The value of (hot) coals

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48rob

48rob

Feeling the Heat
Oct 11, 2010
308
Illinois
I've read a lot of posts new and old about people having trouble with coals taking up space they want/need for more wood.
I'm new to all this...I don't understand why you would want to "burn down", or "remove" hot coals to make room for more fresh wood.

We burn wood to make heat to keep our homes comfortable.
Hot coals produce heat, and thus keep us warm.
Does fresh wood produce so much more heat that one would want to waste the heat being offered by the coals?

Yesterday as an example, I burned all day, from 5:45am until 8:30pm (my stove is in my shop).
I maintained a room temperature of around 74 degrees most of the day.
At 6:40pm I put a couple rounds on the fire closed off the air as far as it would go and went in the house.
At 8:30pm I went back out.
The stove had a ton of glowing red coals (shop temp was now 86 degrees) I added 1 large round (left the air on the lowest setting) then went in and did not come back out until 6:45am this morning.

At 6:45 this morning, the stove temp was a mere 85 degrees but the shop was reasonably warm at 61 degrees (outside temp was 6 degrees).
The stove had a few hot coals, enough I was able to lay up some kindling and splits, and have the hot coals ignite them (no matches) in less than 5 minutes.
My glass was clean too (boasting a little here
c2b1634c5e514d3b0dbd635fa7776ec7994f960e.gif


).

If the stove was in my house and I'd have added another round later in the evening, I think I could have maintained an easy 70+ degrees all night.

Am I missing some critical part of burning, and not getting the long burn times I want because I'm leaving a lot of coals?

Rob
 
There is no doubt that my stove produces more heat packed with red oak than it does with a bed of coals. When it gets real cold, for PA that's in the teens and windy, I'll shovel coals out if I have to just to get a good fire roaring. It's rare, but I've been known to do it a few times.
 
Those you shovel out makes a good steak on the grill......just sayin'

I have done that a lot of times if the timing is right just transfer them to the grill
 
In response to your last line, There are many definitions of burn time. For me one cycle is apx 5 am load stove for day, get it cooking in the secondaries then leave for my shop. When I return anywhere from 8-12 hrs later I start over. there are just enough coals left to restart without a match. The 30nc is still warm to the touch but not really adding much to the overall temp inside at that point. A load of red coals in this stove is still putting out plenty of heat but it is all relative to what you are comfortable temp wise with.
 
48rob said:
I've read a lot of posts new and old about people having trouble with coals taking up space they want/need for more wood.
I'm new to all this...I don't understand why you would want to "burn down", or "remove" hot coals to make room for more fresh wood.

We burn wood to make heat to keep our homes comfortable.
Hot coals produce heat, and thus keep us warm.
Does fresh wood produce so much more heat that one would want to waste the heat being offered by the coals?

Yesterday as an example, I burned all day, from 5:45am until 8:30pm (my stove is in my shop).
I maintained a room temperature of around 74 degrees most of the day.
At 6:40pm I put a couple rounds on the fire closed off the air as far as it would go and went in the house.
At 8:30pm I went back out.
The stove had a ton of glowing red coals (shop temp was now 86 degrees) I added 1 large round (left the air on the lowest setting) then went in and did not come back out until 6:45am this morning.

At 6:45 this morning, the stove temp was a mere 85 degrees but the shop was reasonably warm at 61 degrees (outside temp was 6 degrees).
The stove had a few hot coals, enough I was able to lay up some kindling and splits, and have the hot coals ignite them (no matches) in less than 5 minutes.
My glass was clean too (boasting a little here
c2b1634c5e514d3b0dbd635fa7776ec7994f960e.gif


).

If the stove was in my house and I'd have added another round later in the evening, I think I could have maintained an easy 70+ degrees all night.

Am I missing some critical part of burning, and not getting the long burn times I want because I'm leaving a lot of coals?

Rob
Click to expand...

