A Survey Of Sorts - Small Firebox Burn Times...

[Peter B.]

A Survey Of Sorts - Small Firebox Burn Times...

After adding some firebrick along the lower back and sides of my stove, I roughly calculate the remaining (usable) firebox capacity at about 1.5 cubic feet.

I'm wondering what other people are getting in the way of burn times from similarly sized fireboxes?

For the sake of this discussion, 'burn time' should be considered the time between reloads if burning *continuously*... or put another way, the cycle from a reload on a good bed of coals to the next reload... on hot coals... when continuous heat output is desired.

I don't typically stuff the firebox solid, so routinely, I may only be using a little over a single cubic foot on reloads.

Nor have I made 'a study' of my own results as yet, but what I've been seeing is something on the order of 3-4 hours... with a secondary/catalyst surge for about two hours and a following 'coast down' of another two.

Yes, in warmer weather (20*+) I'm apt to wait a good deal longer between reloads, but comparison becomes impossible unless continuous burns are being considered.

However, I might also ask if anyone can reliably make it 8-10 hours with coals enough for a relight with a 1.5 cubic foot firebox?

Thanks for all replies.

Peter B.

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[begreen]

I would get 3-6 hrs of good burn in the Castine with that size firebox burning softwood. There would be coals after 8hrs if I wasn't pushing for good heat.

 

[adrpga498]

I'm currently getting 7-8 hours with all hardwoods.

 

[Todd]

I know the little Woodstock Keystone and Palladian have about a 1.4 fire box and some people here are claiming 10+ burns between reloads. I measured my usable fire box which comes in at about 1.8 and I've gotten as long as 16 hours between reloads in the shoulder seasons and 12 hours pretty consistently. Burn times drop down to 7-10 in colder winter months.

 

[AQUALUNG1919]

I can get about 6-8 hours from my little jotul if i don't need the heat to badly, when it is cold, 0-10*, 3-4 hours.

 

[DBoon]

For the sake of this discussion, ‘burn time’ should be considered the time between reloads if burning *continuously*... or put another way, the cycle from a reload on a good bed of coals to the next reload… on hot coals… when continuous heat output is desired.

I have a 1.6 cubic foot Lopi Answer. In the dead of winter when it is 10-20 degrees outside, I will go for 4 hours between loads burning nicely seasoned hard maple. I get about a 20 to 30 minute warm up time from 350 degrees to 550+ degrees, then I shut it down in stages until it is burning gasses, then after about 2 hours from the initial re-load, it's starting to coal but is still putting out good heat.

However, I might also ask if anyone can reliably make it 8-10 hours with coals enough for a relight with a 1.5 cubic foot firebox?

Yes, just two nights ago it was quite cold overnight (8 degrees F was the low), and I filled it up around 10pm when the firebox was at 450 degrees, shut the primary air down completely by 10:30pm, went to bed, and at 8am I still had coals and was able to relight from them. It helps to have a nice ash bed if you want to get that kind of coal lifetime.

 

[elmoleaf]

My stove is rated at 1.26 cu ft firebox I think. Small enough that I cut my wood to 14" long.
I've never really timed it...but I think it's about 2-3 hours at most between reloads. However, I burn pretty hot...600-650F range and like to add wood when it's still at least at 450F. I also don't stuff the firebox...1 or 2 splits at a time, when I could probably fit 3 or 4 (if they're smaller).
Overnight burns? That'd be last load at 10pm and still hot embers at 6am. Only time that happened was when I was burning partially seasoned sassafrass...in other words, green wood.
Could probably approach 8 hours again if I had some dense oak and turned the air intake much lower.

 

[Bobbin]

Right now I'm feeding the Classic roughly 3 times/day. The overnight burn is the longest one, usually about 10hrs., and there are enough coals to ignite a new load IF I consolodate them and add tinder before adding the splits. Typically, the stove will be in 150-200 degree range and it will take 10-15 minutes to come up to ideal range to engage the combustor. I make sure I have my coffee with me. The other "feedings" will be splits on top of a nice, hot bed of coals; shove 'em in, and "set it and forget it". I do not stuff the stove full, either, if I did it could be too warm in the studio (the Classic is more stove than the space requires but I like it better than the Keystone or the Palladian).

