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dehumidifier for "green" wood

Post in 'The Wood Shed' started by sw mariner, Feb 12, 2010.

  1. roddy

    roddy Member

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    welli ice fish,alot,but i also take wood seriously....i have DE-HUMIDIFICATION DRY KILNS where i work (hardwood lumber wholesale) and we take green wood (fresh cut lumber) and dry it to 6 % moisture in 12 days,so i wouldn,t doubt you could dry some firewood to USEABLE levels in your home with a de-humidifier in fairly short order...dont shoot the messenger....

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  2. LLigetfa

    LLigetfa Minister of Fire

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    I'm guessing 1 inch thick wood, 2 at the most. If you split up your firewood into kin'lin then it too could dry as fast or even faster.
  3. roddy

    roddy Member

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    sure,its 1 inch thick down to 6%moisture.....3 to 4 inch pieces to 15-16% moisture takes the same time aprox....i,m not saying its ideal,i,m just saying i believe the op has a valid point and technique,and those who dont wish to embrace technology can take the model t back to the wood pile to check wether or not splits are dry after 5 years or whatever...
  4. LLigetfa

    LLigetfa Minister of Fire

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    It's not about embracing technology, it's about embracing reality. There is no new technology in a dehumidifier, nature has been dehumidifying the air before the cavemen discovered fire.
  5. Battenkiller

    Battenkiller Minister of Fire

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    And doing it pretty cheaply as well.

    Here's a cost breakdown from a maker of commercial dehumidification kilns. Note that the Nyle L50, the smallest unit they make, takes 36 days to get 1200 bd.ft. of fresh cut oak down to 7% MC. Don't even begin to think you'll get the same result by using a room dehumidifier in your basement. The cost at .07/kWh for drying 1000 bd.ft. (about a cord) is $30.52. I pay twice that for electric, so it would cost me $60/cord to dry a load, and... it would take me six months to do all my wood (5 cord). Better to burn it green and take the loss in heat output.

    Kilns that cost money to run are only suitable for usable lumber and retail firewood operations, not for firewood you plan to burn yourself. If you're stuck with wet wood, try what I've been doing. Let nature lower the moisture in the air and then heat that air up once it comes inside your home to drive down the relative humidity. Since you're already heating with the stove, might as well get the drying done for free.

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  6. ikessky

    ikessky Minister of Fire

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    Electricity is expensive and the sun is free. Why not just cut the wood early and make sure it's properly dried without having to spend extra money running your dehumidifier?

    Admittedly, I run the dehumidifier in the wood room when I throw a new load in from outside. I didn't get my piles tarped overly well and some of the wood ended up getting a little wet. So, with the furnace running in that room and the dehumidifier going, everything is usually back to where it needs to be in 24 hours or so.
  7. skyline

    skyline Burning Hunk

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    It seems these "drying wood" topics generally come back to the same basic discourse. The guys with 3+ years supply will argue that's the only way to "properly" dry wood and the guys who don't are looking for a faster way to dry their wood. For me, I first applaud the ones (LLigetfa etc.) organized and ambitious enough to have plenty of wood racked up ahead of time. For the rest of us, I'm hoping we can find the best and cheapest ways to dry our wood faster. I and few others won't ignore the fact that kilns can dry wood below our needs in a few days and they aren't even trying to do it as fast as possible but slowly enough not to degrade their lumber. The trick is to to apply these same principles of air movement, elevated temperature and lower RH cheaply. For most it doesn't have to be in 2 weeks, but if in 6-12 months it's ready to burn and comes out 5-10% drier than a typical stack job in our area, we're making progress.

    I have no doubt a dry basement with air movement and a furnace will dry wood way faster than outside in my rainy climate. I don't have such a basement but I don't need to have 2 weeks fast either. If I had a way outside to guarantee dry in 6 months I would be "stoked".

