SMPW wrote:
My existing floor standing boiler has now died on me and I have now
the opportunity to buy and install a more efficient boiler. The
problem is that the house (1901 circa) has the original single pipe
system (mild steel pipe work) that is gravity fed and runs
throughout the whole house servicing 20 rads.This in itself seems to
be a problem if, as per building regs I go down the line of
purchasing a condensing boiler, as I believe there are a number of
issues.
British Gas have a policy where buy they won't touch the system as far
as the installation of a condensing boiler is concerned and GASFORCE
quoted £10k to install a 65 kw commercial boiler (the new boiler would
be sited about 6ft from the old boiler) which to me seems a rip off.
My preference would be to for a condensing boiler if it can be
installed and provide the efficiency over a non - condensing boiler,
although I have yet to speak to a plumber who
can give consistent advice. Would it be better to go for a high
efficient gas boiler assuming I get an exception cert.

Commercial boilers are very expensive. I would consider using 2 domestic
boilers. I would have a separate pump for each with a non-return valve in
case one of the boilers goes out of action or choose to run just the one.