 

[albertj03]

My little CFM has I believe a 1.26 cu ft firebox and I can get 2 hours of hot burning and another 1 hour of red coals hot enough to get a fresh load started. This is burning red oak, maple and birch and I don't stuff the box full. I usually will lay two medium splits e/w and two small splits diagonally across the top. If I stuff the box full at around 11 PM and then cut the air almost all the way off I will still have some hot coals at 6 - 6:30 AM that will come to life when I crack the stove door. My chimney is very tall and the stove is in the basement so I have a strong draft that I believe speeds up the burning some. The goal for next season is to have a much larger stove.

 

[nojo]

Could you guys also post the temps you are burning at? On my trailblazer classic 1700 I got about 3 hours from load-in to mostly coals and had it between 400 and 500 for about an hour and half. The firebox is small like 1.3-1.5 cubic ft. Ive got a 30ft chimney though so I try to regulate the draft with the pipe damper. It can get raging when the intake is closed.

 

[Peter B.]

Could you guys also post the temps you are burning at?

One of the greatest frustrations for me trying to learn by 'lurking' here is that there is <NO> universal, uniform method of measuring operating temps... so <NO> meaningful comparison between any but identical stoves, identical thermometers placed at identical locations on the stove.

If I ran the circus, every one of you would have a flue probe (not a surface thermometer) at about 12-18 inches from the stove top... just like me.

And another probe near the top exit of the stove... just like me.

But most thermometers lie anyway... and are really only useful for relative temps.

Having said all that, the flue probe (which I've probably trusted for too many years now) at 12" above stove top typically reads 400-600* when the stove is actively throwing heat.

Meanwhile, the stovetop (internal) probe (which doesn't come close to agreeing with the flue probe in kitchen oven tests) reading the temp immediately above the catalyst likes to report temps between 1000*-1600*... whether the cat is actually engaged or not.

Yes, I can get comparable temps at the same location... cat 'on' or 'off'.

I sure wish there were _accurate_ thermometers available and a law that dictated where they were placed.

But... as near as I can tell, it's all a crap shoot.

Peter B.

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[jetmech]

Not sure of the size of the firebox on my intrepid ii but its small, Mine has a cat and i dont load it slam full.. I have burned ash and oak in it and still have coals 7 to 8 hours later . I think the type and quality of wood is the biggest factor in burn times.

 

[DBoon]

Hi Nojo - my stove cruises at 550 degrees stovetop when loaded with a medium hardwood, like cherry, and at 600 degrees stovetop when loaded with hard maple.

I agree with Peter B. that it is tough to compare temps, especially stovetop temps. My flue pipe is inaccessible for a flue probe temp given that it runs straight up and out of the stove and into the chimney. If anyone has any ideas on hold to solve this with a reasonably priced flue temperature monitor that doesn't require me to remove the stove for installation, I would be very happy to listen.

 

[argus66]

i too get 6 to sometimes 8 hrs out of my little f3 cb. it works better if i have a thick ash bed going. just had a 6 day fire go out, only because temps went up tp 50.

 

[BrowningBAR]

I have an intrepid II and a Vigilant.

Vigilant:
I keep the Vigilant running between 450°-600°. During the day, once it hits 350° I through throw in another load (a day time load is not as packed as an overnight load). Average winter day, that means 4-5 hours between loads. Sometimes longer. At night I pack the stove with as much wood as possible and will come down to find the stove sitting at 300°-350° with enough coals for an easy restart after 6-8 hours.

IntrpidII:
I burn between 550° and 650°. I full day time load will last about 3+ hours. At night I pack it tight and will find the stove sitting at 300°-350° with an easy restart from existing coals.

Now the reason why I posted the Vigilant first (which has a bigger mouth to feed) is to show the difference. The Vigilant running at 350° degrees is still warming the room. The Intrepid running at anything below 400° isn't doing much to keep the area warm. So, even though I wake up to both stoves being at roughly the same temps, the smaller stove isn't putting out the same type of heat.

When I replace the Intrepid I will be going for a larger firebox. I am CONSTANTLY checking the temperature on the damn thing as I know anything under 500° isn't getting the job done.

 

[Backwoods Savage]

Could you guys also post the temps you are burning at?

One of the greatest frustrations for me trying to learn by 'lurking' here is that there is <NO> universal, uniform method of measuring operating temps... so <NO> meaningful comparison between any but identical stoves, identical thermometers placed at identical locations on the stove.

If I ran the circus, every one of you would have a flue probe (not a surface thermometer) at about 12-18 inches from the stove top... just like me.

And another probe near the top exit of the stove... just like me.

But most thermometers lie anyway... and are really only useful for relative temps.

