Picking a wood stove for a 30x36' hoop house.

[DancingWolf]

Status update, thread necromancy!

I wanted two 30*, or 60* bends, rather than such an unholy stretch of horizontal but I don't have any draft issues except when it was warming up. Greenhouse is currently venting all the fumes, the gasses killed all the gnats, so I doubt its nice stuff to be breathing even though my CO meter reads zero PPM but the sensor limitation is 30PPM.

Aside from my face feelling a little weird (chemicals), my only gripe is the hearth gets hot. Aside from stacking bricks on bare dirt, is there anything I can do to help insulate the wood supports underneath? only the center blocks are warm underneath but the stove has only been running for about two hours and not even a full load at that.

In hind sight I should have just made that side of the greenhouse corrugated metal and just run double wall stove pipe through it. For some reason I've been thinking chimney pipe was double walled pipe and it ended up being several hundred dollars in excess.

Oh, and it blasts heat. Don't wana be within four feet of it so I'm quite happy about giving it that extra clearance. Need to check on it again in an hour or so to make sure its not misbehaving on me. Loaded it up with mostly cedar and cardboard boxes, some oak rounds.

Bottom barrel registered >700*F, Top one at the front is 500*F, and the flue around the middle / wall is 300F which leaves much to be desired but the stove also wasn't packed full of wood. I need to put sand in the bottom of it and line it with fire bricks which will make it last years longer and probably help keep my hearth from lighting on fire.

There is a very dirty joke somewhere in this, but I digress, I have this thing sealed up nice and tight with cement and gaskets everywhere. Theres a little gap on the door, screws, and damper, but the fire consumes all of its oxygen within seconds of closing the door. I haven't installed a 2" pipe for airflow yet. Upon opening the door, I get a nice jet of flames coming back out as the fire explodes back to life. Will make a note of this.

-update-

A few hours later, so far nothing looks melted or burnt and the coals in the bottom barrel are coasting with a nice glow. Even with the door open and venting the gases, it was much warmer inside. I need to get a thermometer in/out door, supposedly barrel stoves can put out a 40-60*F difference between indoor and outdoor temps, even in single wall. Hope I didn't gas my plants to death.

 

[MAD MARK]

Oh boy.

Goodluck with that. Wish ya the best.

 

[bholler]

Wow.

 

[Ashful]

 

[SpaceBus]

If it works, then it works!

 

[bholler]

If it works, then it works!

Untill his green house burns down

 

[DancingWolf]

Untill his green house burns down

Which is why I posted an update here, if anyone has any improvements to add. . .

Flue can't go through the roof, only the nearest wall.

 

[barnaclebob]

How long did it put out useable heat?

 

[bholler]

Which is why I posted an update here, if anyone has any improvements to add. . .

Flue can't go through the roof, only the nearest wall.

Chimney needs to be higher way to long of a horizontal run. Chimney needs to be properly supported. And barrel stoves are scary as hell I have seen way to many melted distorted barrels and way to many fires caused by them to ever be ok with one. Oh and at the least the paint should have been burnt off outside. I hope there aren't any plants in there now

 

[Traveler004]

I'm hoping someone has some experience in picking an adequate wood stove for a hoop house (30x36', 6 mil poly film, single wall, 13-14' high in the center). Its in USDA zone 8B of Texas and we don't have too many nights below freezing, but it does stay 16-24*F for three consecutive says out of the year at some point and there are plenty of cold nights between November 15 and March 15. I'm growing Cactus and succulents inside it and I want to keep it a minimum of 45-55*F inside all winter. It will also contain vegetables near spring. The stove will be on a treated 2X6 floor, probably with a piece of concrete board and patio stones for a hearth.

Wood supply isn't an issue, I already burn it in brush piles to remove it, I'm constantly clearing brush. Most of what I'll be burning is cedar and bird berry (thicker trunk pieces), mixed with southern live oak as it becomes available. I'm aware of the creosote buildup from cedar and that it burns faster and hotter than other woods, so hopefully I can get a stove that handles it, or work around it with a smaller fire, heat loading the greenhouse during the day, etc.

The list:
Right now I'm looking at the Drolet HT2000 (probably out of my price range), Drolet Austral II, and the china harbor (northern tool) Model 2016EB. I prefer to avoid anything from China, it rarely lasts, but people seem satisfied with the Northern Tool 100,000BTU unit. The Vogelzang ponderosa also peeked my interest for its price and box capacity, but its from China. I would love to opt for the Model 2016EB for its price but the question is... will it hold up for at least 5-10 years? I'm picking up locally from either Costco or northern tool, and its tax exempt so I don't have to worry about that. I also looked at the Englander 30, but the thinner 1/4th inch metal has me shying away since if it got sprayed with water, it might warp.

