The Low Pressure (LP) Switch monitors the refrigeration system for a loss of refrigerant charge. And it may also be helpful in stopping the evaporator (indoor) coil from freezing up due to a dirty filter or low airflow over the coil.
A LP switch is connected to the suction, or “low” side of the system to sense suction pressure.
Low pressures can occur in air conditioning systems when the refrigerant has escaped. When this occurs, the contacts in the LP switch open and break the electrical supply to the compressor clutch, thus stopping its operation. LP switches can also be used as an operating control. And to operate the system by a pressure setting that corresponds to a temperature setting. By properly setting the LP switch, the temperature can also be controlled.