Introduction: How to Modify a Fridge Compressor Into a Silent Air Compressor

Picture of How to Modify a Fridge Compressor Into a Silent Air Compressor
Here is my how to on modifying fridge compressors into silent air compressors. They are ideal if you need:
+ a silent compressor
+ a high pressure compressor
+ have little space and/or don't need a typical shop compressor

Typical fridge compressors are 100 - 300 watt units, deliver 0.7 - 1 CFM of air and can reach pressures over 500 psi.

Here is a video where I discuss the process briefly (I'll make a new one soon - feel free to comment or ask questions)

 
 

There are two ways to get a fridge compressor you want to turn into an air compressor:
A) buy a salvaged compressor
B) salvage one yourself from an old fridge

In case you choose option B then you have to remove the compressor from the fridge yourself - that process is described in the next step. If you already have a salvaged compressor then go to step 2.

Step 1: How to Remove the Compressor From a Fridge

Picture of How to Remove the Compressor From a Fridge



Quite a lot of fridges are thrown out even though the compressor is perfectly ok. You can test it by plugging it in and the compressor should start. If that's the case you can proceed to wire, as shown here (requires an on/off switch all the other parts are already there)


In some cases the compressor is working, but its starting circuitry is broken - and the owner didn't knew it. I have experienced this on two occasions so it is not rare at all. You can test the compressor electrically using an ohm meter

Here is my video on how to perform this:
 

 



The pic below shows where to cut the copper tubes. You should always salvage as much of tubing as you can. It doesn't really matter what tool you use just make sure not to crimp the tubes - nice square cuts are preffered. 

Don't forget to salvage the mains cable with the plug. Most fridges have a sort of junction box right on the side of the compressor as well as starting relay/PTC relay (all of it is house in a rectangular plastic enclosures you find on the side of the compressor). There will be a wire running from the fridge compressor to the inside of the fridge - it goes to the thermostat and powers the light inside the fridge - again the longer the lenght that you salvage the better.

Step 2: Finishing, Adding All Blows and Whistles ( Work in Progress - Sorry)

Picture of Finishing, Adding All Blows and Whistles ( Work in Progress - Sorry)

I do realise you might have some problems with wiring - I'll make a video on it soon

once you have the compressor and have it running you need:
1) way to connect the output tube (ie your air output) - ALREADY MADE A VIDEO ON IT (go to the last step)
2) an overpressure valve (ie a pop off valve - for safety reasons)
3) water/oil filter


Step 1 involves buying a pop off valve
Step 3 is covered in one of the pics - you might buy an off the shelf water oil seperator but my homemade filter works just fine

Step 3: Attaching to the Output Tube

Picture of Attaching to the Output Tube
Once you have the compressor running you need to find a way to securely attach a fitting to it's output tube. Of course you can just use a clamp and put a lenght of air line onto it, but that's not the best method - especially if you plan to use the compressor at more than 10-15 bar.

Here is a simple compression fitting that can be build using just 2 male - femal fittings, 2 or more rubber washers and  2 steel washers. It's pretty straight forward -> the rubber washers are sandwiched between the two fittings and the entire assembly is put onto the output tube. Once in place you tighten the fittings and that compresses the rubber washers forcing them to form a seal around the tube.

Here's a video I've just made on this


The compression fitting holds onto it surprisingly securely - I have never had any leaks or problems with it. It's greatest advantage is that is servicable - meaning that you can untighten the fitting and remove it if you have to

Comments

mark49 (author)2017-04-29

You must be very careful using home made compressors. I worked on a job several years ago where we used a home made compressor consisting of a belt driven freezer compressor, a pressure switch and a hot water tank used for air storage. The compressor was located in a garage under a bedroom. The pressure switch malfunctioned and the compressor didn't shut off resulting in a rocket that went from the garage through the bedroom and out through the the roof of the house. This sheared a section out of a 2X12 floor joist as it went. I often wonder how much pressure was built up in that hot water tank. By the grace of God no one was hurt. A safety pressure release valve is always a good idea.

bobkitsmilr (author)2017-03-08

Get these type compressor pumps free!

And, these free ones are better then the
small fridge ones - go to a HVAC company and ask for an old compressor/pump
from a HVAC heat pump.

