Pressure vessels of 10 cubic feet (0.28 m3) or more internal gross volume shall use one or more rupture member(s) or dual pressure-relief valves where discharging to the atmosphere. Dual pressure-relief valves shall be installed with a three-way valve to allow testing or repair. Where dual relief valves are used, the valve shall comply with Section 1113.5.
Exception: A single relief valve shall be permitted on pressure vessels of 10 cubic feet (0.28 m3) or more internal gross volume where in accordance with the following conditions:
- The relief valves are located on the lowside of the system.
- The vessel is provided with shutoff valves designed to allow pumpdown of the refrigerant charge of the pressure vessel.
- Other pressure vessels in the system are separately protected in accordance with Section 1113.1. [ASHRAE 15:126.96.36.199]