Advice on Slowing Down Burn/Off Gassing

[Statefan86]

New (since November) woodburner, burning an Osburn 2400. Love it! I've been trying different things/ways of burning, and am always looking to improve my methods (mostly from reading on here). The main issue I'm having right now is that I would like to be able to slow down the wood off-gassing after a reload. My method is as follows:

After I have a nice coal bed and stove top temps are around 250-350, I rake the coals to the front and open the air all the way. Let it cruise there for about 20 more mins or so to coax the last bit of good heat out of it and reduce the size of the coals. Then I proceed with a new, full load (such as for overnight). I'm loading E-W as I Feel I can control it more (my splits are pretty small, 2-3"). It takes a while to get going (45 mins until air is fully closed, but that's for a different thread....), but once it's rolling, it gets hot in a hurry.

Within an hour, I'm approaching 600 and the tubes start to glow, with blow torch secondaries on all 3 tubes. Stove top temps climb probably to 650-700 and level off (don't know for sure, IR thermometer just says "overheat" after 615. I will say I can always find somewhere on the front and middle of the stovetop that stays in the 500s, so I'm guessing further back is approaching 700). Anyway, I'm not really concerned about the temps. The tubes are glowing, but I feel it is burning just as it should be.

What I would like, is to be able to slow down the wood off-gassing to be able to better control the temps, keep them around 600, and achieve longer burn times. I'm getting 8 hour burns pretty easily, but I just feel like the thing is blazing through the first part of the burn cycle faster than it needs to be. Part of the problem no doubt is the wood...average is 20% MC...some better, some worse. I can't just throw a new load in, wait for a few mins, then shut her down. I have to leave the door cracked for 15 mins, shut it, see I'm snuffing out the fire, open it back up, then do it all over again until it stays rolling with the door shut, then start slooooowlly closing the air. By that point it's blazing and pas the point of no return as far as burning it slowly. The other issue I think is my splits. They are too small and burning too hot. I stuff maybe 15 of them in the stove. Next year I hope to have some big nasties, at least for the overnight loading.

What do yall think? Splits too small to have a slower burn, and I need to be happy with an 8 hour burn (and of course get a thermometer better suited to the job)? Or are there any other tricks?

Edit to add: also, the flaming stage lasts 2 hours max. After that, it's all coals. Just seems I should be able to slow down the blow torch secondaries and burn a bit longer.

 

[BobUrban]

8hours is pretty good heat producing time and you seem happy with that. With larger splits and a round or two you likely will slow the opening blast furnace a bit but may not see that translate to extending the burn time on the other end. It is all a bit of trial and error with every stove but certainly it sounds like you are burning kindling and that will off gas fast once you get it going.

 

[Swedishchef]

Howdy!!

If the off gassing is happening to fast you are reloading when it is still too hot with too small of splits. Try waiting longer between reloads.

Yes, my stoves only gets 2 hours of flames as well. Split size impacts the rate of off gassing (as boburban mentioned). Coals also give off good heat.

I simply reload when I barely have any coals left. If I reload too fast, it an inferno and I need to close my air 100%. So what I like to do is put a couple of small splits on the bottom, larger pieces on top, get it going with the door open for a few minutes. Then I close the door and start closing down the air.

Happy burning!

Andrew

 

[Sledhead00]

New (since November) woodburner, burning an Osburn 2400. Love it! I've been trying different things/ways of burning, and am always looking to improve my methods (mostly from reading on here). The main issue I'm having right now is that I would like to be able to slow down the wood off-gassing after a reload. My method is as follows:

After I have a nice coal bed and stove top temps are around 250-350, I rake the coals to the front and open the air all the way. Let it cruise there for about 20 more mins or so to coax the last bit of good heat out of it and reduce the size of the coals. Then I proceed with a new, full load (such as for overnight). I'm loading E-W as I Feel I can control it more (my splits are pretty small, 2-3"). It takes a while to get going (45 mins until air is fully closed, but that's for a different thread....), but once it's rolling, it gets hot in a hurry.

Within an hour, I'm approaching 600 and the tubes start to glow, with blow torch secondaries on all 3 tubes. Stove top temps climb probably to 650-700 and level off (don't know for sure, IR thermometer just says "overheat" after 615. I will say I can always find somewhere on the front and middle of the stovetop that stays in the 500s, so I'm guessing further back is approaching 700). Anyway, I'm not really concerned about the temps. The tubes are glowing, but I feel it is burning just as it should be.