    In my experiment with just a fan, my fir split lost 16% moisture (729 ml) and alder 39% (1091 ml) in 7 days for about $0.58 of electricity. (35w x 24 x 7 x .10/kwh). That's still more $ than I want to regularly spend but I suspect I could run the fan about half the time(when the RH is low) and achieve similar results. I figure with accelerated drying of the outside of the wood, the gradient between the wet interior and dry exterior is created and that even on days so humid the split isn't losing moisture, it's still moving from inside towards the edges when it can be lost later.

    A meteorologist friend told me that weather stations thermometers are standard at 6' above ground because temperatures are commonly 5-6 degrees cooler (summer time) at ground level in non-windy conditions. I'm guessing that temperature change is mostly in the last foot near the ground. That combined with moisture from the ground could greatly elevate RH during the drying season so I'll stack my wood at least 8" off the ground with visqueen underneath which should keep the RH lower and the temperature higher. With a week of wind at the beginning, I might guarantee 6 months. I'll let you know. Now to add some free solar heat and convection.

    We know dry wood is best but may or may not notice the difference between wood at 22% vs 18% but if drying tips we pick up here can make that difference, it might mean lot less energy wasted.
  8. roddy

    roddy Member

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    but i can control the speed and the amount of de-humidfication with the twist of a dial nature.....not so much controlling humidity and the drying process,that there amigo is new technology(compared to cavemen tech anyway)
  9. EL DRIFTO

    EL DRIFTO New Member

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    it's really humid here during the summer, so once a year, just before i fire up the central AC for the first time, i run the AC system continuously for 24 hours, with the forced air side & cold air return wide open, in the basement alone.

    it's all sealed concrete, but it still gets muggy to the point of mildew, but after my 80,000 btu dehumidifier, it's dry. :zip:

    i haven't taken any actual RH measurements...

    i'll burn whatever i come across, but i'll make sure it's split as soon as possible i guess.

    natural drying seems like it would only happen half the year here & i'll probably let it sit inside as long as i can in the winter, regardless.

    my house gets so dry in the winter that a box fan in the basement seems to dry very quickly

    i admire the weighting, etc...facts & interesting
  10. dave7965

    dave7965 New Member

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    I'm not convinced that standard stacking is the best way to season wood...even if on pallets in a sunny spot. The wood is just too close together to get good airflow and drying....especially after rain. This assumes of course that you don't have 2 plus years worth of wood in which case stacking would be just fine. However I typically can only give 6 to 9 months before needing it to burn. Criss cross stacking is ideal but takes time and wastes space.
  11. iceman

    iceman Minister of Fire

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    there can be some truth to the op. he didnt say what the mc was in his wood he just said it was dry .. we are all trying to figure out/ argue. but everyone here is in single digits of mc for their comparisons/ examples... maybe his wood is somewhere around 15-20% (prolly closer to 20) i keep a de humidifier on in the summer and have to empty it every 3days... winter time it is on max and from dec to end of march gets nothing april starts running a little bit on max... point i am making is if he is indeed getting 2 gallons the water is coming from somewhere... he said its birch and maple? who knows ... due to the fact he hasnt given us a mc we wont know exactly whats going on, to try and compare HIS stuff with.... but if it does work -great if it doesnt really work but he thinks its does- great!
  12. Battenkiller

    Battenkiller Minister of Fire

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    And you can meet them all over on the "How Freakin' Huge Is Your Woodlot?" thread.

    My woodlot is less than an acre, mostly groomed lawn. I have two large maples that could probably provide enough wood for an entire season. There is a smaller red maple... maybe a cord including the twigs. Four or five box elders, an American Redbud and numerous elderberry bushes in my "hedgerow". I have enough space to store about 4 cord, but I burn 5. I have no truck, no tractor, both boys have moved out and I have many health problems related to doing too much, too soon, too often. I have zero interest in double or triple handling 15 cord of oak or such to get it "seasoned". Dry is what I want. I get it in an unconventional manner, but my autumn procured wood burns as well as any I've kept for three years once I've sufficiently tortured it.

