Introduction: D.I.Y Ultra Quiet Shop Compressor From a Refrigerator Motor (compressor)

Picture of D.I.Y Ultra Quiet Shop Compressor From a Refrigerator Motor (compressor)

I needed to build a very quiet, higher capacity compressor for my Industrial Design Studio shop, since the one I have is quite loud and does not have the capacity that I was comfortable with for my urethane casting work.

In this Instructable I show you how to build a light duty compressor from parts you can buy on Ebay and or your local hardware store, Home Depot, Lowes, Menards, or a scrap yard, using a refrigerator (fridge) motor compressor. This is not for using heavy power tools or spray painting a car. It's for blowing off parts, maybe airbrushing if you add an air/oil dryer to it or just need some air in your shop for various projects. Add your own optional Motörhead badges too. See the Video below for full details. It's a great companion to this Instructable tutorial.

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Step 1: Get a Compressor Air Tank and Fridge Motor

Picture of Get a Compressor Air Tank and Fridge Motor

I sourced a 6 gallon unwanted Bostich air tank on eBay for $35 including shipping from a fellow in Indiana. I then needed a refrigerator compressor..... I got lucky and have a buddy I play hockey with that is in the small appliance repair business. Joe was able to get me a new replacement unit that was not needed on a recent job. He was also able to get me some of the copper tubing I needed for the project to connect the compressor to the tank.

Step 2: Making the Adapter to Mate the Compressor to the Tank

Picture of Making the Adapter to Mate the Compressor to the Tank

The first thing I built an adapter plate to mate the tank to the compressor motor. I made this from form sheet metal from an old "Big Iron" IBM server cover. I made a cardboard template of the hole pattern to follow and then transferred it to the sheet metal and folded the edges for extra strength. Then I applied a bit of primer and paint to finish the exposed metal. See the video for the details.

Step 3: Drain and Replace the Existing Oil

Picture of Drain and Replace the Existing Oil

Next I drained and replaced the original oil in the compressor with 10W40 weight motor oil for added protection. Most fridge compressors have a separate filler tube for this purpose, since mine was a replacement unit it has a rubber stopper, yours may be crimped or soldered shut, if its from an old fridge.

Step 4: Mount the Bracket and the Compressor

Picture of Mount the Bracket and the Compressor

First I mounted the bracket to the tank, then the compressor motor on the sheet metal bracket I made and connected the compressor to the bracket with some 1/4-20 Allen head bolts washers and lock nuts.

Step 5: Connect the Compressor to the Tank With Some Copper Tubing and Add a Saftey Relief Valve

Picture of Connect the Compressor to the Tank With Some Copper Tubing and Add a Saftey Relief Valve

Next I connected the compressor side to the tank with some 1/4" copper tubing and a one way check valve to keep the air from flowing out of the tank back through the compressor inlet. I soldered the copper tubing to the compressor. I would suggest using some compression fitting to the tank and the compressor so you can fix things easier should you ever need to do so.

I used a brake line tubing bender that I rented from my local auto parts store to bend the copper tubing. You can fill the tube with sand or ice to bend it as well. See the Video for more details.

Next I added the 125 psi safety relief valve to the bottom of the tank. It's 1/4" threaded part and they are readily available on ebay or the store. Be safe you don't want this thing to explode.

Step 6: Build the Business Side of the Compressor, the Air Outlet!

Picture of Build the Business Side of the Compressor, the Air Outlet!

On the business side of the compressor I used some parts I had laying around including a pressure shut off valve that I had from when I attended college at Pratt in the late 80's from my dorm airbrush set up! It still all works great and is able to turn the motor on an off with no issues. I also used a main pressure gauge and added a pressure regulator so I could adjust how much air comes out of the tank. Additionally I added a quick disconnect to I an easily connect an air hose to the tank.

Step 7: Electrical Wiring

Picture of Electrical Wiring

I connected the compressor motor to the on/off pressure Furnas switch. There is a run and a start and a ground to connect to the pressure switch. There is usually a wiring diagram included with your on off pressure switch, follow those instructions when wiring, they may differ from what I did.

Then for the AC outlet power I added a computer electric socket connector to the set up so I can remove the power cord if I need to as well. I epoxied the connector to the underside of the tank bracket so it was out of the way. See the video for more detail.

