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Amount of Wood Burned per Day

Post in 'The Hearth Room - Wood Stoves and Fireplaces' started by byQ, May 31, 2013.

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  1. Prof

    Prof Burning Hunk

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    Heat is the transfer of energy between two systems. In the case of wood burning, the transfer occurs between the wood and the room. There is only so much energy in 40 lbs of wood. I agree, a stove and a MH transfer energy in differnt ways. More specifically, the ways in which heat transfers (conduction, convection, and radiation) are in differnt proportions. However, short of something magical that breaks the laws of physics, the amount of energy in a given quantity of wood is fixed--so I don't see how the mason could be correct if making a comparison between a MH and an EPA wood stove.
    fox9988 likes this.

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  2. byQ

    byQ Member

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    In the case of a woodstove the transfer occurs between the burning wood/gasses and the air in the room.
    In the case of the masonry heater the transfer occurs between the burning wood/gasses and the objects in the room (which than pass their energy to the air).

    Lightbulb moment - the heat from a wood stove, warms the air first than this air warms the objects in the room. And the heat from the masonry heater warms the objects in the room first and than the objects warm the air. The wood stove does not warm the objects in the room. The air that it warms warms the objects in the room.
    The masonry heater does not warm the air in the room. It warms the objects in the room which than warms the air.

    This all seems to boil down to the differences between radiant heat and convective heat. As some wood stove manufacturers are incorporating more thermal mass into their designs these differences are important to understand for wood stove buyers. Woodstock soapstone vs Jotul wood stove. They heat differently - not as extremely different as say a steel wood stove and masonry heater. The woodstock is tapping into the radiant form of heat, more so.
  3. Hogwildz

    Hogwildz Minister of Fire

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    Disagree. Both a stove and a masonry heater heat the air, and the objects in the room. A forced air furnace is the only appliance I can think of that strictly heat the air. Both let off heat by burning wood and transferring through the body of the appliance.
  4. Highbeam

    Highbeam Minister of Fire

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    Uh no, heat is heat. We measure it in btus. It's a real finite thing.

    Comfort is different. Either way, byQ is right, there is essentially zero margin for improvement with 80% from stoves. You need to lose some heat up the flue to get a natural draft.
  5. begreen

    begreen Mooderator Staff Member

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    Both wood burning metal, soapstone or masonry stoves are convective and radiant to some degree. They both heat the air and radiate directly objects in the room. How well either does the job depends on the stove design and placement.
  6. Sprinter

    Sprinter Minister of Fire

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    We have to be careful about whether we are talking about combustion efficiency, transfer efficiency, or overall efficiency. EPA defines overall efficiency as the product of combustion efficiency*transfer efficiency. Lennox's Grandview 230 model was the only maker I saw that published both.

    Masonry's may be capable of 90% combustion efficiency due to the fact that fuel is burned at such a hot, fast rate. But conventional stoves can be 90% also, due to the secondary and/or cat designs. Sometimes I wonder if sellers use their combustion efficiency and compare it with the transfer efficiency of their competitors.

    IMO, efficiencies of all good designs are so close as to be negligible for all practical purposes (although it makes for interesting discussion). All of these figures assume optimal conditions and operation, and that variable is much more important.
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  7. Highbeam

    Highbeam Minister of Fire

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    So true. We are really splitting hairs here. The difference between best and worst of the current lineup is a split of wood.
  8. byQ

    byQ Member

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    I don't believe this is true between a masonry heater and a wood stove (maybe between 2 EPA wood stoves). They operate on different principals, heating in different ways. One is 10,000 lbs and the other is 300#'s. For a professional in the field of heating to claim he can put 30#'s of wood in his device while another device requires more than twice this amount tells me there is more than hair splitting going on. And it's not just one masonry heater professional - I've heard similar from several of them.
  9. Hogwildz

    Hogwildz Minister of Fire

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    Just don't drink the grape Koolaid and you will be fine.
  10. fox9988

    fox9988 Minister of Fire

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    I give up :confused:
  11. PapaDave

    PapaDave Minister of Fire

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    May be too late.:rolleyes:
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  12. Backwoods Savage

    Backwoods Savage Minister of Fire

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    Do not forget that if you are talking about putting wood into an already heated stove there is a huge difference in how much heat you get into a room. The big masonry heaters can be great for radiating heat just like the soapstone. However, consider first how much wood it can take to heat all that stone! In the big masonry heaters that can amount to a lot.

    One good example is taking an extreme which does happen quite a bit. One day in January a warm front comes through and suddenly the outside temperature is 50 degrees. It might stay that way 2 or 3 days then just as suddenly, one night the temperature drops to zero or below. Now that is a situation where it really can make a big difference in the type of stove you have.
    swagler85, Joful and Sprinter like this.
  13. Sprinter

    Sprinter Minister of Fire

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    I was thinking along those lines as well. Our shoulder seasons are interminable it seems. The last couple of months have been quite variable, especially within one day. Lately, it's been very cool in the morning, so I just make a quick small, hot fire which quickly takes the chill off because the stove heats up quickly, but the afternoons are warm, even 65-70 like today, and a warm stove is the last thing I need in the afternoon. I would hate to not have the control over the heat output within the day. I'd say maybe half of the burning season it's like that, and a large warm heating surface would actually be a disadvantage. Even in January, I like to have better control over the heat output.
  14. Backwoods Savage

    Backwoods Savage Minister of Fire

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    I agree Sprinter and that is about the first thing I thought about when we first heard about the big masonry heaters. Here is one big sucker at the Woodstock factory. The picture really does not do it justice for how big that thing really is. I do not remember the weight other than it was, WOW!

