# Wood stove hack-secondary burn tubes added



## sesmith

A week or 2 ago I put a question out on this forum here:
http://www.arboristsite.com/showthread.php?t=85750
Basically, I wanted to know if replacing my stove with a more modern EPA stove would save me much wood. Since I cut my own wood and our stove is in the cellar (where it's not part of the furniture in the living room), it would be pretty hard to justify the $2500+ for a new one, and the one I've got heats the house pretty well. One of the replies was from KSWoodsMan, who said he had put secondary burn tubes in his older stove with good results. Now why didn't I think of that! So instead of cutting wood in the cold yesterday, I worked on the stove. The 1st picture below is of the tube assemblies as they were going to look in the stove. The 2nd is of the tubes mounted in the stove and the 3rd is of the outside. The tubes run up the sides of the stove. Secondary air can be controlled from the gate valves and shut off if there were ever a chimney fire. Then it enters the front of the stove over the fire, is routed through solid pipe to the rear of the stove for preheating, and then is dumped into the top of the burn area just under the baffle through the holes drilled down the length of the burn tubes. I didn't weld the tubes in place in case I ever have to change them, so I added a couple extra 1" washers so the coupling inside the stove and elbow outside the stove could be tightened against the stove wall and sealed with high temperature masonry caulk.

So far, I'm kind of impressed with my cob job. After a lot of experimenting today, I'm finding that I can get nice long hot burns by leaving the secondary valves wide open and closing the primary controls way more closed than I would normally run them. The secondary air doesn't just make the wood burn faster. In fact, it looks like I may be getting longer burns than I would normally get and put out the same or more heat. When the fire is burning at a good rate, opening up the secondaries from the closed position without changing the primary controls gets me about a 100 degree gain measured on the stovepipe. So I guess they're working. Unfortunately, since I don't have a glass door I can't see them working like you guys with the new stoves can  So if my stove burns a little cleaner and I burn a little less for the same heat, I'll have it made.

So now for the disclaimer. I'm not recommending anyone try this on their own stove. If you try this on your old stove and trash the stove or burn your house down, I don't want to hear about it  If you do try it and it works, or you improve on my design, let me know so we can compare notes.


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## 046

nice job!


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## November Wolf

Nice work! + rep here.


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## Paso One

All New pipe You must be rich  Nice job hope it works great!


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## husky455rancher

im new to wood stoves. what do secondary air tubes actually do? i see i have them in the insert i have but not in my woodstove. i would be inclined to hack up my stove if it is worth the effort. great job bt looks real nice. what type pipe did you use? anything special or just plain steel pipe?


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## volks-man

husky455rancher said:


> im new to wood stoves. what do secondary air tubes actually do? i see i have them in the insert i have but not in my woodstove. i would be inclined to hack up my stove if it is worth the effort. great job bt looks real nice. what type pipe did you use? anything special or just plain steel pipe?



cooler oxygen rich air hits hot rising wood gases and whal-la, the fumes ignite rather than going up the chimney! do it right and your firewood will _cook_ on top of a coal bed rather than burn. the flames will actually be burning above the wood rather than on it!


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## sesmith

husky455rancher said:


> what type pipe did you use? anything special or just plain steel pipe?



3/4 id (1" od) black pipe.


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## Haywire Haywood

Nice work! Now ya gotta do what that other fellow did and hack in a window. 

Ian


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## FJH

Mighty fine install!I wonder why you need a fancy tube with holes to do this job?Why not just set of pipes termenating at the baffle mixing air at the baffles edge You could still run the preheat tube and delete the hole filled tube and still have the same effect could you not??Just a question in my mind?If you ever study your fire with the door open the flames tend to follow around the edge of the baffle.


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## Haywire Haywood

volks-man said:


> cooler oxygen rich air hits hot rising wood gases and whal-la, the fumes ignite rather than going up the chimney!




If this is correct, could the preheat pipe actually be counter productive?

Ian


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## mtfallsmikey

Good job!...rep deserved.  :newbie:


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## Zodiac45

Looks good and alot higher tech than what I was thinking. Be interesting too see if you infact use less wood and get longer , hotter burns over time. In the old Tempwood stoves that I replied about in the first thread, they used two tubes perpendicular too the stove top pointed down (downdraft) with sliding air controls (just a flat plates). Very simple but quite effective. Here's a pix of how those worked.


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## itn

Great job on your overfire air project. This is part of what 20yr old coal plants are doing to retrofit and reduce NOx emissions.


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## MotorSeven

Nice job & rep for having the stones to just "do it". I have also been thinking of modding my shop stove. It has a really large opening straight to the flue. I put in a vintage cast iron 6" flue damper & it helped keep more heat in the box, but it still screams for more mods. 
Will that schedule 40 pipe sag when it gets really hot? Be the guinea pig & stoke it up.......... Please keep us posted on it's performance. 

RD


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## Wet1

Nice job.

MS,
No, black pipe should hold up for many years.


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## 046

how big a factor is "cooler" intake air temps? 

doesn't some wood stoves route intake air to pre-heat? 



volks-man said:


> cooler oxygen rich air hits hot rising wood gases and whal-la, the fumes ignite rather than going up the chimney! do it right and your firewood will _cook_ on top of a coal bed rather than burn. the flames will actually be burning above the wood rather than on it!


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## AOD

I think "cooler" is a relative term. The gases at the top of the firebox are anything but "cool" when a hot fire is going. The idea of preheating is so that the secondary air you introduce into the firebox is hot enough as to not self-extinguish the hot gases at the top of the firebox, and to promote a vigorous burn.


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## Crofter

The idea of the small holes is to introduce good mixing of air with the volatile gases to get the combustion as soon as possible near the back of the stove; just dumping it out of the open ended pipes close to the baffle would likely burn it but that would happen further along toward the exit pipe so less heat gained.

The air flow through the pipes should keep them from getting hot enough to sag or scale up too badly. The thinner stainless tubes in the patent heaters have less mass and likely are a bit quicker to heat up to light off temperatures. I like watching the fire through the glass door when the flame is more blue than yellow; almost like watching a natural gas flame.

How much heat you gain by good secondary combustion of the volatile gasses depends a lot on the type of wood; my guess is it would be a lot higher savings on on pine or fir than on the hard woods.

Nice retro fit project Sesmith!


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## MJR

That is an interesting point Crofler. I wonder if one could soak some wood in copper sulfate. The out gassing should be blue/green. You should be able to see the difference in the secondary combustion rates?


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## JONSEREDFAN6069

i understand the burn tubes but what are the taps on the front for? sorry maybe a dumb question but i want all the info i can get before trying on my stove.


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## Haywire Haywood

The valves are to cut off the air supply in case of a flue fire

Ian


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## JONSEREDFAN6069

ok, woodent a ball valve work better in that situation. one motion and they are closed rather than 3 or 4 turns of the tap


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## Cowboy Billy

Awesome Job. I have been thinking of putting a secondary air on mine. I was going to buy air tubes from a newer stove. But yours is a much better idea. Thanks for posting it. I am not going to do mine until summer but I will let you know how it turns out.

Billy


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## woodguy105

Sweet! Be nice to get a peek inside while she's cooking to see those flames dance!

I'd rep ya but I don't know how!


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## WidowMaker

Wet1 said:


> Nice job.
> 
> MS,
> No, black pipe should hold up for many years.



====

I had to replace the black pipe on my Lopi Endeavor about every 3 yrs. I finally put in stainless steel, end of problem.YMMV...


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## volks-man

Haywire Haywood said:


> If this is correct, could the preheat pipe actually be counter productive?
> 
> Ian





046 said:


> how big a factor is "cooler" intake air temps?
> 
> doesn't some wood stoves route intake air to pre-heat?





