Zone valves regulate temperature in different areas of a building using hydronic systems. Each zone valve has a motor unit connected to a valve body, with electronic valves being common in homes. Large buildings use compressed air or vacuum-operated valves controlled by centralized systems.
A zone valve can be used to regulate the temperature in different zones of a structure heated primarily by a hydronic system. Hydronics involves the use of heat transfer to heat or cool a structure using water as the primary medium. Areas of the facility can be artificially zoned through which the flow of water is controlled by valves. Each zone valve typically consists of a motor unit mechanically connected to a valve body. Most zone valves used in homes are electronic, although commercial and industrial applications often use units operated by compressed air or vacuum.
Hydronic systems using zone valves can include separate hot and cold water piping loops or individual integrated systems. Early hydronic systems typically had a boiler to heat the water and a chiller or cooling tower to cool the water, each of which had its own set of pipes throughout the building. Modern systems include compact units known as refrigeration boiler systems that can direct hot or cold water to a home or other structure with the use of zone valves. Each room or other area of the building can have its own zone valve to allow hot or cold water to enter the relevant pipes.
Most home hydronic systems use electronic zone valves that consist of an electric motor and valve body. The motor can be a simple alternating current (AC) unit that can fully open or close the valve depending on which side is energized, or it can be a device that is activated by heating a wax pellet. Units with wax motors are usually closed by spring action unless power is applied to the thermistor to heat the wax. Each zone valve is typically controlled from a central location, although there may be separate thermostats in each room.
In the event of a power failure or motor malfunction, electric zone valves often have a manual bypass function. This can be useful for maintaining a comfortable temperature in each zone even if the control system is not working properly. Without this feature an AC motor zone valve would remain in its last position, while wax motor valves would close by spring action.
Large buildings often use zone valves operated by a centralized source of compressed air or vacuum. In both of these cases the natural state of the valve is typically open, so the application of vacuum or pressure can force it to close. A variety of complex building management systems can be used with these types of zone valves, allowing the room to be tightly controlled from a central location.
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