In message , Dave Fawthrop
writes

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.

Objective is to save space.

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.

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

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


Dave,

AFAIK, You have to look at Heating and DHW separately. Whilst 10Kw might
be enough for Heating, you need much more to get a decent temperature
rise and flow for DHW. It looks like 24Kw gives a 9l/m flow with a 35C
rise in temp, and you wouldnt want any less than this. In fact, having
had 24Kw boilers, I would definitely buy a more powerful one the next
time - for DHW, not heating.

Hope this helps - Others who are experts may give a better answer.

--
Richard Faulkner