AOD said:


> I think "cooler" is a relative term. The gases at the top of the firebox are anything but "cool" when a hot fire is going. The idea of preheating is so that the secondary air you introduce into the firebox is hot enough as to not self-extinguish the hot gases at the top of the firebox, and to promote a vigorous burn.



honestly guys, i have no idea how or why this stuff works.  i likened it to the air injection system on older gm vehicles. cooler oxygen rich air was injected in to the exhaust manifold just outside the head. this resulted in the unburned hydrocarbons burning. why? how? i dunno! also reminds me of the 'bessemer process' in making steel. if you inject molten steel with cool oxygen rich air the contaminents burn off giving you purer steel.
what is it that lakeside's sig says?


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## Techstuf

If he doesn't want to do the door mod, he could maybe go to a used appliance dealer or junkyard. See if he could score a piece of oven glass or other tempered glass to fit over the stove doorway. Put a bead of silicone around the edge and press it up against the doorway to occasionally inspect or show off the results of his conflagration creation.


TS


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## Haywire Haywood

he could install a piece of stove gasket on the glass and just hold it against the opening using an oven mitt to watch the flame... get a thick oven mitt though LOL.

Ian


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## farmermike

This is an interesting post. Question, does the secondary burn only work if its a good hot fire? What about when its just idling along? My stove in the barn has a manual damper in the door and most of the time its almost closed. This is a great idea and I could install one easily.


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## volks-man

my stove must be hot, with a good bed of coals. i must shut the regular draft for best effect. the hotter the stove the better it draws through the tubes when you shut the draft down.
oh yeah, no damper whatsoever. if you had one and closed it i would think you would slow the draft too much.

i can throw a peice of wood in on top of just coals and shut the door with draft shut....
and the wood starts charring with flames burning above it. it almost looks like gas flames shooting out of the holes! neat stuff!


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## volks-man

*for those unfamiliar*

here is a fast vid of the effect. not the best example but sufficient. looks a lot like a backdraft. the flames are moving toward the camera and away from the holes in the top of the firebox. notice the bottom of the wood is barely burning. this is an example of wood gasification.
<embed width="448" height="361" type="application/x-shockwave-flash" wmode="transparent" src="http://i263.photobucket.com/player.swf?file=http://vid263.photobucket.com/albums/ii150/volks-man/PICT0794.flv">


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## chainsaway

*hot oxygen-rich air*

it is guesstimated that about one third of the wood's potential heat is lost in smoke in older wood stoves. so an "easy" way to get more bang for the same buck woulb be to find a way to ignite that smoke. thats where the air tubes come in play; they provide oxygen-rich air right where the smoke is (after the flammes) therefore in the O2-poor area. the snag is that this new air has to be as hot as possible so the smoke self-ignites on contact to get the full bang benefit. this is why there is quit a bit of metal ducting exposed to the fire before this new air exists the holes, the last thing you want to do is cool the smoke...hope this helps!
cheers alain


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## Moddoo

Looks very well done.

It's hard to tell from the pics, but if you have room to extend the shelf to make the flame travel a bit longer, that will help some also.

here's another thread with a few pics of my furnace modded.
http://www.arboristsite.com/showthread.php?t=37370&page=2
and one with some pics of the door that I made.
http://www.arboristsite.com/showthread.php?t=77617


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## itn

Yes, pre-heat your over-fire air as much as you can. Then continue to deprive your intitial combustion air. It will vary depending on your wood and moisture.


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## husky455rancher

i can throw a peice of wood in on top of just coals and shut the door with draft shut....
and the wood starts charring with flames burning above it. it almost looks like gas flames shooting out of the holes! neat stuff![/QUOTE]

ok i get it now. i always wondered how why the fire looked like it was comming from inside the tubes on my insert. i just thought the fire was kinda over the wood alot of the time .cuse the firebox is so damn small and it had no where to go. 


so essentially the tubes just hold the heat above the fire and allow the gasses to burn more? would you leave both valves all the way open all the time or do you gotta play with them?


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## sesmith

TreeCo said:


> I was thinking gate valves must have been used because they are often all brass where ball valves usually have seals that may not take high temperatures.
> 
> ??


You've got it right. Also, I used the gate valves cause initially I thought I'd be regulating them partly closed, not leaving them wide open.


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## sesmith

Crofter said:


> The idea of the small holes is to introduce good mixing of air with the volatile gases to get the combustion as soon as possible near the back of the stove; just dumping it out of the open ended pipes close to the baffle would likely burn it but that would happen further along toward the exit pipe so less heat gained.



Yea, that's what I had in mind. The long run of pipe from the valves up the side of the stove and to the back before going into the burn tubes was to get as much preheating as possible. More preheating of the secondary air is better. The secondary combustion won't occur until around 1100 degrees. Cooler air will just quench the fire. I also aimed the jets toward the center of the stove instead of down for this reason though I doubt it would have mattered much which way they point. Most of the air probably exits toward the rear of the stove (at the beginning of the burn tubes). FWIW, I made the last 6 holes (the ones at the front of the stove) a little larger cause they were at the end of the run and would get less air. Also, since most of the air is going to leave the pipe at the beginning of the run, It has more time to mix and burn if the beginning of the run is at the rear of the stove.

No guys, I'm not getting rid of my cast iron door cause I kind of like it  I really wanted to see the tubes work in the worst way tho. Unfortunately, when the door is opened, the secondary draft stops and you can't see a thing. So I had the bright idea to open the door and add some air...like with a vacuum cleaner blowing in reverse. Yesterday this worked and I got a real nice blue blast furnace thing going. Today I tried to take a couple of pictures and didn't have a lot of luck cause I didn't get the stove quite hot enough. But the pics below at least give you the idea. The 1st is with the door open and no secondary air. The 2nd is with secondary air added to the right side tube only. I got a little flare, but since things weren't hot enough I didn't get the nice blue flames I saw yesterday.

Also, I noticed a major improvement in emissions when I left for work today shortly after starting a fire. Normally, I'm embarrassed to say, I'd have been fogging the road outside my house when I leave for work. Today, there was very little smoke. (I'll try to post some pics when I get some time to take them) I built a fire at about 7 am and set it on a slow burn. Got home tonite at 6. The house was only 2 degrees colder and I had a good bed of coals to work with. Normally, I would have been playing boy scout with about 2 coals and scraps on the floor to start the fire after 11 hours. I'm loving this thing. I'd have been happy if I bought a new stove and it worked this well. The fact that I was able to do it for less than a hundred bucks is icing on the cake.


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## sesmith

TreeCo said:


> I think the biggest reason shutting down the secondary air to burn down a large bed of coals works is because the primary air is usually enters right at coal level. Secondary air most likely just cools down the fire box in coal burn down mode.
> 
> Just rambling off theories! Don't quote me.



I wondered about this too. Yesterday I measured temps at the same place on the stove pipe (my point and shoot IR thermometer doesn't go much over 500 degrees) at various times during the burn with the secondaries opened and closed. At no time did leaving them open decrease the temp. When they're working, the temp. increases with them open. When they're not working at the end of the burn, they have no effect on the flue temp.


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## outdoorlivin247

Could you take picture thru the door...JK...Great build...


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## sesmith

outdoorlivin247 said:


> Could you take picture thru the door...JK...Great build...



Those were pics thru the door (with the door opened). Any closer and I melt the camera. Since the door is cast I can't see in and take pics during the burn.


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## wigglesworth

*I wondered what that thing was in the top of my stove*

Seriously though, i never heard of it, and i thought you know i have a tube in the top of my stove that has a dampner knob on it. Well wouldnt you know, it works. I dont have glass doors, but i opened the door and there it was flames burning on top of the wood until the fresh air hits and then they disappear. Cool thread.


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## vwboomer

I think I may give this a shot this spring. The worst that can happen is nothing changes and then just leave the valves shut.
I don't think I'm allowed to upgrade to a better furnace, so any improvements I can make on what I have is worth the effort.

Question on the baffle though. On mine, a baffle is built into the collar that sits in the exit to the radiator:






Do you think I would need an additional baffle plate to keep the air down farther, or would the existing baffle sufficiently restrict flow?


