My brother-in-law has a traditional system boiler (not room sealed) with
the flue fed into a chimney stack that also contains the unused flue
from the living room. The building is a chalet bungalow (with loft
conversion) with numerous windows and nowhere on an outside wall to hang
a new boiler except high on the gable ends which would be (to say the
least) extremely inconvenient (and even that might fall foul of the flue
near window exclusion zone).

The boiler is getting old and he has been told by the firm that services
it that any replacement *must* be a condensing boiler and that the
replacement *must not* use the chimney. I haven't taken much notice of
developments over recent years but ISTR recent discussion that said that
lack of suitable position could make a non condensing boiler a
legitimate replacement.

I am not sure why the chimney should be a no-no these days. Is it due to
the difficulty of fitting a condensate drain or some other reason that
as yet hasn't occurred to me? If it is just verboten for condensing
boilers I presume that a replacement non condensing boiler could
continue to use the existing flue subject to modern safeguards. (I am
not sure whether or not it is actually lined but I presume it is as the
house was built as late as 1968).

--
Roger

"roger" wrote
| My brother-in-law has a traditional system boiler (not room
| sealed) with the flue fed into a chimney stack that also
| contains the unused flue from the living room. ...
| The boiler is getting old and he has been told by the firm
| that services it that any replacement *must* be a condensing
| boiler and that the replacement *must not* use the chimney.
| I haven't taken much notice of developments over recent years
| but ISTR recent discussion that said that lack of suitable
| position could make a non condensing boiler a legitimate
| replacement.

Correct about exemptions on grounds of positioning. See the thread
"Condensing boilers rule?" starting at
http://groups.google.co.uk/groups?q=...&lr=&selm=co0d
ic%24vls%241%40news.freedom2surf.net

where Andy Hall posted a link to
http://www.odpm.gov.uk/stellent/grou.../page/odpm_bre
g_032807.hcsp

However on both efficiency and safety grounds an open-flued boiler is
undesirable. Andy Hall posted a nice summary in the thread "condensing
boiler flue" at
http://groups.google.co.uk/groups?q=...l=en&lr=&selm=
0uuervc2io484foe9fkf0jao0bf11ak7dg%404ax.com&rnum= 1

(Those links are to the old version of googlegroups.)

Owain

The message
from "Owain" contains these words:

snip

Thanks.

I will follow up the links shortly. I read off line so not too easy. Cut
and paste on the first one ran into wrapping problems and the shortened
link overwhelmed with me with numerous threads.

--
Roger

I am not sure why the chimney should be a no-no these days. Is it due to
the difficulty of fitting a condensate drain or some other reason that
as yet hasn't occurred to me?

There's nothing stopping you sticking a modern condensing boiler's flue up a
chimney, besides the difficulties involved in any bends in the flue and
terminating the top without expensive scaffolding. If you go this route,
choose a boiler with a "drainpipe" flue option, such as a Celcius 25,
amongst others. These are far cheaper and more flexible than conventional
concentric flue extension pieces.

Obviously, you do need the condensate drain. Only you know the layout enough
to know if a drain is feasible.

Another alternative is to go straight up from a convenient location straight
through the roof. My boiler is in the loft with such an arrangement, as
putting it through the chimney stack seemed like too much hassle.

Christian.

The message t
from "Christian McArdle" contains
these words:

Thanks.

I am not sure why the chimney should be a no-no these days. Is it due to
the difficulty of fitting a condensate drain or some other reason that
as yet hasn't occurred to me?

There's nothing stopping you sticking a modern condensing boiler's flue up a
chimney, besides the difficulties involved in any bends in the flue and
terminating the top without expensive scaffolding. If you go this route,
choose a boiler with a "drainpipe" flue option, such as a Celcius 25,
amongst others. These are far cheaper and more flexible than conventional
concentric flue extension pieces.

If it is on the first floor then there would be less flue to worry about
being straight but would still have to break in from the side so would
require a rightangle elbow within the flue. Doesn't look too promising
to me even before I establish whether it is the boiler flue of the
living room fire flue behind the adjacent (plastered) brickwork.

Obviously, you do need the condensate drain. Only you know the layout enough
to know if a drain is feasible.

The joists run the right way for an easy run through the floor void on
the first floor at least and I think the joists run the same direction
in the kitchen should it be possible to shoehorn a boiler into the
original position for the cf boiler but that would involve a very long
vertical flue.

Another alternative is to go straight up from a convenient location straight
through the roof. My boiler is in the loft with such an arrangement, as
putting it through the chimney stack seemed like too much hassle.

It being a chalet bungalow straight out sideways would also go through
the roof and with a 45 degree pitch roof that wouldn't seem to make much
difference to the seal as it goes through the roof. It is however at the
front of the house so don't know weather the planners might get uppity.

Both potential upstairs positions would be on interior stud walls but
the one remote from the chimney (ie flue out through the roof) would
probably be better and both are reasonably close to the existing
pipework.

--
Roger