Home made silent compressor question

[smooftie]

Hi all, I have a small workshop compressor (20L) that I would like convert to run on a fridge compressor. Question is does it matter what the donor compressor comes out of. I have been offered a bar fridge as a donor which comes at the right price, free. Will this be big enough or should I look for something else. Thanks in advance.

 

[ad fez]

i dont know buddy, but a couple of members on here have had experience with building them so maybe one of them will be along to help you out...... i would imagine it would be, just be sure to connect up with flexible hoses so if yo find its not big enough then you can always attach another with relative ease

 

[saument1986]

I made one with a compressor from an old fridge I tried to build one with a small compressor from a mini freezer and it struggled to build past 50psi on a 4 gal tank you could try yours and see but I had better luck with one from the refrigerator

 

[Madbrush]

Hi all, I have a small workshop compressor (20L) that I would like convert to run on a fridge compressor. Question is does it matter what the donor compressor comes out of. I have been offered a bar fridge as a donor which comes at the right price, free. Will this be big enough or should I look for something else. Thanks in advance.

A bar fridge will be pumping a maximum of 2 liters of cfc gas, and only off and on at that, I fear trying to constantly fill a 20 liter tank will be more than the poor thing can handle, I think you would be looking at something in the region of an industrial freezer, using the wrong size fridge motor would be short lived.

I have been doing a little research into this myself, and because the information available is so vague, and no one seems to know the exact requirements and instead just wing it, I plan to ask advice at a local company on what I should be looking for, as much as I like the idea of building my own, I would rather nor take the risk of building something that could be dangerous.

Because of space restrictions, the parts I already have are the six liter tank, which can withstand a maximum of 12 bar, 1 bar = 14.5 psi, i won't go higher than a 10 bar compressor (fridge motor), I have all the piping and wiring, all I need is the donor motor and adjustable pressure cut off switch, the pressure switch costs around $25 new, the motor as you say can be free of charge but needs to be professionally de-gassed, trying to do this your self could land you in some trouble.

There is bound to be a compressor company near you, I would check first with them, a refrigeration company would also do.

Basically you should consider the time it would take to fill your tank, if this is extremely long your motor will quickly burn out.

 

[JTairbrush]

I built a home built silent compressor several years ago and its quite easy to do, especially if your using a working compressor as your donor, as it has all the parts you need, except the silent compressor motor. As far using a bar fridge motor, that may work ok because typically commercial refrigerators have more powerful compressors than residential refrigerators. The parts you need are a pressure switch, on/off switch and one way valve. All these items should already be installed on your existing compressor and should be usable. Remove the existing noisy compressor motor, figure a way to fasten down the fridge compressor, wire it up and attach the air lines. You may need some compression fittings to attach the copper tubing from the compressor to the tank. The hot wire goes from the compressor goes to the on/off switch, then the hot wire from the plug goes to the on/off switch. The neutral wire from the compressor goes directly to the white wire on the plug. The green ground wire on the plug goes to any metal screw on the compressor. The only real issue with these fridge motors is there is no way to monitor the oil level since they are sealed units. Make sure you install a water/oil filter as these motors do discharge some oil. As far as replacing the lost oil, there is no accurate way to judge how much you loose, so what I did was to add a little bit of synthetic refrigerator oil every so often. You can get this oil at an HVAC parts supply company. You must use this special oil for these compressors and let the jobber know the brand and model of the motor so he can hopefully sell you the correct oil. My homebuilt silent compressor lasted for 2 years before the motor died. Hope this helps. Let me know if you have any questions.

 

[WhiteKnight]

I agree with Madbrush if when you say bar fridge you mean the kind that fit under a counter 3ft x 2ft, it will not be able to keep up, if it takes more than 5 minutes to fill your tank it will burnout in no time. If your compressor can fill your reservoir to 100 psi under 2 minutes it should have no problem with heating (if your reservoir is not too small, which would loose it's pressure too quickly, so as to need to be refiled sooner). Your compressor should be able to rest a bit between fills.

Like JTairbrush said, on a fridge you have all the components you need to turn on and off the motor (that is the relay switch in which the thermostat connects to, to signal to the compressor to start, you just need to connect the pressure switch where the thermostat was connected).

For the oil since it is no longer used for refrigeration it does not need refrigerator oil (sorry JT), refrigerator oil is actually very smelly (The one that was in mine was) It can be replaced safely with mineral oil you buy at the pharmacy (which smells nothing). To drain the motor, you will have to turn it upside down, and the oil will come out of the intake ports (where the air is sucked in the motor), be careful because there are usually two of them. Make sure to collect it in a container so you can measure how much oil was in there so you can put the same amount back in. Putting the oil back is not too hard you just need to connect a hose to one of the intake lines and place the other end in the container containing the correct amount of new oil it should suck it up, you can block the other intake line with your finger so it goes faster. If it does not start sucking the oil after a few seconds make sure that everything is connected correctly, you don't want to run the motor too long without oil.