Rob, just a word of caution: you put on a large round and later some kindling and splits......then left the draft on the lowest setting. You can do this sometimes and get away with it but I would definitely not do that as a regular thing. Open that draft full before you even open the firebox door. After adding wood, leave the draft open a bit longer. The worst part of the burn for producing creosote is right at first. Remember that the first thing that happens when you add wood is that the moisture evaporates. Where does that moisture go? With the draft on the lowest setting, how quickly can that smoke exit the chimney? The answers to these questions tell you why we recommend having the draft set full open on reloads and usually 10 minutes or much longer, depending on the fire. Once the wood gets charred, then you can usually dial the draft down and all will be well.

I agree there is a lot of heat in those coals. Think about a fire you may have had, say, for a weiner roast. The roasting is done when the coaling stage is there and not in the flames. Also think about how much heat is in those coals. Even more so in the stove. However, you indeed can get too many coals. But to me it is not good burning practice to empty the hot coals rather than use them for the heat they give. It's sort of like dumping some fuel oil on the ground rather than letting it burn in the furnace. But that idea of using them on the grill doesn't sound all bad. lol
 
There is no doubt that my stove produces more heat packed with red oak than it does with a bed of coals.
Click to expand...

When you think about it like that, it does make sense.
Since the hot coals are the tail end of the burn cycle, fresh wood will produce a greater volume of heat than the coals.

Thanks for the help!

Rob
 
And when you think about it like that, thank your lucky stars you have a good bed of coals to get that red oak burning. The point is, you need the coals; just don't need the stove half full of them. If you time the cycle right you can burn the coals down and still get the benefit of the heat they will give.
 
Red oak gives me alot more heat then the coals. But i do burn them down and it gives good heat also.
 
Corey, nobody will doubt you will always get more heat when you have wood in that stove but most folks also reap the heat benefits of the coals too. I feel sorry for those few who throw the coals outdoors rather than using that heat.
 
Rob, just a word of caution: you put on a large round and later some kindling and splits…...then left the draft on the lowest setting.

(I put on a couple rounds, then closed the air, came out later and added another round without changing the air)

You can do this sometimes and get away with it but I would definitely not do that as a regular thing. Open that draft full before you even open the firebox door. After adding wood, leave the draft open a bit longer. The worst part of the burn for producing creosote is right at first.

Remember that the first thing that happens when you add wood is that the moisture evaporates. Where does that moisture go? With the draft on the lowest setting, how quickly can that smoke exit the chimney?
The answers to these questions tell you why we recommend having the draft set full open on reloads and usually 10 minutes or much longer, depending on the fire. Once the wood gets charred, then you can usually dial the draft down and all will be well.
Click to expand...

Dennis,

Caution accepted.

I learned that lesson the first week.
Putting fresh wood on a low or smoldering fire and closing the air too much makes a lot of smoke, and creosote.
Under those circumstances, I can't do what I was describing in my original post...


I failed to give you guys as many details as I should have, so let me add some information.

Since the stove is in the shop, and I go in about seven every evening, I'm experimenting with ways to keep the building reasonably warm until I come back out around 6:00am.

I'm getting much better at keeping the room a steady 72-74 degrees during the day.
A little before seven at night, after burning all day, the stove is hot, there is a good bed of hot coals, and the draft is good.
All is working very well with the air at the lowest setting, I believe, because the glass is now staying clean, and there is only smoke for a few minutes after loading new wood.

When I say the stove is "hot" I mean I'm getting temp readings of 450 degrees on average when I reload.
It takes maybe 30 seconds for the coal bed to ignite the new rounds.
If I were to open the air under these conditions, it would get far too hot I think...

I've come back out to the shop an hour or so after loading the rounds, and they are now nice red coals, with stove temps around 500 degrees.
The shop room temperature is up around 85-86 degrees.
This would be uncomfortable in the house, but since I'm no longer in the room, it works for me.

