Jotul F118 Black Bear

[paperman]

Great Site 1st time on the site. Quick question. Why does Yotul say the Black Bear produces 60,000 btu's when the EPA site says it only produces 12,000 to 23,500 btu's? What am I missing???

Thanks in advance

 

[Todd]

Depends on the firewood type used in the test. EPA uses Doug Fir, Jotul probably used a denser more BTU packed hardwood.

 

[DAKSY]

If you're talking about the EPA rating card that appears inside ALL the Jotul stoves, I was told by our Jotul rep that it's the max BTU rating that the stove will output within the first hour of burn time. The 55 - 60K BTU output will take a little longer to reach...

 

[argus66]

kick ass stove one of the best for a small home.

 

[Dakotas Dad]

Great Site 1st time on the site. Quick question. Why does Yotul say the Black Bear produces 60,000 btu's when the EPA site says it only produces 12,000 to 23,500 btu's? What am I missing???

Thanks in advance

It's the difference between WFO and a more realistic heat output when USING the stove for heating your home. And test methods. If EVERYTHING is perfect.. you can, for a short time, make 60k, but in practice with unknown wood/flue/install issues.. you will probably see fewer btu's.

Kind of like EPA mileage in my Mustang GT.. seems I am supposed to get around 18 avg.. and it may be that high if you count all the sideways miles... but I doubt it. :cheese:

 

[Battenkiller]

Below is the EPA test data for the Jotul line. Some of it doesn't even make sense to me. A 602 CB blowing the doors off an Oslo F500 at peak burn? Maybe because the Oslo took so long to get to peak it wasn't within the time frame of the test? Could be.

Look at this chart of an old burn test for a Jotul 602. It confirms what Daksy says about the timing of the stove's peak output, at least for this burn cycle in this stove. During this test, the 602 didn't hit its peak until 3 1/2 hours into the burn.

 

[begreen]

Never saw anything like that with our 602, maybe I was pushing it too hard to stay in the ~15,000 btu range? It's going in the greenhouse in a month, so I will get a chance to try again. I'm curious about the testing in absence of the baffle plate. Is this common? Without it, I would think it would burn dirtier and perhaps less hot?

 

[Battenkiller]

Never saw anything like that with our 602, maybe I was pushing it too hard to stay in the ~15,000 btu range? It's going in the greenhouse in a month, so I will get a chance to try again. I'm curious about the testing in absence of the baffle plate. Is this common? Without it, I would think it would burn dirtier and perhaps less hot?

Yeah, I thought that was kind of odd. The text didn't say why the test was performed that way. The section I took this from was about controllability, not output or efficiency, so maybe it wasn't the best example to cite. I don't see that much info on modern stoves regarding heat output over time, and I thought the chart was interesting. It clearly has an initial peak and then a secondary one three hours later. Can't say that the output would have been the same with the baffle in place (I think you're right, probably higher). I suspect the shape of the curve might be similar, except for the second peak might be lower than the initial one.

Here's another one from the same source. It shows a Morso 2B over the course of a 9-hour run. This is more what I would expect from a typical stove based on personal experience. I also agree with the author's assessment of the cause of the initial peak - the burning of combustible gases. This would occur during the first hour or so in a non-cat EPA stove because of the secondary burn. It also shows secondary peaks several hours in, but not as pronounced as in the first chart, and certainly not higher than the 1-hour peak

So, I guess I'm clueless as to why a modern stove would not reach it's peak output within the time frame of the EPA test. Somewhere I have the test method the EPA specifies, but I can't find it right now. I thought it went on for a lot longer than an hour and required refills. I don't know how or even if they actually measure heat output, but I do know that they arbitrarily assign either 63% or 72% for efficiency, depending on whether or not the stove has a cat combustor. If they had hard data regarding BTU output, it would be relatively easy to give each stove a unique and more precise efficiency rating than they do, given that they load the stove with precise amounts of fuel. I think they are mostly concerned with particulate emissions, aren't they?

I don't have much faith in stove output ratings anyway, and I'd just ignore that EPA card and figure out my size needs based firebox size and on what folks here have experienced with the same or similar stoves.

 

[begreen]

That looks much more like our typical burn and btus, though we die out after about 3-4 hrs. That could be our wood.

Maybe by taking the baffle out of the 602 they were able to pack it with twice the amount of wood then choked it down?

 

[fossil]

...I don't have much faith in stove output ratings anyway, and I'd just ignore that EPA card and figure out my size needs based firebox size and on what folks here have experienced with the same or similar stoves.

Agreed...and to add that taking into account the fuel you typically have available to you (hardwood or softwood) is an important factor. Rick

 

[Battenkiller]

Maybe by taking the baffle out of the 602 they were able to pack it with twice the amount of wood then choked it down?

Choked way down they got this. Long smoldering burn, but ain't that the way we all used to burn back then? :roll: :red:

 

[Todd]

BK, interesting charts, where did you find them?

 

[precaud]

Just to clarify, the rating is btu's/hour, i.e. if the stove maintained a particular burn rate for an hour, that is how many btu's it would produce. But as you can clearly see in the charts BK posted, these small stoves don't maintain anywhere near their highest rate of output for very long. In general, I find the output figures assigned by marketing departments to be more misleading than the EPA test figures. One is much better off going by firebox volume and ignoring the output figures.

 

[Battenkiller]

BK, interesting charts, where did you find them?

They are from an old woodburning manual I have, dated from the 70s - "The Woodburner's Encyclopedia", by Dr. Jay Shelton. Shelton was a leading solid fuel researcher back then. Concise and easy to understand, it has lot's of useful info about combustion, efficiency, draft, stove and flue design, heat transfer theory, safety, etc. Not all fluff like lots of the newer books I've read. Also, lots of antiquated notions that are no longer relevant in the EPA era (flue pipe heat exchangers, for example). Despite it's shortcomings, it's still the bible for most of my needs. My copy is certainly worn and dog-eared from use.

 

[precaud]

Back in the early-mid 80's my business was right across the street from Shelton's test lab. I didn't get to know him well, but I did hang out a bit and got to buy a few stoves from him for next to nothing after he was done testing them. His "Solid Fuels Encyclopedia" has long been a reference of mine.