Chilly1 -

Evacuate to 500 microns, break vacuum to 0 psi with refrigerant (the one you wish to use in the system.) evac to 500 micron again and break vacume a second time to 0 psi as before. Now pull a vacuum to 250 microns this will take a few hours and will insure that the system is completly free of contaminants. Break vacuum to 0 psi and add the oil with an oil pump replacing the same amount you last removed. You then pull a vacuum to 500 microns. This compleats the clean and flush of your system. It may seem excessive to evacuate it so many times but it is the best way to insure a clean system .


Gary Lloyd -

I agree. A triple evacuation with a mediocre vacuum pump will do a better job than a single evacuation with the best pump on the market.

Another trick is to break the vacuum on the high side. This pushes the leftover residuals through the system to the low side. Then on the next evacuation, open the low side valve to the pump first.

If you have nitrogen available, the vacuum should be broken with nitrogen after the first evacuation. The compressor oil will not absorb the nitrogen, so the second evacuation will go much faster. This can save a lot of time.

How do you know by gauges when is 500 or 250 micron of vacum?

Well at sea level pressures :

0 mircons = 29.921 inhg
250 mircons = 29.91 inhg
500 mircons = 29.90 inhg

You'll need an electronic mircon guage to read the vacuum accurately though, as everyone says standard dial guages are not all that accurate. If this is wrong, please correct me.

Ok ... Do I understand that the Best way to triple evac a system is :

1st evac from both the high and low sides open, close the low side, then break to 0 psi with N2 on the high side, close high side ... 2nd evac from low side then break vac to 0 psi with refrigerant of choice ( low side or high side break ? ) ... then finally low side evac, breaking to 0 psi again on low side. :?

Tnx

Maybe Gary can give us a better answer on this.

I was never sure of how well I was vacuuming until I got a vacuum gauge. They are awesome! I found mine on e-bay for $60. It was well worth the money.

As far as I know, when your using your manifold gauges, you can only guess at how well of a vacuum your pulling.

Would you guys give this a reply ... treat it like an overclocked evac ... you know, the best first start to building a World Class system ... that's what we're after!

Back when I started in the trade, vacuum pumps were huge and heavy, and micron gauges were non-existant. There were very rare systems, primarily absorbers, that had vacuum pumps permanently installed. We used to pipe the vacuum pump discharge into a container of oil and count the bubbles per minute. For smaller systems we used a refrigerator compressor and triple evacuated, but not into microns. I tend to think of microns as overkill, but then I'm from the really old school.

LOL!! Ok Gary, I'll make sure I have a sight glass and a watch ...

There are lots of newfangled gadgets out there, and it would be inexcusable for a professional not to have these, but I'm not certain that the extra expense is justified for the hobbyist, and it doesn't mean you can't do a good job. Back in the good old days, we built some top quality equipment and a lot of it is still working today.

AAHH - "The Good Old Days" - How sweet it was. :wink:

Hey Gary ... what! Did we miss your birthday or somthn ...

Is chilly1 saying that you need to take your oil b4 you vacuum and then put it back in?

Chilly1 was answering a question for me when he made that post. At that time I had drained the oil out of a compressor because it was old and I was changing it. You don't need to change the compressor oil every time you evacuate the system.
Does that answer your question?

Yup.... it sounded a bit wierd to change the oil on every evacuation....