These three HVAC quick reference polystyrene cards are double sided and designed to be used with Air Conditioners and Heat Pumps to measure the refrigerant level in a unit, charge refrigerant, troubleshoot refrigerant based problems, and measure heat transfer to determine if there is a problem. Find the Target Subcooling to measure the refrigerant level of systems with a TXV metering device Use Subcooling to determine if a system is undercharged, correctly charged, or overcharged Find the Target Superheat to measure the refrigerant level of systems with a fixed orifice metering device Use Total Superheat to determine if a system is undercharged, correctly charged, or overcharged Use Delta T to determine if the system is exchanging heat properly Use the P/T Chart to find the Saturated Temp of 5 common refrigerants Use the Guide to determine how to find the Bubble and Dew Saturated Temps of Blend Refrigerants Use the Refrigerant Weight Chart to calculate the amount of refrigerant needed per foot of tubing Use the Guide to weigh in the full or partial refrigerant charge into an empty vacuumed unit Flexible Weather and UV Resistant Polystyrene Card Material Tested 0F130F Three Cards Double Sided per Pack HVAC Technician Resource