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Gadget Freak Case #249: The Heatilator Helper

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Ann R. Thryft
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Not pretty but looks like it does the job
Ann R. Thryft   12/6/2013 11:20:30 AM
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Well, it isn't beautiful but it sure looks functional. Preserving heat is a big topic right now where I live--we're having record lows at night. I've got an excellent woodstove as our main heat source so I don't need this gadget, but many people here in the mountains have installed inserts in fireplaces as an alternative to a woodstove. They could definitely use this.



modorney
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Elegant, practical solution
modorney   12/9/2013 2:09:12 PM
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The most satisfying aspect of this is the use of existing "junk box" parts.  Like the PJT - my thought would be to create a three second delay with a 555, but then I'd have to go buy one.  Using "correctly mismatched" diodes means not having to buy temperature sensors.  A great design, Dick!

DickN
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Re: Not pretty but looks like it does the job
DickN   12/19/2013 4:55:16 PM
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Well, the photo DN chose for the title could be made worse only by showing all the insulation packed around the fan in the final installation.  When they finally get the video up, you'll see what it looks like installed.  Could have made it fancier if I'd considered consumer appeal, but the really ugly parts are hidden in the air duct.  You'll see those too in the video, "warts and all"!

78RPM
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Load on the motor
78RPM   12/6/2013 1:22:37 PM
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Ann, like you, we heat with wood using an outdoor wood furnace. I do feel a little guilty about smoke and CO2 I'm adding to the forest mountain air and would like a way to capture it.

I have a couple of suggestions for Dick. You could have used a MOSFET for Q4 to be more efficient than an NPN transistor. I notice you use a tight hysteresis of 0.4V. The valve flap somewhat restricts air flow and produces load on the fan. How about using some louvers that just snap open and closed using two small solenoids that are only active during the transition second between open and closed?  This would completely open the air path and reduce load on the fan.

Ann R. Thryft
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Re: Load on the motor
Ann R. Thryft   12/6/2013 1:31:35 PM
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So you're another woodburner, 78RPM! But I'm curious--you say it's an outdoor wood furnace. What is that and how does heat get transferred inside efficiently where you need it?

78RPM
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Re: Load on the motor
78RPM   12/6/2013 2:47:11 PM
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Ann, yes, I feed my Empyre outdoor furnace twice a day for a 2800 sq. ft. house. It has a 400 gallon water jacket. When the water temperature falls to 160 degrees, a damper fans the flames. The damper stops at 172 degrees and the fire smoulders. The hot water is piped under the house through a heat exchanger. A second water circuit circulates under the floor in five zones plus the garage. If the outside water in the exchanger falls to 109 degrees (like if I forgot to feed the furnace), then electric heating of the floor circuit takes over. It's quiet and comfortable with warm floors.

I have 64 acres of forest land so I have sustainable supply using dead trees, crooked trees, and growth that needs to be thinned for a healthy forest. I just wish I had a way to capture the smoke and creosote to reduce my carbon footprint.

Ann R. Thryft
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Re: Load on the motor
Ann R. Thryft   12/6/2013 3:15:00 PM
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Thanks for the explanations, guys. I'd heard of heatilators way back when but not outdoor wood furnaces. Sounds like an excellent system.
Free wood? Wow, wish we had that here in the Northern California mountains. One cord of good-quality, dry, burnable oak and madrone for my EPA-approved stove now costs $400 here. I usually burn 2-3 per winter. A chunk of forest acreage would be nice, too. This winter we're excited because the local electric company trimmed a great big madrone and we got about 1/2 cord from it, saving us about $200 next winter.



Dangela
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Re: Load on the motor
Dangela   12/9/2013 9:27:01 AM
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I get a load of slab wood for about $300 here in upstate NY. It's all hardwoods and is about 9 face cords or about 3 cords. It's from a local company that makes shipping skids. I go through that and about half a tank of fuel oil each winter. I have 10 acres of woods but can't be bothered cutting and splitting all that wood each year. I bolted a thermal switch onto the back of the stove and use it to control the fan that blows air through the stove. It closes at 160 and opens at 140 degrees.  It makes it so it's not blowing unless the stove is hot. It also lets me know if the stove needs more wood in the middle of the night if I don't hear the fan blowing.