Step 8: Making It Ultra Quiet: Adding an Intake Manifold

Picture of Making It Ultra Quiet: Adding an Intake Manifold

The key to making the whole thing ultra quiet is building a intake manifold that absorbs the sound of the compressor. For this I used a spent metal aerosol travel shaving cream can. It already had openings at both ends and was perfect for my needs. I packed it with some brass wool to help absorb the sound of the compressor and added some pink packing foam for a filter. The combination of the metal can and the brass wool significantly mutes the sound and makes the whole set up extremely quite.

Step 9: Customize It With Some Motörhead Logos

Picture of Customize It With Some Motörhead Logos

Last but not least I added some Motörhead badges I cast to give it some character. R.I.P Lemmy Kilmister

This was a super fun build and an essential piece of shop equipment to have when making Industrial Design models and prototypes. Visit my web site for more information about Botzen Design I and how I can help design your next consumer product.

A bit about me. I am an Industrial Designer living in Southfield MI USA. I have a home-based Industrial design studio "Botzen Design" and have been designing consumer products for 25+ years ranging from sunglasses for Bauch & Lomb, Traps eyewear, entry level luxury vehicles for Ford, wireless charging PowerMat for Homedics, to magnetic toys for Guidecraft. I specializes in tabletop and handheld products, ranging from routers to cosmetic products to Bluetooth devices and everything in between, I also teach Industrial Design at Wayne State University and CCS (College for Creative Studies)

Follow me on Twitter @botzendesign and Subscribe to my Youtube channel if you like the video and want to see more in the future.

Also check out my previous instructable about silicone casting


Diy Tech (author)2017-10-14

I am working on a lil bit same thing. I just want to know how muhc imp is oil trap filter for a setup like this ? how much oil it sprays in the output air ??

botzendesign (author)Diy Tech2017-10-15

Very little to none, I have a trap and it never traps moisture or oil that I can see.

Diy Tech (author)botzendesign2017-10-15

Okay thanks boss

M2aestro (author)2016-07-26

I did something a bit different with a refrigerator compressor; the cooling path was used with air only flowing through it at high pressure after running that same air through a simple stainless heat exchanger radiator, such as used in automotive oil cooling. A condensate trap was placed between this device and the refrigerator cooling double wall tube, such that it ran through the outer tube, and thence to air compressor receiving tank. The air with reduced oil vapor content through the cooling loop on the refrigerator compressor, with a thermostat set 4 degrees above freezing. This delivered fairly dry air to the receiving tank, to be more specific about that detail.

This gave me very dry air with negligible oil vapor so that air bearing parts would never have condensation between the surfaces of relative motion.

I used another one with the same thermostat setting to cool water, and ran an antifreeze solution through the cooling loop outer tube for better heat conduction that pure water, and added protection against freezing. The water antifreeze solution was pumped by a cheap but efficient pump from WW Granger, and was on a bang on/bang off thermostat control with a two degrees sensitivity, and cooled a sump through a tubing coil immersed in the sump. This is better than a more sensitive setting on a proportional flow valve because there is actually a heat gain with pressure drop through such a valve. I used a second pumped stage from this sump to another sump with the same kind of bang on, bang off valve and a one millidegree F sensitivity diode circuit to control the second sump to plus/minus 2 millidegrees with a variable heat load on the second sump in a 30 degrees variable ambient shirtsleeve environment. This enabled us to control some proprietary hardware that generated heat to a temperature that could be set anywhere from about 24 degrees C to 30 degrees C, but likely could have been set in a much wider range with the same stability, and not use mixing valves with feed-forward servo software, etc. We had considerable thermal mass working for us; perhaps in a circuit with similar heat loads and a negligible thermal mass we would have had a much tougher task.

botzendesign (author)M2aestro2016-07-26

Wow, cool. can you post pictures of this set up. I think there are a few here that would like to see it, me included. I thought about a dryer, but it seems like a lot of extra for the return on investment.

M2aestro (author)botzendesign2016-08-16

See my other post, please, on how long ago this was (25 years). We have no surviving pictures.

