wood burning stove

[mailstarclipper]

Has anyone had success installing a woodburning stove in a 1960's bungalow fireplace. I did it last year and although not burning wonderful it was far better than the open fire. Now it tends to spoke more with the odd puff coming out through the air vents. As the fireplace only had a 4 inch wide gap by 14 inches long and the flue from the stoove was six inches I made a stainless adapter so that the 6 inch flu goes into two four inch flues. Any ideas please to improve it.

Thanks

Smokeyone

PS No blockage in the chimney.

[andrewpreece]

Several things: there is an optimum ratio of fire inlet size to flue size ( areas and if you stray too far from it ( i.e. the flue is small and the frontal inlet area of the fire is large ), you will get problems. Offhand I do not have the exact figure for that ratio, I'm sure you can find it out if you want to. Second, alot of these fires require a class A flue, which I believe is at least 16 feet high. The positioning of your chimney may affect the fir, as really your chimney needs to exit well above the roofline. If it emerges off centre on your roof and below the highest point of your roof, that can cause problems.

Other things to look at are downdraughts, caused by gusts or eddies of air spilling off nearby obstructions: to counteract them various chimney pots with baffles or complicated H shapes are available. Also, I hear differential pressure from one side of a house to another ( think prevailing wind raising pressure on one side and creating low pressure on the other ) can cause problems if you have a window or vent open on the low-pressure ( leeward ) side.

Andy.

[mailstarclipper]

Thanks very much for all the info. I'll look into all the points you mentioned. Just off hand the chimney is on the roof centre line, around

20 feet up I would guess. However the chimney top is only about two feet above the centre line.

Smokeyone

[sylva]

I,ve not tried a bungalow

Odd puffs point to buffeting or wind more than lack of draw.

Six inch flue has a cross section of 28sq inch Two 4 inch flues have a cross section of 25sq inch plus more surfaces to drag the flue gas velocity down.

14" by 4" fireplace exit, 56sq inch, is intended to form a Coanda or Benouli effect, by speeding up the flue gases, and thus creating a small depression at the top front of the fireplace (idea first proposed by Count Rumford IIRC). You don't need this with the enclosed stove.

You could try flaring a 6" flue section to the 14 by 4 opening to cut drag but really you want to maintain the 6" flue at a constant diameter all the way up, to keep flue gas velocities constant and avoid cold spots where condensation could occur.

Building regs will normally require a double skinned flue for this sort of installation.

Also consider one of the proprietary chimney cowls that divert wind entering their sides upward and thus create a draw on the chimney.

AJH