough to clean kettles and carboys in. It also houses the water meter, the sump pit, sump pump and the backup sump system complete with a stupidly heavy battery. There’s even ready-to-drink beer in there! Harry Potter never had it so good.

There is an additional 15 square feet of  storage under the stairs of very limited height. It will fit 10 buckets, very handy for grain storage. A 55lb bag fits nicely into 2 buckets. Buckets with lids are $3 each from Vinter’s Cellars in Waterloo, next door to Innocente. The owner James Fields is awesome. http://www.vintnerscellarwaterloo.com/

I usually ferment in a 7 gallon SS Brewtech Brew bucket. Last Christmas I acquired the chilling system that goes with it. It’s basically an immersion chiller built into a modified lid, you supply the controller and a source of cold liquid to run through it. I bought an inkbird ITC-308 controller (≈ $50 from Amazon), a garden fountain pump (≈ $15 from Walmart) and converted my old drink-cooler mash tun to a cold water reservoir. Cold things are easy to come by in the winter here, the tap water is cold and a flat of water bottles kept outside can keep it very cold indeed. When spring, and then summer, came I resorted to keeping those water bottles in my freezer and swapping them out daily. It worked, but was high maintenance and inefficient. What I really needed was a supply of perpetually cold fluid. What I needed was a glycol chiller! Glycol chillers are purpose built, expensive, efficient, expensive and expensive. They’re also eye-wateringly expensive. I did not need a glycol chiller that badly. 

I developed the idea of getting a small fridge to squeeze into the brew cupboard. It would hold a multi-gallon container of water which would be circulated through the brew bucket chilling coils via tubing passed through the fridge wall. A third hole would be required for the power to the pump. An in-line pump could be located outside the fridge but I already had the immersion pump and a third hole is cheaper than a new pump. The extra fridge space would be used to store finished packaged beer, yeast colonies and perhaps hops if the freezer compartment is cold enough. This would also free up space in our main fridge which would be greatly appreciated by my non-beer-loving spouse and much-too-minor-for-beer minor children. I considered but rejected the idea of a fridge large enough to fit the entire fermenter in. It would be too large for my space, draw more power, and have to be kept at fermentation temperature which would rule out yeast and drink storage space.

The Fridge

A new or used fridge would meet my needs, but shopping is largely online this year and garage sales, thrift stores and the like are not happening. A used fridge would have to be very cheap to offset the possibility of poor performance, noise, or other hidden defects that would send me back out hunting again. A few months after starting to look, Walmart came through with a sale on a 3.3 cubic foot compact fridge that would fit the physical requirements and was also quite cheap. $97.97 + tax, delivery included. https://www.walmart.ca/en/ip/hamilton-beach-compact-refrigerator-black/6000196932637

The reviews were generally favourable and most of the poor reviews complained of delivery issues and damage. Cosmetics were not a priority as long as damage didn’t compromise function.  It’s going to have holes punched in it and put it in a basement cupboard. I ordered and it arrived a few days later, both shiny and dent-free. I let it sit for a day to let the coolant settle as per the manufacturer instructions, tested it to verify it worked, then set to work figuring out where to place the holes.

Positioning the Holes

The fridge had an unusual number of large warning labels with some very repetitive phrasing. The bits that stood out read “Risk of fire or explosion. Flammable refrigerant used. Do not puncture refrigerant tubing”.  These phrases appeared no less than eleven times throughout the labels and manual. I got the idea that puncturing the refrigerant tubing might be something to avoid doing. The additional information that the refrigerant in question was isobutane helped explain the manufacturer’s concern, as was the labelling indicating that the blowing agent used to foam up the insulation was cyclopentane. 

Don’t puncture the refrigerant tubing. Got it. Especially don’t puncture it in an oxygen environment with a drill bit that sparks off the metal housing or tubing. Also, don’t make sparks around the insulation that has been thoughtfully inflated with explosive gas.

So where was all the refrigerant tubing? The chilling plate on the interior was obvious enough, as were the tubes around the compressor at the lower rear. The condenser coils were not visible though, apparently integrated into the outer jacket of the fridge. I read the manual, then searched online for a schematic of the coils but found only wiring diagrams. A fridge this cheap has no repair manual because it’s not cost effective to repair one. I’d have to locate the coils myself. 

Ideally I wanted the holes in the right side about 22” from the floor to be level with the fermenter lid. When running, the two sides of the fridge warmed up, definitely coils in there. The top stayed cool, but that wouldn’t work for running water lines because they would pass through the freezer compartment and ice up. The back certainly had wiring and tubing in it, leading up from the compressor, plus it would be difficult to access to connect and disconnect the fermenter. The bottom didn’t have clearance for tubing. That left the door, which definitely did not have coils or wiring in it (hinges too small to conceal lines/wires). I didn’t want the water lines in the door because it would be awkward to open and close, plus it would be at knee-bonking level when I’m using the counter above. I needed to locate the exact position of the right side condenser coils.

