Parallel compressors in a rack system may use:

In a rack system with parallel compressors, using both common suction and discharge headers is a practical design choice. This approach allows multiple compressors to efficiently share the workload and improves the overall performance of the refrigeration system.

Using a common suction header enables all compressors in the rack to draw refrigerant from the same source, ensuring consistent pressure and temperature throughout the system. This setup maximizes the efficiency of the compressors, as they can better balance the refrigeration load and provide a more stable suction pressure.

Additionally, having a common discharge header allows the refrigerant that has been compressed by the different compressors to be routed through a single path toward the condenser. This configuration optimizes the flow of refrigerant and helps maintain proper pressure conditions within the system, ensuring effective heat rejection.

The incorporation of both common suction and discharge headers enhances the reliability and efficiency of the refrigeration system by improving the synchronization between the compressors, allowing them to work together seamlessly. This is particularly important in applications that require consistent cooling performance and energy efficiency.

In contrast, the other options suggest limitations in the design of the system, which may not take full advantage of the efficiencies that a rack refrigeration system can provide when using both common suction and discharge headers.