Fitting 90degree bend to back of stove

[RosietheNB]

Hi all, we’ve got a multi fuel burner for our NB (Vulcan 5.2kw) as it is quite a small stove and we’d like some space on top for a kettle and casserole dish or whatever we were hoping to make use of the vent on the back to attach the flue to. We’d have to have a 90 degree (?) bend to ensure that the flue could then travel straight up and out. Is this allowed with BSS rules as early research seems to indicate we’re not allowed a bend more than 30 degree. Worth noting we’re pribably going to double insulate the flue and our JB boat roof is GRP onto steel if that makes any difference. Thanks in advance!!

[TheBiscuits]

Two bends of not more than 30 degrees is the guidelines - so basically no.

 

Think laterally - get a skinny kettle, and bake spuds in the firebox.

[BEngo]

Our Morso Squirrel stove sits at 45 degrees to the centreline with  a 90 deg bend from the  back outlet  and two more skew bends to make it parallel to the side wall and then to turn it vertical again.  It works fine and has had a BSC without problem since the beginning of the scheme.  BSC was renewed last December.  The flue  was fabricated from 113 mm dia steel pipe.

 

The latest  Code of Practice does indeed suggest no more than two 30 deg bends, so if you want to use double skinned prefabricated flue pipe you will probably not be able to buy a 90 deg bend.  It is not a mandatory Standard so if you can get a flue that fits your wants then you can fit it.   I would note that a length of horizontal pipe from the stove into the bottom  chimeny with the 90 deg bend effectively  inside the chimney would be OK with most stove installation instructions.

 

You will need to find a suitable flue collar, but that should not be a problem- the fasteners should have some big load spreading washers where they pass through the GRP.

 

The other issue will be how you get at the bottom of the flue pipe to empty it when the chimney has been swept.  I go in through the blanking plate in the top of the stove, but this does maen the blanking plate needs to be easy to get off.

 

N.

[David Mack]

If the stove manufacturer provides a rear exit then they are envisaging that some users will indeed fit a right angle bend to connect to a vertical flue. This must therefore be "in accordance with the manufacturer's instructions", and so shoudl be acceptable.

[mark99]

Download the instructions and see if anything that advises no 90's but two 45's instead.

 

90's are NOT recommended on a lot of stoves. Nor horizontal pipes > 150mm long.

Edited February 1, 2019 by mark99

[Clodi]

37 minutes ago, David Mack said:

If the stove manufacturer provides a rear exit then they are envisaging that some users will indeed fit a right angle bend to connect to a vertical flue. This must therefore be "in accordance with the manufacturer's instructions", and so shoudl be acceptable.

As above, I have a hobbit stove which comes with a stainless stove-top for cooking etc and a rear entry flue which attaches to a Tee section of flue. 

Edited February 1, 2019 by Clodi
add link

[RosietheNB]

Thanks everyone  we will definitely consult the manufactures guidelines and hopefully get a safe and practical solution !

[NB Esk]

Mine has a 90 degree back out of the back and has an excellent draught with no problems.  I can reach the bend from the door with a long poker to clear any debris.

 

 

[Chewbacka]

The regs for houses from which the boat regs seem to be devised specifically allow for a 90degree tee for a rear flue outlet.  It’s what I fitted about 6 years ago and was approved by a Hetas guy and a bss inspection.

[mark99]

10 hours ago, Chewbacka said:

The regs for houses from which the boat regs seem to be devised specifically allow for a 90degree tee for a rear flue outlet.  It’s what I fitted about 6 years ago and was approved by a Hetas guy and a bss inspection.

Iirc you allowed 4 bends max in a house with a 90 counting as two. But you do have a decent height to promote the flue draw.

[Bee]

I have a stove with a 90 deg bend. I would suggest that the weight of the flue may be a bit much for the roof to support without flexing and there is a risk of cracking the back of the stove. I would try to work out some support for the flue, I had a root around a builders supply place and adapted a drainpipe support thingy, I expect a heating supply place should be able to suggest something too.

[Mac of Cygnet]

Flues in houses tend to be wider than those in boats.  One of our stoves at home has a horizontal section from the back, but it's 7" diameter.  Flues on smaller boat stoves can be down to 3" or even less.  I'd be concerned that debris could easily and dangerously  block this section, whatever the instructions say.

[Guest]

There used to be a boat on our marina with a 90 degree bend in the flue. The stove was always difficult to control from new, and used to blow smoke back into the cabin. I am no expert but it was a similar stove to mine which behaves OK without a 90 degree bend.
In the case a house, the flue draws much better, probably owing  owing to its increased length and diameter, but again I am no expert on this, or anything.

Edited February 2, 2019 by Guest