The Pressure Relief Collar (PRC) slips over a diffuser inlet to provide a simple and inexpensive solution to control inlet static pressure. To limit excessive diffuser noise and pressure drop, duct static pressure should be below 0.25 in. w.g. A PRC is recommended for applications where duct pressure may exceed the recommended limit, such as installations with a constant volume air handler where multiple prodigy units are operating with a mostly closed damper. As duct
pressure increases past 0.25 in. w.g. calibrated shutters gradually open to release excess air into the ceiling plenum.