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Author Topic: wind blowing down the chimney  (Read 3296 times)
knighty
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« on: November 29, 2011, 09:22:31 PM »

we have a gas bottle type wood burner in the tea room at work

it's not actually made out of a gas bottle but it's almost the same design (it's a bit bit of pipe)

we;re pretty near the coast... and about 100 feet from the river wear so it gets pretty windy,

it doesn't take much wind to blow the smoke back down the chimney and out the bottom of the fire... even if we have a rawing fire and plenty of draw on the chimney Sad

I thought it was because the chimney was too short, so extended it a few meters bit it's no different at all....


burner is a couple of inches wider than a gas bottle type, top loading, with a door at the bottom for ash and holes in the bottom to let ash out - a bit like the grill in a coal fire....
(I know this isn't perfect... but it was given to me foc)

chimney is about 6 inches diameter to start with, with a couple of swept bends rising all the time (made out of flexible lorry exhaust joints), out of the wall and then it's reduced to 5inch diameter and goes straight up... there's a pate above it like a cap to stop rain etc.. coming down...

it didn't have a cap on it before I extended it so I don't think that's making any difference good or bad

do i just need to go higher with the chimney ?  it's probably only a meter above the peak of the roof (it comes out on a low edge not the gable end)

it's only temporary for this winter so I don't want to put too much time/money into it when I have a million other things on the 'to do' list !

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biff
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« Reply #1 on: November 29, 2011, 09:46:51 PM »

one of dem whirlly birlly fings that suck the smoke up into the sky and leave you clear eyed and happy, Grin
       and you could also lower the head of the fire opening,if its an open fire, you can get fancy copper pelmet to come out and trap the smoke from leaving the fire area,,,the possibilities are endless,,
   or you could line the chimney with an s/s liner,and stick a liddle stove in it. a sealed job that leaves no room for naughty smoke.,,,,,,,,,,,,,,,,,,,biff                                                         
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johnrae
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« Reply #2 on: November 29, 2011, 10:17:01 PM »

My ha'penny worth of opinion.  Might well be wrong but here goes.

You offer contradictory information.  You say the fire smokes even with a roaring fire and good draw on the chimney.  Good draw and smoking fire are mutually exclusive terms - unless the chimney is too small to handle the quantity of smoke being made.

Assuming it only smokes when you have a smokey fire and is drawing very slowly then it might not be due to down-draught but actually due to negative pressure in the room.  This can be caused by the wind blowing round the building and a room somewhere having either an open door or window on the leeward (downwind) side.

You might want to try sealing off the bottom ash-holes under the fire basket.  This will slow down the burn rate but also prevent a way for negative pressure to cause a reverse flow in your flue.

I'd also suggest that bits of old exhaust etc do not make a good flue.  Too many joints, restricted diameter and changes of diameter all add up to increased back pressure which has a serious effect on a fires ability to freely exhaust itself.
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knighty
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« Reply #3 on: November 30, 2011, 01:26:13 AM »

sorry I didn't explain very well

the fire is sealed at the top around the lid, air only gets in/out at the bottom

it only smokes into the room when the wind blows down the chimney and blows the smoke out into the room (and flames out the bottom of the ash grill)

with no wind, there is no smoke into the room


what I was trying to say was, even with a roaring fire and plenty of draw the wind can still blow the smoke back down the chimney and into the room
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johnrae
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« Reply #4 on: November 30, 2011, 08:51:19 AM »

Definitely sounds like the room is under negative pressure
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knighty
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« Reply #5 on: November 30, 2011, 01:29:59 PM »

it could well be....

there's a hole in the wall where the combi boiler was (before it burst into flames in the middle of the night and incinerated everything in the tea room)

I'd have bricked it up by now but the chimney is sticking out of there.... there's a few loose brings in the hole to stop too much wind getting in....

and there's no door on the tea room, it leads straight into the factory... which always has big doors wide open...


I didn't think about the air being sucked out of the stove... only blown out

looks like we'll just put up with it over winter or until I get get the new boiler connected up to the radiators !
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biff
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« Reply #6 on: November 30, 2011, 02:27:39 PM »

temp lobby between tea room and factory,,like an air lock,
           this should solve it.
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Justme
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« Reply #7 on: November 30, 2011, 04:25:08 PM »

there's no door on the tea room,

looks like we'll just put up with it over winter or until I get get the new boiler connected up to the radiators !

Or fit a door?
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Baz
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« Reply #8 on: November 30, 2011, 06:24:20 PM »

or at least a blanket across the hole which would also show sudden changes in air pressure while acting as a sort of valve if placed on the inside.
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knighty
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« Reply #9 on: November 30, 2011, 10:15:01 PM »

the door is tricky... lost the last one in the fire...

a mix of health and safety rules + defra rules + the local council inspector for our permission to make petfood permit (this one is also known as an excuse to send me a big bill)

mean that the door has to have at least a transparent section to so we can see out - the factory has to be under observation at all times incase someone comes wondering in and decides to climb into the mincer etc...

and it has to be fire retardant... not just fire retardant, but a special kind of plastic fire retardant which will melt in a fire, fall onto the fire and put it out
(the exact same stuff we had in the tea room previously which burnt to ash)

and the plastic has to be the right kind so bacteria can't attack/live in/on it



so it's easier to go without a door for now

I'll wait until a big meat factory etc.. closes down and then buy one of there doors and adapt it to fit... if I try to buy a new one the salesman eye's will like up like a Christmas tree as he decides which phone number to write after the pound sign on the bill Sad
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biff
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« Reply #10 on: November 30, 2011, 10:44:02 PM »

well knighty,
         there is one sure thing,you will not have workers hanging about doing nothing.they will be running about trying to keep warm if not working.,,,,,,,,biff
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knighty
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« Reply #11 on: December 01, 2011, 02:13:08 AM »

it's the other way around.... it's so warm in there with the wood burner that we're all falling asleep !

but it is nice :-)


the alarm on my phone is set for 1pm for when I actually do fall asleep at lunch time, which happens quite a lot... but I blame that on the long hours
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