On 07/03/18 07:30, Jim K wrote:
The Natural Philosopher Wrote in message:
On 06/03/18 16:54, wrote:
We have a large open fireplace with a cast iron fire basket, but we only
burn logs so I'm considering whether to remove the basket so we can let
a layer of ash build up on the fire brick base and burn on that. Any
comments from those who burn logs in open fires?
if the flue is designed to run with a basket, ou may get smoke escaping
of you lower theh combustion area


I have seen pubs ho have done this raise the thing back with a layer of
bricks..

I suspect there were other (possibly h&s) considerations at work
there, a few inches of hearth height shouldn't have much effect
on open fire flue draw.

Its not a question of draw - its a question of aerodynamics.

I had to reserach all this totally when my builders made a cockup of
making an open fireplace.

In generat the rule of thuimb is that te aperture the place where the
air comes in ABOVE the fire - should be no larger than 3, or at worst 4
times the area of te flue at a reasonably local point.

That makes the inflow speed fast enough to pull the smoke up the chimney
not wander around the room.

I had to fit smoke hoods to achieve this






--
"Anyone who believes that the laws of physics are mere social
conventions is invited to try transgressing those conventions from the
windows of my apartment. (I live on the twenty-first floor.) "

Alan Sokal