The Natural Philosopher wrote in message ...
Rick Dipper wrote:

I had this issue, the opening was too tall, the local fire shop sole me a
small "hood" to fit in the top or the opening.



Ok, I hjad this problem in SPADES when the dumb builder built my
inglenooks.

There is a page on the web that I discovered that covers this all in
detail.

There are a few salient points you need to know.

The most important is that the fire APERTURE - if you like the area
bounded by the grate, the sides of the fire and the lintel over teh top
of it should be no more than 5, or at most 7 times the cross sectional
area of the flue. Any more than this and the velocity of air being drawn
into the fire will not be enough to suck stray smoke into the fire etc etc.

I'm not disagreeing with this comment, but it is possible to work with
aperture ratios approaching 14 if the entry to the chimney is funnelled.
Most standard fire places use an angled restictor throat at the entry to the
chimney, to produce a pressure change which aids gas flow. Sorry, I can't
remember all the details, perhaps someone else can enlighten us. When I
researched the problem of building fireplaces, I found that all the
experienced fireplace experts, said "Try it and see if it works!, but allow
for a fanned flue if it doesn't!!"
I'd agree however that some form of a reduction in aperture is probably the
easiest solution. It's probably worth asking a few questions of an
experienced fireplace showroom, they may have an off the shelf solution for
a few pounds.
Regards
Capitol