Refrigerant amount question

[PD2]

Does anyone know of any methods to determine/calculate the amount of a refrigerant which would currently be in an industrial system?

 

[HVAC-Novice]

Look at manufacturer documents or talk to manufacturer. The equipment determines the mass in the equipment, and the line length determines what is in the system in addition to the equipment.
Usually there is a commission document that should tell what was actually used. Obviously leaks would have reduced the charge.
If you are not sure if it was done by the book, evacuating and weighing is the only option.