Andy Hall wrote:

On Tue, 13 Jan 2004 23:00:11 GMT, Harry Bloomfield
wrote:


It is never more efficient to leave the heating on for a period than to
turn it off.


It can be, depending on the thermal behaviour of the house and the
control system. Systems with setback, optimum start and outside
temperature compensation can result in little or no temperature
overshoot at the wrong times and more accurate temperature control
than where a simple thermostat and timer is used.



That is what I am finding - not that I have the gubbins.- but where huge
thermal masses are involved..

See if this makes sense.

You have a well insulated house but with a big slab of concrete floor.

In order to feel warm in this house not only does the air in the house
have to be warm, but the floor has to get warm too. In the meantime to
compensate for the cold floor the air in the house has to be warmer than
it otherwise needs to be. During this period it loses MORE heat per unit
time than it does once everything is up to temperature.

If this extra heat loss exceeds the savings by having it overall cooler
at might/during the day etc, then you have a net loss.

In my case, it seems to make very little difference which way I play it
to fuel consumption.