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High pressure air compressor using a pair of refrigeration compressors

air-compressor-from-refrigerator-compressors

[Ed] from Ed’s Systems, aka [Aussie50] took some time to demo his high pressure Frankenstein air compressor he stitched together from two refrigeration compressors. The two Danfoss SC15 compressors can produce upwards of 400psi and can run all day at the 300 psi range without overheating. The dual units may get up to pressure quickly considering the small accumulator “tank”, but high CFM isn’t the goal with this build. [Ed] uses the system to massacre some LCD panels with lead, ball bearings, and other high speed projectiles shot from a modified sandblasting gun. Just a bit of air at 400 psi is all you need for this terminator toy.

Don’t think the destruction is wasteful either; [Ed] strives to repair, rebuild, reuse, repurpose and a few other R’s before carefully separating and sorting all the bits for recycling. This modification included lots of salvaged hardware from older teardowns such as high pressure hoses, connectors, accumulator and pressure cutoff switches.

At first it seems strange to see something engineered for R22 refrigerant working so well compressing air. Morphing refrigeration systems into air compressor service is something [Ed] has been doing for a long time. In older videos, “fail and succeed”,  [Ed] shows the ins and outs of building silent air compressors using higher capacity storage tanks. Being no stranger to all variations of domestic and commercial refrigeration systems, [Ed] keeps home built air compressors running safe and problem free for years.

Don’t think this is the only afterlife for old refrigeration compressors, we’ve seen them suck too. You’ll get a few more tidbits, and can watch [Ed’s] video overview of his home built compressor after the break.

If constructing your own shop compressor from salvaged refrigeration systems isn’t incentive enough, then consider the reduction in shop noise. If you used refrigerator compressors, they are designed to run very quiet compared to most standard shop air compressors. Bonus: Even if it failed under these operating conditions you wouldn’t care much when using discarded hardware.

[Ed] shares lots of machine teardowns and alterations so if you’re up for the ride you can check out his YouTube channel “Aussie50”.

Comments

  1. Tom Hargrave says:

    We did this years ago and it worked very well but we kept loosing compressors over time. It’s definitely worth doing if you have a used compressor sitting around and enough tank volume to store a reserve – we used ten old 30 pound freon tanks strung together. Problem is the compressor depends on the closed loop system to return any lubricating oil that’s pumped out and the compressors would eventually pump themselves dry.

    • Drake says:

      That was the point I was going to make but there are inline oiling systems that can be used however the oil needs to be recovered after the compression cycle. So oiler -> compressor -> filter/dryer. Few pieces of extra hardware but it can last a lot longer that way.

      IIRC Jeep enthusiasts have converted the ac compressor into an on-board air compressor using the same technique.

      • psychicpsquirrel says:

        The Jeep guys that use a/c compressors for onboard air mostly use certain models of York compressors. These have a separate internal lubrication system, so there’s no need for inline oiling systems..

    • fonz says:

      yes there is several reasons why a refrigerant compressor won’t last used like that;

      -The oil should circulate or it will run dry.
      -The suction gas should be dried some oil are hygroscopic and decompose to acids when wet.
      -Small refrigerant compressors are mostly cooled by the refrigerant in the suction gas so with out it will run hot

      • password says:

        and generate way more heat because of the amount of phase changing in a normal scenario. I am gonna go out on a limb here and say most had readers here don’t have much experience with refrigeration.

  2. Ren says:

    OK,
    I’d been told that refrigerator compressors are built for the sealed system to not have
    moisture in it. That is why they incorporate a “dryer” (a bulb filled with dessicant). As I’ve been told, introducing atmosphere (with its humidity) will lead to early failure.
    Refrigerators also contain lubricant for the compressor in the sealed system. Care needs to be taken that the lubricant doesn’t react with moisture and is replenished as needed. FWIW

  3. Bracken says:

    I immediately recognised that workshop when I saw the photo, no idea how.