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## KsWoodsMan

Nice, very nice install. It even has a clean look and I like how you went close to the floor to pick up cold drafty air from low in the room for the secondary combustion.

Excellent idea running the pipe to the rear of the stove and back to the front for additional preheating. Maximizing exposure to the air tubes before releasing the air in the chamber.

Now the stove is even more of a Wood Saver.


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## outdoorlivin247

sesmith said:


> Those were pics thru the door (with the door opened). Any closer and I melt the camera. Since the door is cast I can't see in and take pics during the burn.



I saw the door was cast, that is why I said it...Trying to be a smart :censored: ...That didn't work...I can only imagine it being very intense above the wood w/ it closed...


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## sesmith

outdoorlivin247 said:


> I saw the door was cast, that is why I said it...Trying to be a smart :censored: ...That didn't work...I can only imagine it being very intense above the wood w/ it closed...



Duh! I just now went back and saw the "JK" No wonder your 1st post confused me!


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## FJH

sesmith

I think ya should do a *how to* write up on this project where ya got the parts ect and have the Mods stick it to the top of the page a very usefull and relitivly easy day project for people that got the time and skills to do so! But DON'T call it a hackjob thou its a clean looking add on.Call it a retrofit. 

Again a Nice worth while project.


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## mtfallsmikey

I knew those tubes reminded me of something.....had a friend who made a gas grill out of a 275 gal. flat oil tank. He used 1" black pipe with holes drilled in it for the burners, bought air shutters to fit the pipe. Could do 60 chicken halves at once.


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## FJH

Being it is supported front and rear I for see no problems my self!
The rear support may need to be beefed up abit bigger washers or somthing otherwise I'd say good to go.The tubes may droop who knows ,Time will tell I guess.


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## FJH

TreeCo said:


> If black iron worked I'd expect to see in in modern epa stoves. I've only seen stainless.




True


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## flotek

wow ..youve done a wonderful job ,i d love to have that done to my englander addon wood furnace you should start a small business doing them o n the side ,just think of the wood and effort that would save a person over the years ,not to mention the added heat ,they should have come stock this way


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## jester31780

*just asking*

do you save more wood with the secondary burn tubes add if so how much


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## sesmith

jester31780 said:


> do you save more wood with the secondary burn tubes add if so how much


Yes, but too soon to tell how much really (I only put them in last weekend), but a conservative estimate based on this week's wood use would be 15%. If it really Is that much, I'll be pretty happy, as it would lower my typical use from about 6+ cords per year to around 5. This year I was heading for closer to 7 with the cold weather (I used 3 by Jan 10th). We'll see what happens the rest of the season.

Also, below are some pics of the smoke about 20 minutes into a new burn today. The 1st one is with the secondary drafts open. The 2nd is with the secondary drafts closed off.


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## sesmith

TreeCo said:


> If black iron worked I'd expect to see in in modern epa stoves. I've only seen stainless.



The thinner gauge stainless heats up quicker so it comes on line sooner. I'm sure they also engineer the hole size and position and direction of flow to maximize the secondary burn. If I just spent 2500 on a new stove I wouldn't want to see something as low tech as black iron in it! (And if the stove was soapstone, I'd want to see something like kryptonite in it. ) That doesn't mean that black iron won't work...actually it works pretty well. I imagine I'll have to replace it eventually, but the stainless tubes are also made to be replaced when needed. Is this 27 year old stove of mine as clean and efficient as one of the new EPA certified stoves? Heck no. But it is a lot cleaner and more efficient than it was.


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## FJH

Sesmith where did ja get the flanges to go throu the front of the stove what are they called if some one wants to go to a store to buy these a guy should know what they are called.Thats what I was saying about a bit of a write up on the project its a nice clean install the only change I would make would be a set of ball valves althou more pricey they would be more conviniant.
A real fine install bro. Give it some thought on the write up.Ya got the pics
a few words on where ya got the parts what the parts where called ect.


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## sesmith

TreeCo said:


> I don't buy into your line of logic. Basically you are saying stainless steal is used for the bling.
> 
> My $2,400. stove is cast iron.



No, I'm not really saying that. There are a lot of high temp stainlesses out there for just that purpose (ie, burn tubes, grill burn manifolds,etc) so they can be thin and hold up well to heat and corrosion. I am saying if I bought a new stove, I'd want this good stuff, made for the job and not black pipe with holes drilled into it  BTW, black "iron" pipe is really black steel pipe these days, so I'm assuming it should hold up reasonably well in a steel stove. It certainly won't melt, at worst it might sag and/or corrode with time. 

Nothing wrong with cast iron. It's got better heat transfer properties than steel. These new stoves are low-tech looking works of art on the outside and high-tech designed wood burners on the inside (and you do get what you pay for).


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## sesmith

Moddoo said:


> It's hard to tell from the pics, but if you have room to extend the shelf to make the flame travel a bit longer, that will help some also.
> 
> here's another thread with a few pics of my furnace modded.
> http://www.arboristsite.com/showthread.php?t=37370&page=2
> and one with some pics of the door that I made.
> http://www.arboristsite.com/showthread.php?t=77617



I meant to reply to you earlier and say what an awesome job you did on your furnace. Especially the door. I'd love a view like that, but with the drafts in my door, it adds a complication. I could, I suppose, cut a viewing window in the stove over the door...stop me before I get the sawzall out! Or worse yet, the

It would be hard to make my baffle longer cause it just fits up in there. I could make a 2nd piece that clamps on to it and extends it, though. Might try that sometime.


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## Zodiac45

sesmith said:


> No, I'm not really saying that. There are a lot of high temp stainlesses out there for just that purpose (ie, burn tubes, grill burn manifolds,etc) so they can be thin and hold up well to heat and corrosion. ).



heck yeah, look at most chimney liners and flex flue. It's all that 316T stainless alloy. Very thin and last for years.


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## FJH

TreeCo said:


> Just to show I'm paying attention.......
> 
> The quote is from this threads opening post.


Well done Bro ,I wern't paying attention thanks'


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## HardyOWB

Excellent job on the modificaiton. Has anyone done this modification to an OWB? I have a Hardy OWB which has a forced air blower that blows air under the fire. So, I already have an opening (no need to cut another). The opening is about 2"x2" so I could easily run a 1" pipe through there. I think I will give it a try unless, anyone has some concerns.


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## sesmith

HardyOWB said:


> Excellent job on the modificaiton. Has anyone done this modification to an OWB? I have a Hardy OWB which has a forced air blower that blows air under the fire. So, I already have an opening (no need to cut another). The opening is about 2"x2" so I could easily run a 1" pipe through there. I think I will give it a try unless, anyone has some concerns.



Look at the posts from Moddoo earlier in this thread. He's done what you're looking for.


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## scotvl

sorry to bring back an old thread but I want to do this mod to my old Elmira insert and wanted to hear how the op's worked out after extended use.


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## sesmith

scotvl said:


> sorry to bring back an old thread but I want to do this mod to my old Elmira insert and wanted to hear how the op's worked out after extended use.



No problems. I did the stove modification in Jan. '08. The black pipe shows no signs of warping or breakdown in any way. The modification did not damage the stove in any way. It did totally change the way the stove burns, and there is much less smoke coming from the old beast than used to. I do have to be a little more careful as it would be easier to overfire the stove now. As far as wood use goes, I'm kind of unsure at this point. I used 6.3 cords last year and 6.25 cords the year before. I can say though, that I started burning wood earlier last year than the year before, and that last year was quite a bit colder than the year before. So my gut feeling is that it is more efficient, but I don't have a good feeling for how much more it might be.


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## scotvl

Thanks just what I wanted to hear. My Elmira insert has two chambers for cats that get activated when you close a built-in damper the exhaust gases are forced through the cat chambers. I would love to tell you how they work but have never been able to find them. The reason Im telling you about the cats is it should mean my insert can handle the extra heat the secondary tubes will create.


