Blackening linked to a R Brisac chimney

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cathymary
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Blackening linked to a R Brisac chimney




by cathymary » 29/03/08, 15:55

Here is the problem that concerns us enormously: in December 2006 we had a fireplace installed at R Brisac (niagara model): the installer has closed shop since (!).

In 1 year of use, there has been a considerable darkening at the level of the hot air outlets (and on the ceiling where now all the placo plates are outlined in gray!).
illustration with photo at this address:

Image

By trying to look inside the hood, we do not spot any faults (everything looks well insulated) and we do not understand where this darkening comes from? ? ? the draft is good, there is no smoke outlet when the door is opened (which is opened well in 3 stages as advised and always with open draft), at most some ashes are suspended when we load a load of wood.

Of course we burned pine / fir wood (and we know that it is not recommended!) But we maintain the duct well with 2 mechanical sweeping + 1 chemical in the season… so why would air heated by pine be different from air heated by other wood? ? ?


Help: what to do! ! !
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martien007
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by martien007 » 29/03/08, 18:13

Of course we burned pine / fir wood (and we know that it is not recommended!) But we maintain the duct well with 2 mechanical sweeping + 1 chemical in the season… so why would air heated by pine be different from air heated by other wood? ? ?

pine wood = softwood.

this wood fouls the ducts a lot, but does that explain the smoke coming out of the hot air vents?

there must be specialists on this forum that have similar chimneys or on others forums.

Bonne chance.
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by Christophe » 29/03/08, 18:32

The worst at the fouling level would not be the oak?
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by Rabbit » 29/03/08, 18:37

If it is not about smoke, it is certainly about dust
and calcined dust.

so why air heated by pine would be different from air heated by other wood


I guess you took the wise precaution of using
softwood dry and avoid slow combustion .Excelent decision
especially as this avoids clogging the chimney as well as the hearth.
In addition it heats better. Much better than even if the coniferous
burns faster than a hardwood, you should know that for a
same weight all wood has the same energy capacity * a
some details close (in favor of softwoods) .Conclusion if
the same energy is emitted more quickly, the temperature is
higher. D or hotter air, more strongly stirred dust
and greater quantity of burnt dust.


* http://www.dutry.com/lire/qualite-bois.html
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cathymary
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please




by cathymary » 29/03/08, 18:45

thank you for this information, indeed the wood which one burns is quickly "uncontrollable" is strongly flames rising in a fast and important way the hearth in temperature.
except that we live in the middle of a pine and fir region and that providing something else is difficult and expensive: aih!
Could we "filter" the air leaving the vents to retain this dust?
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by cathymary » 14/04/08, 17:02

news !!
we are perhaps on an explanatory trail: another pathologist (nice!) came to see our installation and several faults appear: some can be corrected others not!
first our fireplace requires a supply of fresh air of 2 dm2 of section (a hole of diameter + 20 cm! .... while that which we made 10 cm in diameter !!!): that we will enlarge!
then this type of very high hearth requires a very good draft and therefore little bend in the casing (maximum 15 ° slope ... or here with us the chimney connection is made by an inclination at 45 ° !!!) .... that we can not come back ...
moreover, at the exit of the roof, our chimney just reaches the ridge of the highest roof when it should exceed it by 40 cm !!!! ... that, we are going to try to have a mason raise it up.
In short because (we think!) Of that, the draft is not enough, when opening the door there is smoke that escapes but does not necessarily spread in the room: it is sucked by space located at above the hearth, which communicates with the insulated box ... and then it spreads through the air outlet vents, with the hot air !!!

if this experience can be used by someone who is installing a chimney !!! us, it is no longer possible to contact the installers who got it wrong: the box simply closed !!!
[/B]
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by John » 14/04/08, 20:57

The blackening at the hot air outlets is simply due to the dust contained in the hot air.
The dust contained in the air carbonises on contact with the heating element of the hearth, is transported by hot air and is deposited at the level of the air grilles. It is the same phenomenon that is observed above low-end electric radiators with hot resistance.
The most effective way to combat this phenomenon is to increase the air flow circulating around the fireplace. Increase the size of the hot air grate on the hood (the large one) and facilitate the arrival of fresh air under the chimney. You can also increase the size of the decompression grid (the small one).
A significant part of the soiling is also due to the fumes which escape when you open the door of the fireplace to recharge it. It is a fireplace with an "all height" door and they are the worst from that point of view.
There is an opening at the top of the door between the fireplace and the lintel of the chimney, when you open the door of the fireplace, the smoke slides in this interval and mixes with the hot air from the hood and accentuates the dirt
In any case do not be under any illusions, you can only limit the phenomenon but not remove it. It is a heating system that works by circulation of hot air and it will always make streaks on the ceiling ...
Regarding the draft, this is certainly sufficient for the normal operation of the fireplace with the door closed. A vacuum of 10 Pa is sufficient (which is not much).
By cons when you open the door it takes a huge flow to prevent smoke from escaping. And as the door is open the temperature drops and the vacuum also.
Something that works pretty well. When you want to recharge the fireplace, open a window in the room 5 seconds before to stabilize the pressures (your house is in depression due to CMV and the chimney). Reload the fireplace and then close the room window. Having the window of the room open when you open the fireplace door increases the draft and the flow rate of the chimney flue which limits the outflow of unwanted smoke ... and it costs less expensive than having the duct raised ...
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by denis » 14/04/08, 21:18

don't you care that your fireplace is tight, to the hot air recirculation circuit !! there is danger of intoxication, involves a specialist, the draft is another problem, even if there is a fault here too, the air intake sections are rarely respected !! but it’s not the most serious,
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White would not exist without the dark, but anyway!


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by jc-tergal » 14/04/08, 22:20

cathymary wrote:news !!
we are perhaps on an explanatory trail: another pathologist (nice!) came to see our installation and several faults appear: some can be corrected others not!
first our fireplace requires a supply of fresh air of 2 dm2 of section (a hole of diameter + 20 cm! .... while that which we made 10 cm in diameter !!!): that we will enlarge!
then this type of very high hearth requires a very good draft and therefore little bend in the casing (maximum 15 ° slope ... or here with us the chimney connection is made by an inclination at 45 ° !!!) .... that we can not come back ...
moreover, at the exit of the roof, our chimney just reaches the ridge of the highest roof when it should exceed it by 40 cm !!!! ... that, we are going to try to have a mason raise it up.
In short because (we think!) Of that, the draft is not enough, when opening the door there is smoke that escapes but does not necessarily spread in the room: it is sucked by space located at above the hearth, which communicates with the insulated box ... and then it spreads through the air outlet vents, with the hot air !!!

if this experience can be used by someone who is installing a chimney !!! us, it is no longer possible to contact the installers who got it wrong: the box simply closed !!!
[/B]


I was going to give you this answer because we had the same problem and the explanation by a good pathologist.

Small precision on the wood: In your opinion what is the most used wood in fireplace in Canada ???? The pine and yes and yet they have no more problem than us. It's all about combustion: you take the driest hardwood (oak, frenehetre ...) in the world, you cut the draft like all people do at night to make the fire last, result = bistre and pollution the children because combustion is incomplete. DOnc the real answer is to have a draft always sufficient to have beautiful flames and to know that beyond 1000 ° everything is burned. A good draft allows this temperature in the hearth. Of course you need dry wood or the humidity will lower the temperature etc ...
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cathymary
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by cathymary » 22/04/08, 15:42

thank you for all your comments and / or advice!
we are moving slowly because we have just had the address of our installers' decennial insurance (even if the company has closed, they must insure it seems !!!)
fingers crossed !!! ...
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