Fredxx wrote:
On 26/04/2012 21:12, kent wrote:
On Thursday, 26 April 2012 20:25:40 UTC+1, YAPH wrote:
On Wed, 25 Apr 2012 12:51:19 -0700, kent wrote:

Oh dear, I didn't mean to stir the s*** ! Does this mean I am
unlikely to get any rational answers?!

No, it just means you are likely to get some irrational ones ;-)

Multiple boilers in larger properties is quite a sane idea.
Generally, however, they are ganged together so that either
boiler can run quite efficiently at the lower output required for
heating in spring and autumn- ish weather, with both coming on
together for winter loads. This also gives a degree of fault
tolerance as a fault in one boiler doesn't leave you entirely
without heating, and may not even be noticed in milder weather.
However the controls required (including a mechanism for
detecting that just one boiler has failed, before the other one
goes as well and you really don't have any heating!) is more
complicated and/or expensive. Combi boilers aren't generally ganged
though: in the larger
properties in which ganged boilers would be called for the hot
water demand (e.g. multiple bathrooms etc) is likely to be
greater than even 2 combis working together can supply.

However a 4 bedroom house isn't large enough to likely require
more power for heating than a single domestic boiler can supply
(and if it does you'd be better advised reducing the heat losses
than adding boilers!) Given that the hot water requirement is the
critical factor then some form of stored water system
('Megaflo'-type unvented, or thermal store/ heat bank) or just a
storage combi (e.g. Worcester's Highflows) would be more
appropriate. If you are seriously concerned about backup for when
the boiler goes down a stored water system with immersion heater
and a few cheap convector heaters stored in the attic should do
the trick. --
John Stumbles -- http://yaph.co.uk

The astronomer married a star

Well John it certainly has made for some interesting reading and
encouraged me to look a few technical points up on the internet. The
conclusion I have come to is that for our four bedroom house I
just need a condenser boiler to replace our old regular one (making
sure that the condensing pipe is not in a location where it might
freeze up) and install an electric shower if we really do want
three people showering at the same time! Any idea how much just
replacing the boiler might cost (with labour, not diy)? The idea of
having combi's really came from my wife who wants the airing
cupboard space! Anyway, thanks to all for your comments and
suggestions.

I use Thunderbird and I can't see how to fathom out word wrap issues
either!
I recall a friend who's combi boiler went u/s before Christmas. The
old one was classed as non-repairable, or should we just say that a
couple of plumbers couldn't repair it as it's must easier and remunerative
to
install a new one.

A simple boiler change 5 days before Christmas cost £1,600 on a
boiler I could have got for £500. So the idea of immersion backup
and some electric heating sounds eminently sensible.

Perhaps Adam will be here shortly to advise on power diversity rules
regarding 3 showers?


I would suggest sharing a shower with 2 friends. It saves on all the
diversity calculations.

--
Adam