Charging pressure

[fathihvac]

Hello;
I want to charge 4 coldrooms:
1-positive temperature R12
2-negative temperature R 12
3-positive temperature R 502
4-negative temperature R502
What is the suction (low gauge)pressure for each case
Note that we do not know the refrigerant amount

[Brian_UK]

We have no idea until the system is running and at design temperature.

[Magoo]

Why are you using R12 and R502, have you not heard of global warming, living a desert area of the planet.

[lowcool]

just proves there is a long way to go with this issue.

[Brendon86]

Sounds like you need an experienced technician to help you. There is no way to answer your question correctly. Another tip when charging a system is knowing what to saturated suction temperature to expect before you charge your system. It all depends on the conditions on the day and how the systems are designed. Try to work in temperature to. A pressure is just a pressure and means nothing unless you have a PT chart.

[coolstuf]

Brendan is right, a pressure is just a pressure, use temp. By the way, you can definitely not charge any system by pressure