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Horizontal chimney runs?


dave21478
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Hi,

I have recovered an old wood-burning aga type of thing which I fancy putting into the kitchen. There is an existing chimney, but not in the right place and using it would require a complete kitchen rebuild which I am not doing. If I put it on the back wall, I can run the flue through the wall and into the abandoned garage space behind this wall. On the other side of the garage, there is another chimney stack which I would use with a liner.

So, having to cross this garage horizontally for about 4 meters....is this possible? is it a good idea? Should the tube be horizontal or better with an upwards slope? Anything else to consider? Obviously, the pipe would be supported firmly.

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Dave, I don't know much about the technical side of these things but I do have a large woodburning stove and the way I see it is that the flue would be very difficult and messy to clean.

There is always a fair amount of soot in the flue and that has to be swept out in order for the stove to operate efficiently.  Four metres seems to be a very long horizontal run to me.

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My neighbours had a woodburner fitted into the centre of their living room. This meant a horizontal flue across the ceiling to the chimney stack, some 4 or 5m distance. Well, they had a fire in that flue, something caught in the horizontal section and the pompiers ripped the whole lot down, the box it was encased in and did a lot of damage not to mention the smoke as well - took weeks of insurance speak and repairs. Don't do it if you don't have to, cleaning is not easy and this is why they had the fire because the rammoneur could not reach all the way.
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In the UK the maximum horizontal pipe run allowed under HETAS regs is 30cm.

The main reason is smoke needs to travel vertically as it swirls in a circular spiral motion and can't do this in the horizontal plane, so stalls (to a greater or lesser degree) when travelling horizontally.

If a long sideways rise is a must then there should be an angle of 45o at least.

In the same vein 90o bends are not recommended either as the debris 'rests' in the center of the bend allowing for a reduction of the internal diameter.

Two 45o bends are the way to change direction from horizontal to vertical as the less sharp radius is more conducive to good gas speed and smooth flow.

Last, the serrated bends sold at some bricos are a disaster for gas flow due to the irregular internal surface.
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We visited the chateau at la Rochfoucauld a couple of weeks ago (very nice, by the way) and some of the rooms there are still lived-in; they have woodburners which are set forward from the huge fireplaces, presumably to get more heat directly into the rooms, but the flue starts with a horizontal run from the rear of the woodburners, over a metre back to the fireplace before turning 90 degrees up the chimney. I dread to imagine what the heating bill is like.

If you read that this historic monument has been lost to the nation following a fire perhaps there's a clue here?

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