What is a "secondary burn"?
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The flames don't have to be disconnected from the fuel source to be considered secondary burn but that is a parlor trick that many like to play. Simply extending the flame by using superheated secondary air is also secondary burn.
Check out this graphic from Quadrafire showing different areas of combustion. Basically, primary combustion is when the wood ignites, and secondary combustion is when the gases released by the burning wood get hot enough to burn. It produces a lovely fire while reducing the amount of particulate matter emitted by the stove by up to 90% (so the EPA claims).
(broken link removed to http://www.quadrafire.com/images/qdf_four_zones.jpg)
(broken link removed to http://www.quadrafire.com/images/qdf_four_zones.jpg)
Lots of people stress because they think they need to see flames that appear to be coming out of the secondaries all the time. On my stove, that happens for a very short amount of time. Here's a short clip that shows secondary flames. Watch also for the flame that appears and disappears on the back, right, rear side. This is typical of a longer sustained secondary burn, those mystical flames.
http://www.youtube.com/watch?v=LaHISkSNt4Q
http://www.youtube.com/watch?v=LaHISkSNt4Q
After the initial light show, the secondary can be hard to see. The flames can be pretty faint in the top of the firebox.
You're not going to have the pits of hell in your firebox all the time. There's a lot of heat left as the flames die out and the "charcoal" burns.
Only the first half of my burn cycle is fun to watch.
-SF
You're not going to have the pits of hell in your firebox all the time. There's a lot of heat left as the flames die out and the "charcoal" burns.
Only the first half of my burn cycle is fun to watch.
-SF
![[Hearth.com] What is a "secondary burn"?](/talk/data/attachments/13/13619-d3873e5012d00cc32b3c5c781b8d6ec2.jpg?hash=kzIdGzpF9H)
kenny chaos said:
You call that a secondary burn.... check this one out. Its a bit dark, but he'll get the idea.
http://www.youtube.com/watch?v=Z9wfsHUdTeE
Here is the best video of secondary combustion that I have ever seen.
http://www.youtube.com/watch?v=N-5yFVYSXhw&NR=1
http://www.youtube.com/watch?v=N-5yFVYSXhw&NR=1
80s Burnout said:
Yes, that's certainly a nice secondary burn also. The only point I wanted to make was that it is NOT just the nuclear event that was shown above. Maybe I'm wrong but it seems too many expect flames "coming out of the secondaries" when that's not what's happening at all.
BrotherBart said:
That was my dealer/installer. They have a couple of other videos uploaded as well.
http://www.youtube.com/user/customfireplaces
BrotherBart said:
There's the parlor trick. I can do the same thing with the same stove but it don't last too long. That is NOT normal, lasting, secondary burning.
hiram maxim had a couple of pretty good videos on youtube of a secondary burn as well , i have on my work computer i dont have the links here at home, i'll see if i can find em.
secondary burn is literally a fuel air burn that happens when heat and unburned fuel from the primary (the wood itself burning which is never a complete burn) that reignite in the upper reaches of a firebox.
"reburn" stoves such as a cat stove or a "non-cat" unit actually are designed to take advantage of this happening and its benefits. these stoves supply "secondary air" in certain ways to the hot fuel rich exhaust which normally would exit the unit unburned.
a cat stove uses the primary fire to create fuel for the catalyst to burn. this allows a slow burning smoky fire which many old time stove burners would consider a bad fire. this is done deliberately so that teh catalyst can reburn the "smoke" to create a high level of heat. cat stoves benefit from this technique to give very long burn times and even heat. most cat stoves actually willl give a bit longer burn time than non-cat units of similar size, not always but more often than not.
non-cat stoves utilize a very similar system with a simple twist. the secondary burn actually occurs in either the upper reaches of the firebox itself or a chamber that is designed for this function before the exit point of the stove. essentially the "smoke" from the primary fire is trapped briefly on its way out of the stove and fresh air (secondary air) is mixed into the very volitile environment. this creates a "fuel air burn" which incinerates the bulk of the unburned fuel.
the benefits of this are clear , first, the burning of these substances creates a much higher overall temperature of combustion , giving more heat. and second, it burns away much of the material otherwise would coat the flue creating the "seedbed" for creosote
it should be noted that an epa stove of this type can still allow the formation of creosote so this is by no means meant to give the impression that folks with this type of stove do not need to perform proper chimney inspections before during and after the burning season.
secondary burn is literally a fuel air burn that happens when heat and unburned fuel from the primary (the wood itself burning which is never a complete burn) that reignite in the upper reaches of a firebox.
"reburn" stoves such as a cat stove or a "non-cat" unit actually are designed to take advantage of this happening and its benefits. these stoves supply "secondary air" in certain ways to the hot fuel rich exhaust which normally would exit the unit unburned.
a cat stove uses the primary fire to create fuel for the catalyst to burn. this allows a slow burning smoky fire which many old time stove burners would consider a bad fire. this is done deliberately so that teh catalyst can reburn the "smoke" to create a high level of heat. cat stoves benefit from this technique to give very long burn times and even heat. most cat stoves actually willl give a bit longer burn time than non-cat units of similar size, not always but more often than not.
non-cat stoves utilize a very similar system with a simple twist. the secondary burn actually occurs in either the upper reaches of the firebox itself or a chamber that is designed for this function before the exit point of the stove. essentially the "smoke" from the primary fire is trapped briefly on its way out of the stove and fresh air (secondary air) is mixed into the very volitile environment. this creates a "fuel air burn" which incinerates the bulk of the unburned fuel.
the benefits of this are clear , first, the burning of these substances creates a much higher overall temperature of combustion , giving more heat. and second, it burns away much of the material otherwise would coat the flue creating the "seedbed" for creosote
it should be noted that an epa stove of this type can still allow the formation of creosote so this is by no means meant to give the impression that folks with this type of stove do not need to perform proper chimney inspections before during and after the burning season.
Ditto. Barely char the wood load, jam down the air in one step, and blammo! Pretend burning in the burn tubes for roughly 10 minutes.
claybe said:
a well designed stove connected to a proper chimney should do this on its own , non-cat stoves use an air balance , so as you decrease the primary with your draft control it increases the secondary. it shold be noted that secondary burning isnt always visible, but its pretty danged neat to watch when it is!
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