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Advice on buying or building a wood burning stove  RSS feed

 
Adam Jonathan
Posts: 50
Location: Shenandoah Valley
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Hello Everyone,

Last year we built a RMH, and love it!

However, we live in a 3,000 sq ft old farm house, situated in a valley with very strong gusts of wind.

The house has two flus: one for the RMH, and another available to do some other kind of stove in another part of the house.

We would like to buy or build a stove that would meet the following qualifications:


1. Could burn overnight (vs. the RMH that takes very little fuel), or at least well into the night;

2. That would be capable of holding larger wood than the RMH;

3. That it would not shed (vs. the RMH, which sheds clay and sand); and

4. That radiates heats (vs. the RMH, which retains heat in the thermal battery).

If I can build a stove that meets those qualifications, I'd rather do that than pay a couple thousand dollars I don't have for a manufactured stove.

Any advice would be appreciated. I looked over some other threads, and there was one pretty cool one about a three-tiered Russian stove, but I'm not sure whether or not such a stove would radiate sufficiently.

Cheers,

Adam
 
Chadwick Holmes
Posts: 618
Location: Volant, PA
27
forest garden fungi goat trees wofati woodworking
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Well, if that's really what you are looking for, then my question for guidance would be twofold. Do you need it to be ultra presentable, what kind of BTU needs does it need to cover?

If it doesn't need to look like a wood stove......

There are steel drum kits that make steel drums into wood stoves, they work well, but cleaning the drums as you would for the RMH is suggested.

BTU needs.....

There is an additional expanding kit to have a second drum be a secondary radiation vessel of the exhaust heat, if you really need to put out the heat. I would also say if you can distribute that much heat too, because it really puts it out, and you may overheat one room in this way.

That's the cheapest widely available wood stove system that I know of.
 
Glenn Herbert
gardener
Posts: 2228
Location: Upstate NY, zone 5
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A stove that can burn for many hours unattended without damping down and making creosote and wasting wood is an advanced design project. I don't think any straight woodstove you could build without deep knowledge would be capable of that.

For larger wood capacity, extended heat with quick radiation, you could look at a batch box style RMH with a relatively thin masonry bell either around the heat riser, or following the exhaust from the standard barrel. A bell can be simple to build and very effective. You might even make a bell of two barrels stacked around/over the heat riser, and cover them with cob as needed to hold heat just long enough to last into the night but not for days as a standard bench RMH will.

As for the shedding clay and sand, you apparently have not put a good finishing layer on your RMH. There are plenty of threads in the Rocket Stoves forum about surface finishing, lime plaster, etc.

For detailed information about the batch box with steel barrel bell, see Peter van den Berg's threads in the forums at http://donkey32.proboards.com .
 
Dan Huisjen
Posts: 51
Location: Acadia Region, Maine.
6
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This thread is starting to age a bit, but here goes.

I find myself in a similar situation, in that I have a building where I want to live and I need better heat. My current stove is a Morso 2BO, but it's an older model without any refractory lining or clean burn air supply tubes. It's just not doing the trick.

I have three things I must do. 1) burn more. 2) burn it more efficiently. 3) Reduce the heat demand.

That third one is really the top priority, but It's on the week to month time frame rather than the "get it done before sundown" time frame. If you live in a big leaky house, make it tighter. Hunt for places that air is coming in, and seal them up. Search the attic for holes where air rises out of the house. These include the tops of wall cavities (common in balloon framed houses), the space around the chimney, wiring holes, and the hole where the plumbing vent comes up. Also search the basement walls and seal up holes however you can. If you have heating equipment or plumbing down there, it's part of your heated space, so make it just as airtight as the rest, allowing (of course) for adequate combustion air, preferably by a duct to your burner.

But back to our problem. The Morso is just too small and too inefficient. It's basically a fancy box stove, with and arch over the top and a cute squirrel cast into the side. Last night I stopped at a stove shop and asked if it could be retrofitted. No. It can't. But I also looked around at the offerings there. They carried several common good brands, including Lopi and Jotul. The sales guy pointed out that all of these use the same combustion system and get similar results. These stoves are all about 75% efficient, and the amount of heat they throw and the length of burn time are all basically determined by how big the firebox is. Looking around, I realized that the reason I wasn't seeing that long-burning, controllable output stove is that these are all simple boxes. The secondary burn is right there over the primary wood fire. The efficiency of the hot burn makes all the wood burn up quickly.

