I was lucky enough to be given a 1/5 hp fridge compressor. Now I have been told that some of the compressors take little longer to build up pressure, bigger is better, but who cares anyways. I want to vacuum bag wings and build a compressor was what I need to do.

Before we start out we will need a few supplies

– 1 Fridge Compressor = Free, ask at the local scrap dealer, or Friends.
– 1 Supco 3 n’ 1 (Starter, Relay, Capacitor all in one Unit) = R490 ($66) from Patriot supply in the States Not needed if you have one

– 1 Vacuum Gauge for a motor Car Carburetor , for Measuring vacuum and help setting the Pressure Switch = R149
– 1 Carburetor Vacuum Goody, I find the right name = Free (used to make vacuum switch.)
OR
– Digital SMC vacuum switch from eBay for R215 ($20). Makes life easy and very effective

– 1 meter 6 mm copper tubing from Gas Place = R20 ($2.00)per meter
– 2 meters 8mm Copper tubing from Gas Place = R25 ($2.50) per meter
– 1 Cadac Gas bottle free Donated by the local Gas supplier… Bottles useful life for Gas is Gone, but it great for holding a – Vacuum
– 1 switch lead 240volt = R28 ($2.80)
– 1 12v – 220v Relay
Miscellaneous:
Heat shrink, Reasonably strong spring, Threaded rod, Small Glass Jar, Some Silver Solver and Some regular Solder all lying round the house.

Tools required:
– Soldering / blow torch
– Silver solder
– Small pipe cutter
– Screw Driver
– Craft Knife
– Cigarette Lighter or Heat gun

OKAY, we are ready to go. A safety warning first. If your fridge comes from a working fridge be sure to get a professional to remove the refrigerant from the system. Very old systems contain freon, this gas is very dense an sinks to the bottom of ones lungs pushing the air out, and can potentially suffocate you and kill you.

Lets get cracking

I started assembling the compressor & ran the compressor to check if it works. If your compressor has a working electrical system this will be as easy as connecting it to the mains. Your starter should kick in. My compressor need to have a Supco 3-in-1 unit this was because my units starter was broken and removed. After connecting it per the manufacturers instructions, I flipped the power. It pulls -1 bar Vacuum in a couple of seconds, according to what I have read for Bagging a Foam wing I need -0.2 to -0.3 bar so -1 Bar is pretty impressive. At -0.4 Bar the Foam will Deform.

Compressor connections

There are three connections on a compressor: In, Out, and Process or Suck, Suck, Blow — That sounds rude…
Lets get cracking. Of the three tubes on the compressor, locate the tube used for recycling the oil or Refilling the oil, it’s usually the one in the middle. But it makes no difference, take a tee piece and connect both of the Suck/In tubes to the Gauge, the idea is obvious to get maximum suction. The Fridge Compressor is a sealed unit and works like this any ways. Next Pinch and Solder Process hole. So now we have an in and Out.

I made all the Piping (poor silver soldering included) this piping goes from the out tube to the GAS bottle via a T-Piece. This is where our vacuum will come from. At the end of this tube I connected and quick release valve from an air compressor. The Next tube I rolled two circles in them to help keep the oil in the system as by default, so hopefully by including the rolls the oil will stay in the system.

Quick release

Moving onto the gas bottle, mine was a old LPG gas bottle which had some rust on it, I decided to clean it off by stripping the paint and rust off the Gas bottle. I painted a rust proof Primer on the Bottle. From here I connected an air nipple to the Gas bottle from where I could connect the pressure gauge, this way monitoring the pressure is easy.

Making the Vacuum switch if you don’t buy a digital switch (I would recommend this option as it includes cycling settings).

Diagram of the switch workings
completed switch

I made the Vacuum switch box and I have made a in line oil accumulator / Muffler (an experiment) with 15mm plumbing pipe and stop ends and have added the Gas collector Jar (should theoretically never get here) to the end of the out line. This jar has a tissue Baffle in it, this way there is no noise at all when the compressor runs.

How does it work? Basically, the spring tensions the Vacuum chamber. Screwing the wing nut close wise will add more tension, letting the vacuum in the system go higher, turning it anti-clockwise will release tension switching the compressor off faster. By adding more tension the vacuum chamber will move closed slower and the push rod will take longer to switch the compressor off. The Switch is in a Normally Closed (NC) position, Vacuum chamber is relaxed, and the Spring has no tension of it from the vacuum Chamber. What it does is: When the system, looses air the vacuum chamber will relax and the switch will be tripped closing the breaker, switching the compressor on and the vacuum chamber will be sucked closed again. switching on and off.

SMC digital switch

Using the Digital switch is easier. You buy a relay, when the pressure is monitored to be to low, then the switch closes the relay and the opposite when it’s high. either way the switch / relay gets spliced to the main Lead regulating the power.
The relay splicing
12v - 220v relay

Compressor is now complete.
You should get round -1 Bar from your compressor, which relates to 30 inhg or So. Make sure that the correct pipes are sealed and the correct inlet and out let are used. I finally had time to Finish the Pump’s workings. And it works a treat, it maintains pressure really well loosing only 2.34 inches of vacuum down from 28.65 inches Hg overnight, it can suck 28.65 inches Hg which is just shy of -1 bar. I’m really impressed. The digital pressure gauge work a treat and changes colour from red to green when switched on. I run the switch at the moment on a 12 volt Motorcycle Battery or a 3-cell lipo, so the mains and this circuit are not connected in anyways

Our completed compressor
completed compressor

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