Fridge Parts Make Air Compressor That’s Easy On The Ears

Compressed air is great to have around the shop. The trouble is, most affordable compressors are somewhere between “wake the dead” and “the reason Pete Townshend is deaf” on the decibel scale. But with a little ingenuity and a willingness to compromise on performance, you might find this ultra-quiet, ultra-cheap air compressor a welcome way to keep the peace in your shop.

Yes, this compressor under-performs even a Harbor Freight pancake compressor which can be had for $60 and is ready to work right out of the box. In fact, [Eric Strebel]’s design sort of requires you to buy an air tank, and the easiest way to do that might be just to buy the compressor in the first place. But the off the shelf unit won’t run as quietly as this one does, what with a refrigerator compressor swapped in for the original motor and pump. There’s also a silencer on the input side, fashioned from a shaving cream can and some metal wool. The video below shows the build, and the results are impressive, at least from a noise perspective. Whether it suits your shop depends on your application – it certainly won’t run an impact wrench, but it’ll blow chips off your mill or dust out of your computer.

Fridge compressors are a natural starting point for air compressor builds, like this fire extinguisher based design, or this high-pressure tandem compressor. But if you need high flow and don’t care about the racket, try ganging four HF compressors in parallel.

46 thoughts on “Fridge Parts Make Air Compressor That’s Easy On The Ears

    1. I did similar while I was in school, ~30yrs ago. The tank was a combination of 4 2l Coke bottles. Nylon was tubing glued into the caps with hot glue. And the pressure switch was made out of the thermostat of the deceased freezer which was also the source of the compressor. I opened the capillary tube and soldered it to a piece of brass tubing. Then I tightened the temperature adjustment screws until the spring had max. tension.
      The unit was usable for some airbrush experiments.

  1. Any reason besides space to not have both pumps connected? The stronger pump would have a lower limit switch than the quiet pump and only kick in when you need the extra power.

    Great build. I never considered the compressor in my fridge as useful for anything.

    1. The best comment so far!
      A refrigerator (air conditioner, freezer) is a sealed system, the internal components of the compressor are not designed to be rustproof.
      That is why they have a small dryer bulb attached to the tubing circuit.
      Moisture/humidity drawn into the intake will eventually kill the compressor, maybe by rusting the piston rings to the cylinder, or other parts if it’s a rotary compressor.

      1. Another problem with using a refrigerant compressor is that some of the oils form acids when exposed to humidity in the air.
        That is a large portion of why refrigeration systems are vacuum purged before being charged with the refrigerant of choice for that compressor/system.

        Auto AC systems are notorious for this.

  2. Okay how did you remove the oil vapor out of the air? The motor is submerged in r11 (I think) and is also exposed to the air that you are compressing. Tip the compressor over and oil will leak out of the inlet. Those compressors are good for vacume pumps, if your into making vacume tubes…


  3. You really need an oiler to keep the pump lubricated, as mentioned upthread the oil will eventually slosh out and diffuse from the pump reservoir. Of course it is normal to have oil in compressed air so the output isn’t generally a problem. But I’d second the idea of using both pumps, the quiet one for low volume work and leaving the loud one for more demanding applications.

    1. I built one of these from an old refrigerator pump and it slowly died eventually after the oil was pumped into the tank. So, yeah, you need some sort of mechanism to refill or just add a bit of oil every now and then. I now have a dual head jun-air compressor and that has sight glasses so you can see the oil. The construction is also a bit different so it does not pump oil like AC compressors do.

      1. Unfortunately this units also pump oil out. Normally it collects together with condensed moisture in the tank. But if you forget to empty this regularly then the oil comes out. We had a really oily hose and blow-gun once. Which was basically thrown out then, because it was too difficult to clean.

  4. Quick plumbing note: When soldering (sweating) copper start the feed of the solder at the bottom, not at the top as shown here. Starting at the top can cause the solder to travel around down and meet itself in a way that forms a tiny pinhole at the bottom. I’ve very annoyingly learned this the hard way, one joint I did that failed in a month and another I saw that failed after ten years or so. Both were water, with a stream so fine they almost were invisible. For air that would be even more annoying as it might even be hard to detect until soaping it up.

