Lining chimney for woodburner

[Gyn_Paul]

[quote user="Théière"][quote user="Bill"]

An existing chimney must firstly be given a visual inspection,and make sure it is of a suitable size,a smoke test should be carried out to make sure it is clear of obstruction and check for gas tightness,your chimney should be swept before installing a new appliance,do not attempt to fit a liner without firstly sweeping the chimney,if your chimney passes the the visual inspection and passes the smoke test,it is deemed sound and not a legal requirement to line,lining your chimney has advantages such as increased draw and better efficiency,reduces the risk of chimney fire,and piece of mind having a sealed system

[/quote]

That is pretty much the nuts of the subject Bill.  I was corrected by someone who has been installing in France for years that twin wall (uninsulated) is not yet a requirement even for wood burners so single skin would do. In the UK HETAS only recommend single skin for gas burning flues, wood burning should be twin walled but by now you have probably noticed that in your links etc. Most of the wood burners if not all have the single skin and have been going 15-16 years.  I think the points I made are echoed in the links you have supplied so the final choice is yours.

The UK again recommends wood burners of more than 10kw must have an air supply into the room as the fire will draw in the air to combust and as air is 80% nitrogen 20% oxygen you can see that oxygen depletion is quite easy and so is slipping in to a coma, thankfully rare due to leaky old buildings and our inbuilt sense of stuffy air open the door/window. Likewise slipping into a coma after reading posts from PPP [:)]

[quote user="pachapapa"]

It is amazing how many chimneys in old houses such as mine which have had one metre logs roaring in them for three centuries creating such an updraft that the front door has to be opened to supply air; then a stove and installer arrive and surprise, surprise it needs excruciatingly expensive double walled stainless steel tubing.[:D]

[/quote]

Despite this bloke allegedly having a degree in engineering related matters it seems amazing that they haven't grasped the basic understanding of why a roaring open fire is different to a stove so the chimney/flue designs are different even though your links describe it very well. (open fire 95% of the heat rises up the chimney taking the gasses with it)

[/quote]

...That would certainly be the case if the fire was capable of selectively extracting the oxygen and then recirculating the nitrogen (along with the CO2 and NO for good measure). The more prosaic reality is that the fire would simply draw badly and ultimately go out completely. After all, the control devices on a poele are nothing more sophisticated than means of restricting the air-flow.

And as for sealing the top of the chimney to prevent the flue gasses from sinking back down the chimney cavity..... well all I can say is that it would have to have been a chimney with a pis-poor draw for this to be an issue.

My register plate sits on a metal rail on all 4 sides of the chimney but in no way is this an air-tight seal as can be demonstrated by running a lit taper around the joint: there's a slight up-draft: strong enough to pull the smoke through the joint, but not strong enough to blow out the flame (which is the case if I put same lit taper by the flue inside the poele). This effect is slightly greater when the poele is lit, which will be because the flexi liner radiates heat in a temperature gradient up the chimney, and consequently heats the body of air surrounding it in the chimney cavity. Given that there is a draft at the bottom, this heated air must be being drawn off at the top. However if the register plate (and flue entry hole) was an air-tight seal, then I imagine there might be some local convection currents circulating within the chimney space. but since it's airtight, the composition of the gas is irrelevant  !

Somebody earlier in the thread mentioned flash-over.  I'd be interested to read any technical data to support this seemingly wild notion.

And whilst it's certainly the case that the corrosive effect of a poele's flue gasses will do for lime mortar in the end, this is not like a gas fire's fumes which would silently kill; if fumes from a poele were leaking through the brickwork into - say - a bedroom, you'd be coughing and choking on the smoke and beating a path to the fresh air  l-o-n-g  before the CO levels became an issue. Just think how pleasant it is in a room with a fire that smokes.

;p

[Théière]

[quote user="Gyn_Paul"][quote user="Théière"][quote user="Bill"]

An existing chimney must firstly be given a visual inspection,and make sure it is of a suitable size,a smoke test should be carried out to make sure it is clear of obstruction and check for gas tightness,your chimney should be swept before installing a new appliance,do not attempt to fit a liner without firstly sweeping the chimney,if your chimney passes the the visual inspection and passes the smoke test,it is deemed sound and not a legal requirement to line,lining your chimney has advantages such as increased draw and better efficiency,reduces the risk of chimney fire,and piece of mind having a sealed system

[/quote]

That is pretty much the nuts of the subject Bill.  I was corrected by someone who has been installing in France for years that twin wall (uninsulated) is not yet a requirement even for wood burners so single skin would do. In the UK HETAS only recommend single skin for gas burning flues, wood burning should be twin walled but by now you have probably noticed that in your links etc. Most of the wood burners if not all have the single skin and have been going 15-16 years.  I think the points I made are echoed in the links you have supplied so the final choice is yours.

