On Wed, 30 Jul 2003 12:15:43 +0100, "IMM" wrote:


"Andy Hall" wrote in message
.. .

I mentioned electronic thermostats in my
other post. Another feature
of these is setback where you can drop
the temperature at certain
times rather than off completely.
Once adjusted suitably, you will
get greater comfort. Also it can be less
expensive to run if you just
drop the temperature by 6 degrees
or so overnight rather than
completely off.

Do have any figures to prove this?

Actually yes, but first let me make the point that I did say *can* be
less expensive, not *would* be. It would depend on the circumstances
I am sure.

Remember that I said that I can gather all of the boiler data to a log
on a PC. This includes fan speed (which relates to power level and
gas usage), pump speed, flow and return temperatures and inside and
outside temperatures, as well as whether the boiler is driving CH or
DHW..

Last winter I did experiments over a few week-long periods with a 5
degree setback from 21 to 16 degrees and without setback at all.
I took out the DHW use and looked at the CH only and matched 24 hour
periods when the outside temperature pattern was similar.

There was, on average, a 3-5% lower use of gas when setback was used.


Unless it is sluggish UFH, setting the
temp back does not result in greater economy.

It isn't, but UFH is towards the extreme end of the scale in terms of
thermal inertia. A house with conventional system and masonry walls
still has a thermal inertia, albeit not as great.

In the 1960s the electricity
boards had a slogan "Lag It And Leave It", saying lag a cylinder and leave
the immersion heater on 24/7. Under tests this was slagged as highly
uneconomical. Switching the immersion on when needed or on a clock was
proven to be far more economical.

At that point it probably did. WIth today's insulation, and I have a
100mm layer around my cylinder, the heat loss is negligible - a few
watts. I therefore leave the hot water on 24*7 because it makes no
sense to turn it off. It is very rare that the boiler does a hot
water cycle between 2300 and 0700 unless hot water is drawn.
Before you ask the question, yes I have data for that as well.



..andy

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