Has anyone found that burning ash logs causes problems with tar? For years, I burned ash in my old boiler which was simply a large fire box with a flap for a vent and a chimney, and in the open fire. But since I changed a boiler, ash seems to clog up the system in no time. The logs are not kiln dried but supposed to be dry enough to be used in stoves. The new boiler is a ‘modern’ sort with secondary burn etc.. My chimney sweep insists we burn coal (the boiler is multi-fuel) and put in wood just as an addition, which is really not my idea.
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I'm assuming you are following the instructions that came with the boiler(does it actually heat water or is it just a stove?) to ensure optimum burn? My son and I have multifuel Defra compliant wood burners, with secondary burn etc, but the operation of them is quite different as they are two different makers.One obvious difference is that I have to keep the door closed during start up while his is left open slightly until it's burning well. He also uses a thermometer to judge when the air controls can be adjusted after lighting up and I think I should get one too as sometimes I have difficulty judging when that point has been reached and then the fire sulks - not helpful when I only have it on in the evening and it only gets going when I'm ready for bed! To say nothing of the fact it's then not then burning as clean as it should. From what I have been told(supplier, installer, sweep), and read, mixing coal and wood isn't a good idea since they need different grate and air settings to burn efficiently.
In your position if there are still problems I would be inclined to contact the manufacturer, rather than rely solely on what the sweep says. -
It is a back boiler and slightly over-capacity for my house but this was the only one wood burner I found with a boiler and at a sensible price (not £5,000 plus). I asked the manufacturer about tar but their answer was fairly vague: the secondary burn will help but burning wood always produce some tar. The reason I am almost sure it is ash that is the problem is that for about two weeks I burned birch and the boiler looked like a picture on a wood stove advertisement, with the flame dancing full in the firebox. And I have a thermometer on the chimney which went up to the correct temperature in no time. As soon as I started burning ash, all that changed. This is a pity, as we just had a new delivery of ash very recently. Ah well, I suppose there are lot to learn but at least we are not exactly desperate for heating at the moment!Comment
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How interesting. Ash is supposed to be a good wood to burn not least because it will produce heat even when green - although obviously that's not the best thing to do. Unfortunate if that's not always the case as presumably there's going to be a lot of it around with the trees that are dying. If the birch burnt OK that at least suggests the stove is operating OK, so perhaps mix the ash with other wood? A pity the manufacturer couldn't be more help, but not entirely surprising these days sadly.Originally posted by doversoul1 View Post
And yes, at least there's time to sort out a solution. Which reminds me I need to get my wood order in and gee up the colleague who's supposed to be making me a proper wood store to put it in, rather than the 'temporary'(3 years) pallets, stakes and tarp lash up I produced.Comment
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Since I installed a Stovax multi-fuel stove I have mostly used kiln dried beech which leaves remarkably little ash and very little tar and according to the suppliers is used by some stove manufacturers to test their stoves and measure heat output. I unhesitatingly recommend it.
The Stovax has 9-10kw output, primary and secondary air and works well in a room 23 feet long and 12 feet wide.
I have also used ash both green and seasoned and would always opt for the latter because of the likelihood of tar build-up, despite ash burning when unseasoned.
Perhaps the recommendation to burn coal stems from the higher temperature that results and the burning off of tar deposits.
Have you tried using any of the powders that loosen tar in a chimney?Comment
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Dovers - if your sweep uses a traditional Mary Poppins-type "sweeps head" chimney brush, the problem could be him. Ours uses a system of flexible plastic rods powered by an electric hand drill with interchangeable heads that look like strimmer heads - nylon, wire or light chain for heavy incrustation. They scour, or "ream", the inside of the flue. He blocks the front of the stove with a piece of foam, and kneeling in front of the stove pokes the rods through, and adds rods as required - clean as a whistle, we don't even need dustsheets. It's a single-storey house so only requires 5-6 rods.
We've had a Charlton and Jenrick "Pure Vision" multi-fuel stove for a couple of years, but only burn wood - seasoned mixed hardwood from a reputable supplier. The inside of the stove is "self-cleaning" if you maintain a good burn (it has sensitive air-intake controls, and different settings for wood and coal). It doesn't have a thermometer, but the visual clues are good enough. The firebricks are still white, and I keep the inside of the glass clean which takes a minute or two every day.
We previously had an old Jotl, and I used to sweep the chimney myself, three times a year, and I used that powder that gradus mentioned - but still got tar build-up. We had the chimney lined with clay liners many years ago. Before the new stove was installed he scoured the chimney with the chain attachment and there was a lot of tar, in spite of my efforts. They then inserted a flexible metal flue inside our chimney, which requires cleaning once a year by the above method - only the nylon strimmer head required.
