On Tue, 07 Feb 2012 22:33:02 +0000, Roger Mills wrote:

But are the costs involved in designing/buying/installing extra
control systems less than the cost of gas saved?

Say the parts cost £30, stat, enclosure(s), cable, connectors etc
not
unreasonable. How much gas can you buy for £30, how long would
that
keep the place above 13C.

Don't know for sure, but the economics are completely different from
pond heaters. When we are in the flat in the winter, the marginal cost
of gas is about £2.50 per day to heat the place to a comfortable
temperature during waking hours. If it costs (say) a fifth of that (50p
per day) to keep the place at 13C on a 24x7 basis, that's £15 per month.

They seem sensible ball park figures, though I'm sort of surprised
that you need £2.50 of gas/day. At 10p/kWh (and I don't think gas is
that expensive, 5p/kWh more like it?) that is 25 to 50 kWh of energy
which seems a lot for flat.

With the "waste" heat from the neighbours I don't think you'd need
50p/day (5 to 10 kWh) to keep it above 13C as I don't think it would
get that cool very often. That temperature gradient thing again as
your place cools the greater the temperature gradient and the more
heat flows from your neighbours into your flat. B-)

A temp logger will show the temperature profile but not how much
energy has been used. You need to take readings from the gas meter
for that.

Quite possibly. I don't *think* it's going to freeze if unheated - but
the worrying bit is that I would no longer be insured if it *did*.

And the damage to the flat below could be quite expensive, new
ceilings, replaster walls (or replace plasterboard), carpets,
decoration, perhaps some furnishings...

Interesting - thanks. The only trouble with that one is that the battery
has to be replaced every month,

I did say "Cheap one at random from the first page", unless it's a
really wierd battery I'm sure a larger capacity one could be
attached. Seems a bit odd to have an 83 day logging cycle but only a
30 day battery life. But didn't you say you use the place one week
out of every four so it's only empty for 21 days. B-)

.... and the software doesn't appear to run on anything later than XP.

The Lascar website says that the software for the -LITE and -1 temp
data loggers runs under "Windows 2000/XP/Vista/7". Both are "suitable
for new designs".

--
Cheers
Dave.