  4. bryce says:

    I had built a similiar vaccuum system as the link for vaccuum bagging. Except I had a big reservoir so it wouldn’t cycle so much… It would certainly suck air, but after a few hours it eventually would trip a thermal cutout even with the cycling.

    FYI using it for a compressor can be very dangerous at high PSI! I had heard from a co-worker that knew a guy that got killed that way.

  5. xorpunk says:

    OFF TOPIC: It’d be cool to see someone make an earth or air based refrigerator that doesn’t use electricity that can beat the 8F difference of pot in pot. Maybe use solar power but no chemicals and only compression and/or air ducts, not peltier. High emphasis on easy field repairs and durability..

    This looks like some idiots making potato cannons out of appliance scrap.. Forgive me for being honest..

    • Daniel says:

      There is this novel take on the classic absorption design that uses the Sun to make a huge block of ice every 24 hours. Easy to build, easy to repair and can even be made with salvaged scrap. It requires ammonia though.

  6. John U says:

    Used to have a fridge compressor like this for running an airbrush, works very well (quiet, low power, cheap) but you do need to have a filter/dryer after the compressor and it probably wouldn’t hurt to have an oiler on the input. They are low CFM, but the bigger the fridge you raid them from the more flow you’re likely to get (hint: retail fridges/freezers are much chunkier than domestic).

    As said above, plenty of the 4×4 crowd run A/C compressors to give air supply, they kick out serious CFM but have the same issues with lubrication.

    As my mate has just dismantled a couple of air-suspension compressors I’ll point out that the dryers are just a canister filled with silicon desiccant (he refilled one using crystals from eBay, saving £££) and a mesh filter to keep them put, easy to replicate using a length of pipe with some crystals in plus an inline filter / screen / mesh either end.

    Also, another mate has been known to use 2L coke bottles as air tanks, they’re good for ~300psi and even a full one is quite a cheap thing to buy – tesco value lemonade 15p a bottle! This may be surprising, but supermarkets REALLY want their produce to be non-fatal so there’s a lot of R&D and engineering in a placcy bottle.

    Obviously this is terribly dangerous and many kittens will die, but given that most hobby compressors keep their tanks at about 100-150PSI it’s not too bad as long as you take precautions (EG mount the bottle(s) in a mesh cage or other safe enclosure) and is probably preferable to hauling a random metal pressure vessel out of the trash and pumping it up to deadly PSI. You can trade off capacity (more bottles) for stored pressure (most things don’t need 150psi, 90 may be plenty for many things) in the name of safety.

    • Ren says:

      I noted your use of (pounds) for money, liters for bottle capacity (metric), CFM (cubic feet per minute) and psi (pounds per square inch). Interesting mix of metric and (english) units…

      • oh, and keyboard layouts are stupid too. says:

        Reality is a strange place. The big perception is that Americans only use imperial and the rest of the world only uses metric. In actual practice it seems that everyone uses the same system: whatever is convenient.

        My usage looks like this:
        thousandths of an inch/mills for small or mechanical things
        centimeters and millimeters for smallish things
        inches and fractions for buying most raw material
        metric for buying finished product, except furniture and mechanical things
        grams for solid food, cups or liters for liquid
        feet for short distances, meters for middling distances, miles for long distances
        mph for informal speed, kph/newtons and the like otherwise
        fahrenheit for air, celcius for equipment
        decimal for humans, prefer hex for machines

        All these different types of measurements are arbitrary, even ones based on water (why not carbon or better yet hydrogen?). What matters is internal consistency and usability. My system is based on how things are sold or how they are related to. Recipes call for cups but servings are in grams. When building by hand, fractions are king (golden mean anyone?). Big binary numbers are a pain, decimal base conversion is slow, hex goes between so cleanly. And so on it goes. Just use whatever is comfortable and always label it. Everything works out fine.

        • ChalkBored says:

          Measurements based on water make sense for people. It’s something all civilizations will have, it’s easy to work with, and you can make it somewhat consistent. That makes it easy to spread a water-based standard to the rest of the world with reasonable accuracy, using very little technology.

          • Tony says:

            That’s metric.

