In article .com
, Mad_Trev writes
I think you may have answered your own question here. I have no
idea why it would stick 50cm out from the wall, if a normal coaxial
flue, and though I haven't looked at the pdf file, I suspect it will show
a streamlined looking cowl poking no more than 10cm out of the wall, if
that.
It may be possible to mount it completely flush with the wall, especially if
you
flare the opening in the masonry slightly. You need to examine the regs for
the positioning of flues, there may well be one in the pdf files on the
chaffoteaux
website.

Andy, thanks very much for your help. I looked on the previous page of
the installation booklet and they seem to want the exterior flue tube
to protrude slightly from the outside wall and then the interior flue
tube to protrude from the exterior. Your suggestion of recessing the
whole caboodle makes sense to me (speaking as a fairly dazed novice)
and then perhaps banging a highly permeable vent on the outside to
satisfy the grille fetishists at city hall. I've taken the liberty of
drawing a picture (sorry, it's a stoopid BMP) of what I think it would
look like: http://oreneta.com/baldie/flue.bmp

A fine sketch :-): If you recess the lot behind a single grille you may run
into trouble with the exhaust air not dispersing properly and recirculating
back into the inlet which would upset the boiler's operation.

Try a bit of parallel thinking, the exhaust flue (in the middle) sticks out
furthest to separate the inlet a & exhaust gasses, ok if that can't be done,
think about separating them another way, fabricate (or have fabricated) a
collar that will allow the exhaust pipe to stuck through but will cause the
inlet gasses to be drawn from the side, attach a short duct to this to draw
inlet gas from say a foot away from the exhaust. Then recess both inlet &
exhaust behind separate grilles. Note that such a collar/arrangement is in
common use with many boilers to convert concentric to separate flues,
even if they are not available for your boiler you may be able to source one
for another boiler to use as a starting point.
--
fred