jayprab
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Re: Load on the motor
jayprab   12/9/2013 9:21:37 AM
I have a problem with the general belief that burning wood is, somehow, better than obtaining energy from any other form of carbon-based fuels... Wood is mostly cellulose, C6H10O5. The 6 Cs in there are sequestered carbon, that gets released back into the atmosphere when the wood is burned... In addition, as 78RPM laments, there is really no real way to capture and clean the wood-fire flue gases, which have a LOT more "stuff" in them (creosote, for instance) than do gases generated from burning (refined) propane (C3H8) or natural gas or even oil.... Modern furnaces are much more efficient and can be tuned to run as clean as the state-of-the-art will allow. Not perfect, but it is the best we have... Besides, how many people are lucky enough to have 64 wooded acres (or even 1) to sustain their heating needs? And how many have the time to go through said woods to forage, cut, bring back, chop, stack the wood???!! These less fortunate (and in my opinion, equally misguided) folk simply BUY the wood from someone, who goes into a forest and cuts down trees to meet this demand... Sustainable? Hard wood forests take a LONG time to grow back... So more and more forest area is being cultivated now and we are disrupting animal habitats in the process... I could go on, but you get the picture... So is it THAT much different from pulling oil or gas out of the ground?

mattd
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Re: Load on the motor
mattd   12/9/2013 10:02:43 AM
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jayprab, I am not even close to an expert on this, but there really is a difference between burning wood and burning oil and gas trapped in the ground.  The wood comes from trees, trees which consume the CO2 in our atmosphere and trap it in the form of cellulose as you point out.  However, in the ecological cycle, that is actually a somewhat balanced cycle...

burn tree = release carbon, grow tree = trap released carbon.


Burning oil and natural gas is taking carbon that is currently trapped in the ground and not a part of the ecological cycle and throwing it into the cycle...it is overloading one specific area of the cycle.

Also, do not confuse this with some of the other areas we are destroying our environment.  The people here are talking about maintaining forests in a growth positive manner, as opposed to clear cutting which the wood and paper industries have been known for.  Careful clearing of certain undergrowth and smaller trees from a forest can actually make a better forest to help remove more of the unbalanced CO2 we are putting in the atmosphere.

Constitution_man
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Re: Load on the motor
Constitution_man   12/9/2013 10:03:28 AM
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@ jayprab   Caring? maybe. Concerned? yes indeed.  But your response is indicative of what's wrong with much of our energy, environmental, and clean air policy.  Selected trees NEED to be cut down or they are a source of disease for the forest around them.  And, forested areas NEED thinning to stay healthy.  If we choose NOT TO MANAGE this vast resource, then Mother Nature takes over, a fire starts, and ALL the trees are burned to the ground along with all associated habitat.  Little furry things die, and the damage takes decades to correct.  The release of pollutants in a natural fire is no cleaner than the controlled burn of a home wood burner.  In fact it is far worse when mother nature has it her way because the combustion is often wild and uncontrolled, thus incomplete... leaving a thick black plume of all kinds of nasty stuff in the sky for weeks.  Properly combusted furnace wood burns down slowly and completely, and is NOT greenish sappy material.  It is the responsible citizen who properly manages and harvests the forest for use in a controlled burn, versus the burn of fossil fuels purchased from hostile cultures.  Properly done, forest harvesting is minimally disruptive to the surrounding ecosystem, furry critters and all.  While you have a problem with the beliefs of the responsible steward of the forest [and the person who is smart enough to buy scrap wood], I have a problem with those who assume that land owners are just somehow "lucky".  I've noticed that a lot of "lucky" people in my midst also happen to be those who have worked damn hard for all they enjoy.  

jayprab
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Re: Load on the motor
jayprab   12/9/2013 10:27:44 AM
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Constitution man, you sound angry... When you say we have to MANAGE this 'resource', you are already assuming that everything on this planet is for our consumption and convenience... Forest fires actually do GOOD by returning nutrients to the ground and allowing undergrowth to re-grow (which fauna depend on for nutrition). Sure, some critters die, but that, too, is a part of the NATURAL cycle of things. This process has been going on for far longer than mankind as husbanded the it... Take the canyons in California, where, because of 'managing' the underbrush, the fires, which inevitably occur, actually are much more intense! As for the "...thick black plume of all kinds of nasty stuff in the sky for weeks" left after a forest fire, what do you have to say about volcanic eruptions, then? Mankind, in all it's arrogance, is still insignificant in the face of the AWESOME stuff nature can (and does) throw our way. To think we know it all and can engineer our way out of everything is sheer myopia. Just look at the wealth of examples where we have tried to curtail one problem and created much worse ones... Nature is a hugely multivariate system and is not easily predicted or controlled... Least of all by looking at small subsets of the variables involved...

