On Sun, 7 Sep 2003 18:26:38 +0100, "GB"
wrote:

Thanks IMM and Andy for those very helpful thoughts.

I will have a look at the condensing boiler, but I was put off a bit by the
price and the extra complication. Do the govt. still give a 200
contribution?

Geoff


I'm not sure that the Big Green Boiler Scheme is running any more, but
if you compare even the SEDBUK efficiency of the two Vaillants they
are 79% vs 91%. There are arguments for and against the
measurement method used for this which is supposed to reflect
conditions in a UK house. Another approach looks at the appliance
efficiency directly under different conditions - this will also give a
10-15% difference between modern conventional and condensing
technologies. Don't be fooled by more extravagant claims regarding
condensing boilers. The figures are often stated in comparison with
much older products that had 65% efficiency or even less.

I replaced one of these old 65% efficient products about a year ago
and replaced it with a condensing model and the savings have been
pretty much as the figures would suggest.

The conventional boilers have also improved anyway, but especially
because 78% is now the minimum allowed.

A Turbomax Plus 828 at Discounted Heating is £569, an EcoMax 828 is
£928 - a difference of £359. If you amortise this across the
boiler lifetime (let's be conservative and use 15 years) then you need
to save £24 per annum in gas to make it worth it.

If you take your existing gas bill and assume that the old boiler was
probably about 60% efficient, you can work out whether this pays off.
I suspect it will.

In terms of complexity, nowadays there is not a huge difference
between non condensing and condensing system models. The main
additions are the condensate drainage arrangement which consists of a
plastic overflow pipe in most cases going to a suitable drain.
Some of the early UK manufactured condensing products did have
reliability problems, although this was largely due to poor design and
choice of materials - the condensate is acidic and this has
implications on the choices of materials.
German and Dutch manufacturers have been making them for over 15 years
and they are quite common in those countries.
I don't consider that this is a factor if you are buying a good
quality product like Vaillant. You can pretty much focus on the
energy cost difference.





..andy

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