Definition of burn time

[archer292]

I have read about some incredible burn times on this site. Can someone tell me how the burn time is measured?
Is it from the light of a reload until there are just a few embers left? Is it the actual time between relaods? I have been thinking that it is time between reloads, not the actual time of a fire from start to finish. I would think the time between relaods, if you are burning for optimal heat would be considerably shorter. I am new to heating with wood so please bare with the noobie questions.

 

[Corey]

https://www.hearth.com/talk/threads/12321/

 

[billb3]

I doubt you want too many of us to bare with you.

burn time needs a qualifier.
my seasonal burn time is Spring, Winter and Fall.
In Summer I Coppertone.
(bear with me, I'm getting there)

in your context I would consider time between charges or resupply of wood.
although if in a bar and in need of braggart material One might go with match/fire / no fire ---match.

 

[swestall]

After many iterations of this question my thought is that "burntime" is only useful when you are buying and talking about it with someone. The manufacturers need to specify a time for burn; so they will quote a number from fire start to coals at some stage.

A far better way to think about this is what it takes you to heat your house. From the beginning when you start your fire to the point when you have coals that are not keeping the stove hot enough to heat your house; this is the duration of your heat cycle.

Burners should focus on understanding what the burn cycle is that best supports the heating of their house. Get the stove temp up and then figure out what burn cycle keeps it there in what type of weather. Winter cold or the shoulder (fall/spring) short burn to keep warm cycles. By getting a focus on that and what it takes to make your stove installation work in your house; you will be a happy burner.

If you suspect your burn cycle is excessively short, then it is time to determine if you have a wood problem or a draft problem. No on seems to complain about a burn cycle that is too long, so why get into that.

 

[begreen]

There are two ways to measure, total burn time (TBT) or total heating time (THT). The first is good for sales, but not really meaningful. The second is a measure of the period of usable heat and much more important. This is not an official figure and almost never stated for a stove, but it's what is really important. Consider it say the time from the stove reaching 200 degrees stove top temp to returning back down to 200 degrees.

Unfortunately, sales brochures and marketers only report the TBT which could be hours longer, but fairly meaningless when you are trying to heat your house.

 

[archer292]

200 to 200. Thanks. Hearthstones description is " up to 10hr burn and 12hr heat ".

 

[eernest4]

I might as well stick my big foot in too.

Burn time , being the time the fire actually burns, is 2 to 4 hrs.depending on size of fire box, setting of primary air,initial amount of fuel load,type of wood and size of splits.
However the time that the embers continue to glow after flames cease can be up to another 6 hours more.
But the time that you actually get useable heat out of the stove will be the time that the fire actually burns plus the time until the embers no longer heat the house, which will vary according to wood type burned , amt of initial fuel load & outside temp & inside temp.

THEREFORE, I AM GOING TO INVENT A NEW TERM AND CALL IT USEABLE BURN TIME
& it shall be the amount of time of usuable heat that you get out of the stove. This being the sum of the time of the flames, until they cease and the time of the red glows, until the red glows fail to emit enough heat to keep the house warm. And this time shall be different for every stove, even stoves of the same model ,as varing factors are introduced into the parameters due to the different size houses & different temp encountered in each different stove owner's home. So says eernest4 , so say we all.Amen! %-P ;-P

 

[RedRanger]

Either ya have heat, or ya dont-- Even if the flames have long since burned out.

 

[Jimbob]

Consider it say the time from the stove reaching 200 degrees stove top temp to returning back down to 200 degrees.

That sounds like a good standard to follow. Using that, Summit would be around 6-10 hours on softwood.
6 hours starting the stove from cold, and starting to measure when the stove hits 200.
10 hours when loading onto a bed of embers when top is down to 200, then turning it down in stages as quick as possible while still maintaing flames.
I could go longer, if I would turn it right down right away and let it smoulder.

 

[BotetourtSteve]

I was waiting for someone to get the "my stove does "x" hours" posting going... ;-)

I'm finding the Jotul F600 easily holding 200-300 surface temps after overnight burns (or all day at work/play) of 8-10hrs. No question it will stay 200 10+ easy. The longest I have actually documented it so far was a stovetop still at 200 after 14 hours, and enough coals were available to restart without kindling.

For "regular" burning, I am keeping a temp more like 300 as my minimum before reloading (heavy glowing coals stage), and then run back to 500ish. These burns are averaging 4-6 hours.

Oh, and that's hardwood (oak, ash, hickory).

 

[SlyFerret]

Good info so far. It corroborates what I've learned from the couple months I've been operating my stove.

I found that I had to resist the urge to reload the stove as soon as the flames died out. There is still a lot of usable heat in those coals.

One thing that I didn't see mentioned is to also look at the room temp in the house. I've had to keep an eye on the room temp as well as just the stove temp. If the room temp is over 80 degrees when I fire off a new load, I'll find the stove room over 90 within an hour or so. The problem is, with a well insulated house, you have to figure out the right time to reload when you still have enough coals left to get the new load started, but the house isn't too warm.

