Got a ? about secondary combustion systems

[certified106]

So after looking at pictures of the NC 30 firebox in Danno's thread it seems there are three burn tubes with tons of holes all the way across them and it appears some Lopi stoves look the same. My PE baffle does not look that way at all! in fact there are probably more holes on one burn tube in the 30 than I have in my whole baffle? The T6 baffle has some holes that run from the front of the baffle to the back and then a row across the front of the baffle. Is that what makes the T6 such a slow and easy burner? Don't get me wrong this thing is a serious heater and I can have a 750° stove top if I want one but it will easily run at 600° for hours on end if I don't try to get 750° out of it. I did burn a three log load last night and it was running around 600° on the flue and right at 700° on the or slightly above on the stove top depending where you measured it.

The other thing I have noticed is my flue temps seem like the are pretty low even if I throw a load of oak in the stove on a deep coal bed with the stove top at 450° for extra heat it might burn slightly higher for a while (around 700° on a probe) but settles back down fairly quickly. Normal flue temps are between 500-600° for the most active part of the secondary and then slowly drop off for the rest of the load once the secondaries kick out. Before anyone asks about the chimney I Haven't cleaned it since last year when I put the stove in however I slid the telescoping piece up and looked through it this morning while it was cool and there is nothing in it except for a tiny tiny bit of very fine particles at the very top and does not need cleaned. I have always checked my chimney a couple times during the year but it is pretty common for me to not need to sweep it even with my other stove.

 

[mtcates]

Oxygen and turbulence create the perfect environment for fire. Your stove seems to be doing very well at that. Does not matter whether the oxygen comes from one source or multiple sources as long as the turbulence is present.

 

[certified106]

Yeah, that's true. I guess I should have asked this, for those of you with the burn tubes do your stoves usually have secondaries out of all the tubed on a full load of wood or do you sometimes have a tube that isn't firing. I would love to see the calculations that they use to decide the optimal amount of airflow and size of the secondary air intake.

 

[Huntindog1]

My stove has 4 tubes, each tube is set at different angles , I guess to impact the smoke gases differently. I havent seen all four going at once but I have seen 3, its usually the front one that isn't going. When I stack it high in the front of the box which blocks my view of the front tube it may be firing but I cant see it. Stacking it high in the front really gets the stove hot as it seems like it blocks the heat from the secondary burn from easily escaping up the front of the stove around the open area that the baffle plate doesn't cover.

 

[Blue Vomit]

Yeah, that's true. I guess I should have asked this, for those of you with the burn tubes do your stoves usually have secondaries out of all the tubed on a full load of wood or do you sometimes have a tube that isn't firing. I would love to see the calculations that they use to decide the optimal amount of airflow and size of the secondary air intake.

I don't usually see secondaries from all three burn tubes. On a full load at high temps, the likelihood increases.

 

[leeave96]

Yeah, that's true. I guess I should have asked this, for those of you with the burn tubes do your stoves usually have secondaries out of all the tubed on a full load of wood or do you sometimes have a tube that isn't firing. I would love to see the calculations that they use to decide the optimal amount of airflow and size of the secondary air intake.

I do not get secondaries out of my 30 on all tubes - unless I slam the damper closed. With that, I got a really hot firebox and stove top and with the damper choked down, get an instant of excess smoke. For a minute or two, all the tubes burn until the smoke clears. I think the air is always there coming out of the tubes, just not enough smoke to ignite from the air available. Usually I get mild secondaries on the two rear tubes, in the center section and not much off the front - but again, I have yet to mash the peddle on the 30 hard.

Good luck,
Bill

 

[DexterDay]

Certified - There is 4 tubes in the 30's firebox. My front 3 see the most action, unless I make the "tunnel of love" (BB) and shhot the air through a tunnel of splits to the back of the box (3 splits/ all N/S, with 2 on the bottom and one on top of them, which forces the doghouse air, through said tunnel). Then that back tube lights off quite nicely.

There does seem to be a lot of holes in them. I was looking at an Enerzone 3.4 at a stove shop the other day and couldn't believe how slow and lazy the secondaries were. Stayed there over an hour watching. The guy there said "It just burns". Not matter who runs it in the store, it runs all day like that.. I was impressed. Also had a Regency (dont remember model) that had fewer secondary holes and a slower flame than I am used to.

My secondaries can go fairly slow once she settles. But watching those 2 stoves, just seemed as if they would naturally burn longer. Less air = Longer burns and they were still about 550-600 stove top (both had an Eco-fan on them, spinning away).

 

[Loco Gringo]

Mine has one in front, one in back. The back lights off first but blasts like a line of torches with no visible fire on the wood itself.