Constitution_man
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Re: Load on the motor
Constitution_man   12/9/2013 10:39:37 AM
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Do your homework, jayprab.  There is virtually zero nutritive [agronomic] value to forest fire ash.  If you don't believe me, grab a bagful of what mother nature leaves behind and have a lab do an analysis.  FACT: You won't find those things that promote vegetative growth.  All you will find is a few minor trace mineral elements that were not deficient in the soil beneath before the fire. You have been taught [and are spreading] a myth with no basis.  If forest fire ash were nutritive, the gardening stores and nurseries would sell bags of it for a profit.  And, as a matter of fact the earth and all its bounty ARE for the benefit of mankind, the dominant species.  Stewardship and management are the keys to preservation of this earth we all share, not ignorance.  And, thank you for mentioning the volcano.  Yet another example of Mother Nature wreaking havoc upon herself.  All of mankind could benefit from harnessing the volcano's power 365 days a year, and even moreso if the decanting of that energy kept her from blowing up.  Think about it.

TunaFish#5
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Re: Load on the motor
TunaFish#5   12/9/2013 11:35:56 AM
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@Constitution_man - Dude, I gotta agree with jayrab on the angry thing.

Please continue with your good facts, but take a couple of deep breaths.  I lean to your side of things. but you're getting me spun up -- and it's not even my conversation.

Since I jumped in, I will note that (I'm no chemist but) I took exception with his remark about all 6 Cs going up to the sky.  I don't own a fireplace shovel to clean out the hydronium (OH) ions under the grate.

Tristram
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Re: Load on the motor
Tristram   12/10/2013 6:22:10 PM
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@jayprab  "Mankind, in all it's [sic] arrogance, is still insignificant in the face of the AWESOME stuff nature can (and does) throw our way."

That kind of logic leads to the equally false assumption that nothing we do can disrupt the ecosystem.

All we can do is be the best stewards we can be, studying the literature as it exists and applying it as appropriate.  I, myself, am "lucky" enough to have dropped $100k+ for the 40 acres of "agricultural wasteland" adjacent to my home (and continue to be "lucky" enough to pay taxes thereon) so that I can harvest the deadfall in my woods to heat my house.  I supplement that with cut & split wood from the local sawmill that comes from those portions of the log unfit to make a useable 2x4.

While I cannot manually crosscut a log to save my life, I do split wood with a sledge and wedge: quieter, safer, & more satisfying. Not sure that it's faster but it does help control the paunch that develops as I work in front of the keyboard.

Lance  ==)------------------

Ralphy Boy
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Re: Load on the motor
Ralphy Boy   2/26/2014 5:24:10 PM
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Lance...

I burned wood for years. Rebuilt an old coal parlor stove and modified it to be similar internally and air control wise to what a better Franklin would have.

Splitting the 3 to 5 cords a year to feed it was some of the best exercise I've ever had. Harvested some of that wood myself too from local woodlands, great fun on a good day. Not too bad ever, but then that's just me.

I bought 5 acres 5 years ago and one of the first things I did was plant some fruit and a weeping willow.

Mixed results on the fruit, but the willow went from being a 4 ft high stick to 15 feet of lush in those 5 years. The water table is only a couple feet down all year round.

 http://www.esf.edu/pubprog/brochure/willow/willow.htm

Black willow is native here and I'll be planting some soon, about 2 acres total. Retirement will be one big multi-year experiment in all my favs! Guess I'm just lucky like that.

DickN
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Re: Load on the motor
DickN   12/18/2013 6:09:19 PM
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Using a MOSFET could improve efficiency if I were using a switch-mode output, but this is a purely analog Class A output stage.  Any series device (BJT, MOSFET, rheostat, etc.) would waste the same amount of power at any given operating point.  I considered whether I wanted to add the components to make a PWM output, and noted that (1) the max dissipation in the output stage is around 6W, and it's only used during the heating season, and (2) the cheap transformer I used (can't speak for the one I specified since I didn't test one) wastes more power than that.  The fans have brushless DC motors, so can't run directly on PWM output - I'd have to add an LC filter.

