Twin walled flue

duggo1

Apologies for all the questions, but could anyone advise if 5" British made midtherm HTS (or equivalent!) is suitable for burning smokeless fuel. I hadn't realised that specific 'liners' were needed for smokeless.

wintergirl

Isn't a twin walled flue meant to be 6inch minimum, unless the stove is a defra approved one??
(Are we talking about the rigid ones that go up either inside or outside a house that doesn't have a masonry chimney?)

verydeeppockets

There are two different grades of stainless used in liners - 316 and the more expensive 904.
Smokeless fuel may be more corrosive (note I'm guessing here) so might need the 904 liner or flue.
And as already said, 6" is the minimum standard really, not sure if Hetas still approve a 5" flue - think it's only ok on certain stoves that have a 5" outlet on them.

duggo1

It's a defra approved stove, and it is going to go up entirely outside the house if that helps.
Is there a benefit to 6" flue or is that not required for a 4-5 kW defra stove

duggo1

Deleting duplicate post

muckybutt

verydeeppockets wrote: »

There are two different grades of stainless used in liners - 316 and the more expensive 904.
Smokeless fuel may be more corrosive (note I'm guessing here) so might need the 904 liner or flue.
And as already said, 6" is the minimum standard really, not sure if Hetas still approve a 5" flue - think it's only ok on certain stoves that have a 5" outlet on them.

Slight difference between liners and twin wall, although liners are indeed twin walled with different spec's of stainless etc Twin wall is insulated and comes in lengths that you lock together.

You are indeed correct in saying smokeless can be corrosive, I have seen twin wall rotted because of smokeless use.

duggo1

Thanks muckybutt. I do plan to burn wood mainly, but had hoped perhaps one day a week to burn smokeless. I thought the extra heat would be good for the flue, but maybe not.
Seems a bit of a minefield this multifuel malarkey!

muckybutt

You shouldn't have a problem just burning smokeless occasionally like you plan to duggo, it's when you burn both wood and smokeless you get the problems.

I would recommend you fitting a flue thermometer even with twin wall, a self tapper straight through the middle of the thermometer and that will give you the right burn temps. Make sure it's long enough to go through both walls of the liner though.

duggo1

Unfortunately mr duggo doesn't like the look of flues or stove pipes so they are going straight out the back of the stove. I might see if I can get one to go on the stove itself though.
In the first instance I think we are going to get a big batch of kiln dried wood as the stuff we have been seasoning isn't quite dry enough, and we don't want smoke annoying our neighbours when it's first installed.

Greenfires

Bear in mind that you'll pay a price premium for KD logs. Yes, they may be ready to burn - but in a half decent year, the logs from "Old Bob" or whoever, who seasons his wood properly before selling it, will often be drier than KD - but without the hefty price difference. Kiln driers usually quote at around 20% m/c or below - we get offered it by the container load from Eastern Europe on a weekly basis at least. Briquettes by comparison come in at around 5% m/c or less.

Chimney_Sweep_3

duggo1 wrote: »

Unfortunately mr duggo doesn't like the look of flues or stove pipes so they are going straight out the back of the stove. I might see if I can get one to go on the stove itself though.
In the first instance I think we are going to get a big batch of kiln dried wood as the stuff we have been seasoning isn't quite dry enough, and we don't want smoke annoying our neighbours when it's first installed.

You are only allowed to go 150mm horizontal with a flue, out the back and through a wall will most likely be more than that, do not use a thermometer on twin wall even with a screw through to the inner flue, it will give false readings and may lead to over firing the appliance damaging both flue and appliance.