...and do you have a favorite brand of oil?

For 30 yrs I have changed it after every 2 uses.i prefer jb brand oil...also on a side note,cool master sells a descent 4cfm pump nowadays for 100 bucks.

JB and fresh oil for each use.

Allows me to get down to better than 5 microns.

Thanks, guys -

Guess it's best to regard it as being just another "consumable" cost - used up on every new job.

thanks, im going on 8 months.

i use the oil united sells.

commercial refer tech.

ressy guys are funny when it comes to microns for an airconditioner.

11 years doing markets and wholesale clubs.

installing cases that need to be running and at temp by 6am, you dont have time to get crazy microns, especially connected to a rack system, holding more than 1500lbs of juice, thats running, with just a suction and liquid ball valve that leaks by on the loop when pulled to a deep vacuum.. do your best that night, change the driers when done with job.

new stores, thats different. ill change oil on the big pump once a day and break it with nitro every day for 4 days.

It makes sure ALL the moisture is removed.
It takes a vanishingly small amount of water vapor to really screw up an conditioner.

High vacuum and time


I also had to do Temperature Altitude test chambers.
We routinely needed to get to hard orbit vacuums for testing satellite components
Many with rather nasty refrigerants.

Pulling a hard space vacuum at -70C is a special nightmare.
Made even harder when you have enough lights in the chamber to simulate solar loading of the satellite.
We used liquid nitrogen cooling of chamber walls.

And we had an even larger chamber with huge interconnections used to simulate rapid pressure changes.
Like when you fly a plane nearly vertically and the pressures go all over the place.

After every vacuum.
Yellow Jacket.

Do it before each job.
Why let the oils sit around around absorbing stuff before using it?

Follow-up question: What's your preferred hose for drawing and maintaining a deep vacuum?

Copper pipe with flare fittings.

Flex hose is just not good enough.