why am I getting very little secondary combustion

[buckeye]

Im not sure what the deal is, but im getting very little secondary combustion. I load the stove up and get it burning pretty well, then cut the air down a little bit at a time. I am just not seeing the secondary burn like everyone else talks of seeing. I get the stove up anywhere from 400-500 and still,......not much 2nd burn. I have well seasoned wood.
The only thing that I can think of is that I have a damper installed and have it closed a little more than half way. Would that hav anything to do with secondary burn?
I have been reading and trying to figure it out.

 

[Corie]

Any reason you have a damper installed?

 

[babalu87]

How much wood are you using?

Run it wide open, get it hot and bank it down all the way, that gets it every time here.

 

[BrotherBart]

One thing is that with the pipe damper closed the draft isn't strong enough to pull secondary air into the stove. Of course I don't spend much time in search of secondary burn nirvana anyway. I level the 30 out at five hundred with an inch of primary air damper open and let it cruise for 10+ hours. Not near the hotter than hell peak and rapid fall off that rip'en it and shutting it all the way down produces.

 

[Hogwildz]

Hmm rapid fall off, now I know I love my Summit *grins*

 

[North of 60]

Im not sure what the deal is, but im getting very little secondary combustion. I load the stove up and get it burning pretty well, then cut the air down a little bit at a time. I am just not seeing the secondary burn like everyone else talks of seeing. I get the stove up anywhere from 400-500 and still,......not much 2nd burn. I have well seasoned wood.
The only thing that I can think of is that I have a damper installed and have it closed a little more than half way. Would that hav anything to do with secondary burn?
I have been reading and trying to figure it out.

Ummmm What model of stove are you using?

 

[stoveguy2esw]

Im not sure what the deal is, but im getting very little secondary combustion. I load the stove up and get it burning pretty well, then cut the air down a little bit at a time. I am just not seeing the secondary burn like everyone else talks of seeing. I get the stove up anywhere from 400-500 and still,......not much 2nd burn. I have well seasoned wood.
The only thing that I can think of is that I have a damper installed and have it closed a little more than half way. Would that hav anything to do with secondary burn?
I have been reading and trying to figure it out.

the damper may very well be the issue , depending on the planned "air budget" for the stove , the primary will generally be allowed to get the lions share of the combustion air if the draft control on the stove is opened all the way up and as its closed the ratio into the secondaries increases, bear in mind that the flue is only going to pull so much air anyway and this air is divided by primary and secondary according to the intent of the manufacturer. choking the primary down once the unit has achieved temperatures that will allow secondary combustion using the stoves built in controls for the primary allows more of the division of air into the secondaries (that get air through a seperate path) which helps promote secondary combustion while retarding the primary fire. this makes the wood load last longer and still allows the secondaries to provide heat and burn away the residue from the slow burning primary fire

a damper in the flue however reduces the total draw volume, which means that both the primary and secondary air are denied the full effect of the flue's draw. this along with the possibility that you probably have the primary open further to compensate , doesnt leave enough of the minimized air budget for the secondaries to light off effectively. for starters open the damper in the flue all the way , and close your primary draft control down further after hitting temp , you should see a marked improvement in the secondary fires. this done , when you have the opportunity , remove the damper and seal the flue back up where it was placed. if you look at your manual there is probably no mention of using an in flue damper for this very reason.

 

[buckeye]

Im running the heritage. I thought that it may have something to do with the damper. My stainless liner is 37' and the place I bought the stove installed the damper because they thought when I had my insert that I was losing alot of heat up the flue. That in itself is another story.
Anyway, Mike, that is basically the answer that I was looking for.

 

[Corie]

Lose the damper and see what happens. I'd be more inclined (I know I'm going to take flak for this as usual), to tell you to have a barometric damper installed and set with a draft gauge. Of course, that's just me. Why not remove it, or operate it wide open and see if it improves. If I have a full load roaring and charred good, shutting the air control will almost always result in quite the light show in the top of the firebox.

 

[begreen]

flak flak

I'm confused. The more I read about barometric dampers on wood stoves, the more they seem like a bad idea. But you and web advocate them. Wouldn't adding a barometric damper introduce too much cool air spilling into the flue system? Wouldn't that mean a cooler flue and more conditioned, room air being pulled into the system from the room? Seems this could defeat the efficiency of the stove by pulling in cold outside air into the house. In cold weather during periods of high draft, this might be significant. If there is negative pressure in the house, how is smoke spillage from the damper controlled?

According to John Gulland, a new code provision is being proposed in Canada for woodstoves: “A Barometric damper shall not be installed in the flue vent of an appliance unless the appliance has been certified for use with a barometric damper."

FWIW,I run my stove with a manual key damper, much in the same way that buckeye is running his. With a 37' stack, I would think it to be a necessity. But I get great secondary burn every time. That is unless the wood is crappy, or I close the stack damper too early.

