Fire pumps must have an automatic relief valve set below which of the following pressures at minimum expected suction pressure?

The correct answer indicates that fire pumps must have an automatic relief valve set below the shutoff pressure at the minimum expected suction pressure. The shutoff pressure refers to the maximum pressure that the pump can generate when there is no flow from the discharge. This is an important consideration because if the pressure exceeds what the system can handle, it could lead to potential damage or failure of components within the system.

Setting the automatic relief valve below the shutoff pressure ensures that the system can effectively manage pressure during operation and prevent excess buildup, which could compromise the integrity of the pump and connected piping. This safety measure contributes significantly to the reliability and safety of the fire protection system, ensuring it operates within safe parameters.

Other pressures mentioned, such as start pressure, net pressure, and flow pressure, do not provide the same safety assurance under the same conditions. For instance, the start pressure is concerned with the initial engagement of the pump, while flow pressure refers to the pressure experienced at the discharge when water is flowing, both of which do not account for the risks associated with high-pressure conditions during non-flow scenarios.