These are removed and replaced all the time and
the HVAC company should have properly decommissioned units with
refrigerant already removed and be happy to give you one as they just
dump these in the trash.

I once went to a local HVAC company and
ask if they could sell me a decommissioned HVAC system heater for a green house,
they took me out back and said here are 5 nice HVAC heater units, all
work great, with fans, and you can have one or all for free.

jacob1981 (author)2016-10-09

Hi,

I built a small fridge compressor and is running fine to load air in to tank. I set it to cut in in about 5 bars and cut out 7 bars. Its load in the air fine but when reach cut in 5bars should starts but it doesn't. I think its happens because its too hot and need to cool down. Any idea how to fix it? Ideal will be cut out 7 and cut in 6. Also I notice when using airbrush nad compressor is running, it struggle to load air in to the tank. Any idea how long fridge compressor can run continuously before break?

Thanks.

mtbike2 (author)jacob19812017-02-27

often the problem is not that compressor needs to cool down but rather that it cannot start against the head of pressure. It is best to use an unloaded valve so,that the line between the compressor and tank is empty when it restarts. To do this you need a one way valve in the plumbing to prevent unintended back flow

ElegantAndrogyne (author)2016-09-17

Hi,

if the unit output tube's diameter is right (8mm, 6mm etc.), you can possibly get rid of the whole compression fitting and use standard plug-in fittings for plastic tubes. I did it on my compressor and it works like a charm, no leaks. Just clean the output tube with sandpaper and cover it with a thin and uniform layer of solder, which will prevent the fitting from slipping off.

My compressor has a 5 liter tank from a cheap Stanley portable compressor and it's good enough for pumping tires or blowing the dust off. Working with air tools or painting is out of question, of course :).

SergeyN13 (author)2016-08-04

How to Make air Conditioning With his Own Hands

http://blogsanswers.com/how-to-make-air-conditioning-with-his-own-hands/

vectorization (author)2015-06-17

This is a diagram of a NLY7F compressor. I'm having trouble figuring out which wire to connect to what. Can ye help me out? Thanks a mill. :)

Gelfling6 (author)vectorization2016-07-26

from what I can trace of it, but not being able to see the entire exploded parts view at the top of the picture, You need to connect Neutral (usually the white wire) to connector "N" (obiously marked for Neutral), and the Hot (power) wire to "L" (Line), but then comes the tricky part.. Note connector "C"? the thermostat goes between "L" & "C", so, HERE you would place the pressure switch (pressure low=NC, Pressure peak =NO)the cooling fan needn't be between N & C, the dotted lines are Common-Ground (GND), your main power is the spot marked with the sine wave (at the bottom. the lamp & switch are the 'internal light', so, not required. (note they're connected to the "L" & "N" posts so they get power when the compressor is off. but turns on the light when the switch is closed (door open, AKA a NC SPST switch,) )

Gelfling6 (author)Gelfling62016-07-26

If you plan on using a double-pole pressure switch to cut all power at peak pressure, you need to add a jumper between L & C (bypassing what would have been the thermostat.), and put the output wires from the pressure switch to L & N (and, just to CMA (Cover My A..) , ALWAYS check connections with a ohm/Continuity tester with the circuit un-plugged before adding power!)

nutsack420 (author)2016-04-23

How or where do I drain old oil without tipping it and do I add it in the air in or air out line?

HVACPro (author)2015-05-10

I am a licensed refrigeration technician and I notice that you fail to
mention that this is both ILLEGAL and DANGEROUS. Pressures inside that
system when the unit isn't operating can reach well over 100PSI and when
you cut any of those lines that refrigerant will flash off into a gas
and this will cause an extreme temperature drop and the result will be
instant frost bite if it contacts your skin. You cannot, by law,
intentionally vent any refrigerant into the atmosphere. You state here
and other places that the "freon" used today isn't as bad for the
environment and that is wrong on every level imaginable. Refrigerants
used in low temp equipment are going to be either R22, R134a and in
some cases R404A. These are NOT environmentally safe substances and
therefore are regulated by the EPA. In fact R22 has been phased out
because of this. Venting carries a hefty fine and rest assured this will
be reported accordingly.
Furthermore, using a refrigeration
compressor as an air compressor isn't very wise. The unit uses the
actual refrigerant, that you illegally removed, to cool the internals.
The oil that is inside the system is considered hazardous waste.

r01walker (author)HVACPro2015-11-29

i agree in part. the oil is special in that it will not mix with the refrigerant. their are other non wax based oils that can be used. as far as heat. which is a big issue. i suggest using aluminum heat transfer vanes. the outside housing is powder coated. and that will need to be sanded off. but the vanes could be soldered to the compressor. they do take lots of heat in manufacture. these compressors have been known to run 30 years and be beat all to ____. and still go strong.