  5. Like: inlet muffler/filter
    Like: quiet
    Like: re-purposing a device

    Don’t like: gauge being run over range (outlet gauge near end)
    Don’t like: tinning leads going under screws. Unless the connectors and solder are rated for it, the connections will loosen from creep
    Don’t like: bending the leads after inning. This can start cracking

    Really, really scared by, to the point of not wanting to be within several hundred feet of this: the safety valve on the bottom. Any oil, moisture, crud will get into it and may prevent it from opening. These valves generally must be mounted in a location where they are vertical, dry, and relatively contamination free.

    1. True, the safety valve should have been added to the manifold. The hole he used was for the tank drain. He will need to add a Tee to his Tee or a 5 way. The pressure switch looked kind of old and ragged as well.

      1. Nice moniker,, I think this is the first time we’ve both posted on the same article.
        The original Mr Name Required.
        (from the old HaD ‘Leave a Reply’ bit where it used to ask ‘Name (Required))

      1. Tinning wires is weird for ANY screw-clamp connection. In mains voltage there is a chance that it arcs over and re solders :-) But in low voltage sense wires there were just intermittent connections and false readings.

        1. Tinning is still seen in some, rare, applications, but is generally discouraged or prohibited. Those of us of a certain age may remember wrapping and soldering brass or copper eyelets for screw connections. And may remember trying to get them apart after service at anything greater than milliamps service.

  6. Something that significantly adds to the loudness of air compressors is having the pump mounted to the tank. If you’re using a compressor in a fixed location and want to reduce the noise then mount the pump separate from the tank using vibration isolating mounts. If you need it to be portable then the convenience of the compressor being a single unit is worth the extra noise but vibration isolating mounts will help.

  7. Blow chips off the mill?
    I read a comment in that venerable UK publication Model Engineer many years ago about a metal shop apprentice who was sacked on the spot for using compressed air to blast off swarf from the machine tools.
    It’s a bad idea, don’t do it. Use a pan and brush instead.

    1. TBH I was thinking more about wood dust from a CNC router, but even then a blast of air probably isn’t a great idea. Not that it ever stopped me from cleaning off my table saw with the air hose. Living on the edge…

        1. Not really. Most of the stuff from turning and milling that is steel has pretty decent sized chips, cast iron can be dusty but that is going to be everywhere anyway.

          The thought is that the air can blow chips into the working parts of the machine. This is pretty unlikely to happen especially because most modern machines are set up for water or oil coolant which will keep out chips too.

  8. Airbrush compressors used by artists (miniatures, helmet decoration, etc) are like that, for example those made by Sil-Air. But you need oil to keep it running and filter if you want clean air. Even if you DIY instead of buying the commercial versions.

  9. I doubt this will last real long as per all of the comments above, and the CFM’s you are going to get out of it will be pitiful. However the modern refrigeration compressor are designed to generate high pressures so if you need relatively high pressure air, that may be your ticket. Just don’t expect much flow out of those tiny pistons, and don’t expect clean air and don’t expect the compressor to last a long time. IMHO for a general shop unit get one of the cheepie units from HF and if you have to build something to contain the noise. In my electronics shop I have a little one or one and a half horse direct drive unit and it is just the cats meow for electronics and not too noisy. And sadly, probably less expensive than rolling your on if you pick it up on sale.

  10. Btw, he used a new (replacement part) compressor. For those of us here who would consider just recycling a compressor from an old fridge for that purpose, there are quite heavy environmental problems and regulations there: the thermal fluids used in fridges are typically very harmful greenhouse gases, even the newer fridges (and the very old fridges even contain terribly ozone depleting gases, which is even worse). Consequently, recycling/salvaging a compressor out of a fridge or even opening the fluid loop of a fridge is something that is, in many countries, forbidden to anyone but certified personnel with the proper special equipment to ensure that the heat fluids are captured before opening the circuit and don’t just get out and into the atmosphere.

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