Being told only to burn coal is ludicrous. Another reason for changing your sweep.Comment
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Similar story here. We used a large Franco Belge multi fuel cooker boiler for nearly 30 years and almost always burnt wood that I had cut and stored. Inevitably the clay liners glazed with tar but we never idled the fire -always kept it burning well - so that tar never caused a problem and like RT I swept it each year and a gratifying quantity of honeycomb textured tar came out.Originally posted by Richard Tarleton View Post
The point about visual clues is bang on. If the fire bricks stay clean and the glass stays clear - there is always a slight residue to clean off (short daily chore) - it's likely that all is well inside the chimney, in our case a stainless steel liner inside a masonry chimney.Comment
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I'm possibly talking nonsense or have a false memory, but I THINK some friends of ours had a problem that was traced back to a faulty flue installation: some parts were inserted upside down, causing deposits to accumulate/run back down, rather than 'escape'.
I'm not saying that that's your problem, dovers, as otherwise all seems OK, but it might be worth checking.Comment
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Flues connected the wrong way round will allow condensation/rain/tar to run down the outside of the flue but I wouldn't have thought it would make any difference to the heat inside the flue which is the key consideration. Perhaps a magnetic flue thermometer would help, ours is helpfully marked with the ideal range that the flue should reach to avoid tar - 260 to 465deg.F Above that, too hot, below that tar deposits.Comment
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Many thanks everyone for yur thought and comments.
Our chimney sweep is a young man who started the business two or three years ago. He is equipped with state-of-art (!) powered chain, a mirror, a camera, and various rods and brushes. He is a proud member of the National Association of Chimney Sweeps, and is very obliging and thorough. In short, he is a very good sweep but I have a suspicion that he believes any descent working man would burn coal; burning wood is for peasants or old hippies (if he knows the word, that is). With all this, we don’t argue with him. I am still hoping that the fact that the birch burnt without problems and kept the glass in the door clean means that the problem is not in the boiler itself.
I buy logs from a local farmer who is taking part in or receiving a grant from a forest management scheme. The sweep checked the moisture level of the ash logs which showed as 20% when he first came but that does not mean it’s always the same. I have ordered a moisture meter to make sure the logs are dry enough. The sweep is coming on Saturday and after that, we’ll try buying various logs in small quantity and try out.
In my old boiler, we burnt off-cuts from kiln-dried oak for making beams, and like Richard T and gradus, clean the chimney ourselves. However, about three years ago, the tar in the chimney became concrete hard at the top. This was when we called in a professional. I still don’t know what caused the change but because of this, I am reluctant to go back to the same oak logs.
At the moment, I am burning smokeless coal which burns without the full ventilation but the main purpose is to dry the chimney so that the sweep can use his tool. Without this (burning coal), inside the chimney is too sticky to work at.
I am glad that all this is happening in summer or I might just give up and turn the oil burner full on.Comment
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Friend of mine had a flue nightmare when some building work on the chimney stack disclosed that the chimney had been lined with pipe intended for gas boilers, not wood stoves. It was only a couple of years old and the installer had subsequently gone out of business so they couldn't get any redress for the cost of replacement.Originally posted by Pulcinella View PostComment
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That was the case on our cottage when we bought it - the old Jotul was connected to a gas flue. We discovered this before we started using it, when someone called to have a look at the Jotul, and said we wouldn't be able to light it. Doesn't bear thinking about. When the gas flue was pulled out it turned out to be perished. We had the chimney lined with clay liners soon after - most of which the builder was able to do from the outside - and we continued to use the Jotul (a 1979 model) for many years. The bloke who installed the new one now has it in his garden, asd a planterOriginally posted by oddoneout View Post
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I think the one thing that's "wrong" with all these articles - and often the research too - is that it assumes woodburning = woodburning. It's occasionally mentioned that burning kiln-dried logs is much cleaner, and if burnt at a high enough temperature in a modern appliance there is no smoke coming from the chimneys.Originally posted by Bryn View Post
HETAS is the industry organisation and they point out that that 38% represents a calculation of the amount of wood burnt. If x amount of wood is burnt, it produces y amount of PM2.5 = 38% of the measured PM in the atmosphere. HETAS says that the amount of wood burnt is, in the first place, almost certainly overestimated. In the second place, the instruments can't distinguish what is produced by woodburners specifically. They also claimed, I read somewhere, that the tests were carried out on older stoves rather than modern EcoDesign appliances.
The research says very little about
1. The variation in appliances
2. The type of fuel burnt
3. The efficiency with which the fuel is burnt - always at maximum temperature and not letting the embers die down too low before putting on another log.
We are launched on to a "narrative" here which becomes generally accepted. I think there needs a bit more clarity about this. HETAS is "the industry" and therefore may not be considered impartial, but it makes claims which need to be responded to.It isn't given us to know those rare moments when people are wide open and the lightest touch can wither or heal. A moment too late and we can never reach them any more in this world.Comment
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Not having the scientific know-how which you mention above, my one very strong reason for being in favour of woodburnrs is that wood is a renewable resource. So we must keep renewing it, i.e. getting energy directly from the sun. We must stop exploiting millions of years of past sun-energy in each mined lump of coal or gallon of oil. Anyone listening to Bill Gates' talks on R4?Comment
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