How to Modify a Fridge Compressor Into a Silent Air Compressor

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Introduction: 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




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)

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

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

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40 Comments

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.

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.

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.

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

Your site sucks and it's nothing but spam.

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 :).

How to Make air Conditioning With his Own Hands

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

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. :)

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,) )