Cost is an issue, $1,000 is my budget, $1200 if its super good. Efficiency isn't a priority, just durability and cost, I can always get more wood.

I'm estimating I'll need a bare minimum of 40,000 BTUs but don't want to refill the firebox every 4 hours, so a bigger 75,000 BTU+ unit is desirable. I don't want used, or cast iron. Cast iron, as nice as it is for storing heat, its too inefficient and will burn through wood like its candy.

Please no rocket stoves, barrel stoves, or hot water heaters!

Any information on the federal rebate program is great too. I stumbled over https://www.hearth.com/talk/threads/epa-updated-list-of-595-certified-stoves-for-2020.176138/ , but that list is tiny. Whats the incentive for people to get an EPA stove if only a handful qualify? Seems like a silly program.

Much love

I was actually going to suggest a rocket mass heater (rocket stove surrounded by clay) just because its a greenhouse and you don't have to worry about codes or any regulations. But since you against them, I would go with a biomass heater. But you are so far south you could actually get away with just a compost in the center of the greenhouse. Since you need compost for the plants anyhow you might as well get the heat from it. Anyhow the biomass heater can handle all the wood you mention without a problem as well as leftover oils and paper scraps etc. You load it up and it burns slowly for a long time. But the only one i know of is out of your price range. Along those lines I wonder if a wood gas camp stove would actually be enough for the small amount of heat you need. No one is living in there so as long as you have a carbon monoxide detector, I would do it. Because the chimney alone is going to be over your budget. Just a little super clean burning wood gazifier stove will produce enough heat simply because most of it isn't going up the chimney as it is with wood stoves. But really 2 or 3 or 4 carbon monoxide detectors lol. Apparently these stoves burn so clean they don't release any.. hmm... The other option within your budget you could run copper pipe around the edges to an outside cheapo wood stove you pick up of craigslist or something for a few 100 bucks. You don't need a chimney outside and just use hot water like a boiler. No chimney means it can burn anything. Not the greenest option but might be the cheapest. Maybe (broken link removed to https://cubicminiwoodstoves.com/products/cb-1210-br-cubic-mini-wood-stove)

 

[begreen]

Which is why I posted an update here, if anyone has any improvements to add. . .

Flue can't go through the roof, only the nearest wall.

The long horizontal run of stove pipe is going to soot up quickly. I would lower the stove platform or raise the pass-through so that the stove pipe can have a decent pitch of 1/4" per ft or more.

The chimney support is lousy. Get proper tee and chimney brackets that securely hold and support the tee at the bottom and one more up higher to maintain the 2" clearance requirement. I would also add a length to the chimney to keep embers further away from the plastic. Last, add a 1/2" mesh stainless ember mesh screen to the cap.

 

[Highbeam]

This isn’t a house. Don’t install this in a house.

The stove installation for this tarp shed only needs to be slightly better than a fire pit to vent most of the smoke to the other side of a sheet of plastic. Perfect place to experiment on the ragged edge of safety but readers should not replicate this in a real building.

 

[DancingWolf]

The long horizontal run of stove pipe is going to soot up quickly. I would lower the stove platform or raise the pass-through so that the stove pipe can have a decent pitch of 1/4" per ft or more.

The chimney support is lousy. Get proper tee and chimney brackets that securely hold and support the tee at the bottom and one more up higher to maintain the 2" clearance requirement. I would also add a length to the chimney to keep embers further away from the plastic. Last, add a 1/2" mesh stainless ember mesh screen to the cap.

The way its setup, its not much of a problem to clean it after ever few uses, pop the 90* bend off and sweep it out. I can knock the concrete stones out from under the legs but that will likely put too much heat through the rest of the stones and into the supporting wood frame. The whole pipe run should flex a few inches, though it isn't conductive to being bent. I may pull it from the hearth and see if I can set it directly on blocks and scrape away all the grass. I originally wanted to angle it but it wasn't cooperating with 30* bends which put it through the roof / too close to the wood support beams and 60* bends weren't available.

The support is indeed lousy but its all I had left to work with and the stack had to go up last night, yes, in the middle of the night / cold ass rain. I'll try to get the supports today, likewise, I want another 6-8" section of pipe at the top for clearance but it needs support first before I stack more pipe up. The draft pulls air quite well though and sin ce this isn't an EPA stove, thats not an issue, its purely that I don't want the pipe to melt the plastic. I have some scrap hardware cloth that I can wrap around the cap today, though I didn't see any embers coming out last night.