My procedure is to get the stove hot with a first loading of kindling and then a few small splits. Then, with the second full loading of the stove, I let it burn open (primary and stack damper) until the wood is fully aflame. Next I reduce the primary to about 50%, secondary combustion is strong at this point. Then, depending on the stove top temp, I close down the stack damper, watching the secondary flames. If the stove top is about 400, then I will only close it about 45 degrees and will wait 15 minutes for it to get up to 500. If already pretty hot, I will close it all the way. I use the secondary flames as my guideline, adjusting the primary air at about 60% to 75% closed, depending on the wood load. When adjusting, the goal for me is to damper down the stack + primary air to the point where the secondaries start to get wispy instead of roiling and boiling. Is this the right procedure?

 

[Corie]

I just like the idea of a constantly adjusting draft system, that doesn't require user input and is always providing the exact amount of draft necessary. I agree that most wood stoves don't and shouldn't have them, but the manuals generally say no manual dampers either, so I guess it's up in the air.

I've burned wood with and without them as well as burned coal with and without them and I do like having one for the stable draft it provides. You're correct in that some room air is wasted in diluting the flue gases in order to slow them down, but I've found that the creosote condensing due to barometric damper is quite small, especially with a modern wood stove. Even with a non-certified stove, I haven't seen any alarming build up come from using one.

I'd have one here on my stack, but at 13 feet, I barely have enough draft. No sense diluting it even slightly with a damper.

 

[begreen]

With coal, a barometric damper makes a lot more sense. No creosote and a very steady source of heat. Wood introduces too many variables, like changing levels of heat, varying wood types and seasoning, etc.

FWIW, here is Hearthstone's suggestion:

"EXCESSIVE DRAFT: Contact your dealer to have a draft reading taken. Any draft in excess of 0.1 wc requires a damper in the stovepipe. Some installations may require more than one damper."

Seems the best course of action for buckeye is to have the dealer measure the draft on his stack. Then an appropriate course of action can be discussed.

 

[stoveguy2esw]

im kinda in agreement with john guilland a unit that is designed to operate with this adaptation must be designed to allow more heat into the flue than one that is designed not to have one. modern units do not saturate the flue with heat and volume the way older smoke shelf units did. with a "classic" unit a barometric damper would help attenuate the rapid loss somewhat and allow a better heat transfer by slowing and speeding up combustion by giving air at times through the stove (by closing) and denying it at other times (by opening) with a modern unit (with a preplanned air budget) this could very well hinder the very effect that the stove designer intended. modern units are designed to allow the restriction of closing the primary to actually enhance the secondary, a barometric could counteract that due to the restriction added to the stove through the closing of the secondary.

my theory with this device is it definately isnt for every model or flue setup. though it would be a good thing if an overactive chimney is an issue especially with many modern epa units (non-cats or cats) that cannot be closed all the way down and attenuation is needed. but i would not advocate simply installing one without deciding or finding out from a draft measurement that one would be necessary.

 

[buckeye]

I opened the damper all the way and when I reloaded the stove and let the wood start burning well, I shut the air down and whalla.......big flames from the secondary burn. Now I have to evalutate and see if im getting longer burn times like this or with the damper closed down some and primary open a little more.

 

[stoveguy2esw]

With coal, a barometric damper makes a lot more sense. No creosote and a very steady source of heat. Wood introduces too many variables, like changing levels of heat, varying wood types and seasoning, etc.

FWIW, here is Hearthstone's suggestion:

"EXCESSIVE DRAFT: Contact your dealer to have a draft reading taken. Any draft in excess of 0.1 wc requires a damper in the stovepipe. Some installations may require more than one damper."

Seems the best course of action for buckeye is to have the dealer measure the draft on his stack. Then an appropriate course of action can be discussed.

true BG , 0.1 is a buttload of draft, usually 0.05 inwc is pretty well in the wheelhouse, should operate anything. but 0.1 is a lot , that would need to be attenuated.

 

[BrotherBart]

I opened the damper all the way and when I reloaded the stove and let the wood start burning well, I shut the air down and whalla.......big flames from the secondary burn. Now I have to evalutate and see if im getting longer burn times like this or with the damper closed down some and primary open a little more.

Bingo.

 

[Hogwildz]

I was thinking of getting the Duravent stove adapter/damper just specifically for use in case of a runaway to cut air as far as allowed on stove then close damper. Otherwise I would leave damper open. Anyone see anything wrong with that?

 

[stoveguy2esw]

not at all, as long as you generate 0.05 inwc of draft you are golden damper in there or not

 

[begreen]

I was thinking of getting the Duravent stove adapter/damper just specifically for use in case of a runaway to cut air as far as allowed on stove then close damper. Otherwise I would leave damper open. Anyone see anything wrong with that?

FWIW, I found that when the fire is attempting to runaway in a modern stove, closing the stove pipe damper all the way helps, but doesn't stop it. This was during my early compressed log testing when I had one too many logs on the fire. The way I tamed the fire was to choke the OAK air. Now I'm thinking a damper on the OAK is a more effective safety valve.