(57) The present invention relates to the control of a central heating system.
The system includes a condensing boiler 1, a pump 3 operable to pump hot flow water
leaving the boiler 1 around a circuit having two branches 6 and 7 and an electrically
operated diverter valve 4 operable to direct the flow water to flow into one or other
of the branches.
The branch 6 includes radiators 8 to provide space heating by release of heat from
the flow water and the branch 7 includes a calorifier 10 for heating water stored
in a cylinder 9.
The control unit includes a cylinder thermostat 16, a room termostat 17 and two pipe
thermostats 18 and 19. The thermostat 18 is mounted on the pipework in the space heating
branch 6 downstream of the radiators 8 and the thermostat 19 is mounted on the pipework
in the hot water branch 7 upstream of the cylinder 9.
When both hot water and space heating are required the boiler is operated and hot
water is directed by the valve 4 to flow into the space heating branch 6 until the
water reaches a preset level at the point where the thermostat 18 is mounted. At this
stage the thermostat 18 switches from position e to f and the valve 4 directs the
water to flow into the hot water branch 7. When the water temperature reaches a higher
preset level at the point where the thermostat 19 is mounted it switches from position
g to h. If thermostat 18 has switched back to position e because the temperature of
the water at the thermostat 18 has fallen to below its preset level, the valve 4 directs
the water to flow into the branch 6. The process is then repeated.
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