Timed shutdown control circuit for electric refrigeration and air conditioning systems

Claim 1

A control system for a refrigeration compressor motor comprising a motor starting means adapted to connect the motor to a relatively high voltage source of electric power, a protection circuit for energizing said starter means including a thermally rEsponsive demand switch and at least one condition responsive switch positioned in the circuit to sense a condition and thereupon open said protection circuit and deenergize the motor starting means and a time delay control circuit including a normally closed starter control contact adapted to electrically connect said time delay circuit to a relatively low voltage source of electric power for activation thereby whenever said motor starting means is deenergized, a compressor protection relay having an energization winding and a respective normally closed protection contact, said respective protection contact electrically connected in series with said motor starter means and adapted to be opened to deenergize the motor starting means each time said protection circuit is opened, and an instant reset time delay relay having a respective normally closed time delay contact electrically connected in series with said protection relay energization winding and adapted to remain closed for a predetermined time interval after each energization of said respective instant reset time delay relay to maintain energization of said protection relay energization winding for a predetermined time to prevent closing of said motor protection contact and energization of said motor starter means for said predetermined time.