Regulates Supply Water Temperature to Heating System, Simultaneously Controls Boiler and Injection Pump Speed Use the PC705 Variable Speed Pump Mixing Control to regulate the supply water temperature to a heating system by simultaneously controlling a boiler and the speed of an injection pump. Based on the outdoor air temperature, the PC705 Variable Speed Pump Mixing Control continuously adjusts the boiler differential to optimize the firing cycles of the boiler, prevent large water temperature swings and increase the efficiency of your system. As the heating load changes, the Taco Mixing Control automatically adjusts the injector Circulator, increasing its speed as load increases and slowing it with a decreasing load.