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| The 'CH ON' output from the
programmer applies live, via the room thermostat, to the white wire of the
valve. The 'HW OFF' output is also live as the hot water is set to off.
This applies live to the grey wire. As can be seen from the table (above),
live on both white and grey will cause the valve to take up the 'A'
position. When the valve reaches this position, a micro switch inside the
valve will switch the live coming in on the white wire to the orange wire.
This is used to feed the boiler and fire the system.
When the room thermostat is satisfied, the contact will open thus removing the live from the white wire. This, in turn, will remove the live coming back down the orange wire and the boiler will shut down. In the diagram above, the pump will continue to run via the 'overrun' thermostat in the boiler. This is to disperse latent heat in the boiler and prevent possible damage. If the boiler does not have this facility, the pump will be fed from terminal 8 (same as the boiler) and will shut down at the same time as the boiler. |