Gelfling6 (author)HVACPro2015-06-03

Actually, R134/a (is BORDERLINE Environmentally safe, as most 'Air Duster', Sports Horn, and Even most aerosol products are pressurised with it.. But I well understand your concern, having been a Firefighter/Haz-Mat-II warm-zone first responder.

To the author, I also would HIGHLY suggest bringing a salvage refrigerator to a HVAC contractor, to have the refrigerant safely extracted. (vacuum pump system) (since it could be R12, which is still illegal to vent.) and leaving the system sealed at least 20 minutes before allowing venting to the atmospheric level. I haven't read further into the instructable, But also drain as much of the refrigerant oil as possible, and replace it with air-compressor oil, which will not foam, and cannot be contaminated like the refrigerant oil does. (But NEVER more than the amount you drain! as this will get oil into the output air.)

One note to HVACPro, Not entirely unwise, as most compressors are essentially the same inside, as air-cooled, and using the Air Compressor oil will also provide cooling, carrying the heat to the metal case.. The thickness of the case is usually adequate incase of seizing/exploding. (as long as the case remains welded!) I've seen plenty of videos of converted compressors, and 'Exploratory Autopsies' of failed compressors to know the case is there for a reason. (especially one of a dual-compressor outdoor system, where the crank arms on a 6-cyl. Compressor failed, and shattered inside. Resulting, eventually burned-out the 2nd compressor's windings)

r01walker (author)2015-11-29

i have seen air conditioner compressors used for vacuum pumps. as a suggestion the air conditioning compressor works on a closed system. if the intake line is used in atmosphere might want to be dried and filtered. the oil in the compressor is special and is not designed to be used in this manner. to keep it free of moisture and dirt is best for life of the unit. i don't know where to get that oil. contact Emerson, or the manufacturer. further i do not agree with the hfc theory. big difference between theory and fact Nobel prise and legislation aside. i do believe in being prudent. if you do get a r-22 or older system their are piercing valves to pull down the system and the compressor itself can be used to move the freon out of the unit before further dis-assembly. i actually have 9 9500 btu heat pumps units. i got 10.00 apiece in them. i think i can make a victim or two. thanks for the info.

SergeyV8 (author)2015-11-22

500 psi is huge. It is much larger than max pressures for professional compressors:
http://www.artistsupplysource.com/category/54277/airbrush-compressors-and-accessories/

AirC (author)2015-10-20

You have an awesome article, Now I know how to modify a fridge compressor into a silent air compressor. thanks. i am looking to hear from you. :)

LowEnergy (author)2013-10-14

It's important to note that if you cut the tubes you release the refrigerant. Old refrigerant is bad for the ozone layer...new refrigerants are not as bad for the ozone layer but they still are thousands of time worse for global warming than CO2. So to do this responsibly, you have to either get a fridge that has already had the refrigerant removed, or you have to find a refrigeration technician who can do that for you.

Very cool to make good use of scrap--sorry to have to inject this note of caution.

kerimil (author)LowEnergy2013-10-14

Yes, you are right. But freon hasn't been used for about 20 yrs so vast majority of fridges you will find won't have it. What's more, if you leave an old fridge with freon it will leak out the refrigerant anyway.

ChaitanyaG1 (author)kerimil2015-09-27

It is for y author
I removed compressor from my old fridge .that time it was working
But after words i droped by mistake
It was tilted up side down
Then after it is not working
I tried a lot but it is not workingat al lhelp me out of this!!!.
Plz......

