Outdoor Wood Furnace Info
All-Purpose OWF Discussions => General Outdoor Furnace Discussion => Topic started by: halfpress on January 03, 2011, 04:57:32 PM
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Hello!
Happy New Year to everyone. :)
Had my first load of unsplit "pole wood" (I think that's the term) delivered this past weekend (attaching a few pictures below). Mostly white oak, dropped around late spring and summer. I did this partly because it's more economical, and mostly because the majority of the advice I've received suggests that unsplit logs with a 6-8" diameter and a bit on the greener side will give me a good, long, hot burn per loading.
I'm getting a better handle on mixing the various woods I have - split and unsplit, seasoned and greener... oak, ash, and a little smattering of some pine... to get different burn cycles out of our Heatmor 200CSS. I load it with various mixtures depending on the weather, if I want it heating faster or burning slower with fewer loadings, etc. I'm new to it, but I'm beginning to see the art and science of it all.
So as I cut up these trees that were delivered, I have to decide on lengths. The first two trees I cut tonight I sawed at 24" and, being 8" or so in diameter, are pretty damn heavy (hey, I'm a network engineer, programmer and freelance photographer - not Mr. Brawny lumberjack guy). :) I can move them around, but they aren't the easiest thing to toss into the furnace and I don't need to be running a risk of pulling something or fouling up my back in some manner.
My question is whether more manageable 16" lengths might make more sense. I can toss a row into the back, then a row in front to match and stacking on top of those a layer or so. That would be almost like having a 32" log, only divided in the middle. How would that work in terms of burning efficiency, etc? Too tight (it's a 36" deep firebox)? Maybe just 18" logs stacked in the back and some other stuff in the front?
Does it make sense to load the furnace with a tight stack like this or is it best for things to be more random with appreciable gaps for airflow, etc?
Might be overthinking this, but I'd just like to hear what others do to get the most efficient performance without killing themselves. :)
The photos are of the wood delivery and a shot of my furnace loaded with the split oak I've been using prior to this new delivery.
Thanks!
- Aaron
http://halfpress.com/ (http://halfpress.com/)
http://photos.halfpress.com (http://photos.halfpress.com)
(https://dl.dropbox.com/u/5247775/wood/20110101-_MG_9492.jpg)
(https://dl.dropbox.com/u/5247775/wood/20110101-_MG_9556.jpg)
(https://dl.dropbox.com/u/5247775/wood/20110101-_MG_9577.jpg)
(https://dl.dropbox.com/u/5247775/wood/20110101-_MG_9575.jpg)
(https://dl.dropbox.com/u/5247775/wood/20110101-_MG_9637.jpg)
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i try and keep mine in the round and only cut them to lengths that will go sideways (roll) through the door. this way i can roll them to the back of the stove and then add another one/ If i am loading for a long burn on a cold night i can roll another layer in the same way. i jsut use a long handled shovel to roll them in and if i have some split wood to go on top it will slide pretty easily with a push from the shovel if i put it in lengthwise.
and my personal opinion burning green wood is a waste of BTU's
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I had thought about rolling them sideways, too. That's tempting. My fire door is 24" diagonal and the firebox a good bit wider, so that does present a little bit of a challenge for fitting the width decently vs. lengthwise, though. Hhhmm... must experiment.
I'm trying to mix the wood - greenish and more seasoned - in each load. Can you elaborate on the waste of BTUs? Like to better understand the dynamics. I have burned very seasoned wood in here and it burns up like paper... would go through it incredibly fast.
How do we all get on the same page regarding what is green, what is seasoned, etc? Is there a decent metric for having that conversation?
Thanks!
- Aaron
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you can read all kinds of info on the net about wood. mostly it boils down to something like this...dry wood is considered anything 20 percent or less moisture content if you burn green wood (more than 20 percent and as high as 60 percent) you will use up to half of the available btu's in the wood to boil the water out of the wood before it can burn.
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You can buy a meter to check the moisture content of the wood. Most gassifiers require wood to be seasoned to 25% or less moisture. Most regular OWB's will burn greener wood than that. The drier the wood, though, the better BTU output you get. If you burn green wood, you're wasting some BTU's to dry the wood so it can burn.
Most of my wood is split and in about 18" lengths. I think it's too short. I'm probably going to use longer hunks of wood next year with a lot less splitting (probably halving the wood only). I'd like my wood to be about firebox length (same OWB as you).
If you can't lift the larger wood without hurting yourself, maybe a little lift table could be useful for you. Something that lays on the floor in front of the Heatmor and raises with hydraulic muscle.
