Can I scavenge parts from a minifridge?

September 3, 2018 6:05 PM

Can I (safely & responsibly) scavenge the compressor & coolant system from an old minifridge, to install in my own custom-built insulated box?

Responses to my previous question have me thinking peltier elements aren't the way to go, and we should instead just use a compressor-based cooling system.

I'm looking into getting one of the Dometic compressor cooling units recommended by Pogo_Fuzzybut, but also wondering...

Can I just hack the compressor & coolant system out of an old fridge, or is there significant risk of letting all the coolant out, destroying the ozone layer, etc? Web searching turns up surprisingly few results, mostly for turning a minifridge into a beer fermenter or using a fridge compressor as an air compressor. Neither of these is what I want - I want the old compressor & coolant system, but built into a new box of my own creation.

If this is possible, tips, tricks, and resources would be welcome!

posted by sibilatorix to Technology (8 answers total)

If you break any of the tubing of the sealed system you'll let the refrigerant out and replacing it isn't something you can do without fairly expensive tools (and some technique at at a minimum high pressure soldering). Consumer refrigerants tend to be fairly benign at the personal level (manufacturers know people puncture the aluminum evaporators in these units all the time); ozone depletion risk depends on the specific refrigerant. The tubing most at risk of damage is the spaghetti thin capillary tube. But careful treatment is all that is warranted; they aren't super fragile like a piece of glass or anything.

If you can physically remove the system from the old cabinet and install it in your new cabinet without breaking or kinking any tubing it should still work. You'll also obviously need to create some sort of control system or use the existing and you should be aware that the existing control and be enacted in a couple different ways that you'll have to duplicate when using the existing controls or you'll have problems.

I've seen some minifridges which were assembled at the factory exactly like you are proposing to do (IE: the sealed system was charged before it was put into the cabinet rather than after). If you find a model like this removing the sealed system without damage would be a trivial matter of unscrewing a few pieces of trim and maybe cutting away some expanded foam.
posted by Mitheral at 9:58 PM on September 3, 2018

What Mitheral said. The advantage to the Dometic system is that you can assemble it easily, and without much risk. The downside, being cost, as I'm sure you noticed.

But yes, you can totally take the compressor/evaporator pair out of an existing fridge and place them in a new enclosure. How difficult that is in practice depends on a lot of variables.

The other thing you gotta be mindful of is orientation. Those Dometic compressors are a danfoss design - basically, its a kind of design that is resistant to orientation and such. That means you can place it a way that make sense to the design, without concern about performance.

Many mini-fridges have compressors that rely on being in a particular orientation to work. This might limit your options with regards to your enclosure. After messing with them, be sure to let them sit for several hours or more to let the lubricant settle back into the bottom of the system before starting them.
posted by Pogo_Fuzzybutt at 10:14 PM on September 3, 2018

One other thing. You should be looking for a fridge that has external condenser coils (that black grid on the back or under the fridge). A fridge without a visible condenser is going to have it built into the cabinet (usually directly under the sheet metal at the back) and will therefor have a complete sealed system that is much harder to extract than a fridge with an external, visible condenser.
posted by Mitheral at 10:27 PM on September 3, 2018

Sharp, pointy, or otherwise pinchy type tools will actively try to ruin your day if you do this. It can be done and will only cause pain to your wallet if you fail but it will be touch and go every time you pick up a screwdriver or pair of pliers or (god forbid) a drill or saw and walk toward the device/cabinet.

Good luck!
posted by RolandOfEld at 8:57 AM on September 4, 2018

I have seen people do all sorts of weird stuff with refrigeration systems to make DIY homebrew / kegerator setups. The consensus (my analysis of it anyway) seems to be that the minifridges are difficult to work with because the tubing is so fragile. Supposedly it's difficult to get the whole system out of the insulated box, intact, without causing any leaks. The ones where the cold element inside the fridge is also the icebox (sheet metal thing with vanes molded into it) are considered particularly bad.

Apparently some window AC units are actually pretty good for reuse, if you can find one cheap. They may be way overpowered depending on your application, but I gather some models have flexible hoses between the compressor and evap / condenser coils, which makes repositioning them easier. And the sheet metal around them is easier to remove, exposing the inner workings, than a fridge.

I've always thought than an old dehumidifier would be my pick for a DIY refrigerated system... normally you can just undo a couple of screws and lift the top cover off, exposing the whole works. Dehumidifers are basically just a window AC unit turned on its side, with the air blowing across the cold coils (removing moisture) and then the hot coils (rewarming it). You can use them as either an AC/refrigerator or a heat pump depending on which side you put where. You'll need to add an extra fan, though, since they only use one that's shared across both sets of coils in their as-built configuration.
posted by Kadin2048 at 1:31 PM on September 4, 2018

Seems to me that RV and boat forums might be good places for build-your-own-fridge resources.
posted by We had a deal, Kyle at 1:35 PM on September 4, 2018

Most RV fridges are absorption the upside of which the systems are designed to be pulled out of the casing intact. The downside is you really can't change the layout; they aren't flexible at all.
posted by Mitheral at 9:43 PM on September 4, 2018

Apologies that doesn't directly answer your question, but just in case you haven't thought of it, it's easy to install a thermostat on a chest freezer to put it at refrigerator temperature. If your primary goal is efficiency, that's a pretty good way to go and will require a lot less work on your end.
posted by metasarah at 8:39 AM on September 7, 2018