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.
The second point is that starting fires with e.g. papaer and damp
kindling, does not produce enough heat to overcome the resistance of the
cold air trapped in the flue. Many canadian contributors to the sites I
found that - especially when they had chimneys running up an outside
wall - they needed to get a small blaze going first to 'start' the
chimney. This efect is worsened if the flue is longer and not vertical:
It takes more to start it.
In my case I am in teh process of installing giant cowls to reduce the
effective area of 'draw'...so far with pretty decent results. I couldn't
get teh aperture down to ideal, but its now small enough that it takes
some severe sideways draught to allow a little somoke to escpae. ...in
your case a simple strip along the top of the fire may be enough, or it
may be more aesthetically pleasing to simply raise the grate. My in-laws
have an amazing fire which is actually in the MIDDLE of the wall, with a
log store underneath. Just raising the grate on a couple of blocks
should be enough to stop the problem, or you can test by taping a sheet
of cardboard over the top of the fire aperture.
To ensue the chimney 'starts' well, you need s good blaze from the word
go. That means newspaper and dry kindling, or better a firelighter, or
even as I sometimes do, ten minutes with a plumbers blowlamp to get the
fuel going. Once the cghimney is going, you need to mae sure the room
has adequate ventilation - I have underfloor ducts for the fire to avoid
draughts, they work very well. ANY negative pressure in the room will
stop the fire drawing, sister-in-law had a dreadful fire that wouldn't
draw unless the doors were open. Eventually it was left unattended and
burnt the house down. Literally and seriously.
So the key to a good fire is not too much aperture to flue, warm flue,
and adequate room ventilation and a decent hearth space to avoid
exploding material getting onto flammable stuff. The latter two points
are covered by building regulations which are utterly sensible and
should be studied and applied (or exceeded) rigorously. The design of
flues and apertures is a lost art these days, and should be the subject
of intense google searches for what info there is out there.
Rick
On 4 Dec 2003 11:27:44 -0800, (Tim Pollard) wrote:
Hello
I am new to this group but I'm hoping some fireplace expert can point
me in the right direction with a solution to a problem with my new
fireplace.
I recently extended my living room which would have resulted in my
existing fireplace being off centre. To solve this, my builders
blocked up the old fireplace and made a new opening in the new centre
of the wall, joining this to the existing chimney about 2 metres up.
The chimney is a 30s unlined one. The connection beteween fireplace
and chimney is by a clay flue pipe. The displacement (ie. amount the
fireplace was moved) is about 1.25m.
Now the old fireplace drew perfectly - except it was a 70s built rough
stone horror (just like my granny had in her bungalow built in 1972).
The new one has only been used once, but a small proportion of the
smoke 'leaked out' into the room, making its use a bit untenable! It
wasn't enough to suggest that the chimney was blocked, but rather that
the chimney wasn't drawing as well as it had.
I suspect that the problem comes from a number of factors:
- The opening is taller than it was, so there is a bigger gap between
grate and flue. The builders made a brick insert in the shape of a
gothic arch, 85cm high by 58 wide, 35 deep. The old opening was lower
- around 70cm, I think.
- The clay pipe is roughly 25cm x 25cm, which I suspect is less than
the old one (but I have to be honest and admit that I never did stick
my head up the old opening).
- There is now a bend in the flue which (maybe) reduces the draw
efficiency.
Can anyone tell me what is likely to be the problem and how I should
solve it? I had wondered whether buying a hood to reduce the distance
between the fire and the effective top of the opening would help? If
so, does anyone know where I can get one in the South London (Croydon)
area?
When I'm feeling brave I intend to try putting the grate up on bricks,
to see if raising it closer to the top of the opening will improve
things. Sensible or just a license to smoke some people?!
Any other ideas would be most welcome!
Tim P