Loading, secondary burn, and draft

[mikeathens]

I have been struggling with my Hearthstone Mansfield this year. This is my first full season with it.

As I pour over this forum, I have noted many people saying that they can pack their stove tight with wood over a bed of coals, shut primary air down all the way, and experience secondary combustion almost immediately.

My experience hasn't been so easy. Mine is more like this: load the stove, leaving gaps between splits so that flames will continuously be hitting tubes. Leave primary air open full for 1/2 hour, with flame licks the whole time, but not necessarily secondary going on; stack temp slowly reaches 800 - 900 (internal probe). Sometimes I see smoke out the stack, sometimes not. Then, mess with air control for another 15 minutes, usually having to leave it open 1/4 to 1/3. Most of the time there, secondary flames look good, and then die out, leaving a smouldering pile. Stack temp usually drops slowly to 200 - 400. It seems I either have to maintain stack temp at 600 or so with 1/2 primary air open, or it drops quickly. Sort of like tring to balance a chair on two legs. It either goes forward or back, but you can never get it to balance. If I let stack maintain 600+, I know my stovetop will exceed the max 600.

The stove it doing it's job, but I want to get this secondary issue resolved. I do have creosote build-up, and I have to clean the chimney every month or so. I would LOVE to pack up that firebox and drop primary control to full closed, and watch those seondary flames work. It kills me thinking about all that lost energy escaping in the form of smoke.

I suspect draft problems. I am buying a moisture meter to check wood, but I would be absolutely surprised if it was too damp.

Specs: I have 16' of chimney above the flue collar - 4' connector pipe, and then 12' of selkirk SS prefab chimney. 10' total of the chimney is completely outside - as it is installed in a flat-roof. I live in a pretty deep valley.

Anyone got any clues? Chimney not holding temp well for good draft? Could the hills/valley be causing problems? Combination?

 

[JonOfSunderland]

Same... exact... problem...

But my cause is wet wood. I have a lot of red oak that hasn't quite seasoned long enough and is split rather large. When I use what I know to be very dry Birch, secondaries sustain very nicely with primary shut all the way down.

My installation is 2ft of single wall, then back about 24" horizontal into internal masonry chimney (6x9 clay flue) ~15ft tall from thimble.

When using the questionable wood, I also need to keep the stove between 500-600 and primary 1/2open.

I don't believe I have a draft problem because I don't get smoke spillage when I open the door. Is this the case for you?

 

[Brian VT]

I was gonna say wet wood too. Seems to be the correct answer for most issues.

 

[myzamboni]

Cedar I can shutdown and get secondaries right away. Pine within a couple minutes. Almond/Oak takes a bit longer. I guess the harder the wood the longer you have to burn before shutting it down.

 

[mikeathens]

Jon and brian, I hope you all are right about the wood. I will have to walk to walk of shame if it is, because I have been in denial about it this whole time. I've got some serious revamping of my wood seasoning techniques if this stuff is too wet. Lots of red oak and black locust that has been around a while. Moisture meter is on it's way...

 

[BrotherBart]

I think you just have the challenge that all of us with large firebox wood stoves have to deal with. Us with the 3.5 cf 30-NCs and the guys with the Summits can't run with primary air closed down all of the way either. The Summit guys may think they are but they aren't. The EBT is supplying primary air as needed after the front air control is closed down. EBT was invented because of the problem of maintaining the burn in big-ass stoves. With smaller stoves like my Jotuls the internal temp is easier get up there and maintain for a closed down secondary burn because the fire is in such a confined space and none of the air has to travel very far and the draft doesn't have to be as strong as what is needed to supply a monster box full of burning wood.

Find the sweet spot and don't get ulcers over being able to shut it all the way down. You want complete combustion more than you want to just see gas jets in front of the tubes.

 

[mikeathens]

BB...thanks, I needed to hear that. I still want to double check my wood moisture for sure. I started this thread because I read one from begreen talking aobut how he crams as much wood as he can possibly fit into his T6 and shuts air control all the way. The way I read it, his secondaries kick in almost immediately, and he has no other flame in the box.

