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

The relief valve in a refrigerating system is designed to protect the system by releasing excess pressure to prevent potential damage due to overpressure conditions. The critical aspect to understand is that the relief valve is calibrated to operate at or near the design pressure of the system. This is essential for ensuring safety standards, as it allows the system to function efficiently under normal operating conditions while providing a fail-safe if the pressure approaches unsafe levels.

When pressure exceeds the predetermined threshold, which is closely aligned with the design pressure, the relief valve activates to alleviate that pressure. This mechanism prevents catastrophic failures that could occur if the pressure were to rise uncontrollably. Having the relief valve set at a point near the design pressure ensures that the system can operate efficiently while still being safeguarded against overpressure scenarios.

In contrast, values significantly below the design pressure would not adequately protect the system and could result in premature valve operation, wasting refrigerant and causing inefficiencies. Operating at atmospheric pressure does not apply in this context, as refrigerating systems work under pressure well above atmospheric levels. Excessive pressure thresholds, such as exceeding 20% of the design, might also pose risks, and the relief valve would not be effectively doing its job if it opened only at high-pressure situations.