EPA tests

[EatenByLimestone]

We've had posts here on how they do EPA tests, but I don't remember any posts on why "EPA test BTU" numbers "Seasoned Cordwood BTU" numbers differ sometimes by 50%. IIRC, the EPA test used something like Douglas Fir in square blocks. For seasoned cordwood do they mean locust splits?

Matt

 

[BrotherBart]

The cord wood numbers don't come from EPA testing. They are manufacturer's numbers. Standing in front of the stove shoving wood into it like the fireman on a train.

 

[Battenkiller]

BTU ratings of stoves are a power rating, as in BTU/hour. BTU ratings for cordwood are in potential energy units, as in BTU/cord.

Dense woods like oak and locust may have more heat per unit volume, but less dense woods burn faster. The fact is, almost all woods are capable of the same maximum rate of heat output, but with softwoods you use a lot more volume of wood in that time.

 

[EatenByLimestone]

I get that, guys. Here is an example of what I'm inquiring about:

http://www.drolet.ca/product.aspx?CategoId=1&Id=213&Page=spec



Maximum output - EPA test wood 30 800 BTU/h

Maximum output - seasoned cord wood 85 000 BTU/h



How can the two numbers be so far off from each other? The fuels must be very different. Considering, per lb, wood is about the same there must be many more lbs of wood being used up per hour in the seasoned cord column.

The stove in question has a pretty big fire box:

Exterior dimensions Width: 23.75"
Depth: 26.5"
Height: 30.25"

I can see 80K+ being available from a firebox that large. So what is the EPA doing odd?

Matt

 

[dannynelson77]

See the link below on the ZC fireplace I have. Regarding your question go to the Owners manual on the right side of the page and open it up to page 43. You will have your answer.

http://www.osburn-mfg.com/product.aspx?CategoId=19&Id=439

 

[Battenkiller]

How can the two numbers be so far off from each other? The fuels must be very different. Considering, per lb, wood is about the same there must be many more lbs of wood being used up per hour in the seasoned cord column.

There are many more pounds of wood being used per hour in the second column, but that has nothing to do with the type of wood. It has to do with what BB is saying, that they stoke the piss out of the thing to get the manufacturer's numbers up. There ain't no way you're ever going to get 85,000 BTU/hr out of any 3 cu.ft. stove and into the room except over a very short period of time. That is the highest heat obtainable that they are quoting, but you can hit that figure with Doug Fir just as easily as you can with locust, you'll just have to chuck it in there twice as fast.

BTW, you quoted the height of the stove with legs included. The actual surface area of that stove is about 25 sq.ft. In order to get 85,000 BTU/hr to come off of that stove, the average surface temp for all exposed surfaces would need to be about 700ºF. That pretty freakin' hot. If you ever get it that hot at home, it will be a very short-lived peak.

 

[Todd]

The EPA just tests for emissions with pine but I think they estimate BTU by how much Pine fits in the box. Cordwood BTU's are conducted for manufactures from an independent lab with a denser hardwood so you get much higher numbers. It's kind of funny how manufactures push the EPA GPH numbers but don't post their own cordwood GPH numbers then they turn around and dis the EPA BTU's for their own rigged cordwood BTU number. Nobody burns their stove at full BTU output, most burn at a low more even output. I would like to see manufactures come out with a more realistic output scale but most people that buy stove could care less about these stats anyways.

 

[Slow1]

See the link below on the ZC fireplace I have. Regarding your question go to the Owners manual on the right side of the page and open it up to page 43. You will have your answer.

http://www.osburn-mfg.com/product.aspx?CategoId=19&Id=439

And for those who just don't want to follow all the links.... (found this on page 42 actually)

*Why is the BTU indicated on the EPA label smaller than the one advertised?
You will notice a difference between the BTU output as indicated on the unit’s white EPA label affixed to the glass
and the BTU as advertised on our web site and/or product literature. The maximum BTU output we advertise for
this unit is what will be obtained with a full load of seasoned cordwood inserted inside the firebox. The EPA output,
on the other hand, is what has been obtained during emissions testing. The EPA test procedure requires that a
special type of wood be used and positioned inside the firebox in a manner that does not represent the way the
firebox volume would normally be utilized using seasoned cordwood. The EPA test load is typically much smaller.
Hence, the BTU as per the EPA label is reduced. The BTU output that should be considered by a normal user is the
one we advertise for seasoned cordwood.

 

[dannynelson77]

Yes and that is max output. Meaning you can probably achieve that high of a BTU if you have the thing wide open! and want to go through a load of wood in less than an hour.......

 

[Battenkiller]

Yes and that is max output. Meaning you can probably achieve that high of a BTU if you have the thing wide open! and want to go through a load of wood in less than an hour.......

I agree. And to make matters more confusing, here's the numbers on a much bigger stove, the Blaze King King:

http://www.blazeking.com/wood-king.html

The BKK numbers seem much more realistic as to what you'll actually get out of the stove. 47,000 BTu/hr average high output from a 4.3 cu.ft. firebox. That's something I can actually believe.