The stack looks weak and at first I thought it would just fall off the side, but its surprisingly sturdy, even in all the wind. Its 5' of stack so thats probably why, 7-8' if you include the interior barrel. The pieces lock together on rotation and clamp together. The greenhouse is surrounded by trees and thick forest so its got a wind break on all but the south side.

Though I do have a concern about the stack, I can keep my hands on the outside stack and its only warm in some places, modestly hot on the lowest joint connections. I get that the chimney stack is insulated and supposed to be interior stuff but is that normal? Its Selkirk brand and cost me a small fortune so it better be normal. It said 2" clearance but I'm sure 1" of that is being generous for liability concerns.

How long did it put out useable heat?

I didn't have a big fire in it, just a moderate one to ensure there were no horrendous problems like back smoking and CO buildup. it was burning nice after two hours and I guess it had another two hours of good burn in it. It will probably go for much longer with a larger fire and air control installed. I ran a test fire in it last night because it was pouring rain and fire hazard was minimal in such conditions. Even if it got out of control, its not burning mud.

CO meter wasn't going off so all the smoke inside was off gassing from the paints. I'll add that I didn't burn the paints off before hand because there is no water access at the location and a burn ban was also in effect. Now that its rained and I collected up at least some rain water, its a not much of an issue.

 

[Rickb]

Somebody burnt down my she-shed....

 

[Seasoned Oak]

Leave a few inches of ashes in there between fires ,the bottom will last a lot longer. And get yourself a laser temp gun to ck if anything is getting too hot above the pipes. A good fan will help a lot if you have any place to plug one in to distribute the heat better and keep the stove from getting too hot.

 

[SpaceBus]

Stack bricks around it. Get as much thermal mass as possible into the hoop house and you should have a pretty stout setup for your climate.

 

[DancingWolf]

Leave a few inches of ashes in there between fires ,the bottom will last a lot longer. And get yourself a laser temp gun to ck if anything is getting too hot above the pipes. A good fan will help a lot if you have any place to plug one in to distribute the heat better and keep the stove from getting too hot.

I keep forgetting to get firebricks and 2" pipe + valve (air control) so I can stop leaving the door cracked open. I intend to put sand in the bottom of it and line the bottom half with fire bricks.

Pulled 2' of horizontal pipe out so the total run is about 5' horizontal, still too much but its the best I can get. Likewise I got (2) 2X4s under the wall nub thing, it should be about an inch per foot, maybe a little less, so if 0.25" / 12" is some kind of requirement then thats fixed. I added some 1/4th inch hardware cloth on the top of the stack. Usually spark arrestors are fine mesh, not hardware cloth since it has to stop little specks of carbon, but I'll bite.

Interior of the pipe after one burn, quite nasty. I have a 6" brush on order. 400*F at the wall but thats during a raging fire, I'm guessing its supposed to be 800-1000*F? Insulated pipe says its supposed to carry 1,000*F gases but that would put a stove into glowy red molten territory?

The hearth soaks up quite a bit of warmth, so far I can keep my hands on it but I have a lot of extra big rocks lying around that I can put around the stove. I moved my 25Lb propane tank out for obvious reasons, they used to explode all the time in burn pits and that isn't fun. Most of the off gassing from the paints is done, still some smokey, chemical goodness in there. I did pick up a fan because all the heat wanted to stay around the stove, got a nice fan.

Last pictures are total setup and plant tax.
Seed grown Matucama, grafted to Pereskiopsis.

Fire lit at 6:15, 6:30 ish, nice and hot around 7:30, made my greenhouse uncomfortably warm and I packed it up for the night. I need to check the fire every few hours to get a gauge as to how long it will last since its freezing tonight.

I found 2-3 embers from the first fire still lit this morning but the stove was cold to the touch.

 

[EatenByLimestone]

1/4" is way to small. If you get creosote building up on it, it'll plug in no time. Chimney caps usually have 5/8" or larger.

 

[DancingWolf]

1/4" is way to small. If you get creosote building up on it, it'll plug in no time. Chimney caps usually have 5/8" or larger.

I have half inch available but I already put the stack back together and its a pain to do the ladder dance while holding it. I'll keep an eye on it since its by the door and I pass it every day. 5/8ths makes no sense, embers and sparks would go right through that, it would be like having nothing there at all.