LowEnergy (author)kerimil2013-10-15

That's right--classic freon (CFC), which had the worst ozone layer effect, was phased out in 1995. If you find a 20-year-old or older junk fridge, that's what's in it. The main replacement used since then is HCFC. That has something like 10% of the effect on the ozone layer--not nearly as bad but still pretty bad. And there are HFC refrigerants now that have no effect on the ozone layer.

However, all three--HFC, HCFC and CFC--are bad for global warming--thousands of times worse than CO2! So even if you do this with a fridge made in the last few years, it's a serious problem. In most places, there are programs to make sure fridges are safely taken care of, with the refrigerant collected. They'll pick up old ones for free, or even pay you for them. You can check in your area, or find many of the programs by zip-code here:

http://www.jacoinc.net/recycleNow.aspx

ChaitanyaG1 (author)2015-09-27

I removed compressor from my old fridge .that time it was working
But after words i droped by mistake
It was tilted up side down
Then after it is not working
I tried a lot but it is not workingat al lhelp me out of this!!!.
Plz......

CorreyS1 (author)2015-09-18

Oh wow, how interesting to know that you can modify a fridge compressor into an air compressor. The one in the picture sure reminds about seeing one at a certain compressor service company store. It's actually something that I'm looking for at the moment in order to clean the air ducts.http://www.compressedair-systems.com/services.html

Dyer13 (author)2015-08-30

Waste removal centers and recycling centers have special tools that remove old refrigerant - essentially a needle and hose hooked to vice-grips to capture the gasses. They crimp them directly to the copper tubing. They would probably do this for free or very cheap if you ask around.

DonaldF2 (author)2015-06-16

Air Compressor Journal (author)2015-06-12

Thanks for sharing these great guidelines. Everyone can go through http://aircompressorjournal.com/ to learn more about air compressor. Many thanks. Hope to see more tips in the future.

Air Compressor Journal (author)2015-06-12

Thanks for sharing these great guidelines. Everyone can go through http://aircompressorjournal.com/ to learn more about air compressor. Many thanks. Hope to see more tips in the future.

en2oh (author)2015-01-29

that diagram showing what appears to be an outlet trap seems backward would it not be better to reverse the flow?as you currently have it, once the condensate/oil reaches the outlet tube, it will act as a siphon.

MetalworkingMaster123 (author)2014-11-01

I am using this to build a high pressure bottle burster.

MetalworkingMaster123 (author)2014-11-01

I am using this to build a high pressure bottle burster.

rimar2000 (author)2013-12-23

Very useful instructable. I am using one of these compressors since maybe 30 years. It has very high compression but very low flow. I use it only to inflate my bicycle wheels. I tried to use it to paint, but because of its low flow it did not worked.

antonc81 (author)rimar20002014-08-03

You could run it through a pressure switch to an air tank. The pressure swithc will shut off the compressor when pressure in the tank reaches a preset pressure, then will turn back on when pressure drops below another preset.

rimar2000 (author)antonc812014-08-03

Thanks, antonc81.

kerimil (author)rimar20002013-12-23

You can also use air conditioning compressors - they offer a lot higher flow.

rimar2000 (author)kerimil2013-12-24

Thanks for the info, I didn't know that.

wildnitehawk (author)2013-10-21

guys, if you do want to use refrigerant compressors, please contact your local HVAC technician about recovering the refrigerant inside. The ones that are extremely harmful are R-12, and R22. There are plenty more but in residential applications, these are it. R-134a is considered an HFC which doesn't have chlorine, so it has a 0% ozone depletion. But it's a greenhouse gas. For those wondering, 1 chlorine molecule can destroy 100,000 ozone molecules. So at least contact someone to recover these units.

agguilar (author)2013-09-21

hi, can i use a air conditioner compressor ? thank you!

kerimil (author)agguilar2013-09-22

Yes, of course you can. They are even more practical for everyday use than fridge compressors, because their CFM/minute is higher. I haven't ever built one because they are hard to get where I live but everything is pretty much the same. Here's one thread found on them - http://www.spudfiles.com/forums/i-have-an-a-c-compressor-to-convert-questions-t18828.html

There are like tons more examples there but be warned that the search function really sucks ;-)

potterguytoo (author)2013-06-20

Very clever use of more "throw away" stuff in our disposable society.