Flue liner for woodburning stobe

[Matchless]

I have an older style woodburner with an outlet of approx. 130 mm diameter. This connects to a stainless steel flue liner fitted in the chimney and leading to the underside of the chimney pot. The liner is 2 years old.

I have recently purchase a new glass fronted wood burner that has an outlet of approx. 180 mm diameter, as I believe all new burners have. I would rather not have the expense of  buying and fitting a larger liner and therefore my question is, has anyone had any experience of connecting a larger diameter outlet to a smaller pp flue. Is there a problem with back pressure and flow of gasses. I have been told by several fairly knowledgeable people that I shouldn't have a problem but no one is absolutely  100% sure. I do like definates!

Also, I would like toconnect trunking to the burner to carry the heat upstairs. Any tips of methgods etc?

Matchless

[Deimos]

I am having a new wood burner and flue installed soon (hopefully) and the woodburner has a 150 diam outlet and they are installing a 180 diam flue (which he seemed to suggest was standard (i.e. the other way round to yours.

Doing a bit of maths on cross sectional areas or circles, a diam. of 130 gives a cross sectional area of 65*65*pi=13272 and a diam. of 180 gives a cross sectional area of 90*90*pi=25446, thus the 180 diam is almost double the cross sectional area which is quite a bit bigger.

I was asking the guy who quoted for (and is installing) my wood burner about the heat circulation systems for an insert/foyer and if I could pipe the hot air “outputs” from around the insert in pipes up the chimney round and into the bedroom above (i.e. the standard sort of thing you can buy in the briccos). He was saying that the regulations do not allow the air circulation piper to run up a chimney next to the flue and that there must he a separator wall/panel. I am no expert and am just repeating what this guy was saying but might be worth checking if this might affect your installation.

Ian

[Matchless]

Thanks for that Deimos. I still don't know if this reduction wil affect the flow of smoke or not, so if abyone has the definitive answer, I would love to know.

As the heat circulation, this must be a fairly new regulatiuon as many French houses have the trunking fed from above the fire itself. I'll have to consult les Bricolages.

[Matchless]

Thanks for that Deimos. I still don't know if this reduction wil affect the flow of smoke or not, so if abyone has the definitive answer, I would love to know.

As the heat circulation, this must be a fairly new regulatiuon as many French houses have the trunking fed from above the fire itself. I'll have to consult les Bricolages.

[Matchless]

Thanks for that Deimos. I still don't know if this reduction wil affect the flow of smoke or not, so if abyone has the definitive answer, I would love to know.

As the heat circulation, this must be a fairly new regulatiuon as many French houses have the trunking fed from above the fire itself. I'll have to consult les Bricolages.

[Bobc]

"I have recently purchase a new glass fronted wood burner that has an outlet of approx. 180 mm diameter, as I believe all new burners have. I would rather not have the expense of  buying and fitting a larger liner and therefore my question is, has anyone had any experience of connecting a larger diameter outlet to a smaller pp flue. Is there a problem with back pressure and flow of gasses. I have been told by several fairly knowledgeable people that I shouldn't have a problem but no one is absolutely  100% sure. I do like definates!"

Unfortunately, that is a non-starter. The fluepipe must be at least the same diameter as the stove outlet.The installation manuals for most decent stoves make this very clear.

You have two choices:

If the stove has not been delivered, then possibly you could choose another model with a 150mm outlet - which is more common.

The better solution - at a cost - would be to replace the old flue (which may not even be stainless-steel and in poor condition) with a 180mm double-skin stainless-steel insulated one. Fumistar or similar will cost you around 120 Euros per 940cm length. You can get this from a decent heating supplier - Brossette have branches in most areas of France - www.brossette.fr.

Presumably the supplier of your stove also offers an installation service - this might be worth using for peace of mind.

Regards,

Bob Clarke
http://perso.wanadoo.fr/grindoux

 

[Matchless]

Thanks Bob,

 

My existing flue liner is about 2 years old and is flexible stainless steel. I get so many different answers from reasonably 'knowledgeable?' people from 'It should be OK' to 'There may be some back pressure. As a couple of friends have said, 'Try it ans see!' I would rather not have the expense and work of having to replace the existing liner.

Peter