    I think there needs to be a much bigger discussion of alternative wood drying methods, and much experimentation and data collection. Skyline has done a real fine job of documenting his method, and I think it would be great if we all stopped telling each other how to do it "right" and looked at the problem objectively. I've thrown my ideas out, even though I realize that few folks have the same setup and situation that I do. Doesn't mean they don't have to solve the same problem. A group effort here could yield lots of hard data that could be used to figure out what really works, and when.
  13. iceman

    iceman Minister of Fire

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    not a bad idea at all we could start a thread with ideas/input - supported by some kind of data
    +1 i am in
  14. dave7965

    dave7965 New Member

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    Hey Iceman, what is your "unconventional manner " ? I'm always looking for new ideas.
  15. iceman

    iceman Minister of Fire

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    still thinking..................
    maybe a magnifiyng glass pointed at a mirror pointed towards my stack for a few hrs in the morning and at evening.. hopefully it wont burn!
  16. ikessky

    ikessky Minister of Fire

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    "Dry" is a relative term. Without taking before and after moisture readings of your splits, there is no accurate way of telling when they are at 20% or less. I'm glad for you that you found a way that works for you, but I would caution anyone from stating that it is a sure fire way. I use a dehumidifier for a few days after I throw a fresh load into my furnace room. That, coupled with the radiant heat coming off the furnace, seems to quickly get my wood back to where it was in the fall.

    I'm all for unconventional, but sometimes, the old stand-by is just the best way to do things. Half the sites I go to, guys are trying to find out how to make their 4.3L engines run as strong as 350's. On the other half, guys are trying to find out how to make their MS290 run like a a MS361. There are those that will argue to the death that it's possible and then there are those that will argue to the death that it's not possible. Then there are those with a voice of reason that say that it may be possible, but is it really worth it? To be honest, that's where I'm at with this post. I'm sure it's possible to dry wood different ways, but it's not worth it to me. I have time, space, and access to lots of wood. I'm not going to pay for something that nature does for free for me. I have a hard enough time keeping the humidity down in my basement in the summer and fall months. I'm not about to add to the problem when I don't have to.
  17. Battenkiller

    Battenkiller Minister of Fire

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    "Seasoned" is a much more relative term than "dry". At least I can quantify "dry", but all "seasoned" tells me is how long the wood has been cut. After all the reports of chimney fires in the Northeast due to improperly seasoned wood caused by the extraordinarily rainy summer we've had, I would really question seasoning time alone as an indicator of final moisture content.

    There are so many variables in the outdoors, so many wood types, so many sizes to buck and split to, so many ways to stack, etc. I never stated that my method is a "sure fire" way to dry firewood, but I can guarantee that if someone had an identical setup as I do and burned the way I do and had their wood processed in the way I do and treated it the way I do, it would be quite dry when placed in the box. It would ignite right away and burn very hot and create little creosote and produce tons of heat - all of the magical things that properly "seasoned" wood will do, without the loss in fuel content due to microbial action that always occurs in wood that has been sitting in the outdoors for years.

    Humans have been intentionally burning wood for thousands of years, almost every bit of that time without the aid of a moisture meter. IMO, if you need a moisture meter to tell you if your wood is ready to burn, you don't yet know what you're doing. Heck, you may have a cheap unit (or not know how to properly use a good one), and end up putting wet wood in your firebox and scratching your head about why you can't get any heat out of the stove even though you are using "well seasoned" fuel.

    I encourage all types of experimentation, because even failure teaches. Eventually, if you keep hands alert, and your eyes, ears, nose and mind open, you will arrive at a point where it's all second nature. Experience alone is the final determining factor in achieving and assessing dry fuel. You won't find that on the Internet or in a book, and you certainly can't buy it.
  18. ikessky

    ikessky Minister of Fire

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    I, like you, have developed my own way of drying and burning. Our ways just happen to be different. I do not own a moisture meter and will not be buying one either. I am one of the fortunate ones that has ample room in the country that I can leave a few years worth of wood stacked up.

