questions about pressures

[gkiing]

The low side (blue) gauge on a manifold usually reads from 30" hg to 120 psi. Inches of mercury measures the vacuum (if present) on the low side of the system. Operating the low side in a vacuum means the boiling point of the refrigerant is lower (meaning lower temps). I think 29.97" of mercury is a theoretically perfect vacuum.

My best advice would be to charge the system while under load until you get the lowest possible evap temp and then stop there, it seems to work for me.