Geothermal series Zone Valves by Taco are designed for use in geothermal systems which have high head and allow water into the coil before the heat pump starts. It's a heat-motor, 2-way zon valve with 3-wire terminal block connection, 24V power supply and an end switch. The valves are made of bronze and have a removable powerhead, which allows to service the valve without draining the system or replacing the entire zone valve.