Extracting heat from wood

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MikeThePipe

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Dec 14, 2011
14
Rockies
Ok well I seem to be batting two for two on closed threads so let me start again...

Hi!
Im new to the forum and I want to burn wood to make heat. I am an engineer (software, so all that bootleg stuff you have is the reasin I cant afford a $2000 wood burning stove) but nevermind, cos I enjoy creating things and looking at problems in a new way. So, I have a fireplace. Its a very nice fireplace and I can plumb air to the front og it without any difficulty. It has nice glass sliding doors that do a fine job of making a reall cool looking fire that sends all its heat up the chinmney (about 2% thermally efficient)

So my first idea was a fireplace insert, but what if I change my mind as I want to do? Im stuck with a minimum $100 loss. So my second idea was a craigs list pre EPA. After looking for two months I concluded people are just listing junk. So next idea was a nast cheap Chineese made boxwood. For $130, how can you go wrong? Well this evening my forum welcoming comitted wasted no time in pointeing that out.

So I am going back to my basic needs. Burning wood, extracting heat. Hmmmmm.

Then I saw this video:
http://www.youtube.com/watch?v=ccGcVHVB3eg&feature=related

Perhaps what I should do is just bend up some steel/copper pipe into a grate and and mount it in the flames. Then throttle the fire with the air intake (very doable) and use a house fan with a car radiator in a cabinet.

Are there any engineers here that do inventive stuff like this or is this forum comprised mostly of expensive manufactured wood stove consumers?
 
I can't help you there. I am an expensive manufactured wood stove consumer. What I can offer you is the reason why I am an expensive stove consumer. I paid over 2k for my Jotul because it looks great, performs great, is very reliable, and I don't have to have a House fan or car radiator in my cabinet. I get all my wood fuel for free. I burn about 100 gal of oil each winter. My stove will be just about paid for after the first year of use and It doesn't look like I made it out of copper tubes and grates in my garage.

To each their own. Me personally, I'll pay for a reliable, great looking, low maintenance, efficient heating stove that saves me money.
 
Get a good stove and it will pay for itself. Remember, even with the heat reclaimer idea you have, your open fireplace will still be sucking the warm air out of your home.
 
If you are trying to get some heat out of the fireplace then what your proposing is doable. In fact if I read right this is what you are thinking:

http://www.woodlanddirect.com/Fireplace-Accessories/Fireplace-Heaters-Blowers

I just removed one of these without a blower and the convection alone would put more heat into the room than a standard grate. I took a hair dryer and rigged up a tube one time to blow air in the bottom and it actually put out some very good heat. Here's the issue:

1. There is no way to close the fire down so you are screaming through the wood. I could burn as much in a day that my insert burns in a week.

2. Although you are pumping heat out the top of the box your pulling in a massive amount at the bottom. So all your room air is going up the flue.

3. A fireplace may heat the room it's in but it make the rest of the house colder.

4. You have to keep the doors open on a fireplace to burn. Unless you are there to shut them at the end of the burn all the heat in the house goes right up the flue.

So I guess your are correct that this particular forum is more or less dedicated to people burning expensive consumer devices. It shouldn't be lost that fireplace is the fore father of these expensive consumer stoves and countless years of engineering have gotten them to where they are at. Also not trying to quell your creativity as you may happen on something that makes a current product better, but I wouldn't think you would want to use your home as a test lab until you had it perfected. Now for the reality of what most here are trying to tell you. Yes stoves are expensive and a complete install may cost 3-5K, but just like anything there are good used alternatives out there. If you read through the posts here a great number of people are installing used stoves and inserts. I just installed an older EPA insert a bit over a month ago that cost me $250. By the time I lined the chimney and built a hearth I was in it for 1K. Pretty sure I'll get most of that back in NG savings this year. But you are looking at a time of year when everyone gets their first heat bill and has the same idea as you. Lastly there are a lot of good folks on here with a lot of experience and if you ask their opinion you'll get it. It may not be the one you want.
 
"squeezing blood out of a turnip" i think is an saying my dad used....

you can increase - minimally - the amount of heat put into the room with a hearth heater, but another part of the equation is heat loss up the chimney, which you are not addressing. plus dollar loss in wood consumption. i think i can recall some dp/dt calculus stuff from a hazy period of my life in the early 70's that you could play with with the volume of heat going up the chimney and the volume of heat a hearth heater produces. but it is not worth the effort, for the price of a few cords of wood, get an insert or stove.
 
