So I purchased a tax credit eligible stove,( Englander NC30) but am confused on the eff rateing of the stove. The paper that came with the stove showed it as around 63% eff but the tax credit needs 75% with “lower heating value” . What does lower heating value mean? Is the stove 63% eff when running full tilt and better when not run as hard? I also noticed this when looking at stove spec, one place would say 85% eff and the stove manual would say 63%.for the say stove. Confused.........
Stove Effeciency ratings and the EPA
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For peace of mind, just ignore those EPA numbers, because they don't mean much. You have a very, very efficient stove whose real-life efficiency is going to depend upon you, primarily that you burn dry wood.
For some good points on efficiency, read the posts by Slow1 and Battenkiller on p3 of this current thread: https://www.hearth.com/econtent/index.php/forums/viewthread/59583/P44/
For some good points on efficiency, read the posts by Slow1 and Battenkiller on p3 of this current thread: https://www.hearth.com/econtent/index.php/forums/viewthread/59583/P44/
Todd
Minister of Fire
EPA efficiency numbers are just a guestimate default where they throw all non cat stoves in at 63% and cat stoves at 72%. Manufactures do their own eff tests with an independent lab and come up with the higher LHV eff numbers that you need for your tax break. I think Englander has a certificate on their web site you can download for your taxes.
BLIMP said:
He has the stove already. The only thing that will cause creosote for him is burning wet wood. So he can ignore the EPA numbers, per his concern and discussion. I am not telling the rest of the world to ignore the EPA numbers as a guideline in how to burn more efficiently. But in what the actual efficiency of any one stove is, in the real world? Yes, ignore the EPA numbers. They are default numbers based on burning 2x4s in a lab. (Note to any lab technicians looking to keep warm by burning 2x4s at work this winter and needing to know exactly how much lumber to stockpile: do NOT ignore the EPA numbers!)
Dakotas Dad
Minister of Fire
branchburner said:
yeppers, the EPA numbers are all nice and such, but..
They have NOTHING to do with actually running the stove, and any kind of "heat amount produced", and certainly not much to do with creosote in the chimney.
You bring me the highest EPA rated stove you want, I am positive I can fill the chimney with creosote in a weekend, and my best friend has been burning a NON EPA stove for decades, with never a creosote problem. It's the wood and the operator, not some fictional EPA rating (or lack there of) that is going to clog that pipe.
eman5oh said:
The low heat value is simply the maximum amount of heat that you will actually get out of your wood in a real life situation. Even if you have 0% water in your wood, huge amounts of water are created as a byproduct of wood burning (over half the dry weight of the wood burned). In theory, you could get a lot of heat back just by condensing this water vapor back into a liquid. Per pound of water vapor created, this is the exact amount of heat that is lost per pound by evaporating the excess water in the wood, so it's not inconsequential. Rounded off for convenience, it is about 1000 BTU/pound of water vapor.
In practice, though, this is not desirable since the heat recovered would be way up in the flue where you won't feel it, and you really want to get that all out before it condenses on the walls of your chimney. As well, getting it to condense would mean the flue temp would have to be below 212º and then the draft would suffer. So for all intents and purposes, that latent heat is lost to us and we are stuck with the low heat value in our heating systems.
Below is a chart of low heat values for wood as moisture content varies. Now if you add in all the water formed by combustion itself, you can easily see why there is such a big difference between the two. Since the low heat value is lower than the high heat value, it stands to reason that that burning at 75% of the low heat value just may be about the same as burning at 63% of the high heat value.
Just ignore it. The stove is eligible for the tax credit. Get it, burn in it, and enjoy the heat. Collect the credit in the spring and buy a new saw. ;-)
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I did not mean to start a fire here in the forums, lol. It does not matter that much which of the numbers is right or wrong, I did my research before buying the stove and am happy with my purchase, although I have yet to use it. I am a numbers kind of guy and wanted to know what the deal with the numbers and they ratings would relate to real world use.
I look at the stove numbers a lot like city and highway MPG numbers for cars. Sometimes they correlate well with reality, often they don't, and they are always dependent on the habits of the individual user. Loading your stove for long burns with dry wood is like cruising at 55. Starting up your fire is always a low-efficiency operation.
A good way to observe, but not measure, one aspect of your stove efficiency is to walk outside and look up at the stack. When you see nothing, you feel good. If you are not making any smoke, I think you deserve to randomly pick out whatever percentage number makes you happy!
A good way to observe, but not measure, one aspect of your stove efficiency is to walk outside and look up at the stack. When you see nothing, you feel good. If you are not making any smoke, I think you deserve to randomly pick out whatever percentage number makes you happy!
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