M2aestro (author)botzendesign2016-07-26

I did this for a high precision machinery job about 26 years ago. I no longer can recall where I might have placed pictures of the hardware, although I do recall that I photographed them (drier setup and cooler/temperature stabilizer) with film. What hardware there is out there today would be different, I suspect. The refrigeration compressors were about 200W, I think, had a significant current surge at start, and had a pressure gauge on the refrigerant line. I can't recall much more specifics on them, other than they were on small vibration isolators, but I added fluid pulse dampers to the pump lines and mechanical damping to the connecting hardware to avoid transmitting detectable vibration to the equipment, and the fan on the compressor with the cooling double-wall tubing connected was always blowing across both the compressor and the first level of heat exchanging hardware. A little bit less compact than the assembly in the instructable associated with this thread, although it had no pressure or vacuum tank directly connected in close proximity to the compressor in the case of both the driers and the temperature control units. Incidentally, one can reroute the line than normally comes straight out of those inexpensive 125 psig - 175 psig home compressors and would usually go into the tank, where water and oil vapor often accumulates by re-routing through a heat exchanger like those used as automotive oil cooling radiators, then to a vapor separating bowl with filter...we used a vane trap, followed by a water vapor trap, followed by an oil vapor absorption trap, all with auto drains. The last trap had an oil saturation indicator to keep any vapor not trapped by saturated media from going downstream. Of course, that required monitoring. Later units had a differential pressure switch on a loop before/after the trap to detect saturation of filter media to signal shutting down when filter was saturated. All components off the shelves of filter suppliers.

jakespeed (author)2016-07-31

That's a cool design that would work well for an air-brush.

Do you have the part number for the switch and a wiring diagram that that shows the connections to the switch?

M2aestro (author)jakespeed2016-08-16

No; refrigerator compressors are terrible compressors for air brush supplies without a specialized oil and moisture removal filter set. Read the other comments before you get too excited about that misapplication of hardware!

M2aestro (author)2016-08-16

I am sorry, but I must acknowledge to all that no matter how cool what I described as a coolant chiller in one application and as an air drier (identical basic device before accessories) as the second device might be, I can no longer provide photographs of the devices and systems because we did not save the documents after about 10 years had passed. The last one was executed about 25 years ago, but the basic technology hasn't changed.

By the way, I second whole-heartedly all of the comments about how using refrigeration compressors for air supply pressures is a very poor idea, both because of lubricant mist contamination of the air, and because of the low delivery volumes. It is not difficult to find very good mist removal filters, and I have even seen one ;that used a roll of toilet paper as the oil vapor removing element, where that roll of toilet paper happened to be a good fit into an old metal bowl filter housing fro a sediment filter. The problem with that one was there there was not a very efficient mode for monitoring the useful life of the filter, except by monitoring the reduction of flow at free flow setting, or the increase in pressure drop for a set flow through that filter. Many ways to make cheap substitutes out there, but few that I would describe as elegant solutions.

cnaughtin (author)2016-07-28

This is a WONDERFUL idea for a home shop or small parts shop. I need one badly! This needs to be commercially made.

Lovot (author)2016-07-27

I have done stuff with refrigeration compressors before, and the pressure relief valve is a definitely must, I tested a refrigeration compressor to see how much pressure it took before it would stall, it went over the upper limit of my 900PSI gauge, and started blowing rubber seals around the time figured finding the limit was probably not going to happen without a gauge off an oxygen regulator and higher pressure connections. there was no tank connected, only a couple feet of 1/4" ID high pressure hose, so it this all happened pretty fast. I'm going to guess it cleared 1000PSI before I shut it off.

JustinV35 (author)2016-07-26

Very cool. You've inspired me to hang onto the old computer case sides that I normally scrap from old computers that people give me and I recycle. Glad I saw this!

ryanjohnlenz (author)2016-07-26

Wow! Super well done. It makes me wonder why this style of quiet (albeit low-volume) compressor isn't more popular. I'd much rather have a larger tank (and/or a longer-refill time) than a nasty loud compressor.

tk42967 (author)2016-07-26

I have one made from a very old fridge. It starts to sputter at 80 psi. Also, you need an oil separator on the output and you have to constantly add oil.

It's still better than nothing or what you could find at HF. THis will not run air tools tho.

