NU-22B® Superheat / Subcooling Slide Chart
It is important for technicians to be as accurate as possible with the amount of refrigerant charge on air conditioning systems with fixed orifices or TXV metering devices. Fixed orifices are the most critical charged system and must be charged by target compressor superheat for the best system efficiency and capacity. According to Energy Star research over 1% of air conditioning energy is wasted for each 1% error in refrigerant charge. Systems that use a TXV as a metering device are not as critical, but must be charged to designed subcooling. To high subcooling (overcharged) will decrease efficiency and to low subcooling (undercharged) will decrease capacity.