With my mansfield, as stated, I have to be careful about how the wood is placed in the box, and I definitely have to leave gaps for flame to impinge on the secondary tubes.

Also, I suspect something is up since 1) I have to burn at pretty high temps to get complete secondary combustion,and 2) even when it looks like things are going well with my burn tubes, I sometimes still see (I least think) pretty heavy smoke coming from the stack.

If I just put a couple splits in with lots of unoccupied room in the firebox, that's when I see the most complete and consistent combustion.

How's this sound to you?

 

[Highbeam]

"begreen talking aobut how he crams as much wood as he can possibly fit into his T6 and shuts air control all the way. The way I read it, his secondaries kick in almost immediately, and he has no other flame in the box. "

That's how my heritage runs except I wouldn't say almost immediately, the wood load needs to heat up before I get sustained ghost flames. Then when the draft is at zero the only fire you see is the fire on the roof and maybe a small flicker in front of the doghouse. Really cool.

 

[mikeathens]

Secondary ghost flames are incredibly cool, and my mansfield does this, but it is short lived - maybe 10-15 minutes and then dies out when I set a low primary air setting. Like I said in that other heritage thread, seems like a moisture meter is a necessity in my case. But what if it's not a moisture issue?

I guess maybe I can pose that question when (dare I say "if") it arises - after my new meter comes.

 

[fossil]

Just as a point of interest, after establishing a good flaming burn, I can shut the primary completely (in a couple of steps) on my little Century shop stove and leave it shut during most of the burn cycle, and delight in watching the ghost flames do their seductive dance. On my big Lopi Liberty, on the other hand, I can't do that...I always have to leave it at least cracked open a smidge, otherwise I'll quickly lose the secondary and the fire will die down to a smolder. Rick

EDIT: Now that's got me wondering...seems to me I have a tendency to fill the box on the little stove up pretty close to the baffle, whereas I typically don't stuff the Liberty up that close to the secondary tubes. Perhaps that's a factor?

 

[BrotherBart]

On the big'uns ya gotta have some airwash to push the smoke and other gases from the front pieces back into the fire. With the "doghouse" setups when you shut down the primary slide most of the primary is just shooting at the center of the load. A rolling light show is a lot easier to do with E/W loading. On the PE stoves they are designed for N/S. If I am not mistaken there are secondary air holes running front to back in the baffles aimed sideways down in the firebox which would facilitate good secondary burn on a N/S load. And they have more than one hole shooting air between the spits from the "boost manifold" across the front of the firebox. Ideal setup for N/S burning.

 

[Jags]

Yep Mike, I have posted many-o-times about not buying into this idea that all EPA stoves can be clamped down and still burn efficient. It is simply not true as BroB and Rick (as well as myself) have pointed out. Give it a 5-10% open primary and see if that changes things. It may even need a little more.

I think you are also wise to check the MC of your wood.

Edit: I think BroB's big boy theory is a good part of this.

 

[mikeathens]

I guess I've never come across similar posts around here. One pattern I'm seeing: I can't shut down to less than 25%, If I load up to the tubes (within 1") secondary is affected negatively, gotta burn a bit hotter than I'd expect (maintain chimney at 500-600, minimum), gotta leave plenty of gaps between splits.

One thing I will be trying is loading E-W and intentionally leaving a bit more head room.

Other than the occasional (OK, more than occasional) smoking, this puppy really get's the job done. I mean, load it up, sleep 7 hours, and wake up to 65 degree house when it's 10 outside.

 

[Pagey]

I'm not using a Hearthstone, but I can tell you that thus far with my Endeavor, I cannot completely shut down the primary and get a clean burn. I've experimented with this several times, and typically within 15 to 30 minutes of shutting down the primary, I can go out and see a clearly visible smoke trail. Once I open up the primary a bit, I can go out to see only a heat shimmer coming from the pipe.