The flaps do add noticable aerodynamic load at low speed when they're barely open, but at high speed I doubt the load is significant.  Bear in mind they're held closed by magnets, not springs - once they're free of the magnets it doesn't take much to hold them open.  The added load at low speed does have one useful consequence:  it extends the flow rate range at the low end, since the brushless DC fans can't be electrically slowed down any further.  You'll see the flaps in operation if DN ever gets around to publishing my video.

As for using solenoid-controlled louvers, that's worth considering for a couple of reasons.  When the fire first gets going, there's about a 5-15 minute wait before the fans start up.  The reason is with the flaps closed, the normal convection path is completely blocked and the warm-air sensor gets heat mainly via a secondary circulation path.  Air goes in the bottom of the top register, warms up a little and comes out the top, where the sensor is.  If I had a way to manually trigger the flaps/louvers, that delay would be much shorter.  I can also shorten it by blowing a puff of air into the bottom of the top register.  Another advantage, assuming they can be triggered manually, would be seen during a power failure.  With my design as published, I'd have to either provide battery power, prop the flaps open with sticks inserted through the registers, or take the bottom registers out.

The hysteresis is only to prevent chattering on and off when near the threshold.  There's actually an inherent feedback loop involving the temperature sensors, which is negative feedback during steady-state or pseudo-steady-state operation, but positive feedback when the flaps open or close.  The latter normally prevents unwanted on/off cycling.  As I mentioned above, when the flaps are closed the warm-air sensor doesn't get much heat.  The moment the fans start and the flaps open, that sensor starts to heat rapidly.  Likewise when shutting down, the moment the fans stop and the flaps close that sensor cools down further for lack of warm air flow.  The heat exchanger warms up a little but the warm air inside can't go anywhere.  In fact, if I manually insert a stick to open the flap on that side, the fans will start up again in a couple of minutes (or try to, the sitck is blocking a fan).  These events involve positive feedback from the temperature sensors.

Negative feedback occurs when the system is near steady-state operation.  Let's say the fire has died down and only a small flamelet or a few embers remain.  Heat is still being produced, slowly.  The temperature difference decreases with increasing fan speed.  This may need elaboration for some readers.  Increasing fan speed increases the heat transfer rate (HTR).  HTR is the product of temperature rise, mass flow rate, and specific heat of the medium.  Using mass rather than volume flow rate avoids the need to think about the air density change.  The sensors are monitoring temperature difference (rise), not HTR.  The temperature difference decreases because (1) the air spends less time in the heat exchanger, and (2) with heat being removed more rapidly, the heat exchanger itself runs cooler.  The fan speed seeks an equilibrium that balances this loop.

The above points out another advantage of using solenoid-switched louvers.  When there are only a few hot coals left, it may be preferrable to have the fans start back up after the heat exchanger warms up again.  It would if the flaps didn't close immediately when the fans stop.  Louvers could be set up to close after a delay.

It will be interesting to see how other builders incorporate all this input!

 

armorris
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Nice project
armorris   12/6/2013 2:30:40 PM
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Nice project. I never knew there was ever such a thing as a "heatilator". Definitely old-school technology. You don't see PUTs (programmable unijunction transistiors) much anymore.

An outdoor woodstove is a wood furnace in an outdoor building. It has a heat exchanger inside it that heats water that is piped underground to radiators in the house. All of my relatives in West Virginia have them. They very efficiently burn the wood that is very cheap there. The Forestry Service marks trees that residents can cut down for free. The only cost is the labor to cut down the trees, and you are asked not leave a mess behind. The Forestry Service gets the forests thinned to minimize fire risk without having to hire it done. Everybody wins.

Digerati Ohm
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Re: Nice project
Digerati Ohm   12/9/2013 9:46:50 AM
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I have to agree.  A good thing this wasn't submitted earlier as the GF of the Year competition was difficult enough to decide on.  I'm anxiously awaiting to see how this design turns out next year!

DickN
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Iron
Re: Nice project
DickN   12/20/2013 2:35:55 PM
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I think PUTs are still found in motor speed controls for small appliances and possibly in light dimmers.  SBSs are still available too and used in these applications.  I used the same PUT 7 years ago in a more conventional-looking topology: <http://www.designnews.com/author.asp?section_id=1386&doc_id=219772>.

armorris
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Re: Nice project
armorris   12/20/2013 3:20:51 PM
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DickN,

Thanks for the link. From the looks of your circuit and your construction, it looks like you're an old-timer, like me. I recognized some really old capacitors, there. I take it you constructed this circuit a long time ago. I am also a geezer, who has been designing electronic circuits since adolescence.