Next year, my wood supply will be better. I've been burning Cherry, which burns pretty hot and fast, and doesn't coal real well. I've been getting 4-5 hours from the time I light off a new load to the time that my coal bed is just about right to start another. I could stretch it a little more, but but getting it lit might be pretty tricky.

-SF

 

[dtabor]

Id have to go along with what BotetourtSteve said. I can have my temps at 200 for hours and hours, but at 200*, the only place you're really "feeling" the heat is in front of the stove. 200* wont sustain any type of heat in outer rooms in my big house. I can shut down my damper at bedtime, say 10 and wake up btw 5 and 6 and have it be in the 400*+ range and that means the "stove room" which is living/kitchen/dining area is 65* give or take on a cold day.

As others have said, I think burn time is different to different people and companies who put that ridiculous number on their brochure. I havent used a match since the first fire after break in on my stove this year. I let it "burn out" for a night/day (about 20 hours) and when I stirred up what little ash was in the bottom, I found a small number of coals there. Put on a split and cracked the door and it took off. Now THATS a burn time haha.

I really looked for an answer to this question when I started with the new stove this past fall so Id have something to compare with but found you just cant do it. Set your own definition and follow that. When it varies greatly from what you're used to, look for issues with your wood and stove etc.

 

[Bill]

For me productive heat is 300* minimum. Once below 300* I add more wood.

 

[dtabor]

I also deal with the fact that I dont (wont) get up in the middle of the night to reload and both my wife and I work all day so from about 7a-5p there stove is on its own so my house temps dont get terribly high. I maintain between 70-75 when we are around, and it drops to mid 60's while we are gone unless its brutally cold out and then we might see 60* when we get home.

I havent burned one drop of oil this year so Im not going to complain a bit. At $80/cord, burning 5 cord this winter thats $400 to heat my house compared to well over 1k last year with mostly oil (i ran out of wood and had an old less than acceptable insert).

 

[savageactor7]

Well in the spirit of this topic I decided to do a burn time test with our centrally located QF 4300 ST. Fully loaded it with ash last night at 1130 set it for max burn got up at 530 ( it was 11* out) and it was still putting out sufficient heat with lots of coals.

Took the dogs out then I reloaded it at 615 when the propane stove kicked on…it’s set at 68*…and the thermostat is about 30 ft from the stove. I could have gone another 15 min but if I'm up and I hear that propane stove...I just have to do something about it.

So my max burn time is 15min short of 7hr.

…just say’en mostly we burn for heat and don’t care too much about max burn…but it is relevant when you leave the house....so that's that.

 

[begreen]

sa, intersting numbers. I'm glad I'm not dealing with temps in the teen. However, I don't think that is a reliable measure.

If it was 30 outside would the time be the same? Will another person get the same results? No, because what is really being measured is the stove's ability to keep up with the heat loss of the house. That is going to vary with outside temperature and wind load. Measuring the stove top temp is a more meaningful and objective measure.

 

[savageactor7]

Afternoon BeGreen^ well off the top of my head I would think the stove would burn the same no matter what the outside temp.

But if I understand you correctly if it was 20below this morning I couldn't wait with a stove top temp of 300* like I did this morning cause that would be a 30degree deferential...and chances are the propane stove would have kicked on way earlier than 615, right? That's makes sense.

I agree with the stove top temp in comparison to the outside temp is the determining factor or acceptable long burns. Most of us burn wood to be warmer than we could afford to be with oil or propane...that's our thing.

 

[begreen]

For other folks to be able to determine whether a stove will work for them, we need to take the house out of the equation. What is really important is how long does the stove put out xxx (n) btus. There are so many variables in house construction, insulation, window loss, wind load, exterior temp, that really have nothing to do with the stove. These variables need to be factored out if we are going to make fair comparisons of burn time.

Basically we are heating a sieve. All of our houses are leaking heat to some degree. When someone from Tennessee with newer, well insulated, 2500 sq ft. house puts in a Summit to heat the place with an average 35 degree exterior temp, they are going to likely get very different "heating times" (when the furnace comes on), then someone in upstate NY with an old, 2000 sq. ft. farmhouse fighting 10 degree temps and a howling wind. Let's say the fellow in Tennessee's furnace never comes on. He just makes a fire in the morning from scratch. Does that mean he is getting 24 hr burn times? Not really. It means that the house is holding the heat better and the differential between exterior and interior temps is a lot less. While the fellow in NY is totally fighting the elements and needs to be putting out about 4 times the btus to stop the furnace coming on. The difference is maximum burn time (the Tenn. case) vs maximum output (btus) time (the NY case). The fact that your stove is capable of putting out enough heat to keep the furnace coming on for ~7 hrs under cold conditions is quite respectable. Does that make sense or am I just babbling?

 

[Jags]

BG - you are on the money (as usual). In a thread a while back, you had asked about the performance that I was getting from my quad IR. That is exactly why I listed times and temps. Takes the house out of the equation, and will give usable info for actual heat output. Some houses require a stove of xx btus to be at 400 degrees, but the next house and stove may have the capacity for xyz btus and the stove has to be held at 500 deg. For my house, with a typical 10 deg. day and 10 mph winds, if I don't have the stove at 500+ it ain't gonna heat the house.

I probably just made this more confusing. :shut: