Coaling: What causes it? & Why is it bad?

[Black Jaque Janaviac]

I've read through some thread here and I see some references to "coaling" and it sounds as if it is a bad thing.

Why do you need to avoid or minimize coaling? I just thought it was a natural thing for wood to do when burnt.

It seems like it can be caused by the way you run your stove, not necessarily by the type of wood you burn. How do you avoid it?

 

[Wood Duck]

I think if you burn with a low air setting you are more prone to get a lot of coals. Coals are fine except when you get too many of them, and as a result you can't add enough wood to keep the stove as hot as you'd like. The nice thing about coals is that you can add one or two splits and the stove will stay hot a while, just not perhaps as hot as you'd get with a full load of wood.

Some wood gives more coals than other wood. I think generally dense wood gives more coals than less dense wood.

 

[Huntindog1]

You need to have enough coals to restart the next load but in times like this when its cold your dont have time to let the coals burn down as during that time the house is getting cold when the temps out side are close to 0 and wind chills below 0. Plus during cold weather you burn woods that are more dense to get more btu's of heat into your house. This type wood leaves bigger and more coals. This all adds up to having so many coals now you cant get much wood in your stove. Most people want to get enough wood in the stove for at least an 8 hour burn. So it all becomes an issue.

I have been mixing some softer woods with my harder woods to help the situation.

I have put a small pieces of wood on raked forward coals but it still takes time to burn them down, there is no real easy solution.

 

[corey21]

I like having coals woke up to a nice coal bed this morning. Sometimes i get to much but still that is a good thing to me there is a lot heat in a big coal bed.

 

[Huntindog1]

Well when people go out to make charcoal it a process of burning wood in the absence of oxygen. So I guess we need to open the input air a little more.

From Wikipedia: Charcoal is usually produced by slow pyrolysis, the heating of wood or other substances in the absence of oxygen (see pyrolysis, char and biochar).

 

[mecreature]

rake the coals in a big pile crack the door a tad..... blazing heat...

seems the more coals you got the more you get.

 

[Black Jaque Janaviac]

With my NC-30 if I run the stove with anything but the primary lever closed I can get 800+ stovetop temps real easy. Of course I have it open for starts and reloads, but it seems I can never "run" it at 25%, or 10%, or 1%.

I guess I'm not really "concerned" about coaling. But I'm interested in wringing out the best performance from my NC-30.

When you say 8-hour burns do you literally mean you see flames for 8 hours? I always assumed that meant that after 8 hours you could reload without striking a match.

 

[oldspark]

With my NC-30 if I run the stove with anything but the primary lever closed I can get 800+ stovetop temps real easy. Of course I have it open for starts and reloads, but it seems I can never "run" it at 25%, or 10%, or 1%.

I guess I'm not really "concerned" about coaling. But I'm interested in wringing out the best performance from my NC-30.

When you say 8-hour burns do you literally mean you see flames for 8 hours? I always assumed that meant that after 8 hours you could reload without striking a match.

Why cant you run it at 25% or below?

 

[BrowningBAR]

With my NC-30 if I run the stove with anything but the primary lever closed I can get 800+ stovetop temps real easy. Of course I have it open for starts and reloads, but it seems I can never "run" it at 25%, or 10%, or 1%.

I guess I'm not really "concerned" about coaling. But I'm interested in wringing out the best performance from my NC-30.

When you say 8-hour burns do you literally mean you see flames for 8 hours? I always assumed that meant that after 8 hours you could reload without striking a match.

I can maintain 8+ hours of stove top temps of over 300 degrees on the 30. At peak output I can have the air "closed." I will open up the air gradually throughout the burn to maintain temps and burn down the coals.

 

[DianeB]

dealing with heavy coaling right now - yes have been burning hardwood for the past few nights and the overnights create them as we cut back the air when we head to bed so we have coals in the AM...now have too many coals and hard to get the wood in. Will leave the door open for awhile with a couple of small splits to see if I can get it to burn down. If not - shovel and bucket tomorrow morning

 

[fishingpol]

dealing with heavy coaling right now - yes have been burning hardwood for the past few nights and the overnights create them as we cut back the air when we head to bed so we have coals in the AM...now have too many coals and hard to get the wood in. Will leave the door open for awhile with a couple of small splits to see if I can get it to burn down. If not - shovel and bucket tomorrow morning

Same here. Big coals, less room to load new splits. It can be frustrating with a smaller stove. A good cycle for me is for the coals to burn down smaller, add splits and the open primary air to get it going again. Large coaling means open the primary air sooner to get them to burn down to fit more wood in.