Cabe Atwell
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Re: Nice project
Cabe Atwell   1/20/2014 5:31:22 PM
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Talk about maximizing your heat efficiency! @ 78RPM, some emergency room hospitals have something similar for their drive paths, which use heated water that circulates through piping underneath the asphalt to keep the path ice free in winter months.

Habib Tariq
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Iron
Heatilator helper, an interesting approach
Habib Tariq   12/7/2013 4:19:37 AM
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A very simple and interesting solution to the problem of insulation. The only problem is that fireplaces are not very common anymore, at least not in the cities. But yes for people who can relate to this problem, it does provide a very simple solution to the problem of heat loss through chimneys. 

William K.
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Re: Heatilator helper, an interesting approach
William K.   12/9/2013 3:55:31 PM
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@Habib, in this southeastern part of Michigan many of the currently being built houses do have fireplaces, but that is mostly in the expensive houses. So there are lots of them here. The addition of a small circulation blower is a good idea, and the trick of using the temperature -induced change in diode forward drop is a neat way to have a stable temperature sensing system. Great engineering there. 

And for all of those folks screaming about pollution from heating systems, why don't you all move to southern California where pollution comes only from transportation sources, which in that area everybody must have in that part of the world? 

wlawson
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Iron
burning wood
wlawson   12/9/2013 9:53:23 AM
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I have been heating with wood 95% of the time since 1978  in northern wisconsin.

It takes from 8 to 12 cords of dry wood per year.  typically only 5 to 10 acres of woods is required to generate that amount of fuel forever here in Wisconsin

you need to burn dry wood, other wise a huge amount of cresote is created.  there are basically two types of wood burners here.  the ones that smoulder and run for a day on a load and burn wet wood.  they are approximately 50% efficient and are outlawed in much of wisconsin if you are less than 500 ft from another house. 

the better kind of wood burner burns dry wood and can be up to 80% efficient and generally they are very clean as they burn much hotter and generate mostly CO2 and H2O  and some small particulates and epecially important, the cresote is burned up.  the down side is that they need to be fired several times a day as they consume the dry wood very fast.

The key to burning wood is having a good material handling system.  I have a large wood box (about 1/2 cord) that I can move with the tractor from the primary wood pile to next to the furnace when necessary.  I figure I spend on average about 1 hour per week cutting, splitting (I split everything but Elm by hand, it is faster and provides more exercise) and transporting the wood.

I dry most of the wood at least one year however oak needs to be dried 3 years to get it really dry.

As they say heating with wood heats you twice,   once when you cut it and once when you burn it.

My primary back up is Electric resistance heating now as off peak electric heat is about 1/2 to 1/3 the cost of any other fuel.  ( I do not have natural gas)

Ann R. Thryft
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Re: burning wood
Ann R. Thryft   12/9/2013 11:55:02 AM
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I agree with wlawson: if you're burning dry enough wood and doing it carefully and correctly--and you have an EPA-approved woodstove (which most people don't)--there's almost no creosote buildup. My chimney sweep keeps telling me I could have him come only once every two years because I'm doing all that. Most of his other customers need him twice in one year, i.e., 4x as often. And it's not exactly a choice where I live: it's much cheaper than electric and propane heating, and when the power goes out in winter as it often does here, propane and wood are the only alternatives.

78RPM
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Burning Wood and the Environment
78RPM   12/9/2013 12:49:49 PM
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We are all off the subject of the project itself but let me offer another take on the environmental effects of burning wood. I lived 22 years in Honolulu, then retired to the mountain forest of Montana seven years ago. Until I bought land here I, too, believed that one must never take a stick out of the forest; then in 2005 a forest fire destroyed 20 acres of my trees and several square miles of Forest Service timber. I have pictures of one side of the road where the Forest Service had thinned the trees, and the other side where they had not thinned. Where no thinning had been done you see 100 percent mortality. The thinned side shows almost 100 percent survival of mature trees as burning grass and brush did not find ladder fuel to reach the tree branches.

On my own 64 acres I have learned that when I thin the trees to 220 trees per acre, the remaining trees grow much better. In some areas, I have 400 to 500 per acre and all the trees look like bamboo stalks. Wildlife doesn't like to go through such thicket. After cutting trees, standard tree farm practice is to burn the piles, so I might as well make use of the burn.