What I would like, is to be able to slow down the wood off-gassing to be able to better control the temps, keep them around 600, and achieve longer burn times. I'm getting 8 hour burns pretty easily, but I just feel like the thing is blazing through the first part of the burn cycle faster than it needs to be. Part of the problem no doubt is the wood...average is 20% MC...some better, some worse. I can't just throw a new load in, wait for a few mins, then shut her down. I have to leave the door cracked for 15 mins, shut it, see I'm snuffing out the fire, open it back up, then do it all over again until it stays rolling with the door shut, then start slooooowlly closing the air. By that point it's blazing and pas the point of no return as far as burning it slowly. The other issue I think is my splits. They are too small and burning too hot. I stuff maybe 15 of them in the stove. Next year I hope to have some big nasties, at least for the overnight loading.

What do yall think? Splits too small to have a slower burn, and I need to be happy with an 8 hour burn (and of course get a thermometer better suited to the job)? Or are there any other tricks?

Edit to add: also, the flaming stage lasts 2 hours max. After that, it's all coals. Just seems I should be able to slow down the blow torch secondaries and burn a bit longer.

You're on the right track of thinking... Like was mentioned above some bigger splits I would think help your situation... Bigger in size and less in number splits packed in good and tight I think youll find gets a bit more time for ya.. Bigger splits will take longer to light and should extend your time out to some degree.. I have the same stove and just the other day I only managed to fit 5 splits (red maple) and one giant cherry round and 15hrs later when I came home I still had a 205 stove top temp..
20% moisture isn't horrible either and but if it's taking upwards of an hr of fussing around to get it up to good temps I'd wonder if your % is running a bit higher especially since your burning small splits. I'm able to load up, cruising and shut back down in about 10 mins..
Another possibility with getting the fire going seeing where you are located could be draft... If you're just trying to take the chill out and outside temp is 40-50F that can be more of struggle to get going then it is for me where its 15F...
Edit- When your closing it down how small of increments are you using? You say the the fire takes off beyond control to a degree. Try larger shut down moves. I only usually need 2. Full-half-closed. Occasionally I may go full-half-quarter-closed.
If you snuff the fire out after shutting it down some, give it a few minutes to see if it comes back. I've snuffed it a fire out before and within 5 few minutes ive got lazy flames and secondaries coming back with a vengeance..

 

[Statefan86]

Thanks for all the replies!

I really think it's just a matter of still learning how to best run the stove, and dealing with splits that are on the small side (like most new woodburbers, I bought wood the same week the stove was delivered in October. I'm lucky that it is all decently seasoned, but I don't have any big rounds). Next year I will have a better assortment by cutting my own wood.

As far as draft, yes it can be difficult here in NC. I've found if the temps aren't into the 40s I'm not messing with it. It's a huge external masonry chimney, 15' stack height lined properly with a SS liner and 1/2" of insulation. That being said, its been in the 20s and below most of this week, and draft is no problem. It helps that the chimney is on the leeward end of the house.

As far as closing, yes I typically go in small increments. However, this morning I reloaded after 9 hours from the overnight burn. Needed a few newspapers but was able to get it going from coals. Stuffed it full (15-18) splits N-S, and in 10 mins I had it shut down. Very happy about that. Image below is at the 10 min mark. Closed in 2 steps like sledhead described.

I've found if I reload below ~250 it is harder to get going. I think I just need some dryer kindling (cut it from the same splits, so it needs to be dryer). Also, I've found N-S is MUCH easier to get rolling. It's more set it and forget it, whereas E-W requires some babysitting, letting the bottom layer get blazing before adding more on top. Otherwise, it smokes and smolders, not good. Is this anyone else's experience?

Thanks again everyone...24 this morning and snowing...summertime in the house though! Wife is very happy...

After 8-9 hours, my stove top is generally 175, maybe over 200 back towards the outlet. I figure that is pretty good.

 

[Ashful]

Answer: buy a cat stove! Other than having to fill it with wood once every 12 - 40 hours (dep. on desired burn rate), they're as easy as operating your thermostat. I do not worry about loading direction, split size, or how tight I pack the wood.

 

[Squisher]

Geez ashful that's a helpful reply. Ummm what's the question? Because BK's the answer



To the OP it sounds to me like you've got it dialled in pretty well, part of burning a stove that's capable of putting out serious heat is watching it doesn't get to hot. It's a fine line of reloading to hot and having things heat up quick and potentially run away or reloading to cool and having the wood smoulder for to long before getting up to temps.

For those that can't quite get it, well there's always the BK.

 

[Ashful]

Geez ashful that's a helpful reply. Ummm what's the question? Because BK's the answer

BK isn't the only cat stove, and it was a helpful reply. I've had five wood stoves in four years. It's an appliance, not a marriage. If you realize it's not working as well as another option, then replace it.

 

[Squisher]

So your take on the OP's comments and questions are that the stove isn't working for him?

Also for most people a stove is probably more of a permanent commitment than a marriage in this day and age. Most everyone I know heats with wood, and I know no one who is switching out multiple stoves in a handful of years. I'd wager you're the exception in regards to doing that.

