TECH- Build an air compressor

Here’s my attempt at a tech. I needed an air compressor that was quiet so I could work late into the night (painting while the neighbors are asleep). I started collecting small ¼ HP motors from refrigerators. My initial plan was to connect 4 to have a four HP compressor. I ended up going to the appliance repair shop in my neighborhood and found a used 220v Copeland 2HP freezer compressor for 40 bucks. So I decided to use this instead.
To run a compressor like this you will need a run capacitor, start capacitor, and a potential relay. Now most refrigerator compressors have these attached to them but for the larger compressors you will either have to pull this equipment with it (if you manually pull it from a freezer or central A/C unit) or purchase from someplace like Ebay. For my unit I contacted the distributors of Copeland and asked them what size capacitors I needed and they sent me a response the next day with the following info:
Start capacitor: 145-174microfarad, 220volts, part# 014-0008-51
Run Capacitor: 30 microfarad, 370volts, part#014-0037-10
Potential Relay: 190-200volts, 60Hz (General Electric)), part#040-0166-15
I looked on ebay and found a “kickstart” start capacitor with a built-in relay for 5 bucks and a run capacitor with the proper rating for 8 bucks.
After I gathered all of the equipment that I needed I built a rolling cart for it and hand bent a tabletop (that’s why it looks like crap, no sheet metal brake). I’m using a modified 5 Gal propane tank that I picked up at a swap meet for an air tank. I mounted the tank upside down so that I could drain the water if any accumulated. There are a total of three copper tubes coming out of my compressor. You have to find which one blows air and solder that one to the tank. The other two need to have an air filter attached to them. I still have not done this and will be attaching one soon. I also wired a pressure cut off switch to keep the tank from exploding. I’ve read somewhere that these can pump up to a couple thousand PSI so be careful.
There is only one bad problem with this setup. The pump will push old oil out of it. I have put an oil separator on it and plan on adding another one just in case. To try and keep the oil inside I’m going to coil up the copper line just after the compressor. There’s also no way to put the oil back in unless you pour it back into the compressor from the blow out line because its soldered on that makes it kind of hard. You can attach some sort of screw on cap and that may work. I have seen one of the ¼ HP compressors modified for a dipstick but I have not tried this yet. Many people use these with the smaller versions and don’t have any problems with the loss of oil.
This compressor will fill the 5 Gal tank to 180 PSI in less than a minute and is dead silent. I can open up the air valve and try to let the air out but it will stay at a constant 60 PSI on the gauge. The only real noise it makes is the air escaping if you’re blowing something off. I have used my impact wrench with this and it worked great. I haven’t painted with it yet but that will be soon. You can search the web and find smaller versions of these that are homebuilt. You can also search and find brand new ones that range between 1000 and 3000 dollars. They’re not cheap. Hope you guys enjoyed my tech and thanks again for all the help you guys have given me since I’ve joined HAMB!

 

That is a good idea, but if you do not supply some oil on the intake, it will wear excessively and eventually not work.

BTW, these compressors also can be set up to run as a vacuum pump by using the other tubing connections. They pull a good vacuum for such things as A/C work.

 

You desperately NEED a pressure relief valve - the pressure switch is NOT enough.

 

i'm kinda thinking anything spitting oil won't be paint friendly.... let us know how it does though!

 

I think I'd double-check how much you can safely pressurize an LP tank, too. 180 sounds a bit on the high side.

Roger

 

Years ago, before I had a garage or full size compressor, I used a small compressor from a discarded fridge to inflate tires.
I had it mounted on a simple stand with a handle for portability.

Worked great and although it had no shut off, I think the hand pump fill hose I used would act as a "fuse" and burst or pop off before the pressure reached a critical level for the compressor or tire.
Used it for years and then gave it away to a friend who also used it for years!
Might still have it actually!!!

Didn't think about its ability to create vacuum at the time, but that itself makes it worthwhile to dig up another one now.
Actually....my crusty garage fridge is about to meet its doom....

Problem solved!