Zone Control Valve
Zone Control Valve is a system designed to separate the area in case of maintenance and to get the indication of fire zone on a combination of Butterfly valve, Flow Switch, Pressure Gauge and Test & Drain Valves.
For electrical zone valves, the motor is often a small shaded-pole synchronous motor combined with a rotary switch that can disconnect the motor at either of the two stopping points (“valve open” or “valve closed”). In this way, applying power to the “open valve” terminal causes the motor to run until the valve is open while applying power at the “close valve” terminal causes the motor to run until the valve is closed. The motor is commonly powered from the same 24 volt ac power source that is used for the rest of the control system. This allows the zone valves to be directly controlled by low-voltage thermostats and wired with low-voltage wiring. This style of valves requires the use of an SPDT thermostat or relay.
Zone valves can also be constructed using wax motors and a spring-return mechanism. In this case, the valve is normally closed by the force of the spring but can be opened by the force of the wax motor. Removal of electrical power re-closes the valve. This style of zone valve operates with a perfectly ordinary SPST thermostat.
For vacuum- or pneumatically operated zone valves, the thermostat usually switches the pressure or vacuum on or off, causing a spring-loaded rubber diaphragm to move and actuate the valve. Unlike the electrical zone valves, these valves automatically return to the default position without the application of any power, and the default position is usually “open”, allowing heat to flow.