 

[bholler]

Yeah that stove will clog 1/4" mesh in a few days

 

[Highbeam]

I have half inch available but I already put the stack back together and its a pain to do the ladder dance while holding it. I'll keep an eye on it since its by the door and I pass it every day. 5/8ths makes no sense, embers and sparks would go right through that, it would be like having nothing there at all.

It’s not really effective at catching sparks, think big chunks of floating cardboard.

 

[begreen]

That's an improvement, though the flue temp is high. Metal tape is not rated for this use. Use 3 screws per pipe joint, 120º apart, to ensure it is secure. The tee still looks like it needs a proper support and another length of chimney pipe should be added. Then you should be able to close off the key damper when the fire is burning well, which should help drop the flue temp after the damper.

I think DuraTech's cap screen is 1/2" stainless steel mesh.

 

[Seasoned Oak]

That second barrel makes all the difference in bringing down the flue pipe temps. Without it you could be in the cherry red zone. Id go for small hot fires over big slow smoldering ones.

 

[DancingWolf]

I toyed with the damper and closed up the door, opened the 2" plug, without air control there isn't much I can do about it eating up wood, but it does put the heat out. Fire dropped down to glowing / burning coals and cooled off a bit after 2-3 hours, so I restocked it with the new adjustments.

If I make enough money next year, I may replace it with propane heating, but having a local place install it would be preferable. I know they do tank installs and supply some local greenhouses, so I'll probably buy the unit I want, probably the tank too, pour a slab and have a working party do the rest.

The stove will stay in place for a grid down scenario, hurricanes wipe out the refineries, or for whatever reason I can't get access to propane, so I consider it a worthy investment. I keep two 25lb canisters of propane on hand because my small greenhouse is heated with electricity and it only takes one cold night without power to kill almost everything. Got a backup MADE IN AMERICA heater for it since my China trash patio heater clogged up. I may rip out all the safety crap in it just to see if thats the cause of failure. All one piece so its pretty difficult.

I had intended to keep the greenhouse warm all winter long but feeding a stove wood that rolls in creosote and eats more than I do is about as sustainable as keeping it warm all winter with propane, *cough* not very sustainable. Running it on just the freezing nights like tonight, the convenience and safety of propane would win, since I would not require 700+ gallons of propane, but far less. Texas only has a few weeks worth of below freezing nights. Usually in Jan 1st - March 1st, with all things, there are exceptions.

Given the costs, I'm not satisfied with the barrel heater but it will work for this winter, that is unless I can make it burn longer. Also gives the air a nice smokey flavor which has already gotten old.

That's an improvement, though the flue temp is high. Metal tape is not rated for this use. Use 3 screws per pipe joint, 120º apart, to ensure it is secure. The tee still looks like it needs a proper support and another length of chimney pipe should be added. Then you should be able to close off the key damper when the fire is burning well, which should help drop the flue temp after the damper.

I think DuraTech's cap screen is 1/2" stainless steel mesh.

I'll probably discard the spark arrestor when it clogs up, rather than replace it. For as expensive as this stamped metal cap was, you would think they could include some adequate cloth.

The flue temp is high? Doesn't creosote build up at <400? Just a page ago I was told 250 was way too cold for wall temps. . . Color me ignorant on wood stoves, I just want heat. Do I stick my thermometer on the bottom barrel? It would register >700 there.

I did use three screws but I also used tape as well because it helps keep the smoke in the stack. The last DIY stove attempt from years ago leaked smoke from every crevice, so I sealed everything up as tight as I could get it. The tee piece is locked into place and supported by a piece of 6-8" insulated wall pipe, it has like 7-8 locking cuts in it. The Tee is also being pulled up a bit by the supports and hardware ribbon. I was going to buy a support but there were none available, was told I would probably have to build one but its a short stack and probably not required since its secured by other means. That steel ribbon is held in with several 2 1/2" screws, as are the supports

What temps should I see at the wall?
-edit-

First DDG search gave me https://hearth.com/talk/wiki/what-is-a-safe-flue-temp-what-is-too-hot/ I suppose all is in order then. The insulated pipe is rated for continuous 1,000F use, I think 1,200 short duration, so 400 at the wall (600-800 in tube) during peak flames would probably be within the rating.

 

[begreen]

I did use three screws but I also used tape as well because it helps keep the smoke in the stack.

With proper draft there is a vacuum in the stove pipe. The smoke will stay inside.

The flue temp is high? Doesn't creosote build up at <400?

You are reading surface temp. The flue gas temp in the pipe is much hotter. It's inexact, especially on a horizontal run, but figure it to be 1.5 to 2x hotter in the pipe.