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## scotvl

sorry about the wall of text but Im posting from my cell's browser and its a pain.


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## ericjeeper

I am glad you brought this thread back up.. I might give it a try on my owb. Worse thing I would have to do would be to weld a plug over the hole if it fails.
My biggest downfall will be supporting the pipe inside.. I am not about to climb in there to weld anything to the roof.. Been there when I built it.. It was clean then.. Now it looks like the inside of a used oil drum. lol
I might try cutting two holes in the face side by side. One being the supply and the other being a capped off nipple to just support the weight.
so it would be a u-shaped piece. consisting of two long pieces of pipe. Two close nipples, one cap, two 90s and one nipple to set the distance apart on the u end and One valve to control the flow. Do I really need a small blower? or will the draft just pull its own air?


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## scotvl

Sounds good and I'm pretty sure you don't need a blower.


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## ericjeeper

*well it is installed.*

I used two 3/4 inch pipes 30 inches long and a 4 inch nipple for my huey/.

I will not be able to see if it is going to work til it gets cold out.. 56° here now.. I already had to dump some heat this afternoon while playing with the installed secondaries.. My garage is about 85.. I might go out there and sleep on the floor tonight.. as it is toasty warm/.


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## scotvl

Any pics?


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## ericjeeper

This is the tubes installed. The holes are on the left tube.. Are there any flames that look like gas jets coming out of the holes? No.. Is it working? I am not sure.


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## 12vdzl

Pic didn't show.

Would the OWB be hot enough to actually make the secondarys work? I was thinking of doing this to my Hawken, but doubt i will. It would probably take a solenoid to kick open after the stove has reached an optimal temp.

Ericjeeper hope it works for ya!!


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## Haywire Haywood

TreeCo said:


> The outside surface of my firebox is often 350 to 400F.



The manual for my Oslo said the optimum surface temps are 400-600F. If it goes much over 450, I have meat falling off the bone.. 

Ian


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## DAN666981

thats a great job looks clean and neat


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## powerstroke73L

Nice job! I want to try something similar with my Englander. I priced out doing something similar (NPT style pipe through the front) in stainless and I should be able to get it done for under $100. Type 316 stainless steel pipe should last longer than my firebox!


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## jburner

powerstroke - I've got the same stove as you do, thought of doing the same thing. What design have you thought up? 

I thought of going in just to the right and left of the ash door, underneath the welded steel on the inside that holds the "ash grate", 90 degree up through the floor of the ash grate up to the baffle plate, and then 90 degree toward the front. 

Don't know if I can't get myself to do it though, I just got the furnace and don't really want to void my warranty?!?


----------



## laynes69

The baffle like tree co was saying has to be insulated to help achieve higher temps for proper combustion. Some baffles are firebrick, ceramic board, or like mine a stainless steel insulated baffle. Both of my secondary air channels preheat the air for 2 feet before going into the firebox, then another 2 feet in the firebox where is comes out at 4 tubes. Fully firebricked interior also. When operating, the tubes and baffle glow from the secondaries.


----------



## demographic

Great thread, I don't suppose anyone has any links to any stove design resources?

Might make my gas bottle stoves a bit more efficient.


----------



## ericjeeper

I have found that if I do not plug the inlet fitting off.. The boiler will run away. came home to 209° I dumped the heat into the garage floor. Ut would have climbed higher I feel cept it was out of wood..


----------



## jburner

ericjeeper - Where are your pictures?


----------



## 12vdzl

ericjeeper said:


> I have found that if I do not plug the inlet fitting off.. The boiler will run away. came home to 209° I dumped the heat into the garage floor. Ut would have climbed higher I feel cept it was out of wood..



For this reason is why i was thinking you'd need to add a solenoid or 2 that will allow or shutdown secondary air. But i was thinking the sol. would open after the upper firebox has reached a certain temp (not sure what that is ?) then of course shutdown when the water reaches it's temp.


----------



## Nonprophet

Just thought I'd chime in on this thread as I recently bought an older wood stove called "The Elm." They're really pretty cool and unique stoves, you can find out more about them here 

The guy who created the website has been retrofitting some of them with secondary burn tubes, and he's got a couple videos on Youtube showing the secondary burn. The best one showing the secondary burn is this one, about 5:40 into the video.

He also has a photo gallery with some images that have some nice close-ups of the secondary burn tubes and how they're installed--you can view the photo gallery here.

I'm going to restore my Elm (repaint, regasket, etc.) and I also plan on installing a set of the secondary burn tubes.

Hope this helps some people who are thinking about adding burn tubes to their stove.

NP


----------



## Nonprophet

TreeCo said:


> The Elm looks interesting.
> 
> The secondary air tubes do not appear to be in the main air flow channel which is a red flag IMO.
> 
> Most stoves today are using an 'air wash' system to keep the glass clean and I don't see that in this stove either.
> 
> Still an interesting stove and quite good looking!
> 
> Any idea on asking price?
> 
> I'm some concerns about parts should something happen to what looks like a very small company.



In his pics, the secondary air tubes are located just under the large interior baffle--with the air "jet holes" pointed towards the underside of the baffle where the smoke and gasses accumulate. In his videos, he's clearly getting secondary burn, so it must be working to at least some degree. 

You're right in that I don't see a built in airwash system to keep the glass clean, however I've spoken with a few other Elm Stove owners and they all say the the glass stays clean......so maybe there's something going on there we're not aware of.

Another point of interest is that the glass widow is actually a Pyrex pie plate that can be bought at most stores for about $7.............

I'm with you on the parts thing, however there does seem to be a VERY loyal following for these stoves and he seems to have just about all the parts available. They have a well deserved reputation for being very well built and easy to use and maintain. I especially like the fact that because they're round there are no welds to crack, no high-stress corners etc. Another added benefit of the barrel design is that if you load up the stove for an overnight burn, the splits naturally roll into the center (on top of the coals) as the fire burns......

I saw a guy on another forum who just bought a brand new one. It was a relatively fancy model with the secondary air tubes, nickel plated Elm logo and ash pan, side warming racks, etc. He paid $1,750 for his. Smaller models and ones with less bling are also available, but I don't know the cost on those.

NP


----------



## Haywire Haywood

I think it's a very attractive stove, nice departure from the usual box. The only drawbacks I see are that it's very deep front to back with it's 24" capacity, so it wouldn't be very good for the space challenged to install and no ash pan. On the other hand, loading north/south like that would make filling it easy.

Ian


----------



## Nonprophet

Haywire Haywood said:


> I think it's a very attractive stove, nice departure from the usual box. The only drawbacks I see are that it's very deep front to back with it's 24" capacity, so it wouldn't be very good for the space challenged to install and no ash pan. On the other hand, loading north/south like that would make filling it easy.
> 
> Ian



Yeah, they're not an ideal stove for the space-challenged, that's for sure! They also don't have any heat shields built in to them, so the clearances aren't so great, but, if you have a spot for them they sure are great stoves!

There's also a smaller 18" model available, as well as a larger 36" model.


NP


----------



## kees53

*secondary combustion*

Hi all

I am new here, and I fall in this house with the following.

secondary combustion is not as easy then some here predent.

I am busy with my own woodstove in holland to make a insert.

I have some calculations done and it is that a baffle is the best way one of 1.6 sq ft for preheating and 1.5 sq ft for second preheating so it is capable to get enough heat without a very big fire,

You van find a lot in the google search on patents.

I have a french woodstove with a lot of room to make it working, it will be some weeks to complete.

I have seen a couple of pictures with a baffle this has only preheating above the fire, but you need also a vertical baffle behind the fire to help make the air hot.

Some have used pipes I am not very impressed of that because you have to make the fire very hot to let it work.

http://www.cham.co.uk/phoenics/d_polis/d_applic/d_comb/secomb/y263.htm

http://mb-soft.com/juca/print/315.html

and my burn with a smal pipe who don,t work well only when heated heavely.







