What safety device prevents the startup of a centrifugal refrigeration compressor?

The correct choice is the vane closed switch, which plays a crucial role in the operation of a centrifugal refrigeration compressor by ensuring safe and efficient function during startup.

A centrifugal refrigeration compressor relies on proper airflow and refrigerant flow to operate effectively. The vane closed switch detects the position of the vanes in the compressor. If the vanes are closed, it indicates that the compressor is not ready for operation, potentially preventing damage from starting under incorrect conditions. This switch acts as a safeguard to inhibit the compressor from starting until it is confirmed that the system is in the correct state for operation.

In contrast, while high pressure switches, low temperature switches, and liquid level switches serve important roles in refrigeration systems, they address different specific concerns. High pressure switches respond to excessive pressure conditions, low temperature switches activate based on temperature thresholds, and liquid level switches manage refrigerant levels. However, these devices do not directly prevent the startup of the compressor based on the operational state of its internal vanes, which is the primary function of the vane closed switch.