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Definitely not keen on screwing up my back. It's not so heavy I can't lift it - definitely not... just not easy to load and therefore a greater change of hosing some back muscles. :) I'm going to tinker with the sizes a bit to see what feels best. My main questions were about how densely to pack it - whether it ends up being lengthwise or crosswise, with few logs or with many.
I was given the impression unsplit wood would yield a slower, better burn with fewer loadings. I realize greener wood causes the furnace to spend more of its time drying the wood out. In the balance, though, does this longer burn cycle pay off in any way? Aside from trying to just load it twice daily (smaller, split, very dry wood just burns up way too fast in our system)... does this type of wood load (unsplit and greener) fit well with heating a large, older home with cast iron radiators? We don't need instant heat so much as a real workhorse out there that doesn't burn out in a split second. :)
Thanks!
- Aaron
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i think mass storage and burning dry wood would be the best route..if you think your dry wood (that can give much better heat output than yoru green wood) is burning up too quickly then why not let it burn and store the heat so your old rads can sihpon it off slowly. you may lose a few btu from "leaking" out of your storage tank bu ti would think you would lose less than you would boiling off the moisture of the green wood ??
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"somewhat" green wood is not good.. get you a quality moisture meter and you'll notice a good increase in burn times when your moisture content is between 17-22%
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what is a good moisture meter to get?
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Not going to swear it's a good one - but it was affordable and I ordered it from Amazon last night:
http://www.amazon.com/General-Tools-MMD4E-Digital-Moisture/dp/B00275F5O2/ref=sr_1_3?ie=UTF8&qid=1294170698&sr=8-3 (http://www.amazon.com/General-Tools-MMD4E-Digital-Moisture/dp/B00275F5O2/ref=sr_1_3?ie=UTF8&qid=1294170698&sr=8-3)
There are certainly more expensive models out. For my needs, if it's reasonably accurate, I'll be in good shape. Should arrive on Thursday (free two-day with Amazon Prime), so I'll let you know then.
I'll also know how green my "greenish" firewood delivery is by then. The Heatmor manual says anything up to 30% moisture content is pretty ideal. I've no idea if what I have is beyond that or not. Best I understand, these 15-16ft poles of mostly white oak I have were dropped in either late spring or early summer... so probably six - eight months old.
Four of them at 24" long pretty well fill my 200CSS to somewhat above the suggested load level. This morning was the first time I've loaded it exclusively with these new logs, so I'll see how the burn goes today. It's just now getting over 40 degrees today and will drop back into the 20's again tonight. And, yes, these 24" logs were heavy and unwieldy enough that there is no question I'm cutting them shorter going forward - even if that means more individual pieces making a full load of the furnace.
Keep ya posted!
- Aaron
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Ok, now I can continue the debate with some real figures. My General MMD4E Moisture Meter arrived from Amazon today. I tested a variety of woods I've been burning and have some numbers to work with.
The original, fireplace-sized highly seasoned oak pieces I have - which I use practically as kindling in my Heatmor now - measure anywhere from 5% - 9% moisture content. They are dry as a bone.
The large, split oak pieces I burned the last half of December are mostly gone - but the two pieces I still had around measure around 14%, I think. It burned quite well and relatively slowly due to sheer size - but it was mostly split wood and therefore had a lot of surface area.
The new load I got that I started this discussion about seems to be around 20% - 24% when I measure against the freshly cut end, nearest the center of randomly selected logs. Naturally, as I measure outward with the prongs toward the bark that drops down to about 9 - 10% on the fresh cut face. But one prong on the center and the other just off it peaks at the highest at around 24%.
My Heatmor 200CSS manual says 20 - 30% is ideal, and diameters of 6, 8 and (in some cases) 10" unsplit. Sounds like I might be right in the sweet spot.
Assuming I'm measuring right and this thing is at all accurate, would this still be considered "green" wood?
Thanks!
- Aaron
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There is nothing wrong with stacking two rows of wood in a furnace. Air gaps are more necessary when burning greener wood because it helps the wood dry and helps burn the gas that the wood puts off. The cleanest burning fire is a very hot fire. To get a hot fire the wood needs to be able to get air. I have noticed that furnaces often burn cleaner when there is a way for the air to get all the way to the top of the burn chamber allowing the smoke to burn off. Several brand are now coming out with models that have air injected both under and over the fire. These models are more efficient and burn less wood than the standard furnace.
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Yeah - I had a feeling some gaps would help. When I had five 24" logs in there in a tight stack, they burned... but there was far less flame and coals. Seemed to be a really concerted smolder that improved a lot as I pushed them around later in the burn (no shock there, of course). That leads me to wanting to use these much shorter lengths, but still unsplit to find a balance between handling and airflow. Just trying to find that sweet spot between burn times, heat and easier handling. Think I'm getting there.