Googling led me to a technique to do this by mixing up a paste of cornstarch and rubbing alcohol, then smearing a thin coat on the fridge. The theory is that the heat of the coils will evaporate the alcohol, creating a visible pattern of wet and dry paste. The practice is that rubbing alcohol smells a lot, dry and wet cornstarch paste look exactly the same, and making cornstarch slime is more fun when you’re 6 years old. It also makes a mess. A big one. It would have been more fun if it had worked. A forum post and some thoughtful answers didn’t produce any breakthroughs. A thermal camera was suggested, but I didn’t have access to one. What I had was a $12 temperature sensitive mouse pad I bought last year for an abandoned project to make my daughter cadmium/lead-free mood jewelry. https://www.amazon.ca/Grifiti-Sensitive-Changing-Crystal-Changes/dp/B004CN5UK6

I unplugged the fridge for a half hour to let the housing cool, stuck on the mousepad (did I mention the back is conveniently sticky?), and plugged it back in. Bingo!

As you can see, the pad lit up with a very clear pattern of hot and cold stripes. The pattern revealed within 15 seconds of plugging it in but within a minute the warm areas had widened and blurred together. Using some tape and sharpies I mapped out the location of the condenser tubing (shown in blue sharpie), then marked where I wanted the holes to go. I didn’t have much space, the tubes were barely 2” apart and the pump plug required a 1” hole to pass though. The water lines are 5/8“ OD tubing.

At this point I stopped working on it for the day. I had a working fridge and a warranty that was still intact. Those lines were worryingly close together and I had no idea how thick they were or if they were completely straight. The next day I decided to go for it, but developed a plan for drilling the holes with minimal chance of puncturing anything. 

Voiding the Warranty

First I positioned a fire extinguisher within reach, then at lowest speed, drilled a thin pilot hole from the exterior. When I punctured the outer housing I stopped drilling and took a slim allen key, using the short end to probe through the hole and sideways to feel for tubing within the 1/2“ or so that the larger hole would pass through. Probing was easy, the insulation readily broke out of the way and I couldn’t feel tubing in any direction, especially not to the sides. Using the long end I probed directly through the insulation along the route my hole would take to feel for other artifacts in the insulation that had not shown up as heat signatures on the exterior. Like wires. My hole was just a few inches below the thermostat on the interior, and the wiring had to be somewhere. I felt nothing through the insulation, so I drilled the rest of the way through the plastic liner to the interior.

Next, I took a 5/8 “ spade bit with no spurs. I wanted a drill bit that would let me easily see into the hole as I worked. From the fridge interior, I carefully and very slowly drilled the pilot hole through the plastic liner larger until I just barely came through it. I’d cleared the center of the hole for wires but not the rest of it. Using a 5/8“ Forstner bit held in my fingers, I slowly and carefully cut through the insulation feeling for contact with wires or tubing. When I reached the outer casing, I inspected the inside of it for the condenser tubing but saw none. Using the spade bit, I carefully cut from the exterior through the casing. No hiss, no spark, no explosions or fires! I had cut between the coils. Repeat two more times, once with 1” bits for the electrical hole. Fire extinguisher in hand, I plugged the fridge back in. Happy hum. I was done with the scary part! Two of the cut outs had foil tape on one side. Evidently the tubing was taped to the casing interior before the insulation was blown and I cut close to it!

The finished holes looked good, the metal, plastic and insulation all cut cleanly and I deburred the metal edge with a screwdriver. The larger one on the left  is for the pump electrical supply. You can see in the inset photo the black wire I just missed.  

Installing hardware

With the holes in place the rest was easy. Clean up the tape, snake some hoses through, trim them to length, fish through the pump plug, and get a suitable water vessel ready. I stuffed some insulation around the electrical cord, made a plastic plate to hold it and foil taped it in place. This will also prevent the cord from rubbing against the sharp metal hole edge. I used a couple of 1” PVC pipe tees to curve the silicone tubing without kinking it. I used tees rather than elbows because they are much easier to thread tubing through. 

I cut one edge of a drilled carboy bung to feed the cord through and used it to fill the gap around the cord. The water vessel is a 2 gallon cambro food-grade tub. I already had a lid with a 5/8“ hole for accepting an airlock when making kombucha. I just added 2 more holes.

Final notes

The pump runs much better in this configuration than before with my cooler. The hoses have very little vertical run on them and the pump has an easier time pushing water and air bubbles through when it’s first primed. 

I can fit a 6-pack next to the water tank, plus there is lots of door storage too. The little drawer at the bottom may become my yeast storage, for now I’m running it with no beer or yeast in it to work out which setting will keep the temperature where I want it and not freeze anything. At setting 4 (of 5) it seems to be holding steady near 40°F, and the 4 water bottles in the freezer section have frozen solid.

Glycol has been suggested in place of water in the system. It would likely work better but I think I’ll stick to water. Water is cheap, easily replaceable, and easy to clean up. When I disconnect the lines from the fermenter I spill a tablespoon or so of water, easily dealt with over a towel. I hear glycol is sticky. I will have to add something to the water to prevent mold. Bleach would work but might stink up the fridge and make anything else in there unhappy. At this point I’m thinking a very small amount of 5-star iodine sanitizer would be best. I already have some and it’s meant for use with beer equipment. It would stain the lines and tub, but I can live with that. No risk of fire or explosion.