Guide to Heating System Zone Valves: All You Need To Know
A central heating system distributes heat from a central location to a building or room. These systems generally treat the whole house as one big room and depend on single temperature settings and readings to determine when to turn on or off the heat.
This makes it ineffective, as it only regulates the temperature of a room from the location or point where the thermostat is installed.
Creating zones inside your building can help you improve efficiency and temperature comfort by giving you more control over where and when hot water is delivered to your radiators.
Understanding Heating Systems with Split Zones
To understand better how this system operates, take a quick look at the illustration in Figure 1 below. It shows a two-story building having "Zone A" and "Zone B." Different thermostats on each level independently regulate the two zones, and they can be set or scheduled to the required temperatures. Whenever the thermostat detects that it is time to warm the room, an electrical signal is sent to a zone valve, opening hot water flow towards this zone.
Auxiliary limit switches are used in some zone valves to identify whether the valve is entirely open or closed. These switches have signals often used to initiate hot water pumping by activating a pump (circulator) and a boiler. The water then circulates through the circuit, heating the zone until the associated thermostat's temperature is attained. When the limit switch is reached, it sends a final signal to shut the valve and release the limit switch.
Design Considerations for a Zone Valve Heating System
When designing this system, zones can be added to an existing central heating system or built into a new system. Below are key design features to keep in mind to ensure that the system functions well throughout its lifetime.
Zone Valve Type
There are different types of zone valves, but the electric ball valve is one of the most preferred. This is mainly due to their longevity, the slow-close feature that prevents water hammers, high reliability, and low power consumption. When the necessary signal is received, an electric motor inside this valve rotates an internal ball with a bore a quarter round to either open or close the valve.
It does not require any more electricity to stay in either the open or closed position. The valve can sometimes be operated manually through the lever in case of a sudden/scheduled power outage or for testing purposes.
Due to the often high water temperatures, you need to choose specific materials for housing and the seal. For better performance throughout the system's life, you want to choose brass as the valve's housing, EPDM for the O-rings, and Teflon or PTFE for the seal.
Zone Valves Location
The zone valves can be installed close to the circulator (on the hot side) and boiler or towards the end of the zone circuit (cold side). Locating the valve on the cold side helps minimize the chances of potential damage.
Location of Thermostat
Since each zone needs a thermostat to sense and help control the temperature, you should have them installed in an open space and far from an immediate heat source or a refrigerating/freezing unit, as this could lead to incorrect temperature readings.
The size of the building, pressure drop due to valve orifice, length of heating pipes, and the number of zones must all be taken into account to ensure that the circulation pump can provide enough pressure to transport water through them.
Ensure the valves are easily accessible in case of failure. This will also enhance a smooth repair during regular maintenance and repair. Some of the failures common with heating system zone valves include:
In a central heating system, zone valves regulate hot water distribution to the building's different areas (zones). They are often preferred for their extra comfort as well as energy savings. These valves exist in various shapes and sizes, but ball valves with electric actuators are a popular choice for this application.
The latter closes slowly (no water hammer), saves energy, and is durable. If you are figure out the exact zone, find advice from professional.