    I applaud you for experimenting and finding a way that works for you. If you are happy and warm, what does it really matter what I, or anyone, says? Heck, I burn in a pre-EPA wood furnace. If you would ask around here, 95% of the people would tell you how terrible that is. You know what? I stay warm and found a way to burn safely and as efficiently as my equipment allows. That's good enough for me right now. You are correct that if someone had an identical situation and set up as you, they could follow your advice. How often is that the case though? I will still maintain that better evidence of your experiment would be showing before and after moisture readings. That doesn't mean I'm calling you a liar. Just that I would be interested in seeing the actual numbers.

    Again, we just have a difference of opinion. Doesn't make either of us bad people.
  19. Battenkiller

    Battenkiller Minister of Fire

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    I burn in an old "smoke dragon" myself (although I've rarely seen any smoke coming out the chimney), so I feel your pain here in EPA land. Newbies don't have much of a choice, and I suppose I'd be pretty righteous myself after I just spent five grand on a new installation.

    It's a little too late in the season to give you before and after numbers since all of my wood is now basically dry. I'd hardly call what I do an "experiment" since I've been doing it successfully for about 20 years in this place. I have already stated that I would be interested in doing a controlled experiment next season if others are inclined to do the same. I'm a very curious person, and there are many aspects of these discussions that have brought out the latent scientist in me. I would like to quantify exactly how much firewood dries from the ends compared to the sides, and what the differences between species, split lengths and diameters are. I would like to establish controlled drying rates at specific temps and relative humidities, and to use this info to create charts with drying curves for different wood types. I would like to determine how much effect air movement has compared to RH, how much "real world" heat is lost by burning wet wood vs. dry, what flue temps eliminate creosote buildup. Many other things as well.

    Therefore, I have decide to create a woodburning research foundation to investigate all of these things. But research is not cheap, so I will be encouraging donations made directly to the PayPal account of my foundation. Ample amounts of wood of various species will also be required, so it would be a big help if folks could drop off samples (1/2 face cord minimum, please stack neatly) so that I can process them and use them in carefully controlled burns in the foundation stove. I will also be needing some genuine "seasoned" wood for comparison purposes. Quads would be the man to provide this, but folks will have to pitch in to help him out with the gas between Wisconsin and New York.

    A volunteer chimney sweep would also be extremely helpful in order to gather chimney deposits on a weekly basis for evaluation.

    Of course, all of this data would be useless to the owners of the new EPA stoves if it was gathered from burns taking place inside my old smoke dragon, so I will be needing a new Jotul F500 "Oslo" so that I can create an accurate baseline that would be applicable to these users. I'm sure that with the many professionals that visit and contribute to this site, there will be no problem procuring a suitable stove for the research. A floor demo would probably be fine, as well as a suitable SS liner for my decrepit old masonry chimney.

    Oh... a couple cases of SuperCedar fire starters would be nice as well.
  20. ikessky

    ikessky Minister of Fire

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    Very nice! However, to successfully quantify your results, you will need someone to duplicate the experiments. Therefore, I will sign on to help you out. I will procure my own wood of varying species, but I will need to have someone donate a Caddy or VaporFire furnace.

    On a serious note, if you do happen to get numbers next year, please post them. I think there are quite a few people out there that would find it interesting. I'm still young and ambitious enough to process skads of firewood, but I know that there are many out there with age and health conditions that can't do what I currently can.
  21. EL DRIFTO

    EL DRIFTO New Member

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    it seems to me that weighing is more accurate of a piece thrown in the stove, than a surface reading

    anyway, i'd like to suggest the RH of the air going into the stove to oxygenate the fire @ 0 RH, 0 F, in the dead of winter as another variable to the ignition process

    still learning, keep it coming :thumbsup:
  22. quads

    quads Minister of Fire

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    I'll just have zapny tell the airplane to drop some off!
  23. skyline

    skyline Burning Hunk

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    Battenkiller, I appreciate your efforts and wish I had your setup. Sorry for the late reply especially after you started having fun with your experiment ideas. I'll sign up as the West coast representative.

