In an earlier contribution to this discussion,
keith wrote:

Please can some one tell me which is most efficient if you want to
get the central heating up to say 22 degrees in time to get up in the
morning....

Leave the thermostat on 22 degrees and have it come on earlier for
longer or
Put it on 26 &/or turn up heater temperature and let it come on later.

I've puzzled so much I'v econvinced myself both ways, but there must
be a scientific answer...
cheers

Not sure it's a question of efficiency! With the system running flat out it
will take a finite time to reach your desired 22 degrees. If you start it
too late to achieve this, you can set the stat to 50 if you like - it ain't
going to make any difference - 'cos if it doesn't even get to 22 it isn't
going to get to a level where the stat operates.

The problem is that the starting time needs to be different depending on how
cold it gets over night. The way to deal with this is to replace your manual
stat with a programmable stat such as the Honeywell CM67 with optimum start.
You tell that what temperature to achieve by when - and it works out for
itself when to start. You won't get much more efficient than that!
--
Cheers,
Set Square
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