            One 1mL of water weighs one grams, and occupies one cubic centimeter. Scales as required, so 1000ml (1 litres) weight 1000 grams (1 kilogram) etc.

            On top of that it takes one calorie to heat that 1ml of water by 1 degree (Celcius or Kelvin).

      • John U says:

        That’s the English way – we use metric for proper engineering (mm, kg, n/m, litres, etc.), traditional units for things which fit better – beer and milk will always be in pints, a sheet of wallboard will always be 8’x4′ even though it’s really 2440mm X 1220mm.

        Except when we talk to Americans and convert everything to chains, newton-furlongs, groats, etc.

  7. bill jackson says:

    Take great care with this. The sealed external housing must be vented to the outside or gradually leakage pressure will build up inside and explode one day.

  8. Peter says:

    “Don’t think the destruction is wasteful either…”
    I can’t believe you are giving him a free pass on this and that no commenter has mentioned this so far. He looks to be destroying functioning displays. So yes, this is wasteful. You can call it art or experimenting because the damage to the screen does look somewhat interesting. But unless there is a very good reason, this is wasteful.

    • vintagepc says:

      It’s not. All those displays have problems that are irrepairable. Just because they light up doesn’t mean they are functional. Most have problems with the driver chips along the edge of the display so while they may still light up, they won’t produce a proper image.

      • Tim says:

        The only thing wrong with that LCD that he destroys is that it isn’t widescreen, in fact its better than some of the ones I currently use. I applaud him for saving things like this from the landfill, but then he goes and burns it and blows it apart and talks about tossing what’s left in the bin (trash). He seems more interested in destruction than recycling properly in his 1700+ videos.

        • FrankTheCat says:

          He recycles things worth saving. If the monitor/TV is able to be repaired for less than it’s worth when functioning, he fixes it. If not, it usually goes back to the dump where he rescued it from, after stripping it of functional spare parts. Every once in a while a plasma panel gets fried using a MOT or two, though.

          Seriously, 95% of the TV’s and other things he messes with are from the local scrap yard, side of the road, or the local appliance shop’s junk pile. They were being thrown out anyway. Obviously you haven’t spent much time watching any of his videos if you think otherwise.

          • Tim says:

            Understood, I am a fan of responsible destruction if that is what this is. I haven’t watched many of the 1700 videos, but I did search for the term “recycle” on his channel. More important than recycling is reuse of junk and I can appreciate him doing that. Releasing hazardous materials through destruction or burning transformers to get to the copper seems a bit irresponsible, thats all.

        • Aussie50 says:

          I never ever said my channel was all about totally recycling anything, its about having fun on a minimal budget, and that does sometimes include using second hand elelctronics, or when I was out of work, making money by extracting copper by burning motors and transformers. you do what you have to do when the landlord is breathing down your neck for money.

    • Aussie50 says:

      I have this issue with people a lot, commenting about a damaged washing machine, Plasma Display or LCD that I happen to be preparing for the recycle depot by having fun with it.
      I am the one on the ground here, spending my time assessing the nature of its fault, and if I deem it unrepairable due to time, or cost issues, like needing a new PDP module, its junked.

  9. Rich C says:

    Has anyone found a way to modify the compressor starting circuit to allow short cycling. I’m trying to use a fridge compressor as a vacuum pump. I find the starting circuit seems to prevent cycle time under about a minute. I think the starting circuit uses a thermistor.

    • aztraph says:

      Not ideal but innovative. the problem you will come across will be that as you reach vacuum conditions the windings of the compressor motor have a tendency to spark or short out, that’s why most vacuum pumps i’ve seen have a motor separate from the pump. you might get away with it if you feed some of the refrigerant you plan on using through the system to keep the pressure up but that’s the same as flushing the system through. up to you and good luck.

      • aztraph says:

        oh sorry, to answer your questions, I.D. the start and run windings, wire a momentary switch to the start and an on/off toggle to the run, mount them side by side and when you turn them on and hear the compressor run, let up on the start switch and let it turn of. kind of a manual start device, those PTC’s in the standard start device are temp sensitive and won’t do a thing till they cool off.

