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The Goldilocks Stove.  RSS feed

 
Dan Huisjen
Posts: 51
Location: Acadia Region, Maine.
6
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So, here I am in "The Treehouse". I'm going to live in this former garage second story this winter. I'm working on air sealing and insulation, but where I am right now, with current outside night temperatures, gives me a similar heat load to what I'll have in the dead of winter with the place buttoned up better. It'll be me and the cat in 600 sq.ft., no running water once the hose freezes, and graywater drains to a leaf pile for waste water. We each have our own litter boxes, with surprisingly similar technology.

I put in a metalbestos chimney, and I'm trying out all the stoves in my collection to see what works.

The first stove was an old Morso 2BO, which is a very cute cast iron box with an arch over the top. I'd say it worked worse than the barrel stove in my shop. It had very poor air supply, and that resulted in a smokey fire unless everything was raked up to the front. There are new versions of this stove which are very efficient, but this isn't one of those. It wasn't keeping me warm enough.

The second stove was a Shenandoah garage heater. This is a vertical barrel with a combustion air supply mechanical thermostatic damper. That part is very nice. But the stove is a brick lined barrel with a grate at the bottom, and no secondary burn. When it was stoked up, it would cook me out. But it wouldn't simmer. If I tried to keep a small fire in it, it would smoke, like an open fire in a big room with a hole in the roof.

So, on to stove #3, which is a Scandia 920 coal stove, in which I'm burning wood. There's an old newspaper ad for this stove here. I replaced the door and ash clean out door gaskets, gave it eight new fire bricks, and hooked it up. The firebox is about 16" wide and 9" deep, and 9" tall to the top of the firebrick. It doesn't hold much wood, but it burns it very well. I can see through the tiny mica slit windows how it has that slow hot flame, almost blue in places, that's the sign of efficient combustion in a stove. And when you lift the grate off the top, there's a flat plate that you can cook on. I haven't tried frying anything, but I've got my big water heating pots on there now and they're up to scalding.

The fire doesn't last very long though. I think I'll replace the coal grates on the bottom with flat steel plates and see if that slows combustion at the bottom. I suppose I could even try lining the ash pan area with fire brick and extending the fire box down there, but that seems like a risky modification.

But let me tell you all about the excitement last night. I had the very first fire for this stove in the late afternoon, and that went well but seemed uncontrolled. I'd replaced the door gasket, but realized the ash tray gasket was still unattended. I had a look and saw that it was totally gone, and I found that I had just enough gasket material, so I got that fixed. Then I had an evening fire, which seemed to be burning slow and hot. I stoked it as full as I could just before bed at 10:00. At 10:20 I heard odd sounds. I pulled out my thermal camera and had a look, and the pipe that was 200° earlier, with a good fire, was now off the chart at over 500°. I was having a chimney fire, burning off all the soot left by the previous two stoves. There I was staring at it in my birthday suit.

I threw on some light clothes, and kept looking. I had it damped all the way down, so I couldn't do anything that way. Nothing catastrophic had happened, but I realized there were some pinholes in my old single wall pipe. I dabbed at them with the gasket adhesive to reduce O2 to the chimney. And I watched. It burned up the soot and slowly cooled. I went back to bed.

And this morning I took the pipe apart and decided that there's no damage, but there are things to do to it. Those things don't stop me from having a fire right now, which is good, because it was 16° out last night and 45° inside when I woke up. (I've got this nice down comforter from the transfer station, in a cover, and I've recently found that sleeping under just that is warmer than if I'm under that plus blankets and sheets...)

So here's my plan: First, I need to put a clean out directly under the vertical metalbestos pipe that goes up through the roof. And I need a brush to sweep that pipe. Second, even though it's all just friction fit right now, it all needs to be screwed together. Third, that first vertical section of pipe, just above the elbow behind the stove, needs to be slightly taller, and I want to use very large hose clamps (or similar) to bundle a bunch of 2" steel tubes around it. Very Facist, in the original non-political sense of the word. This will act as more radiant surface, and convection up through these tubes will cary away even more heat. And it will be very simple to do. And fourth, I need a damper in the flue, rather than just relying on the stove air supply. Oh, and fifth, I'm going to have to cut my log wood smaller, because this 16" firebox really needs 14" or smaller logs. But since much of my wood is clean lumber scrap or industrial hardwood waste blocks in the 2-5" range, this is no big deal. And sixth, maybe I should see about getting that big CO2 extinguisher re-filled and hung somewhere in the treehouse.

And hopefully, once all that's done, this stove will be Just Right!
 
Dan Huisjen
Posts: 51
Location: Acadia Region, Maine.
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After discussing the event with a neighbor who's experienced a chimney fire, he says it wasn't a chimney fire. If it had been a chimney fire, it would have sounded like a jet engine and the chimney cap would have melted away. it was more likely that I over fired the stove, and had no good way to control it.

So, I've added a piece of thin metal plate to the bottom of the firebox, covering the coal grates and reducing the air that can flow up through the bottom of the load. Air will come through a gap in the front from below. I've also replaced some of the stove pipe and added a stove pipe damper, so that if it gets too hot again, I have another means of bringing it under control. I still intend to add a clean-out, but the one I have on hand turned out not to fit with the pipe I had.

Saturday morning, a friend and I will be insulating the floor with blown cellulose. That should reduce my heat demand considerably.
 
He's dead Jim. Grab his tricorder. I'll get his wallet and this tiny ad:
2017 Rocket Mass Heater Workshop Jamboree - 15 workshops in one event
https://permies.com/wiki/63312/permaculture-projects/Rocket-Mass-Heater-Workshop-Jamboree
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