Fireplaces and Chimneys

[Dead Eye]

In my parents house, there is a multi-fuel burning fire that is typically fed with wood however there is recent concern about the build up of tar in the chimney flue which can cause chimney fires. I've done a little research about the best way to get rid of these deposits as they are sticky and can't be removed with a chimney sweep.

A couple of products have shown up as special chemical logs which turn the sticky tar into a brittle compound that breaks up. Other places have recommended burning smokeless fuels for a while as the sulphur released does a similar thing. My question really is has anyone had experience with either options or any further advice on how to get rid of tar from a chimney?

Its been in place for years and years, but recently we've switched our fuel source and this may be the cause of the larger / faster tar build-up. Unfortunately as this fuel is currently completely free its not ideal to switch from using it. Its compressed briquettes of saw dust that comes from a joinery business owned by family friends, although its not 100% clear as to whether this is the cause - its just something that was mentioned by the person who came out to sweep the chimney.

[slimwilly]

I have 2 woodburners on the go here, i don't think there is any tar on the liners,hope not anyway,
we try to let them burn HOT, not too cool as to keep the flue hot and lee=sson the condensation in the flues which cause tar.


I have seen some bad tar runs on stoves and heard of alot of chimney fires.


As to what todo to remove the tar,well i don't know,,


Is there a HETAS website?


Don’t underestimate the advantages of a quality twin wall & insulated liner installation over an existing clay liner or a rendered brick flue designed for an open fire. They may be quiet sound & safe to use but it will not be as efficient with a stove install due to lower gas temperatures in the top 1/3 of the flue. This will give reduced heat output from the stove & lead to condensation on sulphur deposits which results in what will basically be sulphuric acid. This will eat away at the render holding your flue/chimney together & will eventually destroy a non insulated liner far quicker than an insulated one.[/size]

Read more:http://www.diynot.com/forums/trade-talk/hetas-engineers-a-bunch-of-lying-so-and-sos.298134/#ixzz2mLgHLtOF

[Fazerider]

I think those logs that supposedly embrittle tar rely on a slow cool burn which condenses sulphur on the inside of the chimney, it then takes weeks to work and you can't use the fire during that period because it'll vaporise (or worse, burn) the sulphur off. I don't know how a smokeless fuel would help (other than by not adding to the deposits) as they are very low in sulphur.


Stoves with secondary burn do a good job of destroying the tarry compounds in smoke, but work best when running flat out... if the stove is turned down to reduce output, the temperature of the hot air for the secondary burn can get too low. This doesn't matter so much with logs as they cook through fairly quickly, driving off the volatile stuff that causes the problem in the chimney... so if you turn the fire down once the room's up to temperature most of what's left is charcoal which doesn't produce much smoke. Sawdust blocks are less good at conducting heat to the inside so tend to produce creosotes continuously as they burn: turn the stove down, the secondary burn gets inefficient and the nasties can condense in the flue.


I'd ignore the tar until next summer and then try the chemical logs followed by sweeping. Then fit an insulated liner... it keeps the smoke hot and gets it out faster.
In the meantime a flue thermometer may help your parents keep the stove exhaust at the optimum temperature.
Mind you, a chimney fire does an effective job of removing tar... as a neighbour of mine discovered a couple of years back. The plaster explodes off the walls too.

[Dead Eye]

From what I've read, you can continue to use the fire over the 2 week period after burning the "Chimney Cleaning Log". Can't remember where I read it, but smokeless fuels apparently give off sulphur which will help against tar... all sorts of information out there.

The primary purpose of the fire used to be to heat the main room of the house, it now does that in addition to providing hot water and running the central heating which means a toasty house for zero fuel cost. Gas is still connected for summer months and in case the fire can't be used obviously. Temperature control may be the issue, especially since recently the fire is being kept in all day and night, but on a typically slow burn. The chimney already had a lined flue put in not terribly long ago (two years?)

So far from what I've read, the best bet is to burn a few of these cleaning logs, run smokeless fuel for a few weeks then have the chimney swept again to remove the now brittle deposits.

[rustyrider]

Is this only a problem with wood burners?  I've got an open fireplace in the living room and the remains of a pretty lengthy fence.  So, when it's a but chilly, my missus shows her pyrotechnic tendencies and sets fire to a few lumps of wood in the fireplace.  Am I also filling the chimney with tar ready to burst into flames at any time?

