Woodburner...

[john87]

16 minutes ago, Mick Dempsey said:

That explains an issue I had a few years back. 

The smoke goes up the flue, because it is warmer and thus less dense than the outside air and so it rises [as a hot air balloon would] This is why longer flues draw better, they contain more hot air..

 

Now, say it is warmer outside than it is in your house, the opposite happens and the air outside will come DOWN the flue, and, as you say, fill the room with smoke..

 

john..

[Mick Dempsey]

Just now, john87 said:

The smoke goes up the flue, because it is warmer and thus less dense than the outside air and so it rises [as a hot air balloon would] This is why longer flues draw better, they contain more hot air..

 

Now, say it is warmer outside than it is in your house, the opposite happens and the air outside will come DOWN the flue, and, as you say, fill the room with smoke..

 

john..

Don’t think you’re right, it gets pulled because of the Venturi effect (initially at least)

that’s why when the wind is blowing it pulls better.

[john87]

3 minutes ago, Mick Dempsey said:

Don’t think you’re right, it gets pulled because of the Venturi effect (initially at least)

that’s why when the wind is blowing it pulls better.

Have a read of this..

Why Is My Chimney & Fireplace Drafty? - Certified Chimney Sweeps

WWW.HIGHSCHIMNEY.COM

---

Interested in diagnosing a smokey fireplace? Call our chimney experts in the Gaithersburg MD area for a chimney...

 

john..

[openspaceman]

4 hours ago, Stubby said:

Mine had ( still has ) a 7.5" clay liner . A 6" SS liner fits snugly up inside it and the stove is attartched to that . When its been on a few hours the chimny breast in the loft gets warm . So no problem heating the wall here either .

I suppose because it was a snug fit there was no room to pour insulation around the liner and hence the warming of the loft.

 

If you consider what a chimney does, it removes all harmless the products of complete  combustion as well as the toxic  bit from incomplete combustion from the living space and puts them high enough that they will be up and diluted before they reach any neighbours. So logically you don't want any heat going up the chimney. With a gas boiler this is done by transferring any remaining heat from the flue gases to the combustion air and allowing little droplets of water to form. With a log burner there is much more water vapour in the flue gases so they need to be kept warm enough so as not to condense out onto the chimney walls. With our industrial boilers we would extract as much heat from the firebox and send it up the chimney at about 110C, as the chimneys were double insulated  the gases should still have been above 100C at the top. This is one reason why woodburners are never as efficient as natural gas boilers.

 

Now in my case because my stove does not keep burning all night I am happy my stove leaves some excess heat in the flue gases as during the day the chimney breast heats up and then gives up its heat while the fire is out. My 6" flue exhausts into an 8" approx. concrete, cast in situ chimney. Not ideal as this means the flue gases slow down as they pass the register plate. I seldom allow the flue temperature to get above 150C and on a mild day will allow it to drop to around 110.

 

The corollary of this is the batch burning masonry stoves which instead of being regularly loaded with logs during the day are loaded once with a few tens of kg of dry wood and then burned flat out. All the heat is used to heat the masonry surrounds as the flue gases travel through a labyrinth of brickwork. The fire goes out and is sealed and the  brickwork continues to heat the house until the next day when it is reloaded and fired.

[john87]

2 minutes ago, openspaceman said:

The corollary of this is the batch burning masonry stoves which instead of being regularly loaded with logs during the day are loaded once with a few tens of kg of dry wood and then burned flat out. All the heat is used to heat the masonry surrounds as the flue gases travel through a labyrinth of brickwork. The fire goes out and is sealed and the  brickwork continues to heat the house until the next day when it is reloaded and fired.

Never heard of one of them.. What are they like then??

 

john..

[Stubby]

17 minutes ago, openspaceman said:

I suppose because it was a snug fit there was no room to pour insulation around the liner and hence the warming of the loft.

 

 

No , not quite how it is . There is no air gap between the 7.5" clay liner and the chimney wall . Its all pugged in . Also there is not much in the way of " incomplete combustion " once the stove is up to temp . You can tell that by the way the flames " dance" above  the logs with out seeming to touch them . This is the gases being burnt off .

Edited December 14, 2021 by Stubby

[openspaceman]

11 minutes ago, Stubby said:

No , not quite how it is . There is no air gap between the 7.5" clay liner and the chimney wall . Its all pugged in . Also there is not much in the way of " incomplete combustion " once the stove is up to temp . You can tell that by the way the flames " dance" above  the logs with out seeming to touch them . This is the gases being burnt off .

Stop being contrary @Stubby; if there is no air gap then there is no room for insulation and the metal liner touches the clay tiles and conducts heat to them.

 

I know you burn your logs well but even if you see no smoke particulates and carbon monoxide are being produced unless you have a catalytic stove.

 

Norbert Senf of the masonry heaters association in america reckons even if you see no smoke there will be 4000 parts per million and his stoves are amongst the cleanest.

[Stubby]

21 minutes ago, openspaceman said:

Stop being contrary @Stubby; if there is no air gap then there is no room for insulation and the metal liner touches the clay tiles and conducts heat to them.

 

I know you burn your logs well but even if you see no smoke particulates and carbon monoxide are being produced unless you have a catalytic stove.

 

Norbert Senf of the masonry heaters association in america reckons even if you see no smoke there will be 4000 parts per million and his stoves are amongst the cleanest.

Fcuk ! I do my best ! 😁

[Billhook]

Here are a few photos back in 1983 

My big brother standing in front of it who sadly died of non Covid problems last year.

Plus dear old Beatrix the Airedale who died in 1998 aged 16, so lying by a wood fire most of her Winter evenings did not seem to do her much harm

 

The third photo shows the chimney brickwork in the upstairs bedroom , the fifth is the first fire with obviously no air control and the last two are as it us now with a pair of mesh gates to shut for safety overnight or if I leave the room

[Billhook]

Forgot to show the damper control which is an old brass window winder

the metal damper plate goes across the whole width of the throat which is four inches wide and three feet long

When shut it completely shuts off the chimney from the room and is infinitely adjustable until vertical 

When vertical it acts as a shield to prevent any down draught or smoke coming down the throat as the smoke would hit the smoke shelf behind and be taken up with the hot gases

Initially  I had a soot door behind the smoke shelf so I could sweep the chimney into the garage.

But marriage meant the garage was converted into a room and I connected the Aduro stove to the old soot door .

The two fires seem to run together or individually without any problems sharing the same chimney 

 

The second photo is one of the adjustable vents , one on either side, each fed by a four inch pipe set in the concrete floor and fed from outside.