T_om (author)2016-07-26

I have made a couple of these, used as compressors or vacuum pumps. One thing you did not mention, but will find out sooner or later, is that these compressors emit a fine oil mist. Makes them pretty much useless for airbrushing, etc. And they do not have a CFM capacity to use with air tools. They work OK as vacuum pumps PROVIDED you vent them outdoors, otherwise your work area will be covered by a fine oil film after a while. They make pretty poor compressors.

botzendesign (author)T_om2016-07-26

I am using 10-40, so it's quite a bit thicker than the oil that cam e with the unit, should keep the mist down, I have not noticed any oil in my air at all. Has not been an issue for me.

T_om (author)botzendesign2016-07-26

Using it as a compressor, the oil will be coming out the air gun (compressed) side. Which will screw up any sprayed paint you intend to do big time. Used as a vacuum pump, the oil mist is spewed into the shop air.

steveastrouk (author)T_om2016-07-26

+1...and oil appearing as mist is disappearing from your compressor's reservoir. A good oil filter is vital. There are special filters I think that allow the oil to be recovered back to the compressor. inlet.

Phil_S (author)2016-07-26

Commercially, similar compressors based on fridge components were produced by a Danish company and distributed from Scotland, now very like the Werther Sil-Air units. Initially, the attraction in industrial use was the low noise, but the reliability was poor and very rapidly, these units were replaced by conventional oil-free piston types, cheaper and more robust. The need to top up oil reservoirs and oil in the final air just added to the problems. I'm not sure why they failed so rapidly, maybe once removed from the closed loop fridge environment, moisture etc., just wiped them out. I couldn't recommend them for anything other than occasional use.

botzendesign (author)Phil_S2016-07-26

Interesting. Mine is definitely occasional light use.
Thanks for the comment.

Randy Lahey (author)2016-07-26

I made one of the years ago with an air conditioner compressor (which I believe is actually a bit bigger than a fridge compressor). It works great. It's quiet and the CFM is actually pretty good, only a bit slower than the original compressor it replaced which I believe was 4.6 CFM. I've heard they can run a lot higher pressure than a typical compressor. I have also heard that they don't last very long because when the compressor is in its intended device, the refrigerant it cycles lubricates it. Every now and then I'll dump a bit of oil down the air intake to compensate. Because of this, the compressed air it produces might be a bit dirty and could affect things like painting (but could be better for air tools?), but for general use, its fine.

botzendesign (author)Randy Lahey2016-07-26

Agreed, great for general use. Add an oil trap or filter if you need cleaner air, that would make sense.

tomd7735 (author)Randy Lahey2016-07-26

The refrigerant returning from the evaporator cools the compressor motor windings also, as well as returning oil.

Doc_Cottom (author)2016-07-26

There are dozens of 12V emergency auto air compressors available. Harbor Freight has a 100PSI for $34 that I have used for years. I've also have a conventional 5 gal, 120 PSI that was less than $100.

I do my air brush work with the large compressor, with dual regulators, and a dryer to prevent water drops in my paint. Charge the big compressor up until is shuts off, and there will be enough air to air brush for several hours before you have to turn it back on.

botzendesign (author)Doc_Cottom2016-07-26

Yes, a dryer would be needed if you were to spray paint (air brush) with this unit. That could easily be added. I use it mainly for blowing dust and cleaning rapid prototype parts and my pressure tank.

itsjustmescotty (author)2016-07-26

I took a compressor from a 21cu.ft fridge and used it as a vacuum pump for milking my goats. Ran the suction line to a volume tank made from an old propane tank then to the suction tubes - worked great.

Got rid of goats so decided to use it as a compressor for the air bearing on my Darex sharpener that only used a few cu.ft. an hour - didn't work, sigh.

If you do some research you will find that compressor oil is basically mineral oil and ATF is also mineral oil so I replenished my compressor oil with ATF and it worked great.

Went back to shop compressor for the sharpener bearing and vacuum stuff for the fridge motor.

Oh, BTW I run the pressure side thru a piece of foam in an enclosure to recover the oil mist.


ElegantAndrogyne (author)2016-07-26

Hi there, it's a nice project, but I noticed that you placed the safety valve on the bottom of the tank. You should actually use that thread to connect a condensation drain valve (there's always some moisture in the air and as the compressor is used, water condensates and gathers inside the tank). As for the safety valve, connect it somewhere on the upper side (e.g. add a tee between the 4-way connector and pressure gauge).