I do not believe that nature's purpose is to serve man. I'm in the Transcendentalist camp of Thoreau, Alcott, Emerson, who believed that man is another animal and a part of nature. But I do believe that we have to manage some parts of our environment using our best judgment. Hmm. I think I'll look for a way to sequester that smoke.

William K.
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Re: Burning Wood and the Environment
William K.   12/9/2013 3:46:29 PM
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@78RPM, isn't it interesting as to the reality that the unintended consequences of some idea not adequately thought out wind up being rather unpleasant. The whole concept of not using any of the fallen deadwood almost invariably leads to really bad fires with a lot more damage, justy as described. For that reason I have written my (previously) favorite Canadian park off. They changed policy and made it an expensive fine to burn even one twig off the ground. Instead, people bring in firewood from all over, which brings in all kinds of bugs and diseases. But they do get their wish for a collection of tinder and fuel at the base of their great forest, no matter what else may also happen. Why couldn't those politicians think ahead a few years.

Ann R. Thryft
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Re: Burning Wood and the Environment
Ann R. Thryft   12/10/2013 12:27:25 PM
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78RPM, I'm with you on the relationship between humans and nature. Wildfires are a natural way of keeping forests thinned and diseased trees under control. This has been the case for thousands of years, and the US Forest Service finally figured this out when they started doing "controlled" burns. However, those can be hard to control, as they discovered in Idaho in the summer of (I believe) 1998 when a controlled burn got out of hand and devastated thousands of acres in the Salmon-Challis National Forest. The foresters at a state park close to me do this every few years, too, but with a lot more success. So did native Americans throughout California.

78RPM
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Re: Burning Wood and the Environment
78RPM   12/10/2013 1:27:10 PM
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Yes, Ann, controlled burns are a tool for removing ground fuel and ladder fuel, and you rightly point out that they get out of control sometimes. I guess nothing is perfect. But what's important about the facets of this discussion is that the people on this blog are Engineers.  If anyone is going to solve world energy needs in a way that can save the environment, it's the engineers who read this magazine. If you want to predict the future, then invent it. Let's challenge ourselves ladies and gentlemen. Hoooah.

Secondarily, I think of the horrible forest fires this past summer in the U.S. If we had done some sustainable logging, many of those big trees would have survived the fire. But now we have the equivalent of a clear cut decided by flames. We could have provided jobs for loggers and still kept our forests.

Ann R. Thryft
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Re: Burning Wood and the Environment
Ann R. Thryft   12/10/2013 1:36:15 PM
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78RPM, some of the forest fires this summer could be attributed to fuel buildup. Wildfires near me a few summers back when all of California seemed to be burning were made much worse by 50 years or so of buildup. But much of the recent fires in the West problem has been exacerbated by the horrific effects of ongoing super-hot and dry summers due to climate change, which also affected us here during that time. 15% humidity in the redwood forest?! And there's also been devastation of trees throughout the West by beetles, partly because they were so dry. It's a "perfect storm."

Cadman-LT
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What is it
Cadman-LT   12/13/2013 3:13:57 AM
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What is a heatilator? I've never heard that term before. We had a fireplace with blowers where I grew up, just never heard that term before.

bugs
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Re: What is it
bugs   3/6/2014 11:16:52 AM
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In reply to "what is a heatilator", see the company's link at http://www.heatilator.com/.  My parents had one in the house I remember as a child, from the 1950s.  The simplest description of that one, which appears to have been comparable to the one in this article, would be a gravity furnace in the form of a fireplace.  Ours had vents on both sides near the top and bottom of the fireplace opening, and the heat of the fire would encourage convective air flow around the firebox--it greatly increased heating of the room when there was a fire burning.

I can see that this scheme would work--but realistically, if we currently had a heatilator and I tried to install something that looked like the pictures for this, my wife would remove it!

Cadman-LT
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Re: What is it
Cadman-LT   3/12/2014 1:43:55 PM
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bugs, that's what I meant. Only difference is ours had fans to pull the heat out.

Cadman-LT
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Re: What is it
Cadman-LT   3/12/2014 1:46:40 PM
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Ahh, pull it...probably push it, not sure which is more accurate.

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Colorado State University students have created “One Shot Two Shot, Red Shot Blue Shot” -- a Dr. Seuss themed target game where the objective is to get the most points with six shots from the gun.
This solar charge controller, which is placed between a solar panel and a battery, regulates the voltage and current coming from your solar panel. It is used to maintain proper charging voltage on the batteries.
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