 

[Black Jaque Janaviac]

Oldspark,

I have to run it at 0% open. If I crack the primary a bit it seem to bury the needle on my thermometer - with a full load that is. Once it is to the coaling stage I can open it up.

What difference does it make if the coals take up room that would otherwise be filled with splits. The coals are fuel and burning are they not?

 

[jdp1152]

yes, they're fuel and burning, but won't last very long if you're trying to get a warm nights sleep. All really depends on why you're burning. Supplement or ambiance, probably no reason to worry about it. Primary heat, you want to maximize your burn time. Loading on a really hot coal bed means you're going to get shorter burn times....hence burning through your wood pile much sooner. It's all about cycles. While coals produce heat, do they alone produce enough heat to sustain and evening compared to a fresh load of wood? No. The folks that complain about them are those with small fireboxes (which can mean no reloading space at all in many cases) or those who need to time cycles so that they stay warm and can get a good fire going first thing in the morning. It's not like a heat pump that can take a little heat from something cooler and make your house warm. It's a thermal mass that requires being much much warmer than the target temp for surrounding areas.

 

[eyefish2]

My two cents on "coaling" ==> You are not having complete combustion of the wood causing coals - wood burns more slowly in the absence of flames. The coals/chared wood will of course burn down over time. The only issue of "coaling" I can see is that it might indicate you may not be burning hot enough. This in turn may cause buildup of creosote in your flue. If you are burning hot and have a good temp, coaling is what you want. Keeps wood from burning up too fast. If you are not burning hot enough coaling takes place at a lower temp causing creosote in your flue. Let me know if I am full of *&*&^*#. Again, my thoughts.

 

[corey21]

My two cents on "coaling" ==> You are not having complete combustion of the wood causing coals - wood burns more slowly in the absence of flames. The coals/chared wood will of course burn down over time. The only issue of "coaling" I can see is that it might indicate you may not be burning hot enough. This in turn may cause buildup of creosote in your flue. If you are burning hot and have a good temp, coaling is what you want. Keeps wood from burning up too fast. If you are not burning hot enough coaling takes place at a lower temp causing creosote in your flue. Let me know if I am full of *&*&^*#. Again, my thoughts.

When a fire is in the coaling phase there is not no creosote.

 

[Woody Stover]

My coals have been manageable but I might try putting Ash in the back, and the big coal-producing woods like White Oak or BL in the middle or front of the load where the coals can be burning down as the Ash in the back is still burning and producing heat.

 

[evilgriff]

The coaling was an issue for me with the Sirocco 20, but my entire house is a chimney. I found that when it was extremely cold, my furnace made the house feel warmer than the wood stove even though the temperature was warmer with the Sirocco. When I rebuild, I am without a doubt putting in an OAK. I really noticed the air leaks this time. Now tonight it's 20 degrees, and the Sirocco is idling and keeping the house warm easily and I don't notice the leaking doors, windows, walls, roof, outlets, pipes, rim joists, rafters, plywood, foundation, framing, you name it, it leaked. When it was 3 degrees outside I could see my house glowing from 3 miles away. This new stove showed me the weakness of the house itself. Time to budget for upgrades. The stove did it's job, yet the house did not feel comfortable to me, it was more like a campfire.

 

[gyrfalcon]

The folks that complain about them are those with small fireboxes (which can mean no reloading space at all in many cases) or those who need to time cycles so that they stay warm and can get a good fire going first thing in the morning.

You rang? Charcoaling is a huge problem for me in super-cold weather like we've been having-- small firebox, not being able to burn them down enough without the temperature dropping to unacceptable levels (ie, 60 or even less), needing to reload sooner than optimal for the same reason, etc.

Also, the best firewood I can get in quanity here is beech, which zings the stove temp up really fast when split down fairly well. I love the stuff for that, but even when you burn it with the air wide open, it charcoals like crazy. Don't know why it does that, but must be something about the super-dense, gnarly structure. I sometimes get a small amount of black birch (I have to buy c/s/d), which according to all the charts and also in my experience burning it, has roughly the same BTUs and burning time as beech, but it leaves only a really small amount of charcoal even with the air turned pretty far down. Sugar maple also burns nice and clean that way and does fine for me for much of the winter, but when we're down in the single digits and below, it just doesn't produce enough heat in the tiny firebox.

 

[evilgriff]

I have had good results with maple, but so far my favorite wood seems to be ash. A neighbor's ash went down last winter and part landed on my property, which I cut up and stacked late in the summer. I did not think I was going to burn it this year, but I am and it burned fantastic, good heat, long burns. Then hurricane Sandy dropped 2 more on my property, which are cut up but not split as my splitter can't run under 40 degrees. Come spring, that's my first project.

