DIY Dorm-Sized Refrigerator Chiller

Credit: Don Carner

Dorm-sized refrigerator (1 to 1-1/2 cubic feet).
50 to 100 feet of 3/8 inch hard plastic tubing (depending, vinyl isn’t as gooda choice here).
PVC fittings (90 degree elbows or straight connects, threaded or slip).
Silicone sealant
1/2 inch thin-wall PVC pipe (about 1 foot for the ‘thru-the-box’ connections).
Hand drill and 1/2 inch drill bit (or 5/16 inch if you prefer).
Screwdrivers to fit the various hardware of the particular fridge you own.
Rio 2500 or similar pump to push the water through the chiller.

‘A’ = water in from sump
‘B’ = chilled water returned to sump
‘C’ = freezer compartment with temp
probe attached to the inside
wall of the cooling box.
‘D’ = 3/8 inch coiled plastic tubing.
‘E’ = the refrigerator housing and
inner plastic box.
If possible, remove themetal box that isolates the ice cube tray/freezer section, but leave the temp probe alone. This will give a better overall temperature control within the cooling box.

The more coils, the better the ‘pull-down’ effect and the more efficient the unit operates. Depending on the brand/model that you are using, you may encounterinsulation between the housing and the inner box when drilling your input/output holes. There is no need to seal the door. I had originally thought of this, but decided against it as I figured I might needthe access if something went wrong down the road. Besides, it’s a great place to keep youradditives that require refrigeration after opening (and a 6 pack!).

Drill your access holes in the top or sides, it really doesn’t matter. Cut 2 pieces of the PVC pipe about 4 inches each. Insert through the holes drilled and seal VERY WELL with the silicone. You may want to reinforce these pipes with a little Devcon 5 minute epoxy prior to sealing them with the silicone. Keeps’em from sliding back and forth and breaking the cured silicone seal should you want to move the fridge down the road. Glue or thread your fittings onto these 2 access pipes. I used nylon threadednipples to connect the 3/8 inch tubing coils inside the cooling box. Outside, I glued slip fittings reducedto accommodate the tubing running from the Rio 2500 sump pump to the chiller and back to the sump. That’s all there is to it! Remember that the more coils inside the box, the better your cooling effect.

Another point to consider…the farther the run of plastic tubing from your sump to the chiller andback, the greater the line loss due to ambient room temperature. Sit the chiller as CLOSE to the sump or aquarium cabinet as possible. You could use pipe insulation wrapped around the tubingrun(s), but this is rather unsightly and not really necessary unless living in a very hot/humid environment.

Operation is straight-forward. Remember to keep the flow fast enough to prevent freezing of thecoils inside the box. If equipped with a thermostat, your fridge/chiller will be easier to control. Some models only allow you to set the main box temp., not the freezer compartment. That’s another reason why I removed the aluminum ice cube divider and tray. The probe that is attached to the wall of the freezer area will now monitor the entire cavity. Try to use opaque tubing to eliminate algae growth from the sump to the unit and back. You will probably get the black, smudged variety,not the bright green that we see in and around the lighting canopy. I used the milky-white, semi-transparent variety of hard, plastic tubing and experienced this build-up after 6 months or so.

The fridge should set you back $89 to $199 depending on the size you choose. The Rio 2500 runs anywhere from $39.95 (mail order) to $69.95 at your LFS (Local Fish Store). The fittings, tubing and pipe shouldn’t run more than $10 to $15 bucks, depending on how much and what style youchoose. Hopefully you already have a drill and the bit(s). My chiller ran a total of $175 once completed (without the 6 pack), still significantly cheaper than a commercial unit. While not as efficient as commercial chillers, this is a viable alternative and will draw your water temp down surprisingly well. Use a pre-set or variable heater to ‘balance’ the temp within the sump and it’ll become ‘hands-free’!

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Blane Perun

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