New Stove Ratings EPA vs. Manufacturer

[Vermontster]

Hi everyone,

I have enjoyed reading the post here, great information and good time killer as well!

I just brought home my new wood stove tonight, a Lopi Leyden. I bought the stove because of the published (website etc.) ratings of 73,100 -a incredible burn time and top loading convenience.

When I got the stove home I opened the crate and read the EPA card attached to the door, the card says Heat Out put 10,700 to 34,000 btu/hr.
I hadn't seen this card at the store and raised my concern. after looking through some other literature in the stove I found a brochure for all Lopi stoves in this they state that the Btu's are 64,300.

I am planning on calling the store in the morning but if anyone can help me understand where and how these numbers come from I would really appreciate it!

 

[webbie]

My advice - don't try to understand them!

What I really mean is that they are all BS, but I'll explain it in a nicer fashion. Stoves need to be tested for clean burning at certain levels. In order to do this, stove companies design and build the stove partially JUST TO DO THIS, sometimes even to the detriment of proper engineering....but they have to.

One design trick is to limit the air intake control. Others are in exactly the way the stove is fueled during the EPA tests. I'm sure the test lab folks and engineers can tell you more (but it will probably only confuse you)....

So, in order to properly size your stove, you want to use one main measurement.....

How much wood can you fit in there - meaning the cubic feet of the firebox. This stove has a 2.3 cubic foot firebox, which puts it in the "medium" camp as far as stove firebox size. It is a little more efficient than most, so that helps a bit.....

OK, so let's do the math. Depending on wood species, I will guess that you can load 40 lbs of wood (oak) in there - you may find it to be less or more, but let's use that as a calc basis.

40 pounds of wood X 8,000 BTU per pound means the firebox holds 300,000 BTU (approx).
Let's correct that figure for 70% efficiency - meaning you will get 210,000 BTU out of each load into the heated area.

OK, so the stove will burn:
4 hours at 50,000 BTU per hour
6 hours at 35,000
10 hours at 21,000
etc.

The figures quoted on the brochure are MAXIMUM, and the reason they vary is that different woods, chimneys and operators can produce different results. Think of a car that is rated at 125 MPH tops - the tires, the octane of gas, the road slope and other factors may contribute to it going 110 or 130, but none of that matters because you are only going 70 or 80 max on the highway.

I hope that helps you understand......

That is one nice looking stove, BTW.

 

[karl]

Also take a look at the output of the furnace on your house. That will be listed as btus at the bellows or something like that. Or you can take what the furnace is listed as times the efficiency. Then compare that to what Craig is saying. I did this when I bought my stove. It's larger than yours but I used the same formula he did. My insert is rated 97,000 btus by the manufacturer, 43,691 by Chimney Sweep Online (They publish an average btu output over an 8 hour period), and 37,501 by the EPA. According to Craig, and using a 60 pound load of oak. I get

4 hours at 84,000
6 hours at 56,000
10 hours at 33,600

The important number is 336,000 btus. That's what I get out of a load of wood. That's almost twice what my furnace puts out in an hour and after subtracting the loses from my duct work, it's over 2 and half times what my furnace puts out in an hour. Now let's assume my furnace runs two hours out of 10 hours, and I really doubt it runs that much except for very cold days. My Summit is going is still going to put out more heat over the same period of time.


A heating and air guy can measure your house and tell you how many btus it takes to maintain the temperature and you will be surprised at how little it really is. 10,000-20,000 btus continously will keep most houses toasty warm

 

[Vermontster]

Thanks for the info, and fast too!

I am excited about the stove, still, even after I read that EPA card, which stated half the output of what I thought it was, I had to sit down.

I am going from a Vermont Castings Madison Which has a 39,700 btu rating. I feel this is a good upgrade.
I guess I'll have to wait and tell you in January if it was or not.

 

[Corie]

It all comes from the Method 28 EPA testing specifications. The douglas fir loads used and the way they are loaded is not truly comparable to real world hardwood burning. You may not reach the BTU level the manufacturer lists as they (all) tend to be slightly optimistic in their specifications, but you will almost certainly exceed the BTU rating on the EPA door tag.

 

[jjbaer]

double posted...see post below

 

[jjbaer]

The important number is 336,000 btus. That's what I get out of a load of wood. That's almost twice what my furnace puts out in an hour and after subtracting the loses from my duct work, it's over 2 and half times what my furnace puts out in an hour.

Karl,

1) even if your stove held 500,000 BTU it cannot liberate this heat in anything less than several hours because otherwise it would overfire your stove. You furnace can however, CAN liberate well over about 150,000 BTU per hr but your stove can't and 2) your furnace really holds billions of BTU's because its "charge of wood" is an endless pipeline.....which kinda makes that 336,000 BTU charge look small ;-)

 

[Highbeam]

I too was somewhat puzzled by the epa sticker on my new hearthstone. It read a very low btu number in the 30k range. It also listed efficiency and smoke output on a bar graph type scale. My small kid ripped the tag off and helped me pitch it in the file to be forgotten.

 

[webbie]

It is interesting that manufacturers are allowed to print whatever they want on literature and manuals.

My guess is that there are two camps - some just make it up, others take measurements during the "destructive" parts of the lab testing, which is an accurate max. BTU that the stove can withstand at it's listed clearance to walls and floors - but YOU will never get there...

That is, unless you burn particle board as one of my customers did (melted his baffles, etc.)
(Note: this is JackAss stuff - do not burn particle board!)

 

[BrotherBart]

That is, unless you burn particle board as one of my customers did (melted his baffles, etc.)
(Note: this is JackAss stuff - do not burn particle board!)

So you're saying I have to go through this years wood pile and sort the stuff?

 

[Corie]

Looks like the scene outside the burn lab right now. I'm in pallet hell.

 

[begreen]

Priceless BB. That looks like an acute case of palletosis :lol:

 

[karl]

Cast Iron, my point was that my furnace turns on and off at will and the stove burns for hours once it's lit. Therefore, the hight btu output of the furnace and the low btu output of the stove don't really matter. They both put out the same amount of heat over the course of the day.