Meanwhile, I have a Shenandoah garage heater that I'm about to swap in for the Morso. It's ugly, but I'm guessing more efficient. It has a brick lined pit for a firebox. Below that is a shaker grate, and there's a very simple bi-metalic coil that operates a combustion air supply shutter, feeding air in below the grate. A the top, there's a 10" circle with a hinged lid to feed the fire. Just behind that there's a baffle and the flue exit. I should have this installed before sundown.

But if we take this a step further, we could make a taller stove with a narrower firebox, and a controlled secondary combustion air feed tube toward the top, or, better yet, as a separate burning unit. I'd want to start with some sort of steel tank. I'd make a space at the bottom for a grate and a similar mechanical thermostat air supply. I'd use a chimney clean-out for the ash clean out door, which would take a bit of welding to attach but be fairly cheap. And then I'd want the firebox to be a long air tight vertical tube, lined with refractory brick. I'd want a top loading updraft system where the fire is lit at the bottom, and creates wood gas. Then at the top (or piped from the top) there'd need to be a secondary combustion chamber.

I imagine starting a small hot fire in the secondary combustion chamber, using kindling and small logs. This would create a suction and draw air through the primary chamber. Once that suction is established, light the primary fire. Give it just enough air to smolder along and create wood gas, which makes that wood last a long time, but won't give much heat or complete combustion. The wood gas gets drawn into the hot secondary chamber, mixed with more air, and it burns based on that initial secondary priming fire. Once the solid fuel from the priming fire is gone, the heat of the wood gas combustion should sustain itself and keep burning. Now you have the ability to load huge amounts of wood, and burn them almost like an adjustable low pressure gas flame. It's combining the wood gas technology that can be used to run internal combustion engines with the secondary combustion ideas of modern wood stoves.

That's my concept. Someone else may have to work out the details.

One important safety note: Wood gas is mostly carbon monoxide and hydrogen. If these leak, they're both very bad for you. This is why a single body with primary and secondary combustion all in the same tube may be safer, and simpler. And this is why what I'll be pursuing is more of a tower stove with as good of separation for secondary combustion as I can manage.
 
Glenn Herbert
gardener
Posts: 2228
Location: Upstate NY, zone 5
78
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The details of wood gasifier stoves have already been worked out. From what I have read, they are the only practical technology for a long slow burn with good efficiency, if you don't want to have a mass that stores heat for later release. I don't have any experience with these myself, but look around the forums and the net for this term and you should be able to find technical info.
 
Matt Walker
Posts: 241
Location: North Olympic Peninsula
45
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Dan, if I had your needs, and was in your part of the world, I'd just drop the $2.5k on a Woodstock Ideal Steel or the like and be done with it. I've experienced them, they are incredible heaters. As a guy who would much rather tell you to build your own, I don't think it's very practical to DIY for cheaper than those are and get anywhere near the performance. Mud RMH's are perhaps an exception, but as pointed out, they serve different needs. That's my two cents on the "I need a box stove" question, anyway.
 
Dan Huisjen
Posts: 51
Location: Acadia Region, Maine.
6
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Glenn, I should have known.

Matt, those look like very nice stoves. I note that their lowest BTU output is 13,000 BTU per hour. My calculations for my coldest night of the winter say that, once I have everything buttoned up as well as I expect to, I should need 11,000 BTU per hour. Also, the Ideal Steel weighs 620 pounds, which would mean I'd need to think about my 50 PSF floor design load. And Woodstock stoves are all catalytic or catalytic hybrid. I've seen enough catalytic fussiness with my in-laws Dutchwest stove to be put off of them forever.

Right now I'm basking in the inefficient glow of the Shenandoah. I'm hoping to insulate my floor cavity with blown cellulose at the end of the week, which should cut my heat needs in half. A bit more air sealing and roof insulation and I should be down to about a third of my current demand per heating degree day. The interesting thing is that in my current set-up, with current weather and my floor uninsulated, I should need about the same amount of heat that I will in the dead of winter with all the weatherization work done. My new "house" is the second story of my old garage. I've been working on it for 2 1/2 years, and with my more recent ex having left me, I've decided it'll be easier to winter over in here than in my drafty 175 year old Maine farmhouse. My new "treehouse" is only 600 square feet of space. It really shouldn't be that hard to heat.

The simple answer for me is to get any available clean burn small box stove, and plan on throwing in a few sticks when I get up to pee on winter nights. I should make it through the winter on about 1 1/2 cords of hardwood, or a bit more softwood, with a 75% efficient stove. Wood is not that hard to come by, and I shouldn't waste too much time on getting the absolute perfect stove.
 
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