Eh, perhaps.... It's brass so I am not to worried about it rusting. Works as a drain valve as well. I can buy another if I have issues with it it the future, not a big deal really for me.

Totally agreed! the relief valve should be kept away from any source of moisture, so as it will not become contaminated & Jammed (corrosion between the metal surfaces, like putting sand between metal plates) . Also the drain plug should be of the kind that opens inward (pushes into the tank), as this breaks through any contaminants than could jam a normal valve shut.

Gelfling6 (author)2016-07-26

Step #3, 10W40? might not be a good idea.. It's not made for being agitated like the internal workings of a refrigeration compressor (where mechanical parts will be whipping it like cream! or in this case, instant grease.) Compressor specific oils (for regular belt-driven compressors) are made to handle the possibility of air getting mixed, as well as high heat.The oil drained from the compressor is already laden with refrigerant, (if you heat it, It'll actually foam-boil trying to release the refrigerant.) and not the same as compressor oil used in auto shops.) Also, engine oils has a detergent added, which will allow water (from even ambient humidity) to intermix, which will cause the oil to whip-up like a grease. Compressor specific oils, do not have this detergent added.

botzendesign (author)Gelfling62016-07-26

I am guessing a car engine would whip up the oil more than the compressor motor would. This motor runs so infrequently, I doubt it will be an issue. Never even gets warm.

Gelfling6 (author)Gelfling62016-07-26

Also, they make oil filter/recovery units similar to in-line moisture traps. (usually has a metal particle filter inside a semi-sealed glass container, with a drain valve on the bottom) to reduce the oil mist content. This mist may also be because of the 10W40 actually over-heating, practically boiling.... (link to a example trap, )

Andsetinn (author)2016-07-26

Nice job.

I did one of those about 10-15 years ago. It still sits in the corner of my garage and every few months, when I need compressed air, I power it up. No maintenance so far, when the pump fails I'll just replace it. I used a 1 dollar clear plastic fuel filter on the air intake.

The thing to look out for is that standard cheap air compressor pressure switches have very small hole to decompress the pump so it is not under pressure when it starts. When you have low CFM pump like from a refrigerator it will seriously delay the time it takes to reach full pressure. I blocked that hole and installed electronic blow off valve.

botzendesign (author)Andsetinn2016-07-26

No issues either with mine, runs cool and infrequently. Great for my needs

blkadder (author)2016-07-26

Great work utilizing the parts that you had. Only one thing I am curious of; where did you get that awesome Motorhead logo?

botzendesign (author)blkadder2016-07-26

I bought some then cast them, so I can make extra for my gear.

sharpstick (author)2016-07-26

Any idea of CFM?

botzendesign (author)sharpstick2016-07-26

no idea, fills the tank and turns off, works great, runs cool. never gets hot.

WillyD54 (author)2016-07-26

how much was the pressure switch and where can you buy them?

botzendesign (author)WillyD542016-07-26

I had this one, but look on ebay they are redily available

Uncle Kudzu (author)2016-07-25

Well done! The project and the i'ble look great. I had no idea such a thing could be done.

botzendesign (author)Uncle Kudzu2016-07-25

Thank you. Very kind words. Hope you build one and it turns out great. Good luck!

aggiebrett (author)2016-07-25

Cool project, and a beautifully done how-to video. I am DEFINITELY stealing your silencer manifold idea for my existing compressor!

botzendesign (author)aggiebrett2016-07-25

Sweet, thanks for the comment. Glad you liked it.Don't forget to like and follow on my Youtube page. Feel free to share it as well.

tytower (author)2016-07-25

You have a motor with 3 connectors . Usually you have a starter device that attaches to this . You did not mention these connections at all ?

botzendesign (author)tytower2016-07-25

Yes, there is a run and a start and a ground. Correct. I will go back and add that to one of the steps. There is usually a wiring diagram included with your on off pressure switch, follow those instructions when wiring, they may differ from what I did.

Bfargo85 (author)2016-07-24

Could the compressor from a air conditioner work?

botzendesign (author)Bfargo852016-07-25

Yes, it will just take a bit longer to fill the tank if it's a small capacity.

About This Instructable




Bio: Eric Strebel, Industrial Designer of Botzen Design, designs products for industry around the world.
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