Question 221Refrigeration & AC - Assistant Engineer

The correct answer is C) An increase in the suction pressure. In an automatically controlled refrigeration system with a pump down cycle, an increase in the suction pressure will cause the compressor to restart. This is because the pump down cycle is designed to shut off the compressor when the suction pressure drops to a certain level, and an increase in the suction pressure indicates that more refrigerant is needed in the system, triggering the compressor to restart. The other options are incorrect because closing the expansion valve (A) or the solenoid valve (D) would actually decrease the suction pressure, which would not cause the compressor to restart. Decreasing the suction pressure (B) would also not trigger the compressor to restart, as this is the condition that causes the compressor to shut off during the pump down cycle.