On Fri, 14 Nov 2003 22:11:42 +0000, David C. Partridge wrote:
I'm looking to replace an ageing (1986 vintage) e.l.m. leblanc
GLM 5.32 combination boiler (conventional flue).
Both CH and DHW are 37.2kW (128000 btu/hr) net. DHW is fully
modulating, CH modulates to low as it reaches running temperature.
Amazingly for such an old boiler efficiency is quoted at 86%!
I take it you got the figure of 86% from the rating plate on the boiler,
this manufacturer seems to have no boilers listed in the SEDBUK database.
I'm fairly sure that the sedbuk figure if it were available would be a lot
lower.
Flow rate is fine for a shower. Our large bath takes a long time to fill.
If a second tap is turned on it's a bit of a disaster (especially for the
person
under the shower).
I'm considering two options:
a) replacing it with a new combi with a HIGHER DHW output
b) going for system boiler with a heat store or sealed system hot water
tank.
However the DHW store or tank can ONLY go in the loft so pipe runs and
control wiring could get a bit tricky. I'm also concerned about the
economics
of keeping this hot 24/7 (we can't predict DHW use well enough to cope with
the "on twice" syndrome).
I'm currently leaning (strongly) to the first option, but I do realise that
the second
would give better DHW flow.
I've looked at some of the modern combis, but can't find any that can match
this
leblanc which does 16ltr/min for a 35K rise (though a few models from
Vaillant
seem to get close). I don't have the space to install two smaller ones,
and would
worry a lot about finding an engineer with the skills to do this right
anyway (I could
research it and DIM, but don't have the time or the Corgi certification).
Leblanc have withdrawn from UK and no longer make any high
output boilers anyway.
There are probably some combined thermal storage combis which can give
very good flow rates until their energy store is depleted. These are in
one unit although the most capacious are proabably floor standing and
large.
Modern HW cylinders of all types are very well insulated so if you want to
go the route of using a HW cylinder you won't necessarily find it takes a
lot of gas to keep the store warm.
--
Ed Sirett - Property maintainer and registered gas fitter.
The FAQ for uk.diy is at
www.diyfaq.org.uk
Gas fitting FAQ
http://www.makewrite.demon.co.uk/GasFitting.html
Sealed CH FAQ
http://www.makewrite.demon.co.uk/SealedCH.html