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I'm finding that our woodburner needs the flue pipe to be hot in order to draw air through properly.

Now ... when you start the fire the flue is - err - cold ... so the smoke from the fire poors out of the vents and cracks into the room for five minutes ... not nice.

What's the 'proper' way of avoiding this?

Humm,

Don't have these problems myself, is it because you do not have enough 'draw' on your flue?
Possibly the external flue you have needs insulating?

You could try pre-heating the flue with a fan heater or something.

edit..

I usually leave the door ajar to get it really started, that seems to pull a good jet of air through then close it up when it's going well.

I had similar problems with mine. The smoke didn't come out through the closed vents, but did through the open door when I was trying to get it started. I had a straight double skinned flue, and even with a Rotovent (I was too mean to try an electric flue fan!) it wasn't much better.

I put a lot of the problem down to the flue needing to be longer, as it was a bungalow. It did seem to vary with the weather conditions, and I had a feeling it was also something to do with the location. I was on level ground at the foot of a fairly gentle slope to a 600ft ridge on the edge of Exmoor, and a few hundred yards the other way it dropped away a bit and was almost a sea level, with the Bristol Channel not too far away. My neighbour had open fires and often the smoke would go up one chimney and down the other. I once saw a wind map of the area, and seemed to be in a bit of a dead spot, although some nice winds came round the side of the ridge at times. I had no idea how to find out if I was right though.

Make sure you have a window or external door open. Check that you have not draught-proofed your house too well. All the air that goes up the chimney must come into the room from outside.

The little stove in my last place had 30" of horizontal pipe before about 10' of vertical pipe - both iron, uninsulated.

To get this started without a roomful of smoke became a set ritual with a fair mass of scrumpled paper (not the Times or FT)
with a scatter of charcoal dropped over the back of it, and with some good kindling scattered loosely on top.

Light the paper in front of a wide open vent, and keep the door open until flames have taken hold well, then close the door
and let the flames' heat push the plug of cold air out of the chimney.
When it's flaming well, add more kindling across the lay of the first lot.

Some chippings of candle on the paper will help, as will a modest libation -
for instance of meths.

Sealing all the stove's cracks with fire cement, and with stove-cord around the doors, will also help.

It does sound as if the flue has a problem though - a friend once had a similar problem - that was eventually found to be due to nest-building by jackdaws . . . .

Simple country living, it ain't.

Good luck with it.

Billhook

biffvernon wrote:Make sure you have a window or external door open. Check that you have not draught-proofed your house too well. All the air that goes up the chimney must come into the room from outside.

Mine had a vent complying with building regs piped into the room just beside the hearth, and the house was pretty draughty.

I was given a demonstration on fire lighting on my stove by an American (one of the enlightened ones) with years of experience of wood burning. He made the point that every stove has it's own characteristics that you need to learn. Some need a door slightly open, others need vents in certain positions etc. So not only do you have to work out if there's a technical problem, you also have to learn the knack of lighting your own stove!

A flue is unlikely to work correctly if the air pressure in the room is even slightly below the outside air.
Such negative pressure may be caused by extractor fans in kitchens and bathrooms, which should be turned off.
Presuming that the house is warmer than outside, then negative pressure can result from opening upstairs windows whilst trying to light the fire, any upper windows should be shut, and a downstairs door or window opened if required.

Preheating the flue certainly helps, and as suggested above a fan heater could be used, but an electric heat gun as used for paint stripping is better as the air is hotter.
Prepare the fire for lighting in the usual way, and as soon as the match is applied, direct the heat gun up the flue.
A gas blowlamp can also be used, and is handy for lighting the fire also.

The trick I've found with our fire / stove / ceramic monster is to keep the lower door (for ash removal/cleaning) full open when the fire starts. If I try and close the door before the fire is really going I have similar problems with smoke and smells. In fact depending on the wood I usually leave it open a crack right through the three - four hours it takes to consume a load of wood.

I did try playing with the air vents in the main door but found these are too close to the front of the fire. Good at letting smoke out, but not so good at letting air in. The air flow from directly below the fire works far better for getting the beast going. I'm told when it gets really cold here (-20C) if the wood is really cold it is sometimes necessary to apply a fan to get the thing going. At least I think that was what I was told, the conversation was in Gerhunglish.

We also have vents from the garage nearby which provides air for our gas condensing boiler. I guess this also means we get a good supply of air for the fire.

As others have said, each stove behaves a little differently. With mine (which is the same as yours) I light it with the doors closed, but the bottom and top vents open. When it's roaring (it makes a kind of sci-fi throbbing sound) I close the bottom vents 2/3rds of the way, then when it's red hot, I close them completely. When it's going, I control how hot it runs using the top vent.

I mention this because the manual didn't and it took 6 months before a mate came round and showed me how to control it properly.

We have absolutely no problem at all lighting our wood stove.

That's not a smug statement - it's taken years to get right and lots of hassle.

Prior to have the chimney completely re-built the fire was a pig of a job to light and it wouldn't stay in for long, having burnt like crazy. Tight seals now mean it stays low all night and, in the morning, open and vent and whoomph!

One of the biggest hassles since was this: the flue liner, which was fitted in eight foot sections, the very top section slowly (over a period of months) worked its way out. The chinaman's hat had to be removed as the gap was closing. It carried on moving slowly upwards and outwards till about three feet stuck out of the chimney pot, at which point I got a man in to push it back in and rivet it in place. Otherwise it would be four foot out now.

Vortex wrote:I'm finding that our woodburner needs the flue pipe to be hot in order to draw air through properly.

Now ... when you start the fire the flue is - err - cold ... so the smoke from the fire poors out of the vents and cracks into the room for five minutes ... not nice.

What's the 'proper' way of avoiding this?

Sometimes it can be as simple as leaving a door open from another room or from upstairs. I know - I've been there.

I'm no expert on this but I seem to remember seeing a plate that could be placed over the front of an open fireplace that had an electric fan built in. Would it be possible to make something similar for your stove ?

Not wanting to sound smug! But i have had no problems at all with my woodburner - its lit first time every time, no back smoke its great!

Stating the obvious making sure that you use a firelighter and some bone dry kindling makes the job a lot easier.

i have both vents fully open then when the fire is roaring close the top one down and then gradually shut the bottom one as the fire becomes more established.

omnicans wrote:i have both vents fully open then when the fire is roaring close the top one down and then gradually shut the bottom one as the fire becomes more established.

On the woodburner that vortex has, it's the other way around. Bottom first, then top.

Billhooks got it for my money. You've got an outside flu with a 30 deg bend haven't you???

You could improve chances by opening a window on the weather side of the house to kind of force wind up the chimney.

Alternatively you could wait for the wind to change direction

I guess that the metal flu is cooling quicker than the brickwork of your house. This means you have warm air outside the chimney and cold inside it. The cold is sinking and pulling air down the chimney. This would make sense as I expect you're lighting the fire in the evening as the outside air temp is droping. You could try insulating the outside flu with something. e.g. this kind of stuff.

Alternatively, try lighting the fire an hour before the temp really starts dropping outside.