[slimwilly]

If your woodburner has a boiler in it to heat water,rads then this does cool the fumes more and so does need a bit more of a roaring fire to keep them fumes hot.and stop cooling and condensation in the chimnet top end

[VNA - BMW Wank]

You could try burning some anthracite.  It can burn really hot.  You just have to be careful you don't throw too much on and overheat the stove.

But it could be a good option for burning off crap in your chimney.

Is the stove fitted with a stainless liner right up the chimney?

[Hedgetrimmer]

I hope for your sake Santa isn't reading this or he might decide to call elsewhere......

[Dead Eye]

Is this only a problem with wood burners?  I've got an open fireplace in the living room and the remains of a pretty lengthy fence.  So, when it's a but chilly, my missus shows her pyrotechnic tendencies and sets fire to a few lumps of wood in the fireplace.  Am I also filling the chimney with tar ready to burst into flames at any time?

You will likely be affected as well as all wood gives it off to different degrees. However, it doesn't sound like you use the fire much so you may not have too much of a build-up - when was the last time you had the chimney swept?

You could try burning some anthracite.  It can burn really hot.  You just have to be careful you don't throw too much on and overheat the stove.

But it could be a good option for burning off crap in your chimney.

Is the stove fitted with a stainless liner right up the chimney?

Yeah, that's something I'm looking in to - all the smokeless coal products are anthracite from what I can tell. In combination with the chimney cleaning log thing, it might be the best option to get the system back in to proper health. There is a stainless flue all the way up the chimney yes which is also lined

From the seems of things, a bit of TLC and changing the burn pattern should solve the issue - need to keep the chimney hot

[Fazerider]

As Slimwilly says, back boilers can make the situation worse by lowering the exhaust temperature. They are often also sited so near to the fuel that they reduce secondary combustion.
Perhaps your parents could use the sawdust briquettes when they want maximum heat output and switch to smokeless fuel when they have the stove turned down.


Rustyrider: open fires are much smokier, but often produce a fairly loose soot deposit. At least the lower part of the flue is easier to inspect without a stove in the way.
Get the wood is as dry as possible to help it burn more cleanly.

[VNA - BMW Wank]

Yeah, that's something I'm looking in to - all the smokeless coal products are anthracite from what I can tell. In combination with the chimney cleaning log thing, it might be the best option to get the system back in to proper health. There is a stainless flue all the way up the chimney yes which is also lined

I found pure anthracite burns hotter than anything else, but I also discovered that with a DEFRA stove it can run away with itself.  Also blacks up a stove glass like nothing else, a real pain to clean off.  If you wanna put max heat up yer chimney I think it's it's the fuel to do it.

There's all sorts of blends of smokeless coal, and nobody seems to want to tell you what goes into each blend.  I'm told what you want to avoid with a stove is a smokeless coal with a high petrocoke content, it's just another one of those things that blacks up stove glass and hangs in there for grim death.

I've found Surefire Ovoids to be a good option, can be bought from the coal merchant in 50kg bags.  Now I think it's called Surefire only in Scotland.   http://www.fergussoncoal.co.uk/fuel-guide/  I think in England it's sold as Taybrite

[Dead Eye]

Thanks for that The one thing that had caught my eye is Blazebrite (simply because its on offer where I found it) which seem to fit the same criteria. The glass has already been a bit a damaged due to using a crappy cleaning product that wasn't suitable so its become cloudy amongst the rest of the burnt on carbon from the wood - can't see the anthracite being much of a problem in comparison

[BBROWN1664]

For cleaning the glass, we just use a bit of damp kitchen paper dipped in the ash from the fire. works a treat.

[richfzs]

Ammonia soln, will clean your glass up a treat (well it's what my dad always used, I guess he knew what he was doing?!)

[goldfazer]

we use baby wipes for cleaning the fire and glass - very effective!

[Dead Eye]

As a general update, things are proceeding under the best-guess that the use of the fire was incorrect. The long, slow burn all day and night wasn't heating up the chimney which causes a much larger build up of tar / creosote. This has been changed so that the fire is now restarted every evening, but is kept hot. The thermostat has now changed as well so that the water pumped around the radiator system is hotter - this is keeping more energy with the fire, but its also helping to heat the house faster once the pump does kick in

Its not much of a problem really as its only my mum who lives there and most of the time she is at work. Thanks for all the advice from everyone so far ^^

I have no idea what has been done to the glass, but its looking a lot better recently - I couldn't tell that it used to be marked / cloudy the other day so...