got my micron gauge and hooked it up, but cant get a vacuum lower than 5000-1500 microns...did a blank off test to test my vac pump performance and could not get below 1500 microns. My single stage vac pump which I bought second hand I guess is a good 25-30 years old so it may be a bit past it! The Robinair gauge set which came with it - I replaced the spindle o rings and lubed it with Nylog blue to make sure it is vacuum tight.
Any recommendations an new vac pump as far as CFM etc? I guess a two stage pump would be better. I will be doing auto AC and small split systems.
regards,
james.

1500 microns is dang close..
 

It's very close to where you need to be. You might be able to try using the method shown here. It takes an hour I think..
http://www.thermalengineeringcompany...appliances.pdf
Notice their final reading is 350 microns.

The pump I've been using (and a few other DIYers) is the Robinair 15150
Robinair 15150, 15300, and 15500 1.5, 3, and 5 CFM VacuMaster Vacuum Pump - on Sale at the Test Equipment Depot
seems to be a pretty good pump. I recommend buying a few quarts of good pump oil with it.


Here's the vac section of my 1st install.
http://ecorenovator.org/forum/geothe...project-9.html
Reading it, I really wonder about the need for a super low vac..
I saw this "The Mr. Slim manual says 1000 microns (1 Torr) is their target.
That should be easy to beat.."

Before you scrap it, go get a quart or two of vacuum pump oil. Pump and dump, pump and dump, refill and check vacuum. The pump may just have water in the oil and on the moving internal parts. Just changing the oil and running a couple times to flush the grunge out could do wonders.

Actually, 1500-2000 microns is not so bad. It will work for automotive systems as is. The little cheapies that run off compressed air only pull vacuum to this range when new out of the box.

Yeah, I always start off with fresh oil. I hear it might be good to change it after an hour or two of run-time.

I try to always start off with the line set cut off off. Just to see if my hoses and gauge etc can hold a good vac to start with.
That little test run is also a good pump oil report..
If I see it close to 200 microns pretty fast, I know the gear is working well.
That's when I connect to the line set. (via a cut-off).