Every refrigerating system must be protected by which device?

The correct answer is that every refrigerating system must be protected by a pressure relief device. A pressure relief device, such as a pressure relief valve, is crucial for maintaining safety and ensuring that the system does not exceed its maximum allowable pressure. In the event of a malfunction or blockages within the system, pressure can build up to dangerous levels. The pressure relief device is designed to open and release refrigerant when pressure exceeds a predetermined threshold, preventing possible explosions or catastrophic failures. This is a critical component in safeguarding not only the equipment but also the personnel working with or around the refrigerating system.

In contrast, a manual shut-off valve is primarily used for isolating parts of the system for maintenance and does not serve as a safety mechanism for pressure control. A vacuum gauge measures suction pressure and is useful for system diagnostics but does not protect against overpressure scenarios. An expansion valve regulates the flow of refrigerant into the evaporator for proper cooling but is not related to pressure safety directly. Each of these components plays important roles in a refrigerating system, but only a pressure relief device specifically addresses the critical need to manage excessive pressure and ensure safe operation.