Replace Ancient Refrigeration Units with Window Air Conditioners

I have an old Hussmann refrigerator with two sliding glass doors, that was originally used as a refrigerated produce case in a grocery store (I use it to store eggs from my free-range egg farm). This was a nice unit in its day -- it's built like a battleship -- but its refrigeration unit is shot, and was an inefficient dinosaur even when it ran properly.

These old refrigerators are good news/bad news. The good news is that their crummy refrigeration units mean that they cost almost nothing. The bad news is that hteir crummy refrigeration units mean that they're worth almost nothing.

After having mine repaired twice at about $350 each time, I took the advice of the HVAC technician:

"Get a window air conditioner, replace the thermostat so you can turn it down to 40 F, and stick it in the side of the refrigerator."

So I did just that. For $179, I got a new 7,500 BTU air conditioner. I cut a rectangular hole in the side of the refrigerator with a saber saw and installed it, sealing the edges with aluminum tape.

Window air conditioners are cheap, efficient, quiet, and lightweight. You can install them yourself if you know how to saw a rectangular hole in the side of a big metal box and how to do simple wiring.

Sizing Your Air Conditioner to Your Refrigerator

For my purposes, the smallest unit I could find was actually too big, and I ran it on "low" most of the time. I would have been better off with a little 5,000 BTU unit for my 50 cubic-foot refrigerator. You could probably run a small walk-in cooler on a larger window air conditioner!

Converting the Air Conditioner to Refrigeration Work

The only thing you have to modify is the thermostat. Simply replace the original one with one that will go down to refrigerator temperatures. Consumer air conditioners are very flimsy inside. The unit I bought had ducting made out of paper-thin styrofoam. Be gentle!

What you'll want is a line-voltage thermostat with a remote probe, that goes down to 40 F or so, such as the #CR2147 from FarmTek. Put the remote probe right against the cooling fins, which is where the original thermostat is. This is the best method, since if the unit ices up, so will the thermostat probe, and 32 F is cold enough to turn the unit off until it defrosts.

On my installation, I used a thermostat without a remote probe, and sometimes it would ice up really bad. It did this less if I hung it so that some cold air blew over the probe. Depending on the unit, the thermostat may be on push-on connectors, or you may have to cut the wires and use wire nuts. The thermostat should be set up so the contacts are closed when the temperature is high, and open when it's cold enough.

Other Tips

In general, a refrigerator is just a big insulated box, so you can saw holes in it wherever you want. However, there might be heater cable here and there to prevent the unit from freezing up, and wires to run fluorescent lights and such. These are usually in obvious places, but unplug the unit before using the saw! If you find any severed wires, you have the choice of not using the fancy-pants features like lights and defrosters, or opening up the junction box and disconnecting anything you broke. You'll have to do this anyway if you want to keep the lights and stuff, since you'll have to disconnect the old refrigeration unit.

Don't bother removing the old refrigeration unit, fans, or anything else you're not using. They're not doing any harm.

The air conditioner will drip on the outside with water it's condensed out of the cold air. Put a drip pan under it.

Brush or blow the crud out of the air conditioner once in a while.

How Well Does It Work?

My unit died suddenly after four years of continuous operation, which was about what I expected. The original unit never lasted more than a year without needing $350 worth of repairs.

With a more critical operation, I could have bought a spare air conditioner, or even cut a second hole in the refrigerator and had a live spare that would come online with the flip of a switch!

I can even imagine a large cooler with more than one air conditioner powered up at the same time.

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