Working of motorised valves in home heating systems?
Answer:
Systems that heat the home by circulating hot water through radiators or baseboard radiators can have individual control of the temperature in each room or group of rooms by using thermostatically controlled motorized valves to control the water flow.
normally a home heating system would only have 2 motorised valves, 1 for the hot weater and one for the heating (hot water cylinder).
you could have additional motorised valves if it weas a large property and you wanted to seperately control different areas of the house.
the demands of the system (water needs heating or area needs heating) will cause one of the motorised valves to open (the thermostat energises the relevant valve), when the motorised valve is fully open a end stop microswitch will cause the boiler to come on (and in some cases also energise a circulation pump).
if the valve sticks open then the boiler will continue running causing the area to become too hot or overheating the hot water (danger of scalding).
the valves on radiators are not normally motorised, instead they are thermally operated, the heat causes them to expand slightly, restricting the flow of water through the valve.
There are also two very similar types of "three port" motorised valves.
One port, the inlet port, is where the flow from the pump enters, pumping hot water into the valve body.
One port, one of the two outlet ports, is connected to the heating coil in your hot water copper cylinder,
The third port, the second outlet port, is connected to your central heating radiator circuit.
Hence the "motor" part of the "motorised valve" is actually a small electric motor, and it is controlled by your hot water and central heating control system (including roomstat).
The motor can turn the valve to direct flow from the pump to your hot water cylinder, so your hot water gets heated up; and it can turn the valve the opposite way to direct flow from the pump to your central heating pipes, so that your radiators heat up. This depends on what your hot water and central heating controller is telling it to do (there is a version of the valve where both central heating and radiators are both connected to the pump flow).
The valve has a brass body, "T" shaped with three pipes connected, and it has the "motor" part bolted to the body. In the event of motor failure, it is possible to just replace the motor, otherwise the whole valve can be replaced, but at higher cost.
coomon set up is:
two motorised valves (open /shut is governed my the programmer)
newer systems have a bypassvalve (this is usually spring loaded, varaible to enable system balance)
central heating water is usually hotter than domestic hot water and the valves he valves are opened according to requirements.
when your thermostat on the hot water tank reaches it setting i.e 50 c it will shut.
if the heating is still on this valave will be open , when the heating reaches the room temp this valve will also shut and as there is no call for hot water boiler shuts down ,
(can be other way roud of course)
this is where the bypass valve comes in . it acts as a bypass as the two valves are shut and is adjusted to meet the pumps pressure by the spring loading.
in old sytems the boiler shut down end of story , in newer systems the pump will "run" on until the boiler residual heat has all gone (there is a stat in the boiler linked to pump for this) this means more efficient heating
hope this helps
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