Tar in new liner

[zeb]

Well, until this evening I thought I was an expert with woodburning stoves. I've had various models over the past 30 years and never had the problem I found tonight.

The woodburner has been chugging away all day - it, and its new chimney, were installed about 6 weeks ago; the wood (a beech, oak ash mixture) is dry and well seasoned. The stove (a Supra) gets roared daily to boost the heat but it mostly chugs along slowly, and rarely goes out - we bought a similar model (second hand but had only been used once or twice) to the stove we had in our previous house as we found it so efficient.

Anyway, this evening I noticed that the glass is black, the kitchen stinks of tar, and a pool of tar is on the floor under the T trap at the back of the stove.

It's going to take some hours to go out so that it can all be cleaned tomorrow, so a) I'm worried if its safe to leave like this (tar fumes), and b) why should this happen with a newish installation ( a new chimney had been built for it, with a flexi flue liner)?

[JohnRoss]

Your post has caused me some concern as we had a Supra Orlando installed in September and have used it daily from October onwards. It sounds as if yours uses, like ours, back entry for the flue rather than top entry. I have read somewhere that keeping log burning stoves in all night on tick over as it were, promotes tar and soot deposits due to incomplete combustion. The glass in the door does get a little black along the two sides and bottom but not along the top or in the middle. We were told to sweep the chimney twice a year and I had thought to do it just after Christmas and again before the start of the next winter season.

With our old stove we used to burn a chemical log twice a year and sweep before the start of winter but from what you say maybe I should take some action now! Not looking forward to sweeping it as I understand that the appliance has to be pulled forward off the flue and it is very heavy with the two stone panels fitted. Maybe these should be removed first? It looks as if the bottom section of the flue also has to be disassembled to get the brush up it? 

Would be most interested to hear what you find and any tips you or anyone else can pass on......................JR

[bigears]

I'm not an expert, we have two supra both without liners.  The first one we installed about 6 years ago in an external  chimney I built using red flue blocks, it works well.  Its a 9 kw steel model with red verticle sides.  The newer one bought from mr bricolage a couple of years ago is also 9 kw but is all cast iron, and very heavy. It is installed in the existing chimney of the house.  It displays some of the symtoms you describe, in particular the glass has to be cleaned every couple of days.  We burn well seasoned oak.  I think its better to have a smaller capacity fire burning towards full capacity rather than a more powerful one ticking over.  Can you bang in that material (sorry don't know its name) between the outside of the flue and the chimney.  Make sure the air gap above the glass is always unobstructed.  Is the chimney built high enough with regard to the roof line of the house?  You could try taking out the flue liner and run it without for a while.  Sorry cannot really help other than the above. 

[zeb]

Well we've spent the morning unblocking the flue and cleaning it all out. Phew - what a horrible job! Luckily the flue goes up to the ceiling where the block chimney starts, so it was relatively easy to drag it away from the flue to clean it out. The flue was well and truely blocked with tar deposits, so we are obviously using the stove incorrectly, or the problem is the wood.

We've relit it now and it's burning well. I don't think the problem lies with Supras per se John, just its use or misuse. Ours is a Selèstat which is similar to your Orlando, and designed to stay in all night, but....

In future we're going to let it out at night rather than shut it right down, and relight each morning; roar it more often to burn off the deposits; and maybe use different wood. The clean burn usually works OK, obviously we get some blackening of the glass but yesterday, it blackened over totally, and stunk of tar - anyway, I will recognise the signs of a blocked flue in future.

 

[JohnRoss]

Well ok and glad you have managed to clean it out. The spectre of a chimney fire always worries me. I had thought burning the odd chemical log (Buche de Ramonage) has helped as in the past only loose soot has come down on sweeping after using these. I did find a French forum where the view expressed by someone was that they were not effective. More than one American site has suggested that these chemical logs may make some deposits flake off and actually increase the risk of a chimney fire so I really don't know if they are a good thing to use or not. I notice that both our stoves have provision for storing wood underneath and the American sites I referred to say this is a dangerous practice. They also indicate running them overnight is also a no no. Maybe someone with some knowledge could come back on this.