My parents have a Osburn, they are very capable heaters and don't need to be tossed out for a cat stove. I've burned wood my entire life for heat and have no plans to toss my new summit out because it won't idle away for 24hrs.

 

[Ashful]

This whole forum is probably the exception, when it comes to woodburners. I know several here on their second, third stove.

It's fine if you don't like my suggestion. I wasn't considering you, when I made it.

 

[begreen]

Get a room boys. The topic is the stove the OP has, an Osburn 2400.

 

[begreen]

Statefan, I find this year that I am not watching stove top temps as much as flue temps. I used to go by stove top temp for shutting the air down but noted that this would allow for a very hot flue on startup. Now I am shutting down the air much sooner. This leads to slower warm ups, but slower off gassing and longer burntimes. I start turning down the air in increments when the flue reaches about 500F. If you don't have a flue thermometer then you need to go by the fire. As soon as the fire is burning robustly start turning it down.

 

[Sledhead00]

Thanks for all the replies!

I really think it's just a matter of still learning how to best run the stove, and dealing with splits that are on the small side (like most new woodburbers, I bought wood the same week the stove was delivered in October. I'm lucky that it is all decently seasoned, but I don't have any big rounds). Next year I will have a better assortment by cutting my own wood.

As far as draft, yes it can be difficult here in NC. I've found if the temps aren't into the 40s I'm not messing with it. It's a huge external masonry chimney, 15' stack height lined properly with a SS liner and 1/2" of insulation. That being said, its been in the 20s and below most of this week, and draft is no problem. It helps that the chimney is on the leeward end of the house.

As far as closing, yes I typically go in small increments. However, this morning I reloaded after 9 hours from the overnight burn. Needed a few newspapers but was able to get it going from coals. Stuffed it full (15-18) splits N-S, and in 10 mins I had it shut down. Very happy about that. Image below is at the 10 min mark. Closed in 2 steps like sledhead described.

I've found if I reload below ~250 it is harder to get going. I think I just need some dryer kindling (cut it from the same splits, so it needs to be dryer). Also, I've found N-S is MUCH easier to get rolling. It's more set it and forget it, whereas E-W requires some babysitting, letting the bottom layer get blazing before adding more on top. Otherwise, it smokes and smolders, not good. Is this anyone else's experience?

Thanks again everyone...24 this morning and snowing...summertime in the house though! Wife is very happy...

After 8-9 hours, my stove top is generally 175, maybe over 200 back towards the outlet. I figure that is pretty good.

Nice looking fire...

 

[stovelark]

Hi Statefan- just wanted to chime in and say yep, probably nothing more than the small pieces of wood causing the quicker burn through, but if you're going 8hrs plus, sounds like she is doing good. Have sold many Osburn 2400s, not many complaints either. It seems to be a very competent heater, espec for the money spent. The 2300 is also a great heater too. I like my Enviro and will prob get another one but I think you made a great choice. As the snow continues tonite, I am thankful to warm my older bones next to it. Take care.

 

[DBoon]

Based on what you describe as the process you follow to get the fire going, you likely do not have wood as dry as you believe. Good <20% MC wood will light off quickly in a 250-300 degree F stove, and will not take 1 hour. Also, 14 or so small splits in a firebox = lots of surface area so faster off-gassing. Try larger splits in the future, but those larger splits will take longer to dry.

If you can (and I suspect you won't be able to), start turning your air down to 7/8 or 3/4 of full primary air when the stove top hits 300 degrees and then another 1/4 or 1/8 at 400 degrees. This will slow down the off-gassing on a load of small splits, but you may not be able to do this if your wood is less than optimally dry (and I suspect that it is wetter than you think).

 

[NW Pa Burner]

I would have to agree that if you are getting 8 hour burns you are in good shape. With my 2400i I am getting roughly the same burn times (8 to 10) overnight and when gone for work with enough coals left for an easy relight. I think the fan shuts off around 7 hours. To do so though takes loading the insert with a lot of wood and getting it going good before shutting it down otherwise she will smolder. I split rather small too, 3 to 4 by 4 to 5 inches, and will load a few get her going and then load her full. It takes some planning, usually need to start a half hour or so before I plan to walk away from it. Leaving the door cracked will get it going fast right after loading but I don't leave it cracked for too long.

From my experience the EW loading results in the longer burns. When I am home with it I will load two pieces NS then two ES on top and another one or two NS on top. Doing this I can shut down the air real quick and stove top temps will hit about 600 and it'll burn good for about 4 or 5 hours. Only doing this because some of my fuel is higher MC. With an insert have to rely on the way fire looks and a flue thermometer really isn't practical.

 

[nvanhar]

All these guys know far more than I do, so I'm only reading through for my own edification...but wanted to say "Go Pack!" NC transplant now living in VT. ❄️

 

[Smoked]

A damper in the pipe might give you a little added control! Most should not need them but if a strong draft is fueling the inferno, dialing it back a bit might help. I only use mine in higher draft weather conditions.

