Christian McArdle wrote:

I don't know what turns *your* boiler off. In my case it turns itself
off when the temperature of the water in the return path matches its
internal thermostat settings.


The boiler has to turn off properly and allow the circulating water to cool
down. This is for energy efficiency. In very cold weather this won't have
much effect, as the water won't have much chance to cool down anyway.
However, in marginal weather, where the heating might not be required for
hours in the middle of the day, considerable savings can be made.


Yes. You switch of everything, including the pump, on a time clock...



In order to promote this, hot water cylinders have to be reasonably rapid in
recovery, so that the pipes don't remain hot for long periods.


Thats why they are lagged.



Christian.