These link from your site 

http://www.arboristsite.com/showthread.php?t=37370&highlight=secondary+burn+tubes

That is the best way, and can be better if the baffle is extended with a backplate of 1.6 sq ft.

Be the way whare is the place this pictures is discussed, because I will use this in my own stove, it is nice and the best way, the hotter the secondary air the better it wil be.

greetz from holland.


----------



## BigGame

*Secondary Air*

Great info this is a great site, How many CFM will I need to have for the secondary air system.


----------



## kees53

What is CFM I am dutch so explane.

you need a survace of 1.6 sq feet (bigger is better) for the vertikal baffle and 1.5 sq feet for the upper baffle.

this wil heat the air to more than 500 F.

info on the links.

greetz.


----------



## Haywire Haywood

That .uk site was interesting. It looks like an add-on secondary burner. I read something in the last few days about ideally the secondary burn would be a separate chamber so that the heat from the sec. burn wouldn't accelerate primary combustion. 

I can't really take the Juca site too seriously. I thought they were actually out of business but I found a current price list there which surprised me. If they would update their site with current pictures and some new web design, it would come across as little more believable. As it is, it looks like they scanned their info in from 1970s brochures and not much more.

Ian


----------



## Haywire Haywood

kees53 said:


> What is CFM I am dutch so explane.
> 
> you need a surface of 1.6 sq feet (bigger is better) for the vertikal baffle and 1.5 sq feet for the upper baffle.
> 
> this wil heat the air to more than 500 F.
> 
> info on the links.
> 
> greetz.



Cubic Feet per Minute. A measurement of air flow volume. The .uk site said that for their design you would need the same amount as you have for primary combustion.

Ian


----------



## kees53

thanks

I read somewhere that secondary air has to be 3 to 5 times of primary, best is
to make it adjustable with holes in the back of the stove like my plans are..

if you burn wood then you have to shut the primary air, only for coals it is needed, when you start then you need primary, after heating shut it down.

I did this al the time and it works the best, and only for modern stoves with secondary air not for old smoke dragons these need a insert.

some patents here in pdf files so we can learn.


----------



## sesmith

sesmith said:


> No problems. I did the stove modification in Jan. '08. The black pipe shows no signs of warping or breakdown in any way. The modification did not damage the stove in any way. It did totally change the way the stove burns, and there is much less smoke coming from the old beast than used to. I do have to be a little more careful as it would be easier to overfire the stove now. As far as wood use goes, I'm kind of unsure at this point. I used 6.3 cords last year and 6.25 cords the year before. I can say though, that I started burning wood earlier last year than the year before, and that last year was quite a bit colder than the year before. So my gut feeling is that it is more efficient, but I don't have a good feeling for how much more it might be.



Just wanted to drag this thread out of mothballs to say I finally did some calculations. The modification to the stove increased it's efficiency by about 11%. That was the # after I normalized 1 heating season to the other by taking into consideration the difference in heating degree days between the 2 years, and taking into consideration that I did the modification during the heating season, so it wasn't in all season. Also had to factor in the heating oil I used both years. I couldn't make any comparisons this year, though cause I added a solar air heater into the mix (that, by the way, will be worth 26% or a little more, of my heat).


----------



## demographic

sesmith said:


> Just wanted to drag this thread out of mothballs to say I finally did some calculations. The modification to the stove increased it's efficiency by about 11%. That was the # after I normalized 1 heating season to the other by taking into consideration the difference in heating degree days between the 2 years, and taking into consideration that I did the modification during the heating season, so it wasn't in all season. Also had to factor in the heating oil I used both years. I couldn't make any comparisons this year, though cause I added a solar air heater into the mix (that, by the way, will be worth 26% or a little more, of my heat).



Solar air heater? We need pictures, and maybe even a different thread about it.

I'm interested now.


----------



## dolmen

+1


----------



## sesmith

demographic said:


> Solar air heater? We need pictures, and maybe even a different thread about it.
> 
> I'm interested now.



How about a link instead. It's the larger of the 2 here. Scott also put in some performance data I collected on mine toward the bottom of the page:

http://www.n3fjp.com/solar/solarhotair.htm

For lots of other solar DIY info check out the following link:

http://www.builditsolar.com/index.htm

This site is kind of the bible of DIY solar. The 2 downspout collectors referenced in the above link are also buried somewhere in the hot air collector page here too.

As far as another thread on the solar stuff, maybe arborsite should have an alternative energy forum where subjects like, solar, wood gasification, wind, insulation and energy conservation, hydroelectric, etc could live. ********** has something like this. They call the "green forum". There's a lot more activity over here, and it would be better to keep it geared more toward energy and heating, and not "what are you going to plant in your organic garden today" kind of thing. (Just my opinion, though).


----------



## romulus

*Exchange of ideas needed*

Hi to all,

I've asked in another thread, however, no single sole has replied.

I have a Franklin fire box stove, so the doors are not sealed and even may not be sealed since the air intake for burning cannot do for the small openings at the bottom part of the doors. At the top part of the doors, one of the four doors has even a thinner wall at the end to let more air in for combustion.

In order to try the secondary combustion idea, I would have to introduce a vertical baffles to keep the temps high enough (without refractory bricks?!) and perhaps a forcing air blower, say, as produced by Secoh.

Can anybody help me with a piece of advice how to arrange a horizontal baffle with holes instead of tubes. I think the Franklin stove has already an improvised secondary combustion camera, an additional baffle plate with holes added would however better its functioning. But I do not know how to introduce preheated air above the horizontal baffle with holes. Several pics from this website didn't show how to, alas.

I can imagine the way some Tempwood stoves take in air from outside through 2 inlets in the top plate of the stove, so I could put 2 small tubes through the fume output pipe -- for outside air input --- even without any blower. - 

Or else, I'd weld a hearth box insert of stainless steel to the available stove with a gap of about 1 inch to the walls of the stove inside, plate-like, with holes above for preheated air supply. I hope that air is a bad warmth conductor, and the refractory brick insulation lining would then not be needed. Has anyone experienced working with plate-like air ducts instead of tubes without lining? 

Thanks


----------



## sesmith

romulus said:


> Hi to all,
> 
> 
> I have a Franklin fire box stove, so the doors are not sealed and even may not be sealed since the air intake for burning cannot do for the small openings at the bottom part of the doors. At the top part of the doors, one of the four doors has even a thinner wall at the end to let more air in for combustion.




If the stove is not airtight, I can't imagine any benefit of adding secondary air. The problem with a non-airtight stove is that you can't completely control the amount of air coming in, so there would be no need to add additional secondary air. A secondary air system would also not provide any air for combustion if the path of least resistance is a leak elsewhere in the stove.


----------



## connollyr123456

*Stainless steel hardware*

Is the hardware used to hang the pipe stainless steel?


----------



## connollyr123456

*Treemont WoodStove*

I have a treemont unit that I am thinking of adding secondary pipes to the unit to increase it efficiency. Is there more on the correct installation of secondary tubes?


----------



## sesmith

connollyr123456 said:


> Is the hardware used to hang the pipe stainless steel?



No. Just standard issue threaded rod.


----------



## pook

silly 2me= intake pipes should be on bottom so to keep the bottom of the load somewhat cooled & not burning
read "nature of fire" blog in my sig.


----------



## connollyr123456

What did you use to drill holes in the stove?


----------



## sesmith

connollyr123456 said:


> What did you use to drill holes in the stove?


Big drill bit on a half inch drill. I had a step drill that I used, but I remember having to round up a larger drill to finish it off to size. Luckily I found the right size at work and borrowed it for the job.


