chimneys on wood burners

[Traceyh]

We have purchased a three year old 10kw deville poele a bois for burning wood in our lounge. The chimney will go straight up from the fire about 6 m and go just above the apex of the roof. it will not have any bends in it. The fire has a 125mm oulet , and we intend to use 125mm inox to the top, and then put on a hat. However so english friends believe that the diameter of the pipe will be to small at 125mm, and we will not get a good draw and therefore get smoke in the lounge and not up the pipe.

Any ideas?

[Stew]

You are effectively extending the 125mm outlet that the fire already has. I don't see how expanding the flue to a larger diameter will have any beneficial effect as a wider pipe, say 200mm will already be choked by the 125mm outlet.

I reckon it will be fine.

Wait to see if some highly qualified heating engineer posts a reply explaining how a wider pipe will have some venturi effect and pull the smoke out!

Stew

(wondering if, since wooden windows can warp so that they no longer close properly, could they be induced to warp back again if soaked wet and clamped shut for a bit)

[Dog]

125mm pipe is what it's made for it will be fine. On a wood burner the exhaust should be hot. Best way to get a good draw is make sure the room has plenty of incoming air. Wood burners have trouble sending exhaust gasses up a cold flue, so get a good flare up with newspapers going, use a gas torch or some people use hairdriers.

Putting a straight pipe out of the top may make rodding difficult as we have not found flue pipes with rodding points on straight pipes here in France. Also having the fire slightly into the room chucks out more heat. Don't forget to seal the chimney above the wood burner.

One bend will do no harm.

Use well dried wood and you should have no problem.

The Jotul we picked up at the Vide Grenier for €100 had a rebuild and is working beautifully.

PS The Troc in Perigueux on Saturday had two small French ornate and two large colonial style woodburners. The small ones were €75 and the larger €180 each, though the larger ones looked like they needed an overhaul.