are the BTU's offered by manufacturer legit?

[paladin252]

I have an englander 30-nc. i love it. but wish it had just a bit more heat for heating our entire house. So i was just browsing, and the vogelzang ponderosa says it puts out like 150,000 btus where the englander says only 75,000. Can it really produce twice as much heat from essentially the same size firebox? Do they have some weird wizardry that causes this? Its just a metal box with some steel tubes and fire brick. Are they measuring apples to oranges and its hard to get a legitimate rating from one brand to another? It just seems REALLY high in comparison to most 3.5 cubic foot stoves I've looked at. most are 60,000-80,000 btus.

 

[Highbeam]

I have an englander 30-nc. i love it. but wish it had just a bit more heat for heating our entire house. So i was just browsing, and the vogelzang ponderosa says it puts out like 150,000 btus where the englander says only 75,000. Can it really produce twice as much heat from essentially the same size firebox? Do they have some weird wizardry that causes this? Its just a metal box with some steel tubes and fire brick. Are they measuring apples to oranges and its hard to get a legitimate rating from one brand to another? It just seems REALLY high in comparison to most 3.5 cubic foot stoves I've looked at. most are 60,000-80,000 btus.

You are right to wave the BS flag. Some very good manufacturers also mislead folks with this. The best source currently available is the epa approved stoves list that provides btu output specifications.

Also realize that stoves are batch burners so especially with the nc30 you won’t be able to avoid a cycle of output.

Also of note is that the nc30 was never tested (at least no results published)using the same tests that the epa now uses to determine those numbers on the list so you can’t compare your stove. Best you can do is assume your nc30 makes the same numbers as the nc32.

I have an nc30 and when a 3.5 cf box is 800 degrees it is making the same heat as any box the same size at 800 degrees. If there’s some fancy heat exchangers or blowers you can get a little more out.

 

[EatenByLimestone]

Another way you can look at it is that each lb of wood has about 7500btu to give you. If you put 30lbs of wood in there, you could get 225k btu out of it. You could burn it in an hour, or you could burn it in 8 hours. You choose on your heating needs. Lots of other qualifiers are in there such as species, which would dictate how many btu you could physically stuff into the firebox and burn characteristics, moisture content of said wood, chimney, tightness of house, etc.

Adding a blower to your Enhlander will allow you to move the heat around better.

 

[brenndatomu]

Also realize that stoves are batch burners so especially with the nc30 you won’t be able to avoid a cycle of output.

In other words...even if that stove could do 150k BTU (BS!) it would only do it at the peak of the burn, for half an hour or something...then it will trail back off...same with any wood stove...unless we are talking some monster cat stove set on low.

Another way you can look at it is that each lb of wood has about 7500btu to give you. If you put 30lbs of wood in there, you could get 225k btu out of it.

8600...but that is kiln dried...more like 6700 BTU's/ lb at 20% moisture content...then you have to multiply the efficiency of the stove too...so 6700 x .75=5025 BTU's per lb to the house, which will come in a curve...starting small, building to the peak, then tapering off...

 

[brenndatomu]

The best source currently available is the epa approved stoves list that provides btu output specifications.

Here

Woodstove Database | Burnwise | US EPA

 

[Highbeam]

As one of the many operators that have tried to liberate as much heat from a big stove as fast as possible, I can say that you will not be able to burn back to back loads down with less that 3 hours between loads. Coals build up even when using softwoods.

So the peak output of a 50# load (easy with softwoods in a 3.5 cf box) is 50*5000/3= 83000. Now, you’ll still have a few lbs of coals so the 75000 number for the nc30 is surprisingly accurate.

 

[begreen]

In other words...even if that stove could do 150k BTU (BS!) it would only do it at the peak of the burn, for half an hour or something...then it will trail back off...same with any wood stove...unless we are talking some monster cat stove set on low.

8600...but that is kiln dried...more like 6700 BTU's/ lb at 20% moisture content...then you have to multiply the efficiency of the stove too...so 6700 x .75=5025 BTU's per lb to the house, which will come in a curve...starting small, building to the peak, then tapering off...

Exactly right, you will never see 100% of the heat in the wood. Ignore marketing jargon, especially when wildly exagerated in the VGZ case.

 

[peakbagger]

Decades ago when woodstoves got popular again,a professor at UMaine took a small stove and rigged it up in the middle of field and rigged up a tall stack. He and his students put a lot of test equipment all over it. They then fired it up with bone dry softwood kindling and saw how much heat they could get out of it before it melted by continuously ramming in wood. I wasnt there for it but reportedly it was glowing cherry red. I think I remember that they shut down the experiment at some point due to general safety concerns One of the purposes was to illustrate that ratings dont mean squat unless they are performed to specific standard.

 

[bholler]

As far as the epa btu numbers go they are not really a real world representation either. They are determined by loading the stove to a set density based upon the manufacturer supplied capacity. That density is not at all what most of us would consider a full load.

But it is atleast a start and gives a good basis for comparison between stoves even if not what they will do in real operation.