And, yes, my 200CSS is designed to combust its own smoke in the upper part of the chamber. There's a "do not exceed" height marker inside the front door that indicates the proper max loading level. Apparently, loading above that primarily inhibits the ability to combust the smoke and you do get a smokier burn. I've witnessed precisely that effect by loading it much higher to the top of the box vs. staying below that marker. If it's loaded right and it's barreling along, you see virtually no smoke... just wavering heat from the stack like you see coming off pavement in August. :)
Lots of art and science to running an outdoor wood furnace. Have to say that, in a lot of ways, I'm really enjoying learning its personality and experimenting with all these different variables.
Whatever the case, I'm not spending an ungodly sum on propane this winter like the last 10 years! I won't even tell you the obscene expense and volume of propane we burned in past years (last year in particular). Now we just use it for out cooktop. Period. :)
- Aaron
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Glad to hear you are saving lots of money! That is what it is all about!
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it has been the same temp all week here in the U.P. and i have been burning all 2yr old maple, well last nite i decided to load the stove with maple that i cut this summer (pretty green) and wow what a diverence i went a good 8hrs longer between fills.
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I would think that the most inefficient situation is when the wood is burning and the stove is not calling for heat. Stove idle, this is where I get most of my smoke. Overly split and dry wood would tend to burn more at idle periods than "green". Since I have at least 15 grand wrapped up in my system, the last thing I will ever do is pay for wood. So around here it is burn what you get and burn it all. Most of the wood I had stacked at the beginning of the summer is gone. What we are burning now is quite green and what we burn in March will be greener yet. We are just in our second year and have not established a organized staging system or large stockpile of wood yet. I have several huge rounds 30" of oak and crotches but I am just starting construction of my splitter.
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1grnlwn, you may be on to something there. It is true that much of what you see as smoke is burnable energy that is escaping.
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I donno......... I can assure you that my stove will go nearly twice as long on dry wood vs green. As far as smoke when it's on idle? None........... You can stand there and watch the stack for 5 minutes and you "might" see a wisp of smoke. It's extremely rare when it does.
I would have to think your stove is getting to much air while it's idleing if your seeing smoke. My stove will smoke when it's first filled with wood, then when it idles there is virtually none, and after a couple burns on a fresh load of wood, the smoke amount when it's on is very minimal as well.
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what can I say I have a Taylor 1000 and it smokes some during idle, it has always smoked and always will.
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i am not sure where you think smaller wood and dryer wood will burn more at idle times than bigger greener chunks?
you may be right but i figure when the stove is idle it is idle...being that the fire will pull air from where ever it can and it will use that air regaurdless of if there is 1 large ember or 10 small ones. if there is any fire in the stove it will pull for air (and will) use ALL the air it can find no matter if it is green or not. the little air that your stove should be letting in while idle should only be enough to keep the fire from going out so no matter if the wood is green or dry the size of the fire should be controlled by the amount of air not the size or wetness of the wood
my thoughts anyway..and they may be wrong
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what can I say I have a Taylor 1000 and it smokes some during idle, it has always smoked and always will.
Yea.. I'm not trying to down your furnace but taylor stoves aren't as efficient as some of the other models. In your particular instance, green wood may be better. However the math of dry wood vs green isn't in your favor. Willie can throw you some figures backed by fact that you loose about half the btu the wood has by burning it green.
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I am still in the research phase myself so have been to all the sites I could find for OWB's and I think it was on "Shavers" page they had a device that picked up your wood, brought it to door hiegth, then allow you to push it in the burn chamber. Looking at the pictures I think something close could be fabricated with basic metal and welding skills. When I was a young man I thought back problems were a way for lazy people to avoid work, but, after being "down" in my back for a week or so, twice over the past thirty years I now know it is the real deal.
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what can I say I have a Taylor 1000 and it smokes some during idle, it has always smoked and always will.
Yea.. I'm not trying to down your furnace but taylor stoves aren't as efficient as some of the other models. In your particular instance, green wood may be better. However the math of dry wood vs green isn't in your favor. Willie can throw you some figures backed by fact that you loose about half the btu the wood has by burning it green.
Yea I am not saying that green wood would have more btu's just that it may last longer because it will burn slower. My main point was that small pieces of dry wood will burn faster and would burn more at idle than big pieces. That being said, Taylor stoves are more of a workhorse and do not have any fancy features. Right now mine is over-sized because we still have 1 building not hooked up at this time. We tend to collect our wood over the summer to burn that winter and the volume is such that the drying process is not our biggest concern. At this point in the winter we have a lot of wood left but it is all rounds and logs. We are currently building a splitter for the skid steer. Who knows we might burn some seasoned wood next year.