----------



## tex

*Same in OWB?*

I've only skimmed through this thread, so maybe this has been covered. I'll bring it up anyway. Could this same theory be used to increase the efficiency of an OWB? Not the ones with the draft built into the door, but if the blower was in the body of the boiler. I'm thinking a couple of pipes with holes drilled that run under the coal bed for combustion air that then loop back up to the top with more holes drilled for secondary combustion. The theory should work the same, but I'm wondering if the forced draft would mess it up. Any thoughts?:dont-know:


----------



## CTYank

Haywire Haywood said:


> If this is correct, could the preheat pipe actually be counter productive?
> 
> Ian


 
It's not correct. The secondary air needs to be preheated so the mix of that air and the flammable gases is a bit above 1000 F (per Jay Shelton's testing) for there to be secondary combustion. OP's black iron pipe may be short-lived; also his gate valves could be replaced for much less $$ by reducing couplings. (Just a suggestion.)

E.g. my little stove has two preheaters- one is the cast-iron back wall and the other is stainless sheet that forms a chamber with the cast-iron baffle. (Works great.)


----------



## sesmith

CTYank said:


> OP's black iron pipe may be short-lived; also his gate valves could be replaced for much less $$ by reducing couplings. (Just a suggestion.)



You may be right, though the black pipe has been in for 3 seasons, so far with no sign of deterioration or warping. I originally thought I'd be using the gate valves to meter the secondary air, but just leave them open all the way. They are nice to have as a way to be able to shut off the air flow in case there were ever a chimney fire.

As far as the question in the previous post...I know this same thing has been tried on some OWB's. Do a search of the archives here.


----------



## kees53

*nice stiove new idea,*

here the link to a stover who works like a tornado so to speak, it turns around the flames to mix air.

but is it true?

http://www.youtube.com/watch?v=r5cr4R700WI

I have tryed with holes drilled in the sides of the floor and not from unther the floor,
so the firebed gets air from the sidewalls. well it works very nicely.

here the stove inside picture.

http://www.burley.co.uk/pdf/Woodburner 2010 brochure.pdf


----------



## pook

to observe the fire without glass, drill a hole in the door & plug it with a bolt when not observing the fire?


----------



## kees53

pook said:


> to observe the fire without glass, drill a hole in the door & plug it with a bolt when not observing the fire?


 
I don,t mean to watch the fire, I have glass, but the floor where the firebed lays on normally it gets primairy air form beneeth I have change it to from the edges it indeed geives fire a twist like a tornado and so more time to burn before go to the chimney..


----------



## pook

kees53 said:


> I don,t mean to watch the fire, I have glass, but the floor where the firebed lays on normally it gets primairy air form beneeth I have change it to from the edges it indeed geives fire a twist like a tornado and so more time to burn before go to the chimney..


"extended flame path" from tornado sounds good. My son spent years in Utricht & speaks Dutch.


----------



## kees53

pook said:


> "extended flame path" from tornado sounds good. My son spent years in Utricht & speaks Dutch.



That is nice, een goedeavond dan voor je zoon.

to be honest I am more for a way to get a spinning fire in a horizontal way and not vertikal like the burley.

I have in my stove holes just below the shimey exit, and just above the glass window and down in the firebed (not below like the most have and for shure the classic ones) so I have a way found to get a spinning fire who will terminate the shimney way of suck it to fast whaa is the biggest problem. Al the air is preheated.

here the fore in the stove, watch how clean is the glass and the superhot firebed..

http://www.youtube.com/watch?v=eUeGsfb7LL0

here a ather way, a twisting fire on a horizontal way, better than vertical, watch the sparks what it does, you see the direction
of the flames twisting and the smoke back to the firebed..

http://www.youtube.com/watch?v=sTWnavBsNDU

and it is hot very hot last day 220 0C degree in the shimney 20 cm above the stove. .


----------



## Wife'nHubby

pook said:


> to observe the fire without glass, drill a hole in the door & plug it with a bolt when not observing the fire?


 
NOTE: 

To quote the owner of arborist.com:

"TO ALL: After reading much of the information provided by Pook above, it seems to be misinformed and even dangerous in some cases. Please disregard any posts made by him before this post. I have informed him and will inform you all, if you are giving out bad information knowingly you will be banned from this site and if somebody gets hurt by your poor information, you could be personally liable. This could include jail time or be at the very least financially liable. You are personally liable for anything you say on here or any other website!!! Since there seems to be so many posts with poor/dangerous information, I feel it has to be on purpose as nobody can believe many of the things that have been said, which includes the poster. 
Thanks!!! Have a Happy, warm Holiday to everyone!! Also, Thanks to all that try to help others on here and have a genuine interest in making this a site full of good/useful information. 
__________________
Darin Johnson
www.arboristsite.com
Our business is growing"


----------



## TheLazyBFarm

Wife'nHubby said:


> NOTE:
> 
> To quote the owner of arborist.com:
> 
> "TO ALL: After reading much of the information provided by Pook above, it seems to be misinformed and even dangerous in some cases. Please disregard any posts made by him before this post. I have informed him and will inform you all, if you are giving out bad information knowingly you will be banned from this site and if somebody gets hurt by your poor information, you could be personally liable. This could include jail time or be at the very least financially liable. You are personally liable for anything you say on here or any other website!!! Since there seems to be so many posts with poor/dangerous information, I feel it has to be on purpose as nobody can believe many of the things that have been said, which includes the poster.
> Thanks!!! Have a Happy, warm Holiday to everyone!! Also, Thanks to all that try to help others on here and have a genuine interest in making this a site full of good/useful information.
> __________________
> Darin Johnson
> www.arboristsite.com
> Our business is growing"


 
I thought he got banned. Why is he back with bad advice?


----------



## CrappieKeith

You have got to be kidding...drill a hole.

He was banned and for some reason he's back.....:msp_blink::msp_blink:

To quote the owner of arborist.com:

"TO ALL: After reading much of the information provided by Pook above, it seems to be misinformed and even dangerous in some cases. Please disregard any posts made by him before this post. I have informed him and will inform you all, if you are giving out bad information knowingly you will be banned from this site and if somebody gets hurt by your poor information, you could be personally liable. This could include jail time or be at the very least financially liable. You are personally liable for anything you say on here or any other website!!! Since there seems to be so many posts with poor/dangerous information, I feel it has to be on purpose as nobody can believe many of the things that have been said, which includes the poster. 
Thanks!!! Have a Happy, warm Holiday to everyone!! Also, Thanks to all that try to help others on here and have a genuine interest in making this a site full of good/useful information. 
__________________
Darin Johnson
www.arboristsite.com
Our business is growing"


----------



## pook

CrappieKeith said:


> You have got to be kidding...drill a hole.
> 
> He was banned and for some reason he's back.....:msp_blink::msp_blink:
> 
> To quote the owner of arborist.com:
> 
> "TO ALL: After reading much of the information provided by Pook above, it seems to be misinformed and even dangerous in some cases. Please disregard any posts made by him before this post. I have informed him and will inform you all, if you are giving out bad information knowingly you will be banned from this site and if somebody gets hurt by your poor information, you could be personally liable. This could include jail time or be at the very least financially liable. You are personally liable for anything you say on here or any other website!!! Since there seems to be so many posts with poor/dangerous information, I feel it has to be on purpose as nobody can believe many of the things that have been said, which includes the poster.
> Thanks!!! Have a Happy, warm Holiday to everyone!! Also, Thanks to all that try to help others on here and have a genuine interest in making this a site full of good/useful information.
> __________________
> Darin Johnson
> www.arboristsite.com
> Our business is growing"


 Note that the assertion is followed by a ? which means its a question, in hopes that the issue might be furthered & directly addressed instead of "shooting the messenger". Observing the fire is critical 2me & I have drilled many holes without consequence. With an alteration which has already involved drilling for the pipes??????????:biggrinbounce2:


----------



## CrappieKeith

pook said:


> Note that the assertion is followed by a ? which means its a question, in hopes that the issue might be furthered & directly addressed instead of "shooting the messenger". Observing the fire is critical 2me & I have drilled many holes without consequence. With an alteration which has already involved drilling for the pipes??????????:biggrinbounce2:


 
C'mon everybody...Pook just jumped off of a bridge...everyone follow...:bang::bang::bang::bang:

