[park381]

Originally Posted by Neil

As for the heating not working without the water on it will not matter that much. Once the water is as hot as it can be it will only take heat from the boiler as the water in the cylinder cools. With a good insulation jacket this won't be too much. When you have a thermostat on the hot water cylinder you can set the hot water temp so save energy by not having the water hoter than you need it to be. In your case you probably set the hot water temp by adjusting the temperature on the boiler itself.

Wow, think you need to have a look at the different type of heating systems available today Neil. Honeywell "Y" plan to name but one, a 3-port valve will give either hot water only, heating only, or both. If Kate's system is gravity hot water, then the boiler will cycle day and night to retain the temperature in the cylinder, that is unless it is controlled via a time clock. In other words if the boiler is running, some of the boiler output will be going to the hot water.