CentriPro M10412 4" Submersible 3-Wire Motor 1HP; Single Phase, 60Hz is designed and sized for installation in 4" diameter or larger water wells. Three wire motors are a capacitor start induction run design and require a control box with a starting relay and capacitor. Use the CSCR capacitor start/capacitor run control boxes on ½ - 1 HP motors to increase efficiency and motor life and reduce energy consumption.