System for refrigerant charging with constant volume tank

A refrigerant charging system for charging a refrigeration system with a refrigerant, comprising:

• a refrigerant source for supplying the refrigerant;
• a storage vessel;
• an input line fluidly connecting the refrigerant source to the storage vessel;
• an output line extending from the storage vessel and adapted for connection to the refrigeration system;
• a pressure sensor connected directly to the storage vessel;
• a temperature sensor connected directly to the storage vessel;
• and
• a controller communicating with the pressure and temperature sensors, the controller being configured to calculate and verify an initial mass of refrigerant within the storage vessel based on readings from the pressure and temperature sensors connected to the storage vessel, the initial mass being the sum of a required mass of refrigerant to be charged into the refrigerant system and a remaining refrigerant mass in the storage vessel, the remaining refrigerant mass in the storage vessel is an expected remaining refrigerant mass or an actual remaining refrigerant mass.