    Judy by monster stove.JPG
  15. Sprinter

    Sprinter Minister of Fire

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    I read that the weight is the only reason they are EPA exempt. Being exempt, they don't get much attention from the EPA, so we don't have much objective, empirical data about them; only info from the industry. I've come across a few sites that try to be objective and real, but for the most part, it's all puffery and little objective, unbiased data, Which is really too bad, because I have no doubt that they have a useful niche somewhere, if properly designed and skillfully built.

    Edit: I see that there a couple of other reasons for the exempt status: The combustion air cannot be adjusted down, and the fact that most of them are custom built on-site.
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  16. BrotherBart

    BrotherBart Hearth.com LLC Mid-Atlantic Division Staff Member

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    Yeah. If you build less than 50 stoves a year you are exempt.
  17. Sprinter

    Sprinter Minister of Fire

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    Regarding the emissions. Washington State has emissions requirements that are more strict than EPA. This table http://www.ecy.wa.gov/programs/air/indoor_woodsmoke/pdfs/Wood_Masonry.pdf shows measured emissions of the manufactured MH's that are approved in Washington. There aren't a whole lot of approved manufactured units, but it does show that the emissions from these products are in about the same range as epa stoves, some excellent and some pretty high and some in between. Anything not meeting Washington standards won't be here.

    This broad range tells me that there is nothing terribly special about MH's in general, but that, like any other product, it varies between models and design.

    Seems to me that you really won't know how good your heater is until it's all built and do some very expensive testing to measure everything. But who's going to do that? If it's bad, there's not much you can do about it anyway. Maybe some builders have measured their designs and that would be helpful, but the idea of building a one-off is a big gamble, IMO.
  18. DevilsBrew

    DevilsBrew Minister of Fire

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    As a novice, it says a lot to me when I see so many stove manufacturers incorporating mass in their models. This makes it difficult for me to believe that masonry stoves aren't the king of the hill that everyone is trying to knock off.
  19. BrotherBart

    BrotherBart Hearth.com LLC Mid-Atlantic Division Staff Member

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    Yeah anybody that thinks a wood stove doesn't heat objects in the room is cordially invited to sit on my couch very long when the 30-NC is cranking. Evenings with guests start off with drinks on the couch, then moving to the kitchen and then up to bed. To hold down the sweat factor in stages. >>
  20. Sprinter

    Sprinter Minister of Fire

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    Well, they certainly are the king of the thermal mass hill! And they certainly have their place. It's just that there is a practical limit where, for most situations, there begins a diminishing return and even some disadvantages. More is not always better.

    Even a modest amount of extra mass such as in soapstone-lined stoves isn't for everyone. Some people prefer the hotter temperature and more intense radiance of conventional steel stoves.

    It's really unfortunate that so much of the hype (not all of it) is unsubstantiated by good data which makes for a lot of puff and misinformation sometimes.

    Thankfully, there is something for everyone out there.
  21. Ram 1500 with an axe...

    Ram 1500 with an axe... Minister of Fire

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    The original question was a great one, something I will definitely try to keep track of as I go through the next year of burning. I have only a medium insert and the max load is suppose to be 30 #. How about you all, what's your max load? What's the average split weigh, how many do you put in at a time, give or take? Thanks all....
  22. webby3650

    webby3650 Master of Fire

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    Go ahead, build your 3K+lb. heater. I'm anxious to see it complete! I will gladly load my clean burning hybrid 2 x in 24 hrs before I will spend 10,000 hrs and $1000,s debating weather or not a masonry heater will do the job. The new stoves are great heaters! If I had endless $ to spend, then I might give it a shot. But until then, the latest technology and cleanest burning stoves will do the trick!
  23. Sprinter

    Sprinter Minister of Fire

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    The original question did kind of get put aside didn't it. I just weighed what I would use on a cold January day here. About 35#. That's for a 1750 sf single level insulated house on a day with right around freezing temps. House kept at 74 F days and 64 nights. An extreme day in the teens could go 40# if I burn overnight. Often in shoulder season it can be 10 or less. A more typical winter non-January day might be around 25# with day temps in the low 40's.

    Questions for byQ: What part of Idaho are you in (or what kind of climate) and what kind of house are you building for the heater? How warm do you want to keep the house in winter? I'm guessing it will be well insulated.
  24. Ram 1500 with an axe...

    Ram 1500 with an axe... Minister of Fire

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    With taking a guesstimate, for an all day burn, I would think that I may go through 100# a day, but I'm just guessing and need to look into this further....
  25. Ram 1500 with an axe...

    Ram 1500 with an axe... Minister of Fire

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    Also, I just saw you had a homelite 5 ton splitter, can you give any feedback on that? And when your done with that, I see you have a happy wife, can you give a lot of feedback on that......lol
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