Too True, Too True
Brother of The Benz
jgl1, I can not disagree with everything you replied.
Too True, probably 99.99999% of automotve reffers have never had the pressures applied as you are referencing.
Stating time is the factor means as long as you have time; evacuate to a time convient to your work load in the shop. Ofcourse if the work load is light give it time as you feel comfortable with, opposite if the shop is busy.
You probably will not be able to tell one from the other.
My little Welch pump has a blank off of 1500(just a guess as I don't have a gauge for this pressure and the name tag and manual are gone) microns with the non-condensable vent valve closed. Less with it open which is where I operate it initially.
The low pressure scale on the low gauge of the manifold set is just a for reference.
When A/C was offered in the GM automobile, Kent-Moore Tools(provider of toolig for GM) furnished the dealerships with a vac/pump that was a Frigidaire domestic compressor from that division of GM. These pumps were used for many many years until manufactures as Welch and Stokes came on the Toolig provider list.
We are blessed in that the automotive A/C is so over designed to provide us with cooling with less than perfect servicing technique.
I will still pump down as long as I have the time to wait for my little pump to stop burping and then a little more.
I am satisfied with what I do but I wish I could get you to service my A/C for you would do better than my fumbling.
Happy Trails Beep Beep from The Spiderman in Houston!!!