The new EC Motor-Driven, high-efficiency, wet-rotor circulator pump for the residential and commercial HVAC market is designed to improve performance and save energy consumption at the same time. The unit features differential temperature control that adjusts to the system demand to maintain the best heat transfer possible. The four-speed circulator also has three HD modes of operation for proportional control as well as an Auto mode where the pump will automatically adjust to the system resistance to reach its best efficiency point with an LED display, and adjustment buttons for easy set-up. The fluid temperature range for the new Wilo-Star E 21 is 36° F to 230° F, with a maximum operating pressure of 145 PSI (10 Bar). Designed in a cast iron HT 200 pump body, it incorporates an advanced composite PA66+30%GF impeller and ceramic shaft. An optional check valve is also provided for parallel pumping applications.