In article ,
Dave Fawthrop wrote:
I am thinking of replacing my conventional central heating and hot
water system with a gas combination boiler, for my four bedroom
extended semi, with one bathroom. My present system is 25 years old,
when I did the heating calculations and ended up with a 10kw boiler,
which works perfectly well with ample heat output, even in the coldest
weather. When I did the heating calcs, the house was *very* well
insulated, and I have continued adding insulation/double glazing over
the years, so it is now *extremely* well insulated. I am therefore
looking for a combi with less than 10kw output to central heating,
plus enough say 10l/m to the DHW.

With a modulating condenser, the maximum heat output isn't so much of an
issue, since unlike older boilers it will actually increase efficiency
when not running at full output.

Objective is to save space.

Then it's a good choice.

I have looked in Google Groups for old threads, and tried to answer
the questions which may be asked.

Kitchen tap gives 16l/m
Bath tap hot water gives 9l/min
Soft water.

This is the existing storage system? Normally, the bath is fed from larger
bore pipe and should give much better flow - even although if a floor
higher and with less 'head'.

Googleing for combination boilers only gives huge 20+kw models does
anyone here know of anything smaller?

With a combi, you need to size it for decent hot water flow - especially
if you like big baths. This is the real problem with them - they generally
can't fill a bath anywhere as fast as a *decent* storage system.

As I will now be pressurizing the central heating pipes (copper with
Yorkshire fittings) does anyone expect problems with this?

No - they'll be fine.

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Dave Plowman London SW
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