Woodburner Gurus

[Phil L]

I've got a woodburner, multifuel actually, but I wouldn't describe myself as a guru. It's been installed since Oct 2011, so just over a year. I burn mainly scrap timber - door frames, windows, joists etc, the occasional tree (cherry, eucalyptus, oak, sycamore) and a little coal. I don't have a damper, the hole at the back of the burner has a 5ft piece of corrugated flue liner affixed to it and bent up into the (brick) chimney, draws well with vents open, smoulders for hours unvented and I've never had any build up of tar/ creosote. It's used daily from Oct to April, from about 5pm to midnight, using about same volume of timber as you, but this time of year, a kilo of housecoal gives off a hell of a lot more heat than wood alone, I pay £7.50 for a 25kg sack, so about 4 or 5 will last me over winter, f*ck the smokeless s**te off, and the stuff the garages try to sell at £9 for 10kg

[harry]

It depends on what sort of stove your have.

[Dave Liquorice]

Carry on.

[Tim Lamb]

The thermometer on the front of my stove is usually indicating somewhere between 175deg.C and 215deg.C. I guess the first section of flue would be similar.

Whilst not multifuel the clearview claims to meet the requirements of smoke control areas. Once warmed up, there is no visible plume. There is a baffle plate between the firebed and the flue with extra air forming a curtain next to the door glass.

In a fit of nervousness, I shone a torch on the start of the flue last time the fire was cold. Thin film of dark grey powder only.

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[harry]

The combustion gases need a certain buoyancy to overcome the resistance of the chimney and stove. The bouyancy depends on the temperature difference between inside and outside temperatures.

The bouyancy required depends on how convoluted the gas passages/ chimney is, the size of the passages, the length of the passages and the hieght of the chimney.. It varies too on how warm the chimney is and how much energy it takes to warm up the chimney and maintain that temperature.

Conversly, to be efficient the flue gas temperature need to be as low as possible. But not so low as the cause condensation.

So your flue gas temperature needs to be as low as possible so long as the chimney is still functioning/drawing and there is no white smoke which indicates condensation is taking place in the chimney. It's hard to achieve this under all conditions. In practice, natural draught chimneys are bound to be inefficient because they only work well over a narrow range of conditions and they are upset by the outside air/wind conditions.