The HP727-S is an innovative, microcomputer-based single speed controller designed for use in outdoor swimming pool heat pumps. The control features 3 digit LED display, and three push button keys for easy adjustment. The HP727-S monitors both water and evaporator temperature using precise thermistor sensors, and controls the compressor, evaporator fan and circulating pump. In addition, complete diagnostic messages are displayed on the display, which simplifies installation and troubleshooting.