Secondary Burn

[JotulOwner]

I have been reading the comments posted about secondary burn which raised a question......

I know that, when a fire is burning intensely, I can see the blue gas-like flames coming out of the holes up top. I also can see the separations in the flames around those holes when the fire isn't quite as intense. I thought that both of those conditions indicated secondary burn. Beyond that I'm not sure what constitutes a secondary burn. Can anyone elaborate?

Thanks!

 

[burntime]

Get the insert good and hot, add some dry wood, wait 5 minutes and shut the air down...seeing it you will know This is really the best way to see it!

 

[HearthKB]

I have been reading the comments posted about secondary burn which raised a question......

I know that, when a fire is burning intensely, I can see the blue gas-like flames coming out of the holes up top. I also can see the separations in the flames around those holes when the fire isn't quite as intense. I thought that both of those conditions indicated secondary burn. Beyond that I'm not sure what constitutes a secondary burn. Can anyone elaborate?

Thanks!

If you want to know what a secondary burn looks like, check out the thread I started for my Woodstock Fireview. I took a video of the secondary burn.
Here is the link.... Woodstock Fireview Secondary Burn Video

 

[Joey Jones]

Secondary burn looks like a ghost flame...thats the only way i can describe it....when your wood is 6" or more from the burn tubes and you see flames sections jumping off the wood to flash in your fireplace glass...that is secondary burn

 

[Partridge4]

We experienced secondary burn a few nights ago with our brand new Hearthstone Heritage Soapstone. We are total newbies, so it sort of freaked me out. In one of our very first fires (after the two short start up fires), we got it up to 475 degrees, thinking we were cleaning out the stove pipe (manual recommends running the stove hot with air supply fully open for 35-45 minutes, twice a day). Well, after we did that, we shut the air supply down, and to our surprise, the secondary burn began. The freaky part was that the surface temp reached 550 and held! I was semi-panicking that we would overfire the stove. I got on this website and frantically tried to find "help" - I didn't dare open up the air supply again in the event that the temp would get higher. Close to 4 hrs later (1:30 AM!) it cooled down to about 475 so I went to bed : (

I found a thread that explained that shutting down the air supply didn't mean there was no air coming in, just that it had been redirected from below to the secondary air tubes (or something like that).

MY QUESTION IS: Can anyone tell me what is a safe surface temp for a soapstone stove? I find the manual rather vague. We have it back vented out our chimney, so we sit the temp gauge on the stove burner plate that covers what would have been the top vent. Should I be placing the gauge on the soapstone (which registers a lower temp)?

I did call our dealer, but they were so busy, they called back after we had left the house yesterday, and they aren't open today. I thought I understood how to manage temps after reading these forums and the manual, but when the fire is roaring hot and I don't feel we can control it in the manner I thought would (shutting down the air supply), it tests one's heart strength! What am I missing here?

I look forward to the day that I can look back and laugh at my over-reaction. (So does my husband! ) I appreciate any sage advise out there.

OH - I nearly forgot... the secondary burn puts out tremendous heat and is PHENOMENAL to watch - my husband was mesmerized! I would just enjoy watching it at a lower surface temp : )

 

[JotulOwner]

So, from what has been posted here, it seems to me that, to achieve secondary burn (the cleanest fire possible ?), you must get the fire going nice and hot and then turn the air way down (as far closed as it will go?). I have been burning with the air a third open (or more) and with less wood (maybe a few pieces). I guess I am supposed to burn with more wood and less air? I know this burning thing takes some experience to master. I am still working on it :smirk:

 

[guest5234]

So, from what has been posted here, it seems to me that, to achieve secondary burn (the cleanest fire possible ?), you must get the fire going nice and hot and then turn the air way down (as far closed as it will go?). I have been burning with the air a third open (or more) and with less wood (maybe a few pieces). I guess I am supposed to burn with more wood and less air? I know this burning thing takes some experience to master. I am still working on it :smirk:

Thats what I think as well, I have been burning small hot fires but have had no secondry burn I think.....hot big fire and close air down must be the way....


I think.

 

[Joey Jones]

You still have secondary burn in your stove once the temp Is hot enough, but you will see it better when the draft is backed off from a hot burn

 

[SlyFerret]

In my 30, I get secondary above, as well as flames coming directly from the wood itself. I don't try to shut the air down so that I have only the secondaries. When the stove really gets going, it really looks like the pits of hell in there. Flames from the wood in the lower half, and secondary at the top. The entire firebox ends up filled with flames. Stovetop cruises around 550 or so.

Mine is a steel stove though, so my stovetop temp will probably read different than a soapstone stove will.

-SF

 

[BrotherBart]

The thing that gets called secondary burn here is primarily the rolling burn at the top of the firebox during the gasification stage of the burn. This occurs most when a cold stove gets the firebox internal temperature up to the 1000-1100 internal, not stove top, temperature where the gases will maintain a burn. Or, when you reload on top of a hot bed of coals. It takes the form of flames jetting in front of the holes in the air tubes or baffle in a re-burn non-cat. Later in the burn frequently it will settle down to a bluish cloud floating over the wood.

In actuality secondary burn occurs through most of the stages of a burn until the coaling stage. Even when the flames are just licking up from the wood any unburned gases get ignited up at the top of the firebox but it just isn't as dramatic as the early stages. It is why these pups burn so clean. The stuff burning up top is smoke. The smoke burns inside the firebox instead of heading for the great outdoors.

