Stove pipe exit--cooking

[hierony]

It looks like this is the forum section for

heating

in yurts. In this particular case, I'm looking at

heating

my food

I was thinking about the best way to cook my food. Electricity is easy & common, but only really economical if you have grid-tie with multiple circuits. I'm working off just one 15 amp circuit (100 ft extension cord, 12 gauge) so cooking can be tricky. My induction cooktop and slow cookers do well, but I want to switch to solar power eventually. The induction burner would require fairly high power, requiring more batteries & bigger inverter, etc. Plus it's only a single burner. The slow cookers will do fine on solar though (50-150 watts, 500 w*hr daily or such).

So I looked into wood cookstoves. Usually pretty big and cumbersome and expensive or really tiny (think camp/backpacking stove) without a chimney. Eventually I came across the Ecozoom Plancha--a "two-burner" rocket stove with a chimney, albeit $400. See here. At one point I ran across the figure '7.5 liters (~2 gal) water boiled 26 minutes'--pretty respectable power.

Anyhow, the thing uses 2.75" 'chimney' pipe that's up to 8 ft tall. From my reading, this is actually exhaust pipe (from motor vehicles) adapted, so I can't exactly use regular stove pipes/equipment directly. I'll be putting the stove in the middle of the yurt and running the chimney stack through the crown ring.

So the tricky part: I don't know the chimney pipe temp where it'll be going through the crown ring (it should arrive Monday and I'll start testing shortly thereafter). I'll keep the canvas away and use metal flashing to cover one of the crown ring sections. But I also want a good/decent weather seal and the lowest reasonable risk of burning things possible. So I was thinking of getting a silicone flashing boot and a 3" sealed double wall pipe section (12" or so). So it'd go: hot 2.75" chimney pipe inside 3" double wall pipe (1/8" gap ring sealed using some high-temp something or other) going through the silicone flashing boot screwed into the metal flashing in the crown ring.

Other than that, my main worry will be making sure the thing has the appropriate spark arrester and is high enough above the crown ring (3 ft).

Thoughts?

[Jafo]

I am really glad I found an old propane gas range lol. Seriously though, keep us posted on how this works out.

In the winter, we cook on the wood stove from time to time, but mostly slow cooking meals like stews, sauces and pot roasts. I don't even want to think of having to do that in the summer. It would just be too hot.

[Bob Rowlands]

Cooking over a fire in the summer was the norm until quite recently. I did it camping when I was young. No interest now though, I don't like hunkering down if I can avoid it.

As far as wood stove goes, make sure you pipe is tall enough that very few sparks land on the tent while still burning. Just check the system in action and you'll know what is what with it.

I built an arrestor for my pipe from 1/4" welded wire mesh, and doubled it over to make an even tighter mesh. Between that and the stack being 3' above the yurt ring I have maybe six burn holes in my cover after three years of (intermittent) use.

Skinny 2.75" stove pipe will create a very vigorous draw that should burn pretty clean, >based on video I have seen< This is something I do not know from experience so take it as is.

IMO you should have a 3/4" to one inch air gap between the inner pipe and outer pipe. That is the norm for a double wall 'rated' wood stove pipe. Also that is how I built my stove pipe since I wasn't about to spend 300 bucks on a rated double wall pipe.

Be aware that if the bottom of the double wall pipe is exposed to the inside air it will draft to the outside. That of course is a two edged sword.

Good luck.

[hierony]

I'm hoping this cook stove doesn't heat up nearly as much as the standard big wood cook stove. It is designed to cook and not heat space--the rocket design with a good thick ceramic lining should help. It's coming into summer here so I'll find out. Worst case I'll just make an outside cook station. I'll certainly keep you guys posted.

Bob: Three holes in three years is pretty good. But I'll probably be putting on some lumber wraps here shortly (black side out during winter for absorbing heat, white side out during summer for reflecting heat) to protect my canvas a bit. I should probably do an ember burn test to make sure any sparks wouldn't ignite the material & roof... Glad to know the homemade arrester works pretty well.

The unsealed double-walled pipe with inherent drafts is what I'm trying to avoid. I stopped by the hardware store today--they had 3" & 4" pellet stove pipe (double-walled and sealed, the gap filled with stove gasket and the walls crimped together on one end) in both 1 ft & 2 ft lengths for ~$25. I'll have to check the OD on the stove pipe, see what kind of gap I'd have. There was also some bulk 5/16" stove gasket that I could use to bridge the gap between the stove pipe & pellet pipe--I've used high temp stove sealant before, but it was brittle and I'd expect it to break/crack relatively quickly. I wouldn't be surprised if the .75-1" gap was for larger pipe diameters (5-10" ID)--there's probably some convection in there though.

