What safety device is used to prevent excess pressure in a refrigeration system?

In a refrigeration system, the safety device that prevents excess pressure is the pressure relief valve. This valve plays a crucial role in protecting the system from overpressure situations, which can occur due to various factors such as high ambient temperatures or a malfunctioning component. When the pressure in the system exceeds a predetermined level, the pressure relief valve opens to allow refrigerant to escape, thereby reducing the pressure and preventing potential damage to the system components or even catastrophic failures.

The other devices mentioned serve different functions within the refrigeration system. For instance, a thermostat primarily regulates the temperature by controlling the operation of the compressor based on the desired setpoint. The compressor itself is responsible for circulating refrigerant throughout the system, compressing it to facilitate heat exchange, but it does not specifically prevent excess pressure. The expansion valve, on the other hand, controls the flow of refrigerant into the evaporator, and while it plays a role in ensuring efficient operation, it does not have the safety function of relieving excess pressure. This distinction highlights why the pressure relief valve is essential for maintaining system safety and operational integrity.