It may be a lot of money but look what you get for it. A safe, easy to operate 7 months/year piece of equipment that can substantially lower your heating costs. I spent $100 last year on fuel (time is free). 6 years ago, 3000 gallons of propane went through the forced air furnace. We have a 30 year old steel box slammed in our fireplace at the camp that we paid 50 bucks for. Doesn't compare to the $3K+ stove at home from a performance standpoint but is infinitely better than the fireplace.
 
MikeThePipe said:
Are there any engineers here that do inventive stuff like this or is this forum comprised mostly of expensive manufactured wood stove consumers?

Mike:

I'm no engineer, but I enjoy experimenting and modding too. (I heat with the antique - thoroughly modified - stove in my sig.)

However, I like to do things that work when I'm done... and that are at least close to 'right'.

Neither the Vogelzang nor the 'hot water fireplace' conversion are likely to provide you adequate - let alone safe and reliable - heat.

In the end, isn't that what you're looking for? And NOT a 'trial by fire'?

Would you insist on using software you knew to be buggy enough to cause terminal hard disk corruption?

Think about it.

PB

-----
 
Keep and eye on Menards as they just had the Defender High Efficiency Wood Stove on sale for 399 not much more than what you paid.
Its fire box size is compareable with the one you just bought.

Its EPA Certified and UL Approved tested by Omni Labs.
 
I think if you want to play around with the project, then you should think about both extracting heat from the fire and about burning wood completely. In addition to the pipes you mention, is there a way to create secondary burn of the gases and smoke the way a modern stove burns? This requires high heat so maybe it is not feasible because it would mean changing basic construction of the fireplace. The heat extraction part of the system seems sort of ugly but not dangerous (won't burn the house down), so i say go for it.

if your goal is just to heat your house at minimum hassle and highest efficiency, buy a lower cost but new EPA approved stove.
 
MikeThePipe said:
Ok well I seem to be batting two for two on closed threads so let me start again...

Hi!
Im new to the forum and I want to burn wood to make heat. I am an engineer (software, so all that bootleg stuff you have is the reasin I cant afford a $2000 wood burning stove) but nevermind, cos I enjoy creating things and looking at problems in a new way. So, I have a fireplace. Its a very nice fireplace and I can plumb air to the front og it without any difficulty. It has nice glass sliding doors that do a fine job of making a reall cool looking fire that sends all its heat up the chinmney (about 2% thermally efficient)

So my first idea was a fireplace insert, but what if I change my mind as I want to do? Im stuck with a minimum $100 loss. So my second idea was a craigs list pre EPA. After looking for two months I concluded people are just listing junk. So next idea was a nast cheap Chineese made boxwood. For $130, how can you go wrong? Well this evening my forum welcoming comitted wasted no time in pointeing that out.

So I am going back to my basic needs. Burning wood, extracting heat. Hmmmmm.

Then I saw this video:
http://www.youtube.com/watch?v=ccGcVHVB3eg&feature=related

Perhaps what I should do is just bend up some steel/copper pipe into a grate and and mount it in the flames. Then throttle the fire with the air intake (very doable) and use a house fan with a car radiator in a cabinet.

Are there any engineers here that do inventive stuff like this or is this forum comprised mostly of expensive manufactured wood stove consumers?

Hi Mike.
Yes, there are lots of engineers who post here, as well as myriad representation of humanity from all walks of life.
I am keen on a do-over as well; why don't we start with the size of your home, number of floors, rough age of house, type of windows
and some estimate as to the amount of insulation. Also helpful would be a slightly more precise (though not pinpoint) location to get an idea
of the temperature differentials you will be dealing with.

I think if you look into the Englander brand of stoves, you will see that they are not that expensive, certainly not the levels you are quoting.
The issue them becomes ensuring the model you choose is sufficient to the task.
 
Youtube mentos and coke car. Just set a record for distance i believe. However im not about to make one and drive it on the street.

Can your idea be done yes. I dont see why youd write hundreds of lines of code, when far fewer would do.

This is trying to mesh mechanics and themal properties, if it worked it would be sold commerically and we all would have one.

Maybe use this software knowledge you have and try a project such as a thermocouple controller with a PID loop and make digital thermostat mod for stoves. Do a search here on thermometers and youll see a desire/market for something like that.
 