 

[Waulie]

The only difference is the outside temps. When it's warmer out, no one is opening their stove up before the load is done burning (i.e. lots of coals). When it gets real cold out, lots of folks are trying to get more heat out of their stove. It's all relative. A load full of any wood will have a long stage where it's all coals and lots of them. It's only a "bad thing" if your house is losing temps too fast during that stage.

I have good luck throwing two small splits on my coals and burning with the air half open if I want to get a big load in before too long. This works for me because it's get my stove hot enough so I'm not getting cold waiting for coals to burn down. It doesn't work for everyone because there's so many variables with house size, stove size, heat loss, etc., etc. It's another reason to go one stove bigger than you "need".

 

[gyrfalcon]

I have had good results with maple, but so far my favorite wood seems to be ash. A neighbor's ash went down last winter and part landed on my property, which I cut up and stacked late in the summer. I did not think I was going to burn it this year, but I am and it burned fantastic, good heat, long burns. Then hurricane Sandy dropped 2 more on my property, which are cut up but not split as my splitter can't run under 40 degrees. Come spring, that's my first project.

Ash is good stuff, no question. But... just not enough heat in the small quantity my firebox can hold. But it burns like a son of a gun and seasons really fast.
Is your splitter electric? If so, the idea that it can't run under 40 degrees is some crazy bogus thing. I have one of a different brand (Wood-Eze) and misread the instructions thinking it couldn't be *stored* at under 40, and ran it periodically all winter in single digit temps with no problem, although only for an hour or so at a time.

The reason for the caution is that the hydraulic oil might stiffen up in the cold and an electric motor doesn't run hot enough to loosen it up again. But if you have a place to store it that's over 40 (mine lives in a corner of my kitchen when I'm not using it...), it's perfectly fine to haul out and run at much lower temperatures.

I'm not sure what kind of hydraulic fluid it comes with, but there's good stuff you can buy that farm tractors use that's supposed to be good down to -20, and I'm going to replace mine with that next summer sometime and then experiment the following winter. It'd sure be nice to get that thing out of my kitchen...

 

[gyrfalcon]

The only difference is the outside temps. When it's warmer out, no one is opening their stove up before the load is done burning (i.e. lots of coals). When it gets real cold out, lots of folks are trying to get more heat out of their stove. It's all relative. A load full of any wood will have a long stage where it's all coals and lots of them. It's only a "bad thing" if your house is losing temps too fast during that stage.

I have good luck throwing two small splits on my coals and burning with the air half open if I want to get a big load in before too long. This works for me because it's get my stove hot enough so I'm not getting cold waiting for coals to burn down. It doesn't work for everyone because there's so many variables with house size, stove size, heat loss, etc., etc. It's another reason to go one stove bigger than you "need".

Bingo. And that just doesn't work well in a really small stove because the temperature isn't high enough at that stage to burn the coals down very fast.

I only bought the stove I have back before the big run-up in heating oil prices and the big recession rundown in my income, thinking I'd just use it from time to time for pleasure, not for serious heat. I'm at the point now where I'm seriously thinking of raiding the retirement account to get a bigger one. This little guy very nearly does it for me, although it's a pain loading it as frequently as you have to load a small stove (I work from a home office), but man, it sure would be nice not to have the struggle I have now to keep from freezing in really cold weather. I'm at the point this week where getting to 64 in the stove room feels like bliss...

 

[evilgriff]

Personally I feel my stove has done an admirable job, it's the house with the problem. I am sized correctly, and even with the addition we have planned, it will perform well as long as the house is insulated better which it will be. And in my climate, even with the leaky house I have now, it's never like the ice age here. As far as the coaling goes, I decided on the super cold days (all ten of them) to allow the furnace to take some of the load, it stablized temps through all rooms, and even if the stove is coaled at 300 degrees, it is still providing some heat, taking some load off the furnace.
The comfort level difference for me between 0 degrees and 20 degrees is night and day. I only had problems when it was single digits. Thats ok for me. Others heat ALL YEAR with oil. Right now I'm not ready to go cold-turkey. But I do burn wood for 90% of my heat. I'm good with that.

 

[Black Jaque Janaviac]

OK. I'm still not sure why reloading when temps are too hot will result in even more coals the next time.

 

[gyrfalcon]

OK. I'm still not sure why reloading when temps are too hot will result in even more coals the next time.

It's not that the stove is too hot, it's that you're putting a new load of stuff to burn on top of coals that haven't burned down much yet and therefore somewhat stifling their burn underneath the new wood, resulting in charcoal (high temp, low oxygen) rather than ash.