Here is a link to a video of someone who replaces the motor of his compressor with a fridge motor: DIY Silent Compressor

You can find lots of info on this site. Hope it helps

 

[Madbrush]

I agree with Madbrush if when you say bar fridge you mean the kind that fit under a counter 3ft x 2ft, it will not be able to keep up, if it takes more than 5 minutes to fill your tank it will burnout in no time. If your compressor can fill your reservoir to 100 psi under 2 minutes it should have no problem with heating (if your reservoir is not too small, which would loose it's pressure too quickly, so as to need to be refiled sooner). Your compressor should be able to rest a bit between fills.

Like JTairbrush said, on a fridge you have all the components you need to turn on and off the motor (that is the relay switch in which the thermostat connects to, to signal to the compressor to start, you just need to connect the pressure switch where the thermostat was connected).

For the oil since it is no longer used for refrigeration it does not need refrigerator oil (sorry JT), refrigerator oil is actually very smelly (The one that was in mine was) It can be replaced safely with mineral oil you buy at the pharmacy (which smells nothing). To drain the motor, you will have to turn it upside down, and the oil will come out of the intake ports (where the air is sucked in the motor), be careful because there are usually two of them. Make sure to collect it in a container so you can measure how much oil was in there so you can put the same amount back in. Putting the oil back is not to hard you just need to connect a hose to one of the intake lines and place the other end in the container containing the correct amount of new oil it should suck it up, you can block the other intake line with your finger so it goes faster. If it does not start sucking the oil after a few seconds make sure that everything is connected correctly, you don't want to run the motor too long without oil.

Here is a link to a video of someone who replaces the motor of his compressor with a fridge motor: DIY Silent Compressor

You can find lots of info on this site. Hope it helps

Just to add to that, it is wise to attach an air filter to the top of the air intake pipe, this ensures that your air stays clean and doesn't foul your oil or linings.

 

[wmlepage]

I have also done this, I had a junk compressor with a 4.5 gal tank, and access to 2 old fridge compressors, 1 mini and one full size. I am using it all the time now. My small compressor with a tank was having to run too often, and had a hard time maintaing 50+ psi if I was spraying shirts.

Here is the link to the page I used for directions. I believe Tafster also has a youtube vid out there about his homemade compressor as well.
DIY Silent Compressor

 

[ad fez]

Told ya! Loads off info from knowledgeable folk, aren't you glad you found us ! :0)

 

[smooftie]

Thanks all for the input. The thing that sticks out is the comment by Madbrush, lots of info but vague. Ack the gas issue, have already spoken to a local guy who will remove this for me. No issue with it being dangerous as the start/stop and pressure relief valve will remain on the existing compressor tank. So the decision is, I will go with the fridge compressor that I have (domestic not industrial) and see what happens. At the end of the day the only cost is a bit of time. I will post outcome. If it is not successful I will have a look for a bigger donor fridge.

 

[wmlepage]

If the compressor you have is not from a very small fridge, it should be fine, you can always plumb 2 or more together for more capacity. 1 parasite switch van easily power 2. Just a f we more fittings.


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[smooftie]

Ok, so an update. The tank that I am using is a Project Air 20 or 24 L compressor, can't remember which size as I have had this for some time. The fridge compressor is a Danfross NLX13KK.2, here is a link to the compressor tech data, http://www.ra.danfoss.com/Technical...kk2_6mm_r600a_220v_50hz_08-2007_ed520t202.pdf The fridge that it came out of was approx 250L. I removed all the wiring and connected it to the original start wiring from the Project Air compressor. The only wire that was retained was from the thermostat which needs to be looped back to the active to complete the circuit. Other than that it was a quick job to connect the air out from the compressor to the original air in on the tank. Once turned on it took approx 6 minutes to fill the tank from empty and the best bit was there was almost no sound. At this stage I can't tell how it runs with an airbrush connected as I still need to bolt the compressor down. If I find that the compressor is not large enough I have found a source of free fridge compressors. I found a local scrap yard where they collect old fridges to reclaim the copper and steel components. Most of the fridges they get are from people upgrading and are in working order other than they are old. Might be worth a look in your local area. Will post some pics soon.

 

[smooftie]

Done. So I made a couple of changes to the compressor. I reamed out the inlet and outlet to increase the air flow. This has increased the noise slightly but nothing to be worried about. The fill time from empty is not about 5.5 minutes. With the tank full and a Iwata HP-C Plus connected, the are set to 25psi, and the airbrush held fully open, the tank supplies 9 minutes of air before the compressor starts and again with the airbrush held fully open takes 2 minutes to fill. So the cost was, original compressor approx $80, fridge compressor free, band clamps and elec connectors $5. So overall a good result for not much outlay.

 

[nicko321]

Gday smooftie.

I have the same air compressor and have just acquired a fridge compressor motor to attach. I am now going to use the orignal inlet pipe as you have, that looks great.

A few questions though.

Did you change the oil from your fridge motor? if so what did you replace it with?
Is the inlet of the air compressor attached to the outlet with hose? If so did hoseclamps work well enough to hold it?

And finally, is it still working properly and are you happy with it?

Cheers,
Nicko321