Gas fire flue

[hummingbird]

That's really helpful, FiremanT, thanks. I'm pretty sure the kitchen fan wouldn't have been on (not keen on cooking!). The house is a dormer bungalow, and single-storey at the side of the house where the flue is, so I guess it could be affected by higher buildings and trees (and even by my own roof which is higher than the flue).

I'm clearer now about the problem, and what to do about it. All contributions much appreciated : )

 

[gaswizzard]

If you could post up the height of chimney along with any fittings used then 'minimum flue height' can be calculated , at least with this info you won't be flogging a dead horse , maybe this chimney has been borderline regards removal of flue gases from the start?

Is the flue pipe exiting through roof in line with chimney? , if not how much does it offset? , flue pipe/chimney in loft space will have to be exposed if you are dead set on maintaining this particular type of gas fire.

 

[1mowbrayfireplaces]

If you have already fitted an air vent, what about a flueless gas fire.

 

[mysteryman]

You need to have this swept, as already advised. Cobwebs can stop a flue pulling, and they will need mechanical removal - you can't really suck or blow them away.

This can be a dangerous situation - be careful. Like others on this forum, I don't like gas fires. They are wasteful and can be dangerous.

 

[hummingbird]

Thanks for these further replies.

I didn't know about flueless gas fires so thanks for mentioning those.

I think the height of the flue pipe is well below the roof line, even though it's already been extended. I'd be surprised if it could be extended any further as it already rattles in the wind.

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[FiremanT]

I'd be surprised if it could be extended any further as it already rattles in the wind.

So would I!

Seriously, you need to be looking for problems inside the flue, or it's construction.

The following is a website for Solid fuel Flues, but a lot of the content applies to ANY fuel, and may help ypur understanding.

http://www.solidfuel.co.uk/pdfs/curing_chimney_problems.pdf

Your flue terminal is well within regs regarding clearance from your roof. Towards about page 13 or so, it shows the effects of local buildings. You can get the same problem with a hill.

The obvious difficulty with this type of problem is that one needs to be there to get a proper feel for problems. I rarely come across geographical issues, but I guess if you lived in the Lakes or wales it would be a common issue.

 

[gaswizzard]

I think the height of the flue pipe is well below the roof line, even though it's already been extended. I'd be surprised if it could be extended any further as it already rattles in the wind.

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That maybe so but considering this is a bungalow the chimney height could fall short of 'minimum equivalent height' in which case it would spill , we don't know if two 90 bends were used between transfer block and vertical section through roof , and if so this could be the issue , along with what has already been said regards cobwebbs , or maybe the joints weren't raked when the chimney was biult , either way I'd be exposing flue section in roof space if only to establish chimney height is not the issue.

 

[FiremanT]

That maybe so but considering this is a bungalow the chimney height could fall short of 'minimum equivalent height' in which case it would spill ,


The MEH is normally either 3 or 4 metres. Goig on scale compard to the terminal, I would say those are 1 x 450 mm plus 2 x 600mm., giving 1.7M (inc stub through roof). They might even be longer. Add on 2M for lounge giving a min of 3.7 (PLUS length in dormer, whatever that may be). Less allowance for bends.

I would say it probably does exceed the MEH, but everything you say is valid.

 

[gaswizzard]

Minimum equivalent flue height for a gas fire connected to a pre-cast block chimney is 2m , so as you say possibly not a problem , but i'd like to know to be sure to be sure.

 

[hummingbird]

Many thanks for all your thoughts.

I've been doing some research and I've discovered that chimney sweeps do a lot more than sweep the chimney so now I don't know whether to ask a chimney sweep to delve into the roof and inspect the flue, or whether to get my gas engineer back.

If I get a chimney sweep to both deal with the roof/flue and sweep the chimney at the same time, would a gas engineer accept a third-party's say-so as to the size/condition of the flue if he hasn't inpected it for himself?


PS. http://www.solidfuel.co.uk/pdfs/curing_chimney_problems.pdf

FiremanT, this link you posted is tremendous, thanks ever so much. I'll study it properly tomorrow as it's got a bit late now but it looks brilliant!

 

[hummingbird]

Just thought I'd post an update seeing as you were all so helpful when I asked for advice earlier...

The gas engineer has had a roofer remove some of the tiles so that he could look down the flue and he said it's clear. But he's going to raise the flue because he said it's slightly under the correct height and raising it should take it out of a negative pressure area. He'll have to stabilise it with a couple of cables.

A few years ago my neighbour had a 2 storey extension built which has overshadowed my bungalow and made my drive a bit tunnel-like. I'm wondering now if that has affected the draught/pull, or whatever it is that has caused flames to blow back into the room because I don't remember it happening when I first moved here.

 

[gaswizzard]

So what is the chimney height/fittings used?

 

[hummingbird]

I don't know the measurements I'm afraid - if the flue sections are a standard size, it might be possible to tell from the picture...

//www.diynot.com/network/hummingbird/albums/11621/43573

The flue is well below the apex of the roof at the moment because it's a dormer bungalow and the fire/flue is on the single storey section, I've attached some pictures below.

//www.diynot.com/network/hummingbird/albums/11621/44224

//www.diynot.com/network/hummingbird/albums/11621/44225