MARS solid state delay on break timers are designed to prevent short cycling of air conditioning, refrigeration and heat pump compressors. Upon application of power the load is energized. When the thermostat opens, or if there is a momentary loss of power, the load is de-energized and the delay period begins. The compressor will not start again during the delay period. The MARS 32391 is the top selling timer in the industry. Its reliability has been proven in the field by knowledgeable contractors. The MARS 32391 will not be fooled by the thermostat anticipator. Heavy duty MARS timers are offered for higher current applications.