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Woodburner smoke problems

 
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lulubel



Joined: 25 Dec 2009
Posts: 59
Location: Malaga, Spain

PostPosted: Fri Dec 25, 2009 6:09 pm    Post subject: Woodburner smoke problems Reply with quote

Hi, I'm new to the forums (discovered them through a Google search) and I'm really looking forward to looking around and joining in the discussions here, but first (and the reason I was searching in the first place) is I've got a major problem with my woodburner that I hope someone may be able to help with.

Most of the time it's a delight to use, it lights easily and draws well. In fact it draws so well when it's windy that I run it completely shut down and it still roars up the flue.

Recently there's been absolutely no wind, and no matter what I do the room fills with smoke. It started out coming from every joint between the back of the woodburner and where the flue exits the wall. Those are now all sealed with proper sealant and it's stopped leaking there. If the smoke can't get out there it comes out through the door, either through the vents or seaps out through the door seal itself. Every time I open the door a cloud of smoke comes out and through the coughing and watering eyes, it's hard to see what I'm doing as I put wood in.

I'm using wood that's so light and dry you can hardly feel the weight of it in an attempt to limit smoke produced. It's been lit for a few hours today, and the smoke hanging around inside has made the glass door so black you can barely even see that it's lit.

The flue is joined in several places. It comes out the back of the woodburner and turns to vertical until it's close to the ceiling, then turns again, goes through the wall, and then back to vertical. It ends just above the top of the wall (below the apex of the roof) and is topped with a fan that isn't powered but is turned by the wind. This was obviously added after it was installed just over a year ago because the original top was in the shed when we moved in.

It leaks soot from the top of the flue and possibly from further down as well, although it's hard to tell because there's so much black gunk running down the outside of the flue and the wall. It's a spanish system and we're told this is normal.

The house is well ventilated (spanish!) and we've tried opening various downstairs windows for extra ventilation.

Two options I'm thinking of are a taller flue (expensive because it will need bracing) and a powered fan (also expensive unless there's a DIY option?).

Can anyone make any suggestions? At the moment we're having to use gas heaters most of the time, which I hate doing for lots of reasons.
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adam2
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Joined: 02 Jul 2007
Posts: 4889
Location: London UK

PostPosted: Fri Dec 25, 2009 7:35 pm    Post subject: Reply with quote

Might the flue be partialy blocked with soot, tar or other deposits ?

I would be reluctant to light the stove until the flue works correctly.
Wood smoke is less harmfull than that from coal, but can still contain carbon monoxide, which can kill.
If the flue is partialy blocked with tar, then this might ignite and at the very least damage the flue, and possibly burn the house down.

Please take care, and welcome.
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emordnilap



Joined: 05 Sep 2007
Posts: 11132
Location: way out west

PostPosted: Fri Dec 25, 2009 10:51 pm    Post subject: Reply with quote

Welcome lulubel. I would concur with adam2. It has all the sounds of a blockage and it's worth getting in the sweep to clear it, or get yourself some brushes and do it yourself. After the fire's gone out and is completely cool, of course.

If you buy brushes which are a bit big, it's not a huge deal to trim them down to the correct size for your flue.
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JohnB



Joined: 22 May 2006
Posts: 6468
Location: Beautiful sunny West Wales!

PostPosted: Fri Dec 25, 2009 10:58 pm    Post subject: Reply with quote

I used to have a problem with smoke, but not as bad as yours. My neighbour also had a problem with smoke going up one chimney and down the other! I thought it might be something to do with the location of the houses. I replaced the original brick chimney with a double walled flue, and that didn't cure it, even when I fitted a Rotavent.
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ziggy12345



Joined: 28 Nov 2008
Posts: 1235

PostPosted: Sat Dec 26, 2009 6:03 am    Post subject: Reply with quote

Install a flue liner and one of those vents that are bent over 90 degrees and always point downwind.

Cheers
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stumuzz



Joined: 17 Nov 2009
Posts: 900
Location: Anglesey, North Wales

PostPosted: Sat Dec 26, 2009 10:30 am    Post subject: Reply with quote

I had a similar problem when I first installed mine. Intermittently it would fill up with smoke and come out of the joints.

We discovered it was the height of the adjacent chimney pot, when fitting the stove we put in the liner, filled with vermiculite and put the chimney cowl on. This made the chimney cowl lower than the chimney pot next to it. So when the wind was in a certain direction it would hit the higher chimney pot and cause pressure which prevented the smoke from rising.

Raising the height of the cowl above the its neighbour Immediately cured it.

Hope this helps and welcome.
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lulubel



Joined: 25 Dec 2009
Posts: 59
Location: Malaga, Spain

PostPosted: Sat Dec 26, 2009 5:35 pm    Post subject: Reply with quote

Thank you for the suggestions.

Yes, it has crossed my mind that it could be partially blocked. It changed from drawing really well to not drawing at all in the space of 24 hours, and the 2 changes in the weather in that time are that the wind dropped to nothing, and it rained very heavily.

So, it could be that it relies on having some wind to draw. Or it could be that the rain washed tar and soot down and they've collected in the bend at the upper floor level (although there is still plenty of smoke coming from the top of the flue and just hanging in the air). The wind was forecast to get up again this afternoon, so we were hoping to test it, but it's perfectly still at the moment.

Out landlord's coming up anyway on Monday, so I'll give him a call and ask if he's got any brushes. I was just hoping to have found out exactly what the problem was by the time we saw him, and to be able to offer a solution. From my experience with landlords, it's the best way to get problems sovled quickly.
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Catweazle



Joined: 17 Feb 2008
Posts: 1835
Location: Cardigan, South Wales

PostPosted: Sun Dec 27, 2009 2:14 am    Post subject: Reply with quote

The most likely causes have already been posted, but on the off-chance, do you have any tall trees hear your chimney ? I'm told that they can cause a turbulent wind that can disrupt the draught from the chimney.
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RenewableCandy



Joined: 12 Sep 2007
Posts: 11821
Location: York

PostPosted: Sun Dec 27, 2009 11:36 pm    Post subject: Reply with quote

Two possibilities: first have you got a vent where air can come into your room to replace what goes up the chimney? Second, it's not unusual for chimneys to not draw if they end at a height below the roof apex.

The vent thing is now compulsory, from Building Regs I trow: we had to have one installed (on account of having a woodburner in the living room) before we were allowed to have cavity wall insulation.
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lulubel



Joined: 25 Dec 2009
Posts: 59
Location: Malaga, Spain

PostPosted: Thu Dec 31, 2009 3:32 pm    Post subject: Reply with quote

Just a quick update on our woodburner situation.

We managed to test it late last Sunday evening when the wind finally got up, and although it was drawing, it was nothing like what it usually does when it's windy. On Monday morning our landlord came up, and when we told him the problem, he took the flue apart and pulled out all the gunk that had collected in the bend. Flue reassembled, it now works fine.

I think there are a few things that could be done to make it draw better even when it is clean, like increasing the height of the flue so it's above the apex of the roof, but it seems very common in Spain for chimney tops to be low, and it gets very windy up here, so having a tall flue would be a pain unless we really can't manage without it.

And as for vents into the room, I'm aware that's a regulation in the UK, but certainly not here in Spain. We just open a window if we need extra ventilation - as long as the windows aren't swollen shut, of course!
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