The UK again recommends wood burners of more than 10kw must have an air supply into the room as the fire will draw in the air to combust and as air is 80% nitrogen 20% oxygen you can see that oxygen depletion is quite easy and so is slipping in to a coma, thankfully rare due to leaky old buildings and our inbuilt sense of stuffy air open the door/window. Likewise slipping into a coma after reading posts from PPP [:)]

[quote user="pachapapa"]

It is amazing how many chimneys in old houses such as mine which have had one metre logs roaring in them for three centuries creating such an updraft that the front door has to be opened to supply air; then a stove and installer arrive and surprise, surprise it needs excruciatingly expensive double walled stainless steel tubing.[:D]

[/quote]

Despite this bloke allegedly having a degree in engineering related matters it seems amazing that they haven't grasped the basic understanding of why a roaring open fire is different to a stove so the chimney/flue designs are different even though your links describe it very well. (open fire 95% of the heat rises up the chimney taking the gasses with it)

[/quote]

...That would certainly be the case if the fire was capable of selectively extracting the oxygen and then recirculating the nitrogen (along with the CO2 and NO for good measure).  You are partially correct, Nature decides that fire removes the oxygen from air, apart from a little Co2 the remnant is nitrogen which being inert doesn't combust so recirculated sort of.   The more prosaic reality is that the fire would simply draw badly and ultimately go out completely. After all, the control devices on a poele are nothing more sophisticated than means of restricting the air-flow. Yes, as time went on the fire would draw less, the flame would yellow through lack of oxygen and if you were sitting in the vicinity you could pass out. if the fire continued to burn until it went out completely that lack of oxygen in the room would kill you by asphyxiation.

And as for sealing the top of the chimney to prevent the flue gasses from sinking back down the chimney cavity..... well all I can say is that it would have to have been a chimney with a pis-poor draw for this to be an issue.
My register plate sits on a metal rail on all 4 sides of the chimney but in no way is this an air-tight seal as can be demonstrated by running a lit taper around the joint: there's a slight up-draft: strong enough to pull the smoke through the joint, but not strong enough to blow out the flame (which is the case if I put same lit taper by the flue inside the poele). This effect is slightly greater when the poele is lit, which will be because the flexi liner radiates heat in a temperature gradient up the chimney, and consequently heats the body of air surrounding it in the chimney cavity. Given that there is a draft at the bottom, this heated air must be being drawn off at the top. However if the register plate (and flue entry hole) was an air-tight seal, then I imagine there might be some local convection currents circulating within the chimney space. but since it's airtight, the composition of the gas is irrelevant  !
I think you misunderstood me and the posts, I was talking about the use of a full chimney without the flue liner. Considering some of the chimneys in france are 1200mm x 400mm that is such a large volume that gasses moving up the chimney would cool part of the way up and stick tar etc to the walls of the chimney. If the combustion from the fire was good enough this effect is minimised but would involve you having to run your wood burner flat out all of the time.  This is due in part to the register plate keeping more of the heat in the room so less escapes up the chimney. Open fires by contrast loose so much heat up the chimney there is plenty of heat to lift gasses and tar right out the top which is why for hundreds of years the traditional chimney has been fine.
Somebody earlier in the thread mentioned flash-over.  I'd be interested to read any technical data to support this seemingly wild notion. Seemingly wild and fortunately rare, due to incomplete combustion of the fuel unburnt but volatile gasses together with dust (soot) can with a small amount of oxygen spontaneously combust. (my very first trip to the health and safety ship in st Katherine's dock many years ago demonstrated it) but it only takes an ember lifted from the fire into the chimney under the right conditions to set fire to the unburnt gasses which will cause a small bang as it ignites, this can draw air from the top of the chimney down into the chimney causing a much bigger fire. 

http://www.firetactics.com/FLASHOVER%20-%20FIREFIGHTERS%20NIGHTMARE.pdf

http://www.youtube.com/watch?v=HRen2H3DJUQ

And whilst it's certainly the case that the corrosive effect of a poele's flue gasses will do for lime mortar in the end, this is not like a gas fire's fumes which would silently kill; if fumes from a poele were leaking through the brickwork into - say - a bedroom, you'd be coughing and choking on the smoke and beating a path to the fresh air  l-o-n-g  before the CO levels became an issue. Just think how pleasant it is in a room with a fire that smokes. All the more reason to line the chimney which is what the thread was discussing.

;p
[/quote]

Done to death now! ZZZZzzzzzzz [:)]

[pachapapa]

Done to death now! ZZZZzzzzzzz

But it is most amusing to read.

At the moment I am channel zapping between football on Kabel Eins Österreich and the OpernBall on 3Sat so I haven't got time to recall my second form  grammar school lessons on the paradox of the inertness of nitrogen and it's profligate family of nitrogen oxides.[:D]

[Gyn_Paul]

[quote user="pachapapa"]

Done to death now! ZZZZzzzzzzz

But it is most amusing to read.

At the moment I am channel zapping between football on Kabel Eins Österreich and the OpernBall on 3Sat so I haven't got time to recall my second form  grammar school lessons on the paradox of the inertness of nitrogen and it's profligate family of nitrogen oxides.[:D]

[/quote]

Yes I remember Mr Unwin calling it "the do-nothing gas", and then muttering something under his breath, as he turned back to the blackboard, about it properly belonging in group O (I think it was) surrounded by argon, xenon, neon, krypton and the rest of the bunch, "nothing noble about something that does damn-all"  Not a verbatim quote, but near enough.

[Gyn_Paul]

[quote user="pachapapa"]

Done to death now! ZZZZzzzzzzz

But it is most amusing to read.

At the moment I am channel zapping between football on Kabel Eins Österreich and the OpernBall on 3Sat so I haven't got time to recall my second form  grammar school lessons on the paradox of the inertness of nitrogen and it's profligate family of nitrogen oxides.[:D]

[/quote]

Yes I remember Mr Unwin calling it "the do-nothing gas", and then muttering something under his breath, as he turned back to the blackboard, about it properly belonging in group O (I think it was) surrounded by argon, xenon, neon, krypton and the rest of the bunch, nothing noble about something that does damn-all)"  Not a verbatim quote, but near enough.

[Théière]

It's just too common to be noble! [;-)]

Just another non metal

[pachapapa]

Job for weekend,remove catalytic converter for sale on Ebay and let the noble  NOx flow straight out.