Your title for this thread is "Extracting Heat Out of Wood," which makes me believe that you are interested in burning efficiently. The mod stove that is discussed in that YouTube clip is a nice bit of ingenuity, but a heat exchange through the fireplace still has many of the problems of a fireplace -- most of the heat in the room is going up the chimney, there is no ability to control the airflow (making you burn most of the heat in the wood up your chimney), and there is no ability for secondary combustion. All of these means that you really haven't extracted much heat from your wood -- especially compared to what you COULD be doing.

I'm with you on the low-income side of wood burning. I saved up for over a year to buy my stove this summer, but I can tell you it was worth it. I haven't burned any oil this winter, and I'm not expecting to go through the full 275 tank, or anywhere near it. With oil at ~$3.50 around here, that means that the stove really does pay for itself quickly.

Also, you don't necessarily have to commit to a full-size, brand new stove. There are good deals on EPA stoves on Craigslist or the local paper, if you keep your eyes out. And if you keep reading these boards, you'll find there are even more ways to save money on the install. My chimney needed relining and I needed to build a hearth, neither of which I had any money for. Thanks to the know-how I got reading Hearth.com, I scored a free piece of 20 ft stainless steel lining, installed it myself, and built a hearth on my own. Total cost of the stove install, chimney relining, and hearth? -- $50. A chimney sweep came and gave it a quick inspection and said that it looked 100%. I couldn't have afforded the 2k-3k to have had it done professionally, but there are ways to save money without compromising on safety or stove performance. Hang in there and get something EPA!
 
Some good responses here.

>Menards.
Yes I called them several times for another item they had on slae a month or two ago. Their closes store is in montana. Shipping was $260+ so unless any of you happen to be driving to CA for xmas and have room in your car...

>There is no way to close the fire down so you are screaming through the wood... all your room air is going up the flue. Unless you are there to shut them at the end of the burn all the heat in the house goes right up the flue.
Aa I mentioned, tho not in much detail, I plumb air to the fireplace so NO room air goes up the flue. I can also throttle the fire somewhat with this setup.

>you can increase - minimally - the amount of heat put into the room with a hearth heater,
I had not seen those. Thanks for that. They are a little expensive for what they are so I would probably weld up my own, but to use those, I would need to open the glass doors and that would suck room air so thats why I was planning on using recirculating water to extrac the heat.

>if it worked it would be sold commerically and we all would have one.
Ah well now we are moking assumptions about the market. If you have ever had a good idea, patented it, produced it and then tried to sell it, you will know the fallacy of that. Some of the best ideas have died on the rocks of distribution and store placement. In that last few years, the internet has leveled the filed a little, but do any of you know what a Chofu heater is? That is an idea I would love to expand to a wood stove.

If we are talkign about good ideas then a masonry heater is much more efficient than a wood stove. It burns a t maximum efficiency and the radiates the heat (way better) for hours. Dont see any of them for sale at MyGreatlyMarkedUpWoodStove.com...

Englander.
Looked at them over the last three months also. I can get them here, but we are talking 8x the cost.
http://www.homedepot.com/buy/buildi...-ft-satin-black-wood-burning-stove-64876.html

I am trying to heat <1000sqft in a 60's house with roof insulation, double galzed windows and wood floors (that act like a refigerator). The gas furnace does a decent job, and even tho we rarely see temps in the 30s, it costs about $100/mo. So I am not going to save $3k any time soon.

I love the IDEA of a wood stove, but the prices are waaaaay pout of line with thier utility value for me. If I lived on the east coast then your arguments make much more sense.

Havign spoken to a couple of manfr, it is plain that the markup on these nice models is gettign close to that of furniture (500%) and I just dont do that. Vlaue is not assigned by ticket price.

I DETEST the Chinese system, their record on human rights and their carp products. I buy lots of Chinese made things at stores where I can return them, and I return them. I use them and return them. I would buy an american or european product in a hearbeat if I could justify it., but there are a few other expensive items on my shopping list.
 
If the goal is guaranteed heat, then don't waste money. A proper and safe heater is an investment, not a science experiment. This is like the difference between buying a bunch of fuel savings gadgets for a car that are mostly snake oil vs getting a car with great fuel mileage designed in. If you want something that you pay for once and enjoy the warmth and savings for years, it will cost a bit. (And budget for a liner too.) A proper, safe installation will not only help with heating bills, but it's also is power outage insurance and still offers a far better view than television.