    • Peter says:

      There was a HAD article about this:
      http://hackaday.com/2006/09/10/refrigerator-compressor-vacuum-bagging/

      One thing to consider is that cooling is impaired when you use the pump for vacuum rather than pressure. Usually the refrigerant is there to cool and lubricate the motor but in a vacuum configuration, the cooling and lubrication are severely impaired. If you run short duty cycles, it still might last a while.

  10. matt8421 says:

    ** Frankenstein was the doctor, not the monster.

  11. aztraph says:

    I WAS going to bark at this guy for doing this, but after reading the posts, I don’t have anything left to say, Good job guys. I’m SPEECHLESS!

    • Marzipan says:

      Welcome to Hack-A-Day. Unless this is your first time, you should have known that after three hours, all the arse-hats who apparently slept in a Holiday Inn Express last night have already come in and made their snide comments about how the project was a waste of time, a waste of space, a waste of energy, or a waste of [one of a thousand other things typical of Hack-A-Day commenters whine about]. Or, how they could have done it a hundred times better with one hand tied behind their back, in zero-gravity, using only the lint from their bellybutton and their magnetic personality.

      • aztraph says:

        Interestingly enough it didn’t used to be that way, and thanks for the welcome to hack a day, it’s ten years late but thanks anyway. I have noticed of late that posts from those so called ass-hats has improved in quality over that time. The posts have been more specific issues and more relevant to point that I was going to make. definition of a genius is “someone who agrees with you” and all that. I’m not saying on this post that I could have done better, I’m saying that I would have known better than to try because of the misapplication of science.

        That being said, I WAS looking for some comments that didn’t meet the standards of hack a day and was ready to give it a miss until you piped up. congratulations. May I say that you surprised me. Your comment is the only one that meets the requirements for being “less than fully thought through.” although I did like the belly button lint reference, just don’t underestimate that stuff, if can be dangerous.

  12. Tom the Brat says:

    ” [Ed] uses the system to massacre some LCD panels with lead, ball bearings, and other high speed projectiles shot from a modified sandblasting gun.”

    So THAT’s why I’ve been having such a time with LCD panels.

  13. Murray says:

    Tossed out fridge compressors are great. As a student I wired one up as a solder sucker. No filter, no lube, lead solder straight into the compressor. It worked for years untill my mom eventually threw it out. Good engineering.

  14. Error_user_unknown says:

    why cant we have damaged LCD’s like those in sifi. instead we get some flickering screen that dose make a lot of scene. Things are normally more digital in that they work or don’t . rarely do they flicker irregularly.

  15. kerimil says:

    Heh nice I built a bunch of them too.Great stuff for high pressure spudguns (all metal of course and proper pressure rated parts) – I used them at up to 700 psi. I know a guy who supposedly over 1200 psi or so and then he blew the gasket inside the compressor – yeah I know kind of dumb of him IMHO.

    how to one removing one from a fridge -> http://www.youtube.com/watch?v=k08kYVoXZrQ

    As well as two on testing the compressor (windings) and a PTC relay. Useful stuff really as all the fridges I encountered had a perfectly good compressors, but the PTC relays were broken. Yeah, you heard me right – not sure if incompetent handymen or people concluded it will be cheaper to buy a new one than to repair the onld one.

    anyway here they are:

    and

  16. Mistbooster says:

    I prefer the Cubigell MP14 model over the danfoss one, even though it is not as old and obsolete ^_^

  17. KleenexCommando says:

    Hope he is properly disposing of the refrigerant out of those things, speaking of recycling…

    • Aussie50 says:

      The compressors are New-Old Stock from Danfoss Australia, I still have a dozen in their sealed boxes.
      but I do own a recovery setup for dealing with old AC systems and fridges. clean R12 and R22 is worth good money. R12 worth almost its weight in gold!.

  18. prashanth says:

    can this compressor be used anywhere ??
    i mean is this compressor used in the requirement of high pressure or it required any changes ??

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