I have a moisture meter ordered to verify the content of my wood, but I've even tried this with some oak that my dad has had split, stacked, and covered anywhere between 12 and 24 months. As soon as my meter arrives, I'll check to see just how dry the oak is, but it should be pretty much ready to burn.

I would love to be able to close it down all the way and let it burn all night, but I just can't seem to do so and get a clean burn.

 

[fossil]

I never load N-S...neither of my stoves is particularly conducive to that, especially the little Century. Almost all my burning is E-W, or nearly so. Rick

 

[mikeathens]

I have a moisture meter ordered to verify the content of my wood, but I've even tried this with some oak that my dad has had split, stacked, and covered anywhere between 12 and 24 months. As soon as my meter arrives, I'll check to see just how dry the oak is, but it should be pretty much ready to burn.

I'm using the same wood - read oak split and stacked under roof for slightly more than a year. We shall see what the holy meter says. There are some people who swear that read oak has to be stacked for a MINIMUM of 24 months. Some say one year.

I would love to rule this part of the equation out.

 

[bokehman]

Leave primary air open full for 1/2 hour, with flame licks the whole time, but not necessarily secondary going on [...] Sometimes I see smoke out the stack, sometimes not. Then, [...] secondary flames [...] die out, leaving a smouldering pile. [...] I do have creosote build-up, and I have to clean the chimney every month

This sounds like a wood problem to me, especially the bit about needing to clean the flue so often.

 

[mikeathens]

Creosote occurrs because I choke the primary air down, note secondary, and go off to bed either because I'm too tired or have had one too many beers. When I have the time to sit and watch, that's when I see that the secondary dies out pretty soon, usually on weekends.

I hope you are right, though.

I'm going to pay close attention tonight to loading E-W and leaivng a bit more head room.

 

[Pagey]

I have a moisture meter ordered to verify the content of my wood, but I've even tried this with some oak that my dad has had split, stacked, and covered anywhere between 12 and 24 months. As soon as my meter arrives, I'll check to see just how dry the oak is, but it should be pretty much ready to burn.

I'm using the same wood - read oak split and stacked under roof for slightly more than a year. We shall see what the holy meter says. There are some people who swear that read oak has to be stacked for a MINIMUM of 24 months. Some say one year.

I would love to rule this part of the equation out.

As would I. I know that some of the wood I am burning is less than ideal, but on the flip side it is far, far from being green wood. However, I also suspect that if the wood were too moist, I'd not be able to hit that "sweet spot" at all which produces nothing more than a heat shimmer from the chimney. I'll post my results as soon as I get ze meter!

 

[ba_jie]

I have been struggling with my newly installed Jotul 450 with similar problems for the last 2 weeks.
But i have been holding off posting my questions because i think it's my lacking of experience operating the stove.
Plus, there seems so many things that can go wrong i really don't know how to ask question about stove under performance.

I am really glad Mike asked this question for me.
My limited experience so far are:

1. I have to leave the stove door not completely closed to maintain reasonable flame when i am buring a medium size stick(about 3~4 inch).
2. I haven't get any luck to bring the room temp above 55 degree(but i do have high ceiling and large open space).
3. I do have lot of buildsup on the door glass.
4. I haven't been able to maintain a thick coal bed. Does that mean i didn't load enough fuel? How often do i need to add fuel? It looks to me to maintain coal bed, during a 4~5 buring time, i have to at least feed dozen of 2 inch sticks. That looks to me a lot to maintain the fire.
5. How full do you need to fill the stove to have secondary burning? I didn't get any luck to observe one.

I am somewhat frustrated. If i know burning stove is so hard, i would have had second thought intalling stove by myself. That way at least i can go back to the stove shop for help. Now i am all by my own.

Or it could be the stove problem?
My Jotul 450 was probably 2005~2006 model. Could there be design problem? As i searched this forum, i saw quite a few complaintments about Jotul 450 under performance.

There are so many variables. I don't even know where to blame...

I have been struggling with my Hearthstone Mansfield this year. This is my first full season with it.