I'm thinking that be leaving for the night with a very full bed of hot coals, and a very warm room, that the combination is keeping the room warm, both from the stove radiating heat slowly, and from the structure radiating the heat?

Again, in the morning when I come back out, the glass is clean, there are very few coals left, though if I dig in the ash I can find enough to get the kindling going again, and the room is around 60 degrees.

As soon as the snow and ice go away, I'll be up on the roof again inspecting the flue.

Thanks to you and everyone else that offered an opinion, I appreciate the help and am enjoying the learning experience!

Rob
 
corey21 said:
Red oak gives me alot more heat then the coals. But i do burn them down and it gives good heat also.
Click to expand...

Ah ha! I knew there was a reason iron smelters and blacksmiths use red oak instead of coal.... er ....uh.... well... OK, but at least no stoves use coal to actually produce heat ... oh .....that is out too?

I think the key to getting heat from coals is to have the proper amount of airflow coming from below the coal bed. Too little air and they aren't burning efficiently. Too much and you are just cooling off the firebox. The problem is some stoves don't have a provision for bringing air from under a coal bed. Cracking the ash pan door can work wonders - but some don't have an ash pan. Conversely, wood burns better with airflow simply coming 'at' or even 'above' the stack. Most stoves can provide this easily.

Either way, those hot coals are worth their weight in ....well...coal, so if there is any means to leave them in the stove, that is always the best option.
 
cozy heat said:
I think the key to getting heat from coals is to have the proper amount of airflow coming from below the coal bed. Too little air and they aren't burning efficiently. Too much and you are just cooling off the firebox.
Click to expand...

+1

It is hard to get the optimum amount of air on the coals but I don't expect to get it all that close to perfect. I haven't yet shoveled coals out (thankfully) but I have adopted strategies based on ideas I've read here.

Bottom line seems to be that some amount of planning is required to do it well (isn't that true for most things related to wood burning?). During shoulder season it doesn't really matter - just leave the stove alone after the burn and let the coals hold until next fire however long it may be.

However when it gets really cold and I am trying to reload quickly to maximize the output of the stove I do find I need to watch the stove more. My approach is to watch for when the stove top temp starts to drop and flames have fallen off - this is also when the wood is transitioning to mostly coals. I then start to increase the air. The more heat I'm aiming for the more air (but I keep the cat engaged). I find the coals will brighten up considerably (white hot in spots) and the stone will get very hot on the sides as well as a lot of heat is radiated out the front of the stove. Depending on the load this may last another 2-3 hours (with 450-500* stove side temps) tossing really decent heat. Then once coals are down to just the bottom of the stove I'll disengage the cat and stir them up a bit to get the ash off and either re-load or if I want to burn off more I will leave cat open and air full and let them burn off until they are at the point I do want to load (or timing is right as the case generally is) - they go fast at this point and stone is still very hot so room stays warm.
 
Slow, your method is very close to the way we do it.
 
It all depends on how cold it is outside as to rather the coals are a plus or a minus for me. My house gets pretty chilly when the stove is full of coals and its 20 outside. I put a few good size splits on there, open the stove and enjoy the heat from the splits while burning down the coals. May take a couple sessions of doing
this before I can load it up again..
If I'm at home and can tend to the fire, I rarely fill the stove like I would before going to bed. I can control the coal build up better this way.
 
Westkywood, also try opening that draft full much earlier; even before the fire is down to the coaling stage.
 
One other thing I'm trying to learn/master is to adjust my burn to have the right amount of coals in the morning. Basically the lower my air setting when I go to bed the more coals I'll have, so if I leave it running hotter I can thus have less. So the 'trick' if you will is to set the air higher if I want fewer coals at a given time. The down side to setting it higher is that the stove will run hotter earlier and may end up cooler for a longer period of time in the wee hours. I rather like a more steady burn as the house is warmer in the morning when I get up. So I'm trying to find that balance of the 'right' air setting to get enough coals in the AM. Yesterday morning for example I had too many - I had to boost the air up and leave it for an hour before I loaded. Today it was just about right to load although I had intended to burn them down more as I wanted to dust off the glass.. oh well.
 
