Purpose — Every mechanical refrigeration system that is opened for servicing must be charged before it is returned to service. Also, some models come factory charged, but may need charge adjustment in the field before being placed into service. Regardless of system size, accurate refrigerant charge is critical for many reasons. Figure SP-4-1 summarizes the conditions that result from undercharging, proper charging, and overcharging a system

Charging methods vary with equipment types and manufacturer. The method used also depends on the operating condition of the system and the availability o f charging points in the highpressure and low-pressure sides of the system. It is important to remember that recovered and/or recycled refrigerant can only be recharged into the system from which it was initially recovered, or another one owned by the same customer. The methods described in this procedure are those commonly used to service residential and light commercial equipment. They include:
• Liquid Charging by Weight
• Vapor Charging for Proper Superheat
• Vapor Charging for Proper Subcooling
• Charging with a Recovery/Recycle Unit
• Charging Using Charging Charts

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