R3G220-RD53-03 Fan Blower, RadiCal R3G220 RD Series, IP54, EC Centrifugal. RadiCal fans are one piece backward-curved impellers made of high-tech composite material. These centrifugals feature highly efficient GreenTech EC technology providing low-pressure solutions with backward-curved blades, used primarily as intake fans and do not require a scroll housing.