As I pour over this forum, I have noted many people saying that they can pack their stove tight with wood over a bed of coals, shut primary air down all the way, and experience secondary combustion almost immediately.

My experience hasn't been so easy. Mine is more like this: load the stove, leaving gaps between splits so that flames will continuously be hitting tubes. Leave primary air open full for 1/2 hour, with flame licks the whole time, but not necessarily secondary going on; stack temp slowly reaches 800 - 900 (internal probe). Sometimes I see smoke out the stack, sometimes not. Then, mess with air control for another 15 minutes, usually having to leave it open 1/4 to 1/3. Most of the time there, secondary flames look good, and then die out, leaving a smouldering pile. Stack temp usually drops slowly to 200 - 400. It seems I either have to maintain stack temp at 600 or so with 1/2 primary air open, or it drops quickly. Sort of like tring to balance a chair on two legs. It either goes forward or back, but you can never get it to balance. If I let stack maintain 600+, I know my stovetop will exceed the max 600.

The stove it doing it's job, but I want to get this secondary issue resolved. I do have creosote build-up, and I have to clean the chimney every month or so. I would LOVE to pack up that firebox and drop primary control to full closed, and watch those seondary flames work. It kills me thinking about all that lost energy escaping in the form of smoke.

I suspect draft problems. I am buying a moisture meter to check wood, but I would be absolutely surprised if it was too damp.

Specs: I have 16' of chimney above the flue collar - 4' connector pipe, and then 12' of selkirk SS prefab chimney. 10' total of the chimney is completely outside - as it is installed in a flat-roof. I live in a pretty deep valley.

Anyone got any clues? Chimney not holding temp well for good draft? Could the hills/valley be causing problems? Combination?

 

[Jags]

jie - honestly my first suggestion would be to spend the 15-20 bucks on a moisture meter. They are fun for the whole family and you can share it with friends.

Joking aside - knowing that you have dry firewood is half the battle. You could go spend that same $20 buying a couple of arm loads of prepackaged stuff from the gas station, but then you wouldn't have any new firewood toys to play with.

 

[bokehman]

I haven't been able to maintain a thick coal bed. Does that mean i didn't load enough fuel? How often do i need to add fuel? It looks to me to maintain coal bed, during a 4~5 buring time, i have to at least feed dozen of 2 inch sticks. That looks to me a lot to maintain the fire.

A dozen sticks is good to start a fire but it will burn down in half an hour. After that you need to load up with some good size pieces, say 6" splits.

Or it could be the stove problem?

What have you done for the chimney?

 

[bokehman]

Creosote occurrs because I choke the primary air down, note secondary, and go off to bed

Once my stove is up to temp I always run it with the primary closed, but don't need to clean the liner once a month. If the wood is red oak it does need two years. Last year I tried burning it after only one year with poor results. Now it is two years old I can't believe how little wood I'm using for the same heat output.

 

[ba_jie]

I haven't been able to maintain a thick coal bed. Does that mean i didn't load enough fuel? How often do i need to add fuel? It looks to me to maintain coal bed, during a 4~5 buring time, i have to at least feed dozen of 2 inch sticks. That looks to me a lot to maintain the fire.

A dozen sticks is good to start a fire but it will burn down in half an hour. After that you need to load up with some good size pieces, say 6" splits.
2" is not the length, but diameter. The lenghth is about 20".

Or it could be the stove problem?

What have you done for the chimney?

I don't think i have draft issue. My chimney is 20 ft tall. I do have a offset adapter box installed. But if i keep the stove door ajar for few seconds before i completely open it,
I won't have smoke come out. So seems the draft is ok.

 

[bokehman]

I don't think i have draft issue. My chimney is 20 ft tall. [...] But if i keep the stove door ajar for few seconds before i completely open it, I won't have smoke come out. So seems the draft is ok.

That's not a fair test of draft. I don't get smoke spillage even when everything is stone cold, i.e. when there is almost zero draft. Does it have a SS liner for the whole 20 feet?