I'm starting to see the trend here...

As usual, I'm the odd guy out, doing things for different reasons than most...

In my very small shop, a good load of coals is enough to do the job.

In a home that is multiple times larger, I can see why a load of coals just wouldn't keep you warm, and get you to thinking that they needed to go to get more wood in the stove...

Sometimes it takes me a couple tries to figure these things out...but I've got it now!

Rob
 
Backwoods Savage said:
Westkywood, also try opening that draft full much earlier; even before the fire is down to the coaling stage.
Click to expand...

I gradually open the draft as the fire burns if I'm home to reduce the amount of coals. . After an overnight burn, I've got a ton of coals to burn down.
 
cozy heat said:
corey21 said:
Red oak gives me alot more heat then the coals. But i do burn them down and it gives good heat also.
Click to expand...
Click to expand...

Charcoal or woodcoal is nothing like Coal or Coke used for blacksmithing or smelting or any forge work.
 
I try to burn them down with the air wide open and the cat bypassed on the Fireview. When it gets very cold and windy, my drafty old house is a bit beyond the capabilities of the Fireview so I do from time to time shovel out a bucket or two of coals to make room for fresh wood and the more heat it will give. Burning down the coals only gives me about 400°F stovetop, but a fresh load will get me up around 600°F. The wood is free and the house is cold! I can afford to dump some coals from time to time. For safety's sake, I either dump them in a closed steel trash can or, if available, a snow pile.
 
48rob said:
I'm starting to see the trend here...

Sometimes it takes me a couple tries to figure these things out...but I've got it now!

Rob
Click to expand...

Rob ,sounds like you and I suffer from the same thing, I call it OldTimers... Takes us a while to get it...
 
I've got 2 stoves, one on each side of the house. So I try to time it so that one stove is burning real hot when the other one is burning its coals down. Works well for me until my husband comes home and sees my fire going down in the living room and throws in more wood, thus screwing up my system.
 
nojo said:
cozy heat said:
corey21 said:
Red oak gives me alot more heat then the coals. But i do burn them down and it gives good heat also.
Click to expand...
Click to expand...
f

Charcoal or woodcoal is nothing like Coal or Coke used for blacksmithing or smelting or any forge work.
Click to expand...

That must be why there's a trail called the charcoal road on Riga Plateau in far NW CT, involved in supplying charcoal for the iron-smelting operation there back in the day.
And why so much charcoal iron was produced at Roxbury mines in CT.
And why so much fine swedish steel was charcoal steel.

Could it be because of the freedom from mineral contaminants, like you'd find in coke? :)

Back to the original subject, I find that, when I really need sustained heat output, I leave the air open or mostly open, and feed more frequent small batches of wood. That way the coals don't accumulate nearly as rapidly as when I'm going for a max-efficiency burn. Keeps secondary combustion occupied.
 
boxerdogheidi said:
I've got 2 stoves, one on each side of the house. So I try to time it so that one stove is burning real hot when the other one is burning its coals down. Works well for me until my husband comes home and sees my fire going down in the living room and throws in more wood, thus screwing up my system.
Click to expand...

Stupid Men !!! Oh wait thats what my wife says.... sorry... delete, delete, delete.

She also says she can't trade me in because I have 25 years of training under my belt... and she doesn't want to go through THAT again !!!
 
boxerdogheidi said:
I've got 2 stoves, one on each side of the house. So I try to time it so that one stove is burning real hot when the other one is burning its coals down. Works well for me until my husband comes home and sees my fire going down in the living room and throws in more wood, thus screwing up my system.
Click to expand...

Sounds like a communication failure to me.
 
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