What ensures that a centrifugal compressor starts only under no-load conditions?

A vane closed switch plays a crucial role in ensuring that a centrifugal compressor starts only under no-load conditions. This switch is designed to sense the position of the inlet guide vanes or the control vanes that regulate the flow of refrigerant into the compressor. When these vanes are in the closed position, it indicates that there is minimal or no flow entering the compressor, allowing it to start safely without the risk of damaging the unit due to excessive load.

Starting a centrifugal compressor under load can lead to a range of issues, including equipment strain, increased energy consumption, and potential mechanical failure. Therefore, the vane closed switch is critical as it effectively acts as an interlock, preventing the compressor from starting unless the vanes are closed, ensuring that the machine operates under conditions that are safe and efficient.

The other options, while related to safety and operational integrity, do not specifically ensure that the compressor starts only under no-load conditions as directly as the vane closed switch does.