    Ikessky, I don't have a moisture meter either and figure from what I've read they have enough errors, that without more experience than I want to have with them I'll stick to the scale which I know is right. The trick is to take one (or more) representative split in length and weight, weigh it and then totally dry it completely. Stick it next to your stove with a big "Do not Burn" sign. You'll know it's dry when you can stick it in the convection oven over night and it doesn't lose any more weight. Once you get it to this point you'll know the moisture content that it started at and be able to monitor other pieces along the way. Weight of water lost/ Dry weight. (This is why the moisture content of some wood can be over 100%. Just assume that same starting moisture contents for your other splits that weigh differently at the start. This is different than what I figured in my moisture lost calcs as I used weight / original wet weight since I didn't yet know it's totally dry weight and was more interested in seeing just how much moister was lost by the fans.

    Once this is done you can monitor any split you originally weighed and calculate its moisture content by assuming the same starting moisture content. Battenkiller, I love your classic scale but you'll save yourself headaches if you switch to a kilogram scale where you're not mixing pounds and ounces and every gram lost equals a milliliter of water and spreadsheets can do all the work of calculating moisture lost to BTU's saved. There is definitely a reason scientists use the metric system. They are lazy, I know ;-)

    As I have said before, my ultimate goal is to have a wood shed that takes advantage of what I learn here and through experiments to dry the wood faster than it might otherwise. If I'm going to build it, I want to do it right.

    An interesting thing I read on the kiln operations is that they use the same size stickers between boards so that the air flow from fans is roughly equal so equal drying takes place but also if the stickers are too thick, >1", the air flow is to slow and drying slows down. Not necessarily intuitive.
  24. Battenkiller

    Battenkiller Minister of Fire

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    Skyline, you can leave that split next to the stove until the cows come home. You won't be able to drive off the last bit of water without raising the temp of the wood up to 212º. Most you'll get it down to is about 6% MC, and that will take weeks. For analysis purposes, you need to be able to quickly get it down to 0% MC.

    Best way is to cut thin cross-sections and weigh them on a balance (or a cheapo kitchen dietary scale that weighs in grams). Then put them in the oven at 220º or so for 24 hours, or until they stop losing weight. The same thing can be done very quickly in a microwave oven if the samples are small, but you have to be careful not to go too fast (use many short bursts on "high") or you will set the things on fire from the inside. How would I know that? :red:


    Although you really have no choice but to assume all splits have the same starting moisture content, nothing could be further from the truth. Even within an individual tree, green MC can vary considerably. Best thing would be to determine the starting MC of a large number of randomly selected pieces using the oven method, then averaging them all. My band saw would make quick work of acquiring these samples.

    Oh, I do grams, even milligrams when needed. I scooped up an analytical balance and a triple-beam gram scale when the lab I was working in got lazy and went to all digital scales. The scale in the photo is just an old produce scale I use to measure ultralight canoes (check out the photo) while I'm building them. I'll definitely use metric weights/measures come data collection/analysis time. Then I'll have to convert everything to pounds so I can present the results in BTUs to the woodburning set, but I'll use a spread sheet to do that when the time comes.

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  25. CrawfordCentury

    CrawfordCentury New Member

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    Precisely. It's firewood. Not rocket science. Humans have been making fire for a long time. No need to go poking about your firewood with a moisture reader like space aliens conducting rectal probe research on humans.

    It's firewood.

    It's so easy...even a caveman can do it.

    [​IMG]

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