ALPHA2 15-55F 3-speed cast iron booster pump with a 1-1/2" flanged connection and terminal box, as well as, a 1/2 HP, single phase, 115v motor. It has a flow range of 0-21 GPM and a head range of 0-19 feet. Featuring AUTOADAPT and constant-pressure control modes, Grundfos ALPHA2 pumps provide low energy consumption and high flexibility. This high-efficiency ECM variable speed circulator is designed for a wide variety of heating and hot water recirculation applications.