 

[axeman628]

If you don't have a flue thermometer then you need to go by the fire. As soon as the fire is burning robustly start turning it down.

Have to thank you for this. You mentioned this somewhere else too and I started doing this as well. Going by the fire has given me some of the best results. I think I'm getting the hang of it too, the stove almost regulates itself if you turn down the air correctly using this method. Watching stove temps it still climbs but levels out at a nice temp for a while (about 450 - 500). But like most things, dry wood is the key. Going by the fire on wet wood looks good until it doesn't and becomes a smoldering mess.

Thinking about adding a flue thermometer, is the 500F you mention a probe or surface or surface*2?

 

[pdxdave]

I'm surprised it hasnt been mentioned yet, but since you are loading e/w, i'd highly recommend trying to rake coals to the side rather than front on your reloads. Load larger pieces on the bottom, and smaller up top. Then lay some kindling n/s over the coals you have piled at the side. This should help promote a slower top down burn.

Now for the record, I fully concur with Ashful ! Cat stove is by far the simplest and effective way to get increased burn time and efficiency. 20% mc wood should have no issues at all in most cat stoves.

 

[Wood Duck]

OP, your stove seems to operate like mine, or like mine would if I had only small splits. I think you need larger splits, and that will remedy the problem as much as it can be remedied. I have to wait a while after reload before I cut back the primary air, just as you report. Like you I get only a few hours of yellow flames from a load of wood, then a few more hours of good heat from the coals. Non-cat stoves aren't steady-state burners - they have hotter and cooler portions of the burn cycle. There is still time to get some larger splits seasoned for next winter, provided the wood isn't oak.

 

[OhioBurner©]

I'm not familiar with the stove, but seems like we've hit on all the major points. An 8hr burn is probably good in that stove, but not sure if I'd call 175F at the end as part of the burn time, but that might not be too far off.

Seems like your reloading is good by me, many have said not to reload to hot but 250-350 sounds in the ballpark by me. Not quite sure if your turning it down quick enough, but hard to say without being there. My Jotul which tended to burn too hot, could be turned down to minimum air setting in probably 20 minutes after a 350F reload, and that is with larger splits. A thermo would help here since you can better gauge when you are reloading and the results. The small splits are probably the biggest park of the problem, but you really can't undo that if they are already split. Definitely go bigger if you can, and save the small stuff just for helping a cold start or if your coal bed cools down to much, or just to fill in the little gaps when your trying to stuff it full.

Is this an insert or freestanding? It's hard to imagine you'd need a key damper on a 15' insulated liner, but it's always an option I guess (unless its an insert). I think the small pieces are the main issue. It's a lot more surface area burning...

 

[HisTreeNut]

We also have a non-cat stove and of we fill it up tight, we get a solid 5-7 hours of burn with another 2-3 of decent heat from the coals, depending on kind of wood loaded. We have 18"-20" splits and can fit 4-6 splits on a full load. We also load N-S and not E-W because the wood does not burn as well, especially to the back of our stove. That being said, you are getting pretty decent temps & burn times so I am not sure how much more you can improve it. I would agree with the other posters that larger splits may help and playing with how you rake your coals may help increase your burn time a bit. Not knowing the type of wood you are burning, maybe doing a N-S layer on the bottom with a softer wood, and the rest of the wood E-W may get it re-lit faster for you. Or using softer woods on the layer on top of your coals and harder woods to the top of the softer woods. Just a couple of thoughts...

 

[CheapBassTurd]

Good info for an also new burner here too. In fact, three days. LOL

Our potbelly pig is responding well to half loads of large splits and rounds.
The smalls were disappearing too fast on my test runs to cure the cement and paint.
From the first big burn it's been big chunks thus far. With the old fashioned setup
of a deep firebox with chimney at the back I'm pulling coals forward and putting wood
directly on the brick floor of the thing then push the coals back to the fresh wood.

The 27 inch box easily prefers N/S loading. Burns front to back pretty evenly.
Pull the hot stuff forward, repeat. My coals are about the size of a softball when I reload.
Top of the box was in the low 300's last two cycles. (at reload time)

Luckily we had much dead but not rotted stock to begin with. Very seasoned and lights up well.
After loading I close the door and crack open the vent 1/2 then cut it down to 1/3 or 1/4 open
15 minutes later. The coals are enough to get it going again.

More to learn, and of course will post my results.

CheapMark

 

[begreen]

Watching stove temps it still climbs but levels out at a nice temp for a while (about 450 - 500). But like most things, dry wood is the key. Going by the fire on wet wood looks good until it doesn't and becomes a smoldering mess.

Thinking about adding a flue thermometer, is the 500F you mention a probe or surface or surface*2?

Probe thermometer reading on double-wall stove pipe.