Awkward flue installation

[DodgyJammer]

We'd like to install a stove but I'm a bit stuck about how to route the flue. Local installers haven't been very helpful - it seems they've all got more work than they can handle and they don't want difficult jobs.

We have a newbuild house which is permanently cold in the winter. I'd like to replace a long window with a false chimney breast or recessed fireplace, inside which will sit a multifuel burner. The flue will need to go out through the wall and up the side of the house, avoiding a window immediately upstairs. This drawing shows what I mean:

Untitled

• DodgyJammer
• 26 Jan 2014
• 1

I've read that a flue can have a maximum of 4 bends. Here I'm using two bends to avoid the upstairs window and another two to clear the eaves so I've got no bends left to take the flue from the stove through the wall.

I'm sure my problem is not unique and I'm hoping someone with experience can offer some practical advice. Any ideas would be greatly appreciated!

 

[Blagard]

While bends should be avoided I am not aware of any maximum limit. Where did you read that?

 

[DodgyJammer]

On quite a few websites I've read that four bends is the recommended maximum.

For example here it says...

"The direction of the flue should be straight and vertical where possible. Horizontal runs should be avoided and, in any event, must not exceed 300mm in length. Bends should not exceed 45º to the vertical to maintain natural draft and ease of cleaning. There should be no more than four bends in a flue (a 'Tee-piece' on the rear of the stove counts as two bends). Only one appliance may enter any flue and all flues should be insulated to prevent condensation of water/tar and to protect the building against the effects of chimney fires."

I agree that this seems like guidance rather than regulation (regs seem quite vague) but I want to avoid any building control issues.

I reckon vertical displacement of the flue will be around 6 metres in total. Do you think it would it be acceptable to have 5-6 bends?

 

[Blagard]

There are regulations with regard to access for cleaning and to be honest I don't see your scheme working as it is. This is where using a HETAS installer would be the best way to go because they have to be satisfied that the flue complies.

Your top bends are to clear a verge are they not? So the question there is what is the verge overhang and can it be done without those bends? e.g. can the flue be set further away from the wall at the second external bend to go straight up?

Have you considered using a service such as:
http://www.stovesonline.co.uk/external-insulated-flue-system.html They would need dimensions of all offsets and overhangs. They claim "Another feature is our complete flue design service: flue experts will design a building regs compliant installation for you"

 

[DodgyJammer]

Blagard, thanks very much for the tips. I wasn't aware of this design service and will give it a try.

 

[Norcon]

From the Selkirk website....

http://www.selkirkchimney.co.uk/documents/products/STC BROCHURE.pdf

Page 9 shows a typical stove set up with Class 1 flue.

 

[stuart45]

You can go through the verge.

Untitled

• stuart45
• 26 Jan 2014
• 1

 

[Blagard]

You can go through the verge.

No that's the Eaves! - But good example where the overhang is big enough to do it.

 

[stuart45]

You can go through the verge.

No that's the Eaves! - But good example where the overhang is big enough to do it.

I know that's the eaves, but on his it needs to go through the verge.

 

[DodgyJammer]

Yep, verge I guess, not the eaves. I'm gradually learning the lingo.

The overhang in our case is 32cm including a plastic edging which I guess can be cut away when the tiles are removed. I'll get a builder for this work but just want to make sure it's possible in principle before I send drawings to our friendly building standards people.

I'm wondering if I can avoid the kink around the window by exiting the wall further to the left then going vertical. This would mean...

• 
  Exit stove from top outlet, connecting to approx 1m of single wall flue
  Convert to twin wall flue
  Bend 45 deg back and 45 deg right at the same time
  Pass flue through wall
  Bend back to vertical

This would involve 2 bends, allowing another 2 for the verge if needed, but it would mean going through the wall at an odd angle, skewed from vertical and horizontal. Anyone know if this is possible/sensible?

 

[Norcon]

That's how I would try to do it. If the chimney breast is wide enough and the offset gives you enough before hitting the ceiling.
Then straight up from outside.

135 degree insulated T and plug> 45 elbow > 45 elbow> 45 elbow then vitreous enamel transition connector.

Selkirks off set charts on page 4 gives guideline distances for various flue length sections.

 

[Blagard]

I know that's the eaves, but on his it needs to go through the verge.

My bad! I thought you were titling the photo.

 

[Jackrae]

Be aware that the more kinks (offsets) you have the harder it will be to clean the flue and the greater the likely-hood of deposits building up on the flue walls. If you have any horizontal sections then flue wall deposits will not fall back into the stove so rendering any "self-cleaning" action ineffective.

 

[maltaron]

You can get 15 degree bends to form your offset but as said, its really up to the Hetas man to design it. I would suggest, however, that you shop around for the actual flue, Selkirk are probably the most expensive and there are many other makes cheaper.

 

[Yellowduck]

Just a question....

We are thinking of having a stove in a new kitchen extension, but looking at the picture posted above, does the flue have to extend as far as the one in the picture?

We are on a flight path, and a flu of that height may be considered a danger to aircraft....

Perhaps stupidly, I was thinking that if the stove was against an outside wall, the flu could simply go through the wall and have an outlet fitted, similar to a gas boiler!

Anyone know of any imitation 'woodburning' stoves run on gas?....LOL