With increasing energy costs and growing demands for more efficient cooling systems, the need for accurate superheat measurements has become more important. Unfortunately, some technicians have either forgotten what they were taught about superheat in school or think it’s too much trouble to perform. They learn the procedure early in school and practice it there, but they find it more difficult in the field, largely because of forgotten techniques or ineffective measuring tools. This lack of superheat measurements results in air conditioners that are either undercharged or overcharged and in danger of compressor failure.
Superheat is defined as the difference between the temperature at which the refrigerant boils at a given pressure in the evaporator and the temperature of the refrigerant gas as it leaves the evaporator. In a worst-case scenario with low indoor heat load and the air conditioner still running, if overcharged, the refrigerant in the evaporator would remain in liquid form in the coil and back up into the compressor, steadily destroying it. In a properly tuned system, the refrigerant continues to boil and exits the evaporator as a gas even under the worst possible conditions.