 

[bokehman]

Thats what I think as well, I have been burning small hot fires but have had no secondry burn I think.....hot big fire and close air down must be the way....

What stove have you got? The reason I ask is that the majority of European stoves don't have secondary air. Mine does but it's considered a special feature in the range.

 

[Jerry_NJ]

bokehman,

Why would "...the majority of European stoves don't have a secondary air." be the case? Are you talking including a lagre percentage of old stoves, or are you saying new stoves? I would have guessed the EU would be as strict or more strict as the EPA in the USA.

 

[btj1031]

My stove is presently cruising along at around 650 degrees (edit:F, top of stove thermometer), secondary burn all the way. I know it is secondary burn because of the flame rocketing from the little holes at the top of the firebox. And because the air is choked down pretty well and the fire is having no trouble breathing.

 

[bokehman]

bokehman,

Why would "...the majority of European stoves don't have a secondary air." be the case? Are you talking including a lagre percentage of old stoves, or are you saying new stoves? I would have guessed the EU would be as strict or more strict as the EPA in the USA.

I'm talking current product lines. Follow the link in my signature and you will see. Hergóm is a quality brand but they don't all have secondary air. There are lots of cheap brands and none of them have secondary air.

 

[begreen]

Neil's Jotul has secondary burn. It's not untypical for the southern European heaters to forgo secondary burn. However, in the northern climates where heating efficiency is very important, most stoves have good secondary burn systems. Looks at Jotul, Morso, Franco Belge, Scan, Rais, Stanley, Dovre, etc. stoves and the majority have good secondary burn systems.

 

[Jerry_NJ]

Ok, understood, high efficiency isn't worth a lot of capital investment if you're not going to use it. Still, it is my understanding (maybe my guess) that in the USA EPA requirements are met in stoves/inserts with some form of secondary burn, cat and non-cat types included.

Not an important point, unless I'm wrong about the secondary burn being needed to meet EPA (USA) emission requirement - clean air requirements.

 

[n3pro]

What I find with my Napoleon 1100C the secondary burn is when the flames go up to the top of the box and on both sides I see flames swirling down from the top to the wood. Maybe because it's a small fire box or that dry of wood but I see this as low as 300 flu temp and close to that stove top. It's really cool!

 

[stanb999]

If you want to see the secondary burn.... It's easy.

Put a bunch of small splits 1" X 1" on top of a hot bed of coals.
Give it a few mins. like 5 with the air totally open. Then damp the stove all the way back.

You will see the fire at the wood go out. But the fire at the top will dance and grow huge. This will last several mins. It will look like you have Natural Gas coming out of your air pipes at the top.

The reason your not seeing the secondaries all the time even tho they are burning is that they are blue/red/yellow and the flames off the wood are white and bright.

 

[Jerry_NJ]

Got my first look last night at my new Quadrafire 4100I and my first run with an EPA/secondary-burn device.

Thanks NEPA, your description is particularly helpful. I note the following and reached the following conclusion.

When first light off, and just getting warmed up, mostly small, under 1.5" diameter small and stuff, some of the smallest being just blown down twigs, that snap easily into lengths, but must have too much moisture in them, I could bend down to look up into the top of the insert and saw flames "dancing" across the top air tubes...secondary burn, I'm sure.

Next I moved to larger logs, still all "rounds" and a near 3" in diameter, and seasoned for at least two years. This brought the stove temperature up even higher (better secondary burn conditions?), yet when I looked up into the top of the fire box I could not see secondary burn. The log burn on the floor of the fire box was low and the air was turned down to less than half open, maybe a quarter open. So the top of the fire box was not confused with flames reaching up from the main fire.

Conclusion: On the well seasoned wood there were not much left to burn at the secondary stage, thus I didn't see the secondary burn under the second condition listed above. Alternative, the secondary burn was too light to see, in either case I take it a good indication that the fire was working on very well seasoned wood.

 

[Vic99]

Peg,

I have the smaller brother stove, the homestead. Your firebox is 2.3 cu ft, mine is 2.0.

Your manual states that soapstone top surface temp for your stove should not exceed 600F. Higher is considered overfiring . . . I imagine that if you go over VERY rarely to 620 or so it will be ok, but don't aim for this . . . it could crack the stones or worse.

To stop a run away stove, put a box fan on med or high near the stove and point it partly at the stove so that it blows heat off of the stove and into the room. I do this when temp approaches 580F.

To prevent this, wait until the stove temp is 300 F or less before reloading, 250F or less if you are reloading with mostly pine. I would not recommend burning ALL pine in the firebox unless you are performing a cold start.

550 is a great heat output temp. Good luck.

 

[Partridge4]

Thank you, Vic99. That helps. I want it hot enough to keep the window clear, the inside firebox clear of black shiny coating, and most importantly, a chimney clear of of creosote. Do you open it up twice a day on high burn for 35 -45 minutes like the manual states? I don't want to be too skiddish about the high temps and end up with a chimney fire

We are not using any pine at all. But it seems our wood isn't as seasoned as we thought...

 

[FireWalker]

It never is. The wood that is.

 

[Vic99]

Peg,

When I burn 24/7, usually starting in Nov. I open up once/day for 20-30 minutes as my manual says. This time of the year I open it up every other day.

I didn't have much creosote when it was cleaned this summer.

Start cutting wood for next year now . . . or order it when the season ends in March/April when prices go down. Seasoned doesn't always mean that.