Hi guys. Sorry for the naive questions but now that I have built my own chiller I start understand some thing better so I have some questions.

1) How much should the low-side pressure before I have too much refrigerant inside?
2) When we say that there is a vacuum in the low-side or that the low-side 7" or 8" or whatever Hg what does that mean?
3) Should we charge a system by just watching the evap temp (or the frost on the evap) or with the low-side pressure?

Thats it. Thanks in advance