oil fired boiler questions

[Iain T]

What are the regs regarding the flue position for a flue off an oil boiler - the previous installation had the flue going up the chimney but I want to use that fireplace as a normal wood fire. Is it ok to have a metal chimney outlet coming out of the roof but below the roof top? Can you come out of a wall like a flue on a gas combi in the UK? Thanks for any help

[Opel Fruit<P><BR>Opel Fruit, Dept. 53<P>]

If you have a "normal" apex roof, the top of the flue must extend at least 0.4m above the ridge. It should (the top of the flue) also be 8m from the ridge of an adjacent building. To avoid having lots of flue showing, it is better to have the flue exit as near to the ridge as possible. This also avoids having to guy the flue. If it is a flat roof (unlikely), the top of the flue should be 1.2m above the roof. If the roof is a pent roof, the top of the flue should be 1.2m above the lowest part of the roof, assuming the roof is inclined at less than 15 degrees.

Taking the flue through the wall and up is quite possible, but you must consult the boiler manufacturer for guidance, as each boiler has its own limitations in this respect. There are often limits on horizontal lengths, and the number of turns. You will also need to allow a slight incline away from the boiler in the horizontal.

Also note that flues are quite noisy, even the lagged ones. You may wish to avoid having the flue too close to living areas.

In summary, a long straight flue going straight out of the roof is the most convenient, one suspects! 

[Iain T]

Thanks Opelfruit - would it be possible/legal to take the flue up alongside the chimney stack then at the last minute(ie close to the roof) go through the wall of the chimney stack and vent out of the existing chimney and still have a real fire at ground level - the smoke from the fire having cooled enough to not damage the metal flue? Thanks Iain 

[Opel Fruit<P><BR>Opel Fruit, Dept. 53<P>]

Never done that, and as far as I can glean, it shouldn't be done. It appears that flues cannot share a chimney, and I believe this is to do with the draw of the fire affecting the boiler fuming.

I expect you wouldn't aim to have the boiler and the fire "on" at the same time, but it seems a no-no.

Sorry I cannot be definitive.

Some chimneys have more than one actual flue inside - perhaps this is a possibility?

[Michael]

[quote]What are the regs regarding the flue position for a flue off an oil boiler - the previous installation had the flue going up the chimney but I want to use that fireplace as a normal wood fire. Is it o...[/quote]

IainT. If your previous system used the chimney and i assume the chimney is on an outside wall[i take it you still have the boiler]and the boiler is being repositioned close by,why not fit a flue conversion kit and convert from a conventional boiler to balance flue or low/high level discharge.Save yourself a fortune in twin wall flue pipe etc.Plus i strongly recommend  not mixing solid/flues together in the same chimney.Yes you can have the flue from the boiler comeing out of the roof below the ridge providing there is no opening windows nearby etc,useing an adjustable weather slate or lead made one, the flue needs 50mm clearance from any combustable material through ceiling/roof .Do not decrease the size of any flue off the boiler. Happy flueing.

[Iain T]

Thanks for that Michael - the chimney is actually in the wall between kitchen and stable and so not on the outside, but where the boiler has been positioned there are no windows or anything directly above it so as long as the flue pokes out 50cm from the tiles I should be ok? Can I reuse the flexi pipe from inside the chimney or should it be solid pipe as it will not be enclosed in a chimney? Thanks again.

[Michael]

  Iain T .Do not use the liner again,i would myself put the first metre or so in vitrouse enamel pipe converting to twin wall through ceiling to the height your finishing ,at least 600 above an intersection with the roof [if the roof pitch is about 45degrees]Useing adaptor from vitro to twinwall,ceiling fire plate,adjustable flashing and storm coller,flue terminal.If because you are installing the flue below the level of the ridge and the boiler experiences down draft problems you might have to install an anti down-draft terminal.Natural draft must be checked in the boiler flue pipe or boiler hole no less than 0.75mm w.g not much greater than 5,1W.g really this depends on make of boiler.If there is problems keeping inside the figures laid down by the boiler manufactures then you must install a draught stabiliser in the flue. No matter what, if  your doing the work yourself get somebody to commission it.  My one finger is now tired.Happy flueing.

[Gyn_Paul]

[quote]IainT. If your previous system used the chimney and i assume the chimney is on an outside wall[i take it you still have the boiler]and the boiler is being repositioned close by,why not fit a flue conv...[/quote]

Michael,

are you saying it’s possible to convert ANY oil boiler from a conventional to a balanced flue?

If so, what do I need, what’s it called, and where do I get it?

I’m putting a small, cheap boiler in a tall barn and it would need some 35 feet of vertical piping to reach even the lowest part of the roof pitch. To be able to belt a hole in the wall and vent the fumes straight out/the fresh air straight in would be a God-send!

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