Our conduit is quite long and runs right up to the top of the chimney. The installer pushed it down inside the existing larger diameter conduit which serviced the old log burner and was trapped in concrete so not easy to remove. I would assume this would give a bit of extra security although the extra metal might take longer to heat up and I think deposits may build up more quickly on a cold conduit. We also let the thing burn out at night and relight in the morning. I think that letting it burn slowly during the night may just make the problem of deposits worse. Thanks for coming back with your experience...........................................JR

[JohnRoss]

Took the bottom plate off the T section today and a ton of soot fell out, so much that it must have been backed up to above the entry point into the stove. No sign of any quantity of tar I am glad to say. We have a rotating choke plate just above the back entry point so it is not possible to get a brush up without pulling the stove out and taking off the sections of the flue that come into the room. In the past with our old stove after the chimney had been swept we would have had a fraction of the soot that appeared today. So why so much soot and that is only at the bottom, had it dropped down from above, and after only a couple of months since it was installed?

 

I think I will have to sweep the whole thing soon though peering up the flue with a torch and mirror did not reveal vast quantities of soot hanging on the walls of the liner, stainless steel flexible, but I could only see up a few feet in distance. I am not sure which part of the liner would have the most soot, the bottom which must get relatively hot or further up where the temperature must be less?........................................JR

[Dave&Olive]

hi ok

          this video might throw a bit of light on the subject. might take a long time to load but worth it  ...if it just for the part about burning pine (poplar )

 

             http://www.ec.gc.ca/cleanair-airpur/videos/Woodstove_mgt-Eng.wmv

 

                  Dave

[Le Plombier]

Dave and Olive

I always wondered what Cliff Richards younger brother did for a living

Having seen the video now I know

Le Plombier

[JohnRoss]

Thanks an interesting video and several good points made. I take note of the point about a smaller hot fire rather than a larger smoldering one. I think I will have to consider splitting my logs in 4 rather than half to make the fire smaller as with big logs and really burning hot it is a bit of an awesome beast. Might have to consider something better than my wedge on a handle as rather does the back in! Her lighting method was interesting as the top down approach seems to go against the laws of nature but certainly worth trying. The North South loading is a good idea but could not do it with 50cm logs mores the pity...............Cheers..............JR  

[Callie]

I was interested to read the postings on sooted up flues, and seeing the video.

We put in our Supra about 5 years ago. The first winter, we kept it goin for two weeks. It burned away quite happily during the night and was easy to revive in the morning.

However, it began to get very smokey and we decided to take out the flue. It was full of dry crispy flaky deposits and there was just a tiny hole for the smoke to get through. Luckily it was easy to scrape off with a flue brush.

Since then we have never allowed the fire to burn all night and we haven't had the problem since. I do tap the flue every day with my hands (when it's cold!) just to shake off any small deposits.

We NEVER burn any resinous wood and our wood is very well seasoned, so tar has never been a problem. I do have to stop Mr Callie burning anything plastic though....

[Suandpete]

Thanks for that - we have learnt some of those points through trial and error but it would have been much better if we had known about this video when we had our logburner installed.  I will try the top down method too.

[JohnRoss]

Tried a small but very hot fire in the Supra this morning and guess what, no smoke visible at the top of the chimney. I think in view of what has been said I will have to sweep the liner to be on the safe side. Problem is that we had a rotating choke control put in the bottom of the flue just above the entry point into the back of the stove, called an adaptateur de tirage I think, which means I cannot just take the bottom plate off the T junction and shove the brush up. So the whole stove has to be pulled forward off the T junction and the bottom sections of the flue taken off before sweeping. Not an easy task as the two stone side panels weigh 100 kilograms plus the weight of the stove itself. They can be taken off first but the whole thing becomes a major effort methinks! Something we did not think off when buying it. Having said that it does heat the house very well and the turbo fan underneath makes quite a difference............................................JR 

[JohnRoss]

Just a final note. Hope your Selèstat  is behaving itself Zeb. It could be a combination of smoldering all night and the type of wood you have been burning. I swept the liner today and was surprised at how little soot was up there. The bulk of it must have dropped down into the T section which I emptied the other day. A friend who lives next door to the guy that supplies our logs, mostly oak with the odd one of maybe soft wood, told me today that he does not keep his log pile covered so it looks as though the wood I am burning may be a little damp still. It is stacked up in our barn so I hope it will dry out but I don't know how many weeks this will take. This might account for the amount of soot found in the T section that I referred to earlier.

 

The Supra, Orlando Olliare, was quite easy to pull out once I had removed the two heavy stone panels, 50kg each, and the flue disconnected easily from the bottom of the liner. So I think we will follow the advice given in the video and try and cut our logs smaller and have small but hot fires rather than big smoldering ones. I also will avoid keeping it in at night. There are usually enough glowing embers to get it going again in the morning. Our friend also told us that they burn a chemical log (Buche de Ramonage) or two each year and send off for the proof of ramonage ( Attestation) which they reckon would satisfy the insurance company in case of a chimney fire, hope they are right......................................JR