Question 109Refrigeration & AC - 1st Asst/Chief

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 stop the compressor when the suction pressure drops to a preset low level, indicating that the refrigerant has been pumped out of the evaporator. When the suction pressure then increases, it signals that more refrigerant is needed in the system, and the compressor will automatically restart to replenish the refrigerant charge. The other options are incorrect because decreasing the suction pressure (A) would cause the compressor to shut off, closing the expansion valve (B) would have no direct effect on compressor restart, and closing the solenoid valve (D) would also not trigger the compressor to restart during a pump-down cycle.