Having said all that, the flue probe (which I've probably trusted for too many years now) at 12" above stove top typically reads 400-600* when the stove is actively throwing heat.

Meanwhile, the stovetop (internal) probe (which doesn't come close to agreeing with the flue probe in kitchen oven tests) reading the temp immediately above the catalyst likes to report temps between 1000*-1600*... whether the cat is actually engaged or not.

Yes, I can get comparable temps at the same location... cat 'on' or 'off'.

I sure wish there were _accurate_ thermometers available and a law that dictated where they were placed.

But... as near as I can tell, it's all a crap shoot.

Peter B.

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Peter, having the probe would be nice but I do not find it necessary unless one wants to run a lab or sorts.

As for accurate thermometers, you are right in that they are difficult to find. The only ones we have found to be good are the ones we purchased from Woodstock. We've had others, a couple given to us as gifts, but they have all went into the junk because that is what they are.

At present, we use one thermometer on the top center (just a tad off center) of the stove and another on the pipe which runs horizontally through the wall. I get all the information I need from those two.

It still almost always boils down the the fuel that people put into the stoves. Poor fuel gives poor results. Good fuel makes for happy campers. Poor fuel and the stove just doesn't heat like it should. Good fuel and everyone is warm and the fire is easy to tend.

 

[westkywood]

I had a 1.5 cubic ft firebox with a Drolet savannah. What I didnt like about it was, I had to put the wood in E to W and the wood in the back never burned good unless I burned it with the air intake open atleast 1/3. This really cut down on burn times I should have got. I'd get a good 3 hour burn with maybe 5 hours with decent coals.
I started cutting wood about 8 inches long so I could put the wood in N to S .. I dont miss that stove

 

[nojo]

How did cutting the wood down to 8 inches for N/S loading work for you? I was going to try that with my little trailblazer.

 

[BrowningBAR]

How did cutting the wood down to 8 inches for N/S loading work for you? I was going to try that with my little trailblazer.

I would imagine it worked well (since you are dealing with small chunks of wood, which usually creates a hotter burn), but it must have been a gigantic pain in the ass.

 

[westkywood]

How did cutting the wood down to 8 inches for N/S loading work for you? I was going to try that with my little trailblazer.

As already posted, it was a pain in the arse. But it worked better than anything else I tried. I'd cut them up once the wood was seasoned. Kinda hard to stack 8 inch logs. I made a rack that would hold about 10 logs ( stacked ), then I'd run the chainsaw down the middle to cut the 16 inch logs in half. I'd then throw the pieces in a pile and cover it. The stove ran better because more air could get to the back of the stove.
I still like to have short pieces for my new stove and it holds 18" logs. They're great for daytime burns and filler logs. A friend of mine cut a bunch of wood for me and some of it was cut in 20-25 inch logs, so I had to cut alot of it down. Its a pain but its free wood so I aint complainin. I find the short pieces come in handy...
I tried everything with that little stove. I got the best burns from using the short logs. The guy that had it before me was using small splits ( not short ones ). I bet he never got a long burn.

 

[carinya]

How did cutting the wood down to 8 inches for N/S loading work for you? I was going to try that with my little trailblazer.

As already posted, it was a pain in the arse. ......

must be an english or australian arse lurking in there somewhere with that spelling :cheese:

 

[fredarm]

PE Vista, about a 1.4 cubic ft. firebox. I normally get about 3 to 4 hours from a reload with 3 to 4 medium splits of red/white oak to significant coals and time for another reload. If I stuff the firebox and turn the draft all the way down, I can have some coals the next morning after 8 hours or so, but I don't usually stuff for overnight since I'm not trying to heat solely with wood.

 

[oilstinks]

Englander 13nc i get 5-6 hours burn with enough coals to relight. Perfect rounds not splits placed, packed, and stacked just right i might get 8 hours ut few and far between with yello locust. I dont have much else to burn right now. Maybe a little beech.

 

[myzamboni]

i too get 6 to sometimes 8 hrs out of my little f3 cb. it works better if i have a thick ash bed going. just had a 6 day fire go out, only because temps went up tp 50.

ditto

 

[precaud]

With the Quad 2100M (1.5 cu ft.) I get 7 to 9 hours every morning; it would be longer if I packed the firebox full for the evening's last load. The key to extending burn times is cutting off the air supplies - all of them - and only allow enough "bleed" air into the firebox for the coals to burn down at the desired rate.