Flue Diameter Question
Discussion
Hello all.
Old (ugly and inefficient) open fire went into a twin-walled flue that extends through the ceiling (bungalow), into the loft and out to a purpose-build stack. 200mm internal diameter.
New log burner has a 125mm outlet, which, if I do the job properly, ought to go into a 125mm flexible liner dropped into the twin-walled one.
I'll need an adapater plate (which I can make) with a 125mm centre and a 200mm outside to keep things tidy where the new stove pipe will enter the old twin-wall.
The question is what's the worst case if I give it a go without a liner? I have a Co2 alarm, so no risk on that front. My guess is that worst case is that it doesn't draw as well as it should, in which case a liner goes in. I assume the risk of a chimney fire would be less than with a liner.
Cheers
Old (ugly and inefficient) open fire went into a twin-walled flue that extends through the ceiling (bungalow), into the loft and out to a purpose-build stack. 200mm internal diameter.
New log burner has a 125mm outlet, which, if I do the job properly, ought to go into a 125mm flexible liner dropped into the twin-walled one.
I'll need an adapater plate (which I can make) with a 125mm centre and a 200mm outside to keep things tidy where the new stove pipe will enter the old twin-wall.
The question is what's the worst case if I give it a go without a liner? I have a Co2 alarm, so no risk on that front. My guess is that worst case is that it doesn't draw as well as it should, in which case a liner goes in. I assume the risk of a chimney fire would be less than with a liner.
Cheers
It’s not a legal requirement to have a flue liner, but it’s recommended and you’ll struggle to find any pro who would install a stove without a liner.
So, you could give it a go with your adapter to the 200mm liner and see how it draws. You might need to get a faster fire going initially to get the draw pulling. If it doesn’t work you can always try dropping down the 125mm liner later.
However a 200mm liner will have a cross sectional area (and volume) 2.6 times greater than the 125mm liner, so the difference is significant.
So, you could give it a go with your adapter to the 200mm liner and see how it draws. You might need to get a faster fire going initially to get the draw pulling. If it doesn’t work you can always try dropping down the 125mm liner later.
However a 200mm liner will have a cross sectional area (and volume) 2.6 times greater than the 125mm liner, so the difference is significant.
My immediate thought on reading your post is why would you need a further liner within the twin wall flue (which I assume is an insulated metal flue).
But the regulations are quite complex (and are also covered by Buidling Regulations) so you really ought to take advice from a HETAS installer.
But the regulations are quite complex (and are also covered by Buidling Regulations) so you really ought to take advice from a HETAS installer.
No you don't, you have a CO alarm 
Thanks all.
Yes, CO, my mistake and it seems that this isn't in any way dangerous, so I'll give it a go. I suspect it won't draw as well as it could, but I have another one* in the adjoining lounge so easy to compare performance.
Easy enough to drop a liner in as this is a bungalow and I have a scaffold tower.
Yes, CO, my mistake and it seems that this isn't in any way dangerous, so I'll give it a go. I suspect it won't draw as well as it could, but I have another one* in the adjoining lounge so easy to compare performance.
Easy enough to drop a liner in as this is a bungalow and I have a scaffold tower.
- Other one is a Parkray Eco 5, new one is a Parkray Eco 7.
Turtle Shed said:
Hello all.
Old (ugly and inefficient) open fire went into a twin-walled flue that extends through the ceiling (bungalow), into the loft and out to a purpose-build stack. 200mm internal diameter.
New log burner has a 125mm outlet, which, if I do the job properly, ought to go into a 125mm flexible liner dropped into the twin-walled one.
I'll need an adapater plate (which I can make) with a 125mm centre and a 200mm outside to keep things tidy where the new stove pipe will enter the old twin-wall.
The question is what's the worst case if I give it a go without a liner? I have a Co2 alarm, so no risk on that front. My guess is that worst case is that it doesn't draw as well as it should, in which case a liner goes in. I assume the risk of a chimney fire would be less than with a liner.
Cheers
would be helpfuul to post a few pictures , type of stove , KW output .125mm is a 5" flue system , If you are going through a loft space you are going to need a ventilated Fire stop ,( through ceiling ) then build a metal frame with a cage to stop any combustibles touching the twin wall ) .Old (ugly and inefficient) open fire went into a twin-walled flue that extends through the ceiling (bungalow), into the loft and out to a purpose-build stack. 200mm internal diameter.
New log burner has a 125mm outlet, which, if I do the job properly, ought to go into a 125mm flexible liner dropped into the twin-walled one.
I'll need an adapater plate (which I can make) with a 125mm centre and a 200mm outside to keep things tidy where the new stove pipe will enter the old twin-wall.
The question is what's the worst case if I give it a go without a liner? I have a Co2 alarm, so no risk on that front. My guess is that worst case is that it doesn't draw as well as it should, in which case a liner goes in. I assume the risk of a chimney fire would be less than with a liner.
Cheers
note pictures of charred wood by other poster ........that was very nearly Pyrophoric combustion , sooner or later that would have gone up , those timbers should have been replaced by steel , the wood heats up then cools down then is heated until the molecules of the wood break down and suddenly when you light the stove you have a loft fire ........ then try getting compensation after the fire brigade have done their report !
its not just the c02 alarm its the distance to combustibles . All stoves are different there will be manufactures guidelines on safe distances to combustibles ie Rear of stove / sides front etc.
I would advise to get a HETAS engineer to survey the fireplace and advise accordingly . Remember if you install yourself it wont be registered , so if you sell the property . The buyer will insist on registration and your into a world of pain , or if you have a fire and you have installed yourself your then down the issue of house insurance./
here's how installations can go very wrong
I was called out to survey a property few weeks ago .Because the chimney was leaking ...or more to the point everytime it rained water would pour through the wall ..............but that was only half the story the owner was also getting headaches , we suspected potential carbon monoxide emissions
Newish build circa 2016 . Builder decided it would be a good idea to install a wood burning stove . Unfortunately it came with a European spigot 5.75" so he figured a 6" stove pipe would fit with a bit of fire cement then connected two 6.5" Schiedel twin wall adaptors upside down . He then ran a 6" x 5m 316 ^" stainless steel liner through the chimney to the pot . now he obviously had a problem getting the liner through the chimney so he chose to cut both the lead trays !! .........hence the leak !
No certification , No Carbon monoxide alarm and the builder went back 4 times to unsuccessfully fix the leak !!.
This was the install after 3 repairs . note " the upper part is a twin wall adaptor incorrectly installed into the stove pipe , its touching the plasterboard ( which is a combustible surface ) .
Ist stage to remove plasterboard and see what had been installed.
The two schiedel adaptors that have been fitted are not designed to be installed in this way ( upside down ) or to be installed with an air gap , filled with fire cement which is falling out allowing gases into the room. stove pipes should be installed on the outside so soot residue will fall down into the stove.
the builder has decided to use a steel C beam to secure the twin wall by drilling holes and securing with 3x screws , compromising the integrity of the twin wall .......no one would know because its hidden by plasterboard, .
with adaptors removed we can see a register plate has been installed with the "6 flexible liner , the void was full of vermiculite .... which was damp . note the rust around the plate and .... expandable foam ,,,, which is a combustible !
with plate removed we can see the lower lead tray has been cut to allow the liner to pass through the tray , this is one of the causes of the water ingress .
The Chimney pot was removed with flaunching and Liner pulled
we can now look down at the upper lead tray............this has also been cut
other issues
The neighbours house is identical , for an unknown reason the builder did not install a wood burning stove , you can see where he has retro fitted a lead jacket around the lower Tray to stop driving rain , he also coated the chimney in Storm dry ..........but it still leaked
We inspected the weep holes around the trays .. which also had a copious amount of silicone mastic applied to the brickwork.
we removed bricks on all sides of the weep holes to check the cavity
on all sides of the weep holes we found mortar and an inner course of bricks which would make it impossible for water to flow out of the weep holes , with no where to go it simply overflowed inside the chimney breast intro the property
with inner course removed we can now see the internal lead slate , note the debris mortar around the lip which is touching the sides at the rear .
we can now clean all mortar out and re dress the lead trays upper and lower , moulding it up to form a 1" lip and profiling the lead to allow water to egress via the weep holes
upper tray repaired you can see bricks removed front and back profiled to allow water egress ready for liner install , bricks will then be replaced
.
replace cut lead remove all mastic and repoint brickwork.
Install new 5" 316" stainless steel liner lowered carefully with bricks removed at both trays it can be carefully positioned without damagfing the new profiled lead slate.
the 5" liner has been installed with a Twin wall to Flex adaptor 125mm these are screw on fixings . Then 125mm adjustable clamp installed with 5" TW Pro ( matt black finish ) Twin wall
an adjustable TW Pro Twin wall 300-800 connecting pipe was connected ( these are installed with lockable bands which give a tight seal , it will also allow the stove to be disconnected in the future.
To make a tight seal to the stove . we used a TWpro single wall to twin wall adaptor 125mm . However this would not fit the Stove spigot
so I had a sleeve made to the correct size
Then it was a case of re installed new pink plasterboard , to make this compliant , you cut a 50mm gap around the twin wall and once plastered , a magnetic cover plate is installed this maintains the correct distance to combustibles and gives a nice finish .
the whole chimney was also coated in Properla masonry creme which will allow the inner bricks to dry out is breathable and has a 25 year guarantee
outside
We have installed a safe system the owner has a HETAS certificate and the trays were repaired and tested without the need to remove and rebuild the entire chimney .
its all preventable , but i really would advocate getting an engineer to advise on the correct parts , especially in relation to combustibles
all the best cheers
Edited by Purosangue on Wednesday 25th June 16:49
Purosangue said:
would be helpfuul to post a few pictures , type of stove , KW output .125mm is a 5" flue system , why is it going into a twin wall system ?
its not just the c02 alarm its the distance to combustibles . All stoves are different there will be manufactures guidelines on safe distances to combustibles ie Rear of stove / sides front etc.
I would advise to get a HETAS engineer to survey the fireplace and advise accordingly . Remember if you install yourself it wont be registered , so if you sell the property . The buyer will insist on registration and your into a world of pain , or if you have a fire and you have installed yourself your then down the issue of house insurance./
Thanks for all of those images and sage advice. its not just the c02 alarm its the distance to combustibles . All stoves are different there will be manufactures guidelines on safe distances to combustibles ie Rear of stove / sides front etc.
I would advise to get a HETAS engineer to survey the fireplace and advise accordingly . Remember if you install yourself it wont be registered , so if you sell the property . The buyer will insist on registration and your into a world of pain , or if you have a fire and you have installed yourself your then down the issue of house insurance./
I will post some pictures over the next few days, bit busy at the moment. However:
It's a Parkray Aspect Eco 7: https://www.hunterstoves.co.uk/product/aspect-7-ec... - 4.5-7kw output, 5kw nominal. Distance to combustibles is 450mm and that's no problem.
Going into a twin wall system (Selkirk Metalbestos) because that's what was there already for the open fireplace.That fire worked perfectly well, but was inefiicient. I can inspect the whole twin-wall system and externally all seems good. Nothing is hidden in walls, so if there were any kind of leaks from rain I'd be able to see them. It worked just fine with the open fire.
Insurance and HETAS I'm aware of being of consideration. I wil contact the home insurers to advise, and if they require an inspection then so be it.
I might put a liner in, but see no need to if the log burner functions well without, and there is no safety concern (which is why I started the thread).
If the flue was working fine on the open fire then i would just connect to the twin wall and give it try ?
With a bigger flue ( wider) and not a lot of length ( bungalow ) as said it might not draw as well as with a 125mm flue.
My old house had a 12m high flue and would pull like a train …new house flue is only 3.5m it works fine but on really cold days you need to right technique to get it going.
With a bigger flue ( wider) and not a lot of length ( bungalow ) as said it might not draw as well as with a 125mm flue.
My old house had a 12m high flue and would pull like a train …new house flue is only 3.5m it works fine but on really cold days you need to right technique to get it going.
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