bil

I've seen a bird come down the chimney, and after that the whole room needed decorating.

Terrible stuff soot. You wouldn't believe how far it can go.

rugbymatt

bless

El Capitan

So bil, you will be the man to answer a question I have - maybe.
Twice now I have had a sooted room, once from the fireplace/chimney when I knocked out the fireplace as I am replacing it with a proper wood burner and the dust extractor bag went and split on me, and another time when the electric box in the hall smouldered away while I was in the UK one christmas and I came back to an inch thick black coating on floor walls and ceiling in the hall. Your right, cleaning up soot is not funny.

But to the question. I am going to line the old chimney with a new flue pipe as the old structure is obviously a bit tired and beginning to show signs of weakness. I have seen single wall flue pipe or twin wall flue pipe which slot together and I have already made the access so I can see right up to the top and there is plenty of room for the liner pipe. However, I heard of some special filler granules which you can pour in around a flue pipe once fitted to insulate and stabilise the pipe in the centre of the stack. Do you know if they are avaialable here in Spain and who might stock this stuff by any chance?

bil

OK, I don't know about Spanish liners. In the UK I would tell you to go for the twinwall flexible liner. Make sure it goes the right way up (not kidding) and use a proper connector that protects any ragged ends. Sweep it regularly each year as a chim fire will do it serious damage.

Are you talking about the rigid twinwall? Those have a very bad failure rate in the UK, and we really don't see them very often now. Expansive and with very poor performance.

Don't pick a stove with a butterfly valve in the exhaust tube, and go for a top exit, not a rear one.

Insulate with vermiculite or perlite. If you can get a dictionary and work out how you would describe the product in Spanish.

Hope that helps. If you sweep the chimney, for god's sake use the correct type of hoover with correct filters or the mess will be amazing. Some filters let the soot right thru, NO MATTER WHAT THE SALESMAN/RENTER MIGHT TELL YOU.

El Capitan

Thanks bil, yes I was talking about the rigid twinwall pipes, lengths about 1 or 2 metre long slotting together. Stocked in Leroy Merlin along with single wall and all fittings. If I can find insulation then maybe the twinwall is not necessary at all. Will look up vermiculite etc and see today if they have it. When I had the soot problem, it wasnt due to sweeping chimney but because some tiles had collapsed and the mess was terrible. Construction of the whole stack is most weird with a square centre stack built with flat tiles but surrounded by huge voids either side in the wall where the gases would circulate but no top exit other than up the centre stack. Off to the chimenea shops in a mo. Gracias.

bil

Interesting construction. The single biggest problem we have in the UK is dumbass builders and architects who can't understand basic design. The fireplace opening shouldn't exceed 9 times the x sect area of the least part of the flue. So, don't make the pot smaller than the flue, and don't make the fireplace too big. Happens all the time.

Have you given any thought to making use of the heat provided to heat water or move heat around?

I'm thinking of using a couple of rads to protect the walls behind the stove, and then circulating oil thru it, maybe also picking up heat from the fluepipe and running it thru to two bedrooms which otherwise get pretty cold. I need to research that tho wrto pressure relief and so on, and I'd like to make it free to run, ie with a thermosiphon.

I can't speak re the Spanish twinwall, but IMO the UK one isn't worth having. The internal wall is too thin and very vulnerable to overheating and subsequent corrosion.

Feel free to ask any questions if you would like.

El Capitan

Interesting yes bil and quite unexpected when I dug in. Was huge open fireplace originally which obviously smoked from day 1 according to the stains on the mantlepiece bricks. My diy door addition stopped that and I could keep a wood fire in constant for months with logs around 20 kgs each. However efficiency was not there and some cracks appeared in the wall as it got so hot. Have thought about back boiler etc but at the moment it doesnt seem worth it. Only one storey villa so thermosyphon more difficult to arrange and most promising from today's search is a fan assisted insert at 14 kW which should keep more or less the same fire but pump much more heat into the house compared to into the wall(s). Old fire worked okish with air con unit heat pump on top for 4 bed villa but new unit as planned today should give us more from the wood and at 260 odd euros for 2 tonnes of good dry big hard logs, I would like to milk as much as possible from the fuel. Couldnt find the insulation chips today, only mineral or glass wool blanket and all inserts have butterfly valves on outlet to stack. Saludos.

bil

With short chimneys, the 9 to one rule is even more important, and can even drop to 8 to one or a bit less.

Stains over the fireplace opening are always a dead giveaway.

I'm in a one storey too, but I'm sure a thermo siphon will work, after all, they work on simple setups where the height of the system is only a meter or less. Obviously it's better to use a wide bore tube, say 28 mm and minimise bends etc.

Milk as much as you can from the fuel, but watch out. If you extract too much from the flue gases you will bring the dew point inside the flue, and then you will get creosotes running down the inside of the flue.

Do make sure that all flue joints are the right way round, so that any condensate stays withing the flue. Get that wrong, on just one joint, and you risk all sorts of problems from creosote escaping from the flue.

Cheers, bil

El Capitan

Well interesting weekend, best freestanding claims 90% heat efficiency from fuel, best turbo insert claims 80%. Both much better than an open fire. Good point about getting flue connection the right way around but I guess starting with flu fitting inside fire outlet, then each joint going up has to fit inside the bit below not outside. Its true a thermo syphon doesnt need great height but as I have no hot water tank (yet, until solar goes in) it would mean syphoning to a radiator or more just above the fire height and also an expansion system. I think the hot air option is going to be easiest to install.

bil

You are very right about it should be simple. Each length has a male and female end, and should be presented so that the male end drops down into the female.

Some stoves tho, instead of having a female socket on the top have a sub male or even a male. Deeply stupid, but there you go.

Best thing is to imagine running water down the flue, and none should be able to seep out the joints, but all runs down into the stove..

If you are using the twinwall, make sure you sweep it every year without fail as a chimney fire will do a lot of damage. I have a flat roof which makes it very easy to sweep down into the closed stove. Then, you needn't even take the soot out. Just burn it away with the next fire. I'd remove the throat plate before sweeping and replace it after so the soot doesn't sit on it.

El Capitan

I understand the male dropping down to fit inside the female bil, thanks.

Now I find the twinwall is advertised more for external use to avoid condensation and they recommend single wall inox for lining an existing stack. Unless I modify the top of my existing chimney, I will not be able to sweep from above as it has a "closed" top with slots all the way around.

bil

No problem. Use the single skin, seal the bottom and then backfill with loose insulant. Put a rubber mallet in the flue and bang it about to get the insulant to settle.

Just cut the top of the chimney and put a removeable cap on the top. If you don't and sweep from the bottom, you REALLY need to know what you are doing, plus have a hoover with PROPER filters or the dust will go straight thru, much to your sorrow.

Same Difference

I thought chimneys were just for santa to climb down!

DebsyW

You back from your night out? Had a few??









we haven`t got a chimney.... took a while to explain to the kids when we moved..... had to think on my feet that`s for sure!!!!

Same Difference

So what did you tell em then?