To quote the owner of arborist.com:

"TO ALL: After reading much of the information provided by Pook above, it seems to be misinformed and even dangerous in some cases. Please disregard any posts made by him before this post. I have informed him and will inform you all, if you are giving out bad information knowingly you will be banned from this site and if somebody gets hurt by your poor information, you could be personally liable. This could include jail time or be at the very least financially liable. You are personally liable for anything you say on here or any other website!!! Since there seems to be so many posts with poor/dangerous information, I feel it has to be on purpose as nobody can believe many of the things that have been said, which includes the poster. 
Thanks!!! Have a Happy, warm Holiday to everyone!! Also, Thanks to all that try to help others on here and have a genuine interest in making this a site full of good/useful information. 
__________________
Darin Johnson
www.arboristsite.com
Our business is growing"


----------



## pook

CrappieKeith said:


> C'mon everybody...Pook just jumped off of a bridge...everyone follow...:bang::bang::bang::bang:
> 
> To quote the owner of arborist.com:
> 
> "TO ALL: After reading much of the information provided by Pook above, it seems to be misinformed and even dangerous in some cases. Please disregard any posts made by him before this post. I have informed him and will inform you all, if you are giving out bad information knowingly you will be banned from this site and if somebody gets hurt by your poor information, you could be personally liable. This could include jail time or be at the very least financially liable. You are personally liable for anything you say on here or any other website!!! Since there seems to be so many posts with poor/dangerous information, I feel it has to be on purpose as nobody can believe many of the things that have been said, which includes the poster.
> Thanks!!! Have a Happy, warm Holiday to everyone!! Also, Thanks to all that try to help others on here and have a genuine interest in making this a site full of good/useful information.
> __________________
> Darin Johnson
> www.arboristsite.com
> Our business is growing"


 Nothing like deferring from the issue? Yucons have no visible access to the fire so seeing the fire is insignificant?


----------



## loganj01

pook said:


> Note that the assertion is followed by a ? which means its a question, in hopes that the issue might be furthered & directly addressed instead of "shooting the messenger". Observing the fire is critical 2me & I have drilled many holes without consequence. With an alteration which has already involved drilling for the pipes??????????:biggrinbounce2:


 
I've drilled lots of holes too...but never in the door of my stove  All joking aside, I have to pull the Craft stove out this spring for an overhaul because many years of hot fires have finally warped the damper to the point that it really doesn't work anymore. I'm thinking about adding some secondary tubes to it when it goes back together. I have some 1" schedule 10 stainless pipe. One of the contractors at the plant hooked me up with a piece of 1/4" stainless tread plate that I'm going to hang in the top of the stove as a heat shield between the fire and the damper. Then I'll run the secondary tubes along the bottom, up the back, and attach them to the tread plate. If I leave a couple of inches clearance all the way around the tread plate, that should be enough to keep up my draft (40' masonry chimney) while protecting the damper plate from excess heat?


----------



## pook

loganj01 said:


> I've drilled lots of holes too...but never in the door of my stove  All joking aside, I have to pull the Craft stove out this spring for an overhaul because many years of hot fires have finally warped the damper to the point that it really doesn't work anymore. I'm thinking about adding some secondary tubes to it when it goes back together. I have some 1" schedule 10 stainless pipe. One of the contractors at the plant hooked me up with a piece of 1/4" stainless tread plate that I'm going to hang in the top of the stove as a heat shield between the fire and the damper. Then I'll run the secondary tubes along the bottom, up the back, and attach them to the tread plate. If I leave a couple of inches clearance all the way around the tread plate, that should be enough to keep up my draft (40' masonry chimney) while protecting the damper plate from excess heat?


In order for the 2ndary flame to appear & maintain the temp of the gas mix has to be~1200*f? If the flame disappears, the 2ndary air still goes to the hottest area of the stove. Some steel baffle epa stoves have insulated baffleplates with kawool or similar i think.
The magic of the 2ndary flame is that it esatblishes a hot zone above the woodload so to cook the wood from the top down & burn the gas more evenly than when burning load from the coals up? Read my "nature of fire" blog in my signature?


----------



## weimedog

These guys build an interesting product line..I have one and its perfect for our situation. ( Model "Thermo-Control 500") Something you folks might want to look into. They use stainless for all the water lines internal to the Stove. These aren't boilers so it matters. Especially if the power goes out and the circulators stop for a while..boils out the water..things get hot.


http://nationalstoveworks1.clickforward.com/index.html


----------



## kees53

*afterburn now succes*

Hi All

I have put in a insert, I have preheated air from under the firebed, and with two pipes of 5 x 5 cm to the pipe above the fire, now it wil burn, like hell.

firestones get redhot.

here movie.

YouTube - ‪Video-0004.mp4‬&rlm;


----------



## Misfit138

This guy built an affordable and efficient barrel stove with secondary burn. May be good for brainstorming if someone is venturing into stove building or modification.

Barrel stoves, if done right, are a great bang for the buck if you are building from scratch. 
Here is a site with instructions for building a good, high-thermal-mass barrel stove.
He uses a 35 gallon barrel within a 55 gallon barrel, but you may also simply use one barrel and line the lower half with firebrick.
Place a 1/4" steel plate across the top of the firebrick with a 6" V-notch, and then insulate the top of the steel with more firebrick or rockwool. This way, the barrel will last for many years and the stove will fire like a furnace.


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## corrupt

What would make a better baffle out of the 2 for secondary burn, 8mm steel plate or 1" thick fire brick? I have the steel plate now, but also have spare 9"x4.5"x1" fire bricks that I could make into a baffle if it would be worth while.


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## Misfit138

corrupt said:


> What would make a better baffle out of the 2 for secondary burn, 8mm steel plate or 1" thick fire brick? I have the steel plate now, but also have spare 9"x4.5"x1" fire bricks that I could make into a baffle if it would be worth while.


 
The 8mm plate should be placed at the top of the firebox and have fire brick placed atop it. In this manner, the fire brick will act as an insulator, keeping the intense heat inside the firebox, and the steel plate will become superheated. There is a product called rockwool which will work even better than the firebrick above the plate.
When the unburnt gases rise and come into contact with the superheated plate, they will ignite (in the presence of sufficient oxygen). 
Channeling superheated air up to the plate will enhance the effect.
This can be done (as shown in this thread) with drilled out black pipe. 
The total length of the pipes should be long; about 4 feet or more if possible. In this manner, the air (more accurately, the ocygen in the air) will be sufficiently heated to aid in secondary combustion.
Happy stove building.


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## corrupt

Thanks misfit I have still been playing, although its getting cold now so it will have to come back inside shortly. This is what I have come up with. The channel is 25mmx50mmx3mm steel and the tubes are 20mm stainless and a full fire brick lining. The screws in the back tube are from me trying to block them up to try and get slower air movement as the standard pre heat intakes are only 4 inches long and on the out side of the fire box, they will come out.

The stainless tubes hold the 1" fire brick up, do you think that is enough??


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## corrupt

second pic


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## Misfit138

It looks excellent! Have you tried it yet?


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## corrupt

Thanks misfit, yep I have used it about 6 times so far.
Once it has been running for about an hour and all the bricks are up to temp there is no smoke at all, alright may be a little puff now and then but you have to be looking to see it and only when the clouds are very dark or the sky is blue (I will be in and out of the house about 10 times at different stages checking, the misses thinks im strange).
The best thing is when it dies down a bit and I chuck a fresh log on there and with out adjusting the air supply the whole box is a slow moving ball of flames, its really nice to watch. I like watching it at the very start when the wood first start gassing and you see a little smoke build up then it flashes off is a large flat flame up against the baffle.
I dont get the blue flames out of the secondary pipes like some get but it seems to be doing the job.

