At what pressure would a relief valve in a refrigerating system typically start functioning?

A relief valve in a refrigerating system is designed to operate at a specific pressure, known as the design pressure. This pressure is determined during the system's engineering and design phase, ensuring that the system can handle normal operating conditions without exceeding safety limits. When pressure within the refrigerating circuit approaches this design pressure due to a malfunction or temperature increase, the relief valve opens to prevent overpressure, safeguarding the integrity of the system and preventing potential hazards.

In contrast, the other options refer to pressures that do not align with the intended function of a relief valve. Ambient pressure varies with environmental conditions and is not relevant to safety mechanisms in a closed refrigerating system. Maximum operational pressure refers to the highest pressure the system is expected to reach during regular operation, but the relief valve should activate before this point to prevent reaching hazardous levels. One atmosphere represents a standard pressure at sea level, but it has no connection to the specific operational or safety parameters of the refrigerating system. Thus, the design pressure is the correct reference for when a relief valve should begin functioning.