The capacity control mechanism of a compressor is actuated by what?

The capacity control mechanism of a compressor is primarily actuated by suction pressure. In refrigeration systems, the compressor draws in refrigerant vapor from the evaporator, and the pressure of this vapor is referred to as the suction pressure.

When the suction pressure rises or falls, it signifies changes in the load conditions on the system. For instance, if the suction pressure decreases indicating a lower evaporator load, the compressor may need to reduce its capacity to maintain efficiency and avoid over-compression of the refrigerant. Conversely, if the suction pressure increases, this may signal a higher load, prompting the compressor to increase its capacity to properly handle the additional refrigerant vapor.

This method of controlling capacity allows for more efficient operation of the refrigeration system by adjusting how much refrigerant the compressor handles based on the current demands of the system. This responsiveness helps in optimizing the overall performance and energy usage of the refrigeration unit.