Shane


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## Misfit138

Terrific.
If you really want to get crazy, you can cut down on smoke with a few tricks.
First, when cold-loading the stove, I find that a north-south log orientation facilitates a more efficient, clean burn. This has been the case on every stove I have tried it with. Place the larger logs on the bottom, reducing the size with each level, until the very top level contains only kindling. I light off the kindling with a MAPP gas torch (to my knowledge MAPP gas is no longer available, however there is an alternative product called MAPP-Pro available when this cylinder runs out). I could also lug my acetylene tank up from the cellar, I suppose.. 
Most people I know are surprised when I tell them that I cold-load in this way, and doubly so when I tell them I fire my stove from the top..however, it works very well and smokes less.
Next, woodstoves seem to smoke the least when you let each load burn completely down to ash and ember and then reload north-south as described above.
When hot-reloading, I remove some ash and ember about every 3rd load. I also place the largest logs on the bottom, at the left and right extremities, keeping more moderately size logs in the center. If you have a large enough firebox, you may want to experiment with just one very large log east-west in the back, and continuing with the rest north-south.
Also, in my experience, splitting the hardwoods slightly smaller than your initial intuition tells you is a big help. They will light off faster and burn nearly smoke-free. 
How about some pics from the outside of the stove?


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## BillsAutomotive

sesmith said:


> A week or 2 ago I put a question out on this forum here:
> http://www.arboristsite.com/showthread.php?t=85750
> Basically, I wanted to know if replacing my stove with a more modern EPA stove would save me much wood. Since I cut my own wood and our stove is in the cellar (where it's not part of the furniture in the living room), it would be pretty hard to justify the $2500+ for a new one, and the one I've got heats the house pretty well. One of the replies was from KSWoodsMan, who said he had put secondary burn tubes in his older stove with good results. Now why didn't I think of that! So instead of cutting wood in the cold yesterday, I worked on the stove. The 1st picture below is of the tube assemblies as they were going to look in the stove. The 2nd is of the tubes mounted in the stove and the 3rd is of the outside. The tubes run up the sides of the stove. Secondary air can be controlled from the gate valves and shut off if there were ever a chimney fire. Then it enters the front of the stove over the fire, is routed through solid pipe to the rear of the stove for preheating, and then is dumped into the top of the burn area just under the baffle through the holes drilled down the length of the burn tubes. I didn't weld the tubes in place in case I ever have to change them, so I added a couple extra 1" washers so the coupling inside the stove and elbow outside the stove could be tightened against the stove wall and sealed with high temperature masonry caulk.
> 
> So far, I'm kind of impressed with my cob job. After a lot of experimenting today, I'm finding that I can get nice long hot burns by leaving the secondary valves wide open and closing the primary controls way more closed than I would normally run them. The secondary air doesn't just make the wood burn faster. In fact, it looks like I may be getting longer burns than I would normally get and put out the same or more heat. When the fire is burning at a good rate, opening up the secondaries from the closed position without changing the primary controls gets me about a 100 degree gain measured on the stovepipe. So I guess they're working. Unfortunately, since I don't have a glass door I can't see them working like you guys with the new stoves can  So if my stove burns a little cleaner and I burn a little less for the same heat, I'll have it made.
> 
> So now for the disclaimer. I'm not recommending anyone try this on their own stove. If you try this on your old stove and trash the stove or burn your house down, I don't want to hear about it  If you do try it and it works, or you improve on my design, let me know so we can compare notes.



very nice ,I need to chat with you


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## FJH

Well i bought a used pac energy pre after burn for 300 bucks and made an after burn baffle plate for it, it works well also ,I also made the secondary burn adjustable ,I have also found there was no need for the secondary adjustment, other than in the event of a chimney fire a 1 inch by 2 tube feed directly into the plate would have worked just fine with out a control,I regulate the stove with the origanal draft control and leave the air wide open into the baffle and it still will have coals in the morning if i load before bed 8 to 10 hours it is the midsized stove spectrum i beleive You still need to be able to shut it down in case of a chimney fire but you could plug the holes with a rag or anything for that mater as long as the tubes are accesable and away from the heat!


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## sesmith

BillsAutomotive said:


> very nice ,I need to chat with you



Here's a link to more info on the project and more I did to the stove later:

Improving Efficiency of Older Wood Burner -- Adding Catalytic Combustor


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## FJH

Need rig sesmith !
I'm not going to go any further with my install I have tampered quite enough with the stove I am quite happy with the results of the baffel plate and the stove looks somwhat stock for insurance purposes! Also not really interested in baby sitting worring when or when not to engage the Cat!And I do like to burn news paper and paper trash from time to time .If I were the only one operating that would be fine.


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## maulionc

Hello all,

I've amelia 30 kw with water jacket from kratki factory, efficiency is 66% :





http://www.kratki.eu/static-files/f...127889dd32bb1ec5482ed16-amelia_pw_dane_pl.jpg

I've add vermiculite inside like the new Zuzia 15KW 




I want add secondary combustion but i think is the unique solution to boost efficiency like this stove modification :

Improving Efficiency of Older Wood Burner -- Adding Catalytic Combustor













what do you think

Charles


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## Misfit138

The efficiency of the secondary burn tubes may likely be enhanced by adding rock wool (ceramic fiber blanket) insulation to that plate just above the burn tubes.


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## maulionc

Hello,
i've put vermiculite for the baffle ( see picture)





charles


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## wood burner man

*Is a baffle plate or fire brick needed above the tubes?*

To SESMITH or all others:

This morning I came up with the ingenious idea of adding secondary burn tubes to my WoodChuck wood furnace via the ash pan door below. Hence, only 1 big hole in the middle of the ash pan door would feed air to the tubes. This would be the least intrusive surgical approach. And if it didn't work, I would not have 2 holes at the top of the burning chamber to cover up...like you have!

Then, I found out it was an old idea already invented by someone else. It is like joining the military to fight a war, but then learning the war is over. 
 
Well, here is my question:

--I assume a separate baffle plate (or better yet, a layer of fire bricks) at the roof of the burning chamber is necessary to protect the wood stove from overheating due to the 1000 degree heat generated by the secondary burn, and to promote "light off" of the secondary burn?

My WoodChuck can burn either coal or wood, and does not have an existing ceiling baffle plate, and the fire brick only goes half way up the inside burning chamber. Hence, it is not well protected from high burning temperatures inside the fire box. It does have a big secondary heat exchanger tube on top of the burning chamber with a sliding baffle plate on each end, via a hand operated rod over the fire door.

I observed others had fire brick on the ceiling of the fire box, when they added the secondary burn tubes.

Can I assume my stove is not a good candidate for adding the tubes? My operating manual does not list any internal burning temperature maximum. The manufacturer also does not provide for adding a catalytic converter for my unit. I am not excited about a $2XX catalytic converter, since they plug up in 2-4 years and must be replaced. 

I am mostly concerned about reducing the smoke from the unit, and to a lesser extent reducing wood consumption and gaining efficiency. We don't go through much wood for our home (about 3 cords (+/-) per season), but our neighborhood is getting more populated and I am concerned about complaints about wood smoke from neighbors.


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## doug4k

*woodchuck mod*

i have been considering this mod for my old restored woodchuck that i use in the garage. found this forum and have been researching this mod for awhile. its great to see a completed project that looked so clean. the woodchuck has a huge firebox and with a little welding i think i could add some brackets to install a brick lined secondary chamber similar to a clayton i saw at tsc. dont know if its neccessary. would like to try the pipes only method first and see how hot it gets. i had to weld up some water pipe holes when i restored this unit. they would have been real handy at this point. keep us posted if you do anything to your woodchuck. i doubt ill be able to get to mine this winter.


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## FJH

Adding air to the top of the fire in my opinion will enhance the burn reguardless of the presence of the insulated baffle!
The insulation will make it more efficent is all!


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## DiskDoctor

*Holes?*

Nice work!
I have read and reread this thread with great interest. I found it from a web search, never thought to look here 
;-)

Can you tell me the size and spacing of the holes you drilled? Fabbing is not a problem