 

[simple.serf]

Certified,

My Enerzone has 4 burn tubes and 6 holes in the back wall of the stove for the secondaries. With a full load on hot coals and enough good time for it to catch, I have seen all of them firing ( I just did when I went down to count how many burn tubes I have after just filling the stove for the night). After she settles down, they become more slow and lazy, and will cruise like that for hours... no smoke out the stack.

A friend has a Lopi, and the effect is similar in that stove

What's the old saying... there's more than one way to skin a cat?

 

[stircrazy]

I have the first generation Osburn 1600 with secondary air.

it has one tube in the front and holes drilled in the back top frame for secondary air. it is easy to get the back secondary firring but I have only seen the odd flicker from the front, but then I have never aired down a large load yet.

Steve

 

[BrotherBart]

The PE stoves are optimized for N/S burning. That is why the secondary air outlets up top are the way they are. The 30 was designed to burn E/W. Though few of us here do it.

If I see tubes "firing" more than mixing air with the gases coming off the load then I screwed up loading the stove and turning down the intake at the right times. Light shows are for rock concerts, not wood stoves. Fire blowing out of a bunch of tubes are for gas grills. The reason I trashed mine and went back to BBQing with wood.

 

[Huntindog1]

[youtube]http://www.youtube.com/watch?v=5Hp3beQamQw&feature=youtu.be[/youtube]

 

[BrotherBart]

I always wonder where the youtube videos are of a fire in the stove five or six hours later?

 

[Huntindog1]

Yep as after the gases are all burned up there isnt much to watch. Just splits that looked like carbon logs.

 

[begreen]

I always wonder where the youtube videos are of a fire in the stove five or six hours later?

I suspect you won't see it. The lights are out and the rest is not rated PG. Maybe this is the tertiary combustion scene?

 

[BrotherBart]

I have just GOT to buy a video camera some day. :coolsmirk:

 

[Huntindog1]

Most camera's will do video, this one was done on a camera.

 

[precaud]

Yeah, that's true. I guess I should have asked this, for those of you with the burn tubes do your stoves usually have secondaries out of all the tubed on a full load of wood or do you sometimes have a tube that isn't firing. I would love to see the calculations that they use to decide the optimal amount of airflow and size of the secondary air intake.

If you're not seeing "tongues of flame" apparently emitting from the secondary tube holes, that either means that a) the air is coming out of the holes into a place where there are no unburned gasses, 2) the temps are not high enough for the air and gasses to combust upon contact with each other, or 3) the temps are so high that the air expands and disperses quickly - as soon as it leaves the holes. Typically you only see well-defined secondaries during the earlier part of the burn; once the stove is up to temp, they are less discreet and shorter.

 

[Huntindog1]

I think all those tubes were designed into the stove not so every hole could be firing at once but so as to have coverage of a big area of the upper part of the stove as smoke rises. You can be pretty assured that with all those holes in 4 tubes that the smoke where ever it raises to is going to mix with some super heated air.

 

[precaud]

Huntingdog is right; in most stoves they're just putting 'some' air everywhere up top. But there is a misconception about secondary air: that it is hot enough to ignite the unburned gasses in the firebox on contact. Under most operating conditions, it is not. The "super-heated air" is preheated by channels in the stove body, and is not (cannot be) hotter than the temps in those channels. A stove designer would consider it a complete success to get room-temp air preheated up to 500-600 degrees. But that falls well short of the temps needed for spontaneous combustion to occur.

 

[certified106]

The PE stoves are optimized for N/S burning. That is why the secondary air outlets up top are the way they are. The 30 was designed to burn E/W. Though few of us here do it.

If I see tubes "firing" more than mixing air with the gases coming off the load then I screwed up loading the stove and turning down the intake at the right times. Light shows are for rock concerts, not wood stoves. Fire blowing out of a bunch of tubes are for gas grills. The reason I trashed mine and went back to BBQing with wood.

Makes sense to me I was just questioning it due to the fact I rarely see any type gas grill effect on the secondary combustion on the T6. I do get a little bit of gas grill effect at the very begining of the load on the front holes but as soon as the wood burns off the very front of the log nine times out of ten I just have a nice floating flame in the top of the firebox.

I can attest to the fact this stove really does like to burn N/S and that is the only way I have run it so far and the burn times and controllability of the stove are great. I think a lot of time people are getting the secondary combustion stove temps way to hot before shutting them down which leads to the gas grill effect. I have only played with E/W a couple of times and the stove seemed to be a lot more finicky with air control settings. I went back to N/S due to how easy it was to get it going and shut it down quickly.