If the goal is just some extra warmth on occasion, then a blower grate will help, but at half the cost of a good insert I think it is money poorly spent, unless this is just for an occasional fire.

My suggestion, if it will fit, is to install a made in America, Englander 13NCi. It's currently $1099 because this is peak season. But at least that is the delivered price:
http://www.overstockstoves.com/50tnc13i--epa-certified-noncatalytic-wood-stove--1550131500.html

If you want to save some money, be patient and wait for a good stove on craiglist in the spring or watch home depot and lowes clearance sales in late Jan. and February. Overstockstoves also can have some good sales in late season. There is also a remanufacturer of Englanders, but I don't have that link handy. Maybe someone else can post it.
 
A cheap epa stove from one of the national chains is the best deal out there. They are well made, simple and efficient. Do what you have to do to get one and enjoy your next 30 winters.
 
>My suggestion, if it will fit, is to install a made in America, Englander 13NCi. It’s currently $1099 because this is peak season. But at least that is the delivered price:

Ooooooh I like that.... their number is constantly busy, but I will cal them.

Since we are talkig about heat up the chimney, I saw some numbers recently that put a throttled fireplace at about 10cfm/min and a wood stove at about half that. So even if I get a wood stove, to me, it makes sense to plumb air to it from the outside rather than sucking it out of the house. I bleive these are called "mobil home" wood stoves?
 
What you're talking about is an Outside Air Kit (OAK). Required for mobile home installations, optional in most others. Lots of folks have installed OAKs and are quite happy with them. Sometimes it's just too complicated because of the specifics of the installation location, or the owner simply doesn't want to install one. Most any modern stove or insert will likely give you the option of piping up an OAK or not, as you see fit. Rick
 
I picked up a used englander 30 (the 13's big brother) for under 400 dollars that was used 1 year. The cost to line my chimney myself was about 500. I went from a pre-epa stove (a sturdy fisher) to this new unit and my house stays warmer, my chimney is safer and stays cleaner than ever, I can go longer between reloads, and I went from burning 5.5 to 6 cord of wood per winter to about 4.5 cord.

If money is the issue, keep an eye on craigslist. Sounds like you are in a remote area so your options may be less, but while the old stoves can be very sturdy and very safe, the prices aren't all that much less than a modern unit these epa stoves are truly a step above their predecessors.

Good luck in your search.

pen
 
Its all been said already... Any type of heat exchange is nothing more than a method to move the amount of heat you are releasing someplace else a bit faster. Ift does nothign to get more heat from the same volume of wood - to do that you have to burn more completely and slow the flue gasses enough to extract the heat. Think air tight firebox, insulated reburn chamber , superheated secondary air, catalsysts..

... oh wait we have something like that already - an EPA stove.


IN all seriousness... not trying to have fun at your expense.... Its just that the effort to home brew something that really is going to equal even the least expensive certified stove will take a long time and require an investment in tools and material that will cost more than just buying one. Are you ready to learn welding? Got a plasma cutter handy? You get the idea.

I'm not a software guy though I work at a software company. I did go to Mechanical Engineering school once upon a time. I took heat transfer, thermodynamics, materials science, etc. I did work in the metal shop and if needed I can get those old books out of the attic and lookup the math to design something like this... But there is no way in hell I would waste my time.


Get on Craigslist buy a used EPA stove.
Be happy :)
 
Just saw the rest....

MikeThePipe said:
>if it worked it would be sold commerically and we all would have one.
Ah well now we are moking assumptions about the market. If you have ever had a good idea, patented it, produced it and then tried to sell it, you will know the fallacy of that. Some of the best ideas have died on the rocks of distribution and store placement. In that last few years, the internet has leveled the filed a little, but do any of you know what a Chofu heater is? That is an idea I would love to expand to a wood stove.

You are making assumptions as well. the main reasons many of these don't take off is that they do not address the inefficiency of the open fire or satisfy environmental and safety regulations.

MikeThePipe said:
If we are talkign about good ideas then a masonry heater is much more efficient than a wood stove. It burns a t maximum efficiency and the radiates the heat (way better) for hours. Dont see any of them for sale at MyGreatlyMarkedUpWoodStove.com...

Masonry heaters are out there. The thing is you have to build it into the house. But there are determinately companies that build them. Google search is your friend :)


MikeThePipe said:
I am trying to heat <1000sqft in a 60's house with roof insulation, double galzed windows and wood floors (that act like a refigerator). The gas furnace does a decent job, and even tho we rarely see temps in the 30s, it costs about $100/mo. So I am not going to save $3k any time soon.

With natural gas as dirt cheap as it is today if you are only burning $100 a month there is really nothing that's going to make wood a money saver for you unless you have a free supply of wood available.



MikeThePipe said:
Havign spoken to a couple of manfr, it is plain that the markup on these nice models is getting close to that of furniture (500%) and I just dont do that. Vlaue is not assigned by ticket price.

I DETEST the Chinese system, their record on human rights and their carp products. I buy lots of Chinese made things at stores where I can return them, and I return them. I use them and return them. I would buy an american or european product in a hearbeat if I could justify it., but there are a few other expensive items on my shopping list.

Uhh... I really doubt that. Do you have any idea what it costs to build and run a cast iron foundry? Id be surprised if companies like Vermont Castings, Hearthstone and Woodstock who make their stoves here in New England make even 20% margin. This is not software... people and IP costs are only a fraction of the investment for a stove manufacturer.

If you don't like Chinese made then put down the bucks and support some American jobs. For the small house and mild climate you are in an Englander 17-VL will do. They are well regarded on here, American made and only $700 brand spanking new. There is a 30% tax credit bringing the installed cost down to around $400 (+ pipe/liner costs). A second hand one might only be a couple hundred. As a guy who works with software developers I would bet you have a house full of electronic gadgets worth far more than that. Bottom line, If you can afford to pay a mortgage or rent you should be able to scrape that kinda money up.

You say you have other "expensive things" to buy. Maybe you need to reevaluate your priorities. Is this really as important to you as you are trying to convince yourself it is? Or is its just a thought experiment to pass the time?
 
jharkin said:
Uhh... I really doubt that. Do you have any idea what it costs to build and run a cast iron foundry? Id be surprised if companies like Vermont Castings, Hearthstone and Woodstock who make their stoves here in New England make even 20% margin. This is not software... people and IP costs are only a fraction of the investment for a stove manufacturer.

If you don't like Chinese made then put down the bucks and support some American jobs. For the small house and mild climate you are in an Englander 17-VL will do. They are well regarded on here, American made and only $700 brand spanking new. There is a 30% tax credit bringing the installed cost down to around $400 (+ pipe/liner costs). A second hand one might only be a couple hundred. As a guy who works with software developers I would bet you have a house full of electronic gadgets worth far more than that. Bottom line, If you can afford to pay a mortgage or rent you should be able to scrape that kinda money up.

You say you have other "expensive things" to buy. Maybe you need to reevaluate your priorities. Is this really as important to you as you are trying to convince yourself it is? Or is its just a thought experiment to pass the time?



+1 jharkin. Well said.
 
My own take on things . . . I completely understand not having a lot of money and wanting to get cheap heat . . . but as mentioned earlier there is a difference between spending a little bit of money on things or ideas that may or may not work and spending a little more money for a proven (and safe) design that is known to work. Sometimes one has to look at the long view of things.

If the goal is safe and cheap heat I think the Englander line up would be your best bet . . . or take some time to learn how to identify a good, quality used stove from a beat-up, overfired piece of junk and go used.

Good luck . . . and welcome to the forum.
 
Welcome to the forum indeed. Every one of my posts has received a torrent of angry responses from people that "know better" and when I rest the waters a little (suggesting galvanized pipe forexample), moderators give me factuous statements like "No room for discussion. It’s wrong, it’s not safe, end of story." Its pretty clear to me this forum is cold an uninviting to anyone that has ideas that do not encompass your mainstream, consumeristic approach. OK.

If you want a backslapping club here, thats fine, but please make that clear in the registration process. Heavily moderated forums with a slew of members that jump at the chance to flame newbies are all over the place and its very tiresome. Luckily I am able to sniff this out fairly quickly with the provocative posts I make so I do not waste time in an environment that I am likly to clash with sooner or later.

My humble suggestion if you want to attract new people, is take a more gentle approach and allow people to have thie say. What a boring world it would be if we all thought the same way.
bye bye
 
Bye.
 
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