I guess I'll just have to run the stove a couple times outside to see what the chimney temps are like. I read somewhere that flue gas temp (inside the pipe, a foot or two away from the stove) should be around 900 F/480 C for a clean burn. Cotton will start burning around 250 F/120 C if it's oily, more like 390 F/200 C with a flame source, and auto-ignite at 750 F/400 C (don't quote me, I'm using suspect internet sources). So I'll check to see what the temps are on just the bare stove pipe and then with the double-wall pellet stove pipe (making it effectively triple wall!). That'll tell me if the thing will be cool enough to go near my canvas yurt home.

[Bob Rowlands]

A bit off topic, but I was extremely concerned about my wood stove installation regarding pipe temp and combustibles, the ring and the canvas cover. I mean really edgy to where I was nervously sticking my hand up at the pipe exit through the ring to check the air temps, canvas and ring temps, at various burn times and lengths of time. I even scrtached the paint with my nail to see how soft it was getting. lol I absolutely didn't trust my own install. It took quite a few hot burns before I finally relaxed with the stove cranking out the heat.

Yes my stove pipe is six inches and the outside pipe is eight inches. BTW I originally insulated between the two with fiberglass. Big mistake. Anyone reading this, do 'NOT' do that. Just trust me. Don't do it.

Also, it is always windy here. That helps disburse the few embers that escape the arrestor. While I was going through the initial edgy period I just stood outside and watched the pipe and embers to see what was going on up there. Not only was I concerned about my yurt, but I didn't want to set the field on fire and have the fire department come out and test the waterproofness of my yurt cover. lol

[kochevnik]

Definitely interested on the progress. Can you share some pictures please

[Wintergreen282]

I didn't read your whole post carefully. Good, just too technical and my wood stove is already in. Have you ruled out propane?

Like Jafo, I do use my wood-stove for some cooking, but only if already fired up for heating purposes. Otherwise I cook 100% with a 2 burner Colman propane camp stove. Removing the top cover makes it look sleek - less camping like. Great size for a yurt. Whole thing has worked great!

(Also bought their tiny "oven" which works so so in a pinch.).

Brand new the whole system would be under $200. Waaaay cheaper if you bought second hand or scrounged.

A twenty gallon tank hosed to the outside lasts multiple months - even heating water for dishes, personal hygiene, and up to three hot water bottles to warm up the bed at night (and my friends think I am roughing it! They have no idea just how comfy I stay. Lol). Winter or summer, I've never had a problem - even with extreme New England temps. Last tank fill-up was under $7.

A nice set of cast iron makes clean up a breeze.

I'm fairly smell sensitive and not crazy about the stink of propane heaters, but haven't noticed the stove being an issue. Only when the gas is about to run out - which actually gives you a heads up.

[hierony]

In general I like the idea of wood better than propane. I've a propane heater that I use some for now, and I don't like the atmosphere it makes (full blast heats the place up nice though for the chill, rainy days). It costs $15-19 here to fill up a small tank (~$3.50/gal). The area has trees around, and one of the ideas with this stove is that it can burn just the branches. And there are quite a few brush piles. So in other words, free renewable fuel for the taking! And I'd be reducing burnables in the case of a wild fire.

My main point in posting this was to get stove pipe exit methodology. Most other stuff I've seen is for the modern yurts/wall exits, whereas I'm doing a

center ring

exit. I should have the materials for it all shortly though, for testing. The second point was just to make people aware of a potential option.

I've some pictures and I've used the stove twice so far. Learning it's quirks--I haven't burned wood in stoves much before. I'll try to post some things soon.

[hierony]

In terms of ovens, there's a number of contraptions you can get that sit on top of a burner of whatever fuel source.

For a cute $100 terra cota setup: Terracotta Pizza Oven | World Market

For a slightly different, more metal oven for $125: Artisan Outdoor Oven 30 Accessory

I've seen a few others, too. Don't know how well any of them work (or don't) though...

[Jafo]

I think for heating, you're dead on by using the wood. You will also be able to cook with it, but I think you're going to find it hot to do in the summers and also limiting because there are some things that are a pain to cook. Pasta or deep frying or roasting for example. So you may want to consider at best, an outdoor cooker.

For my yurt, we use propane for the cooking. I generally go through about 40 pounds of it a year, but if I lived there full time? It would be more like 120 I would imagine. That's taking into consideration cooking some of the time on the wood stove.