W.E. Anderson, ZV1234-NO, Series ZV1 Two-Way Zone Valve, 3/4" BSPT, 24 VAC, NO Economical, Manual Override ZV1 Series Zone Valves are ideal for flow control in hot and cold water HVAC systems. Zone valves are typically used in conjunction with a thermostat to control room temperature. The ZV1 is electrically driven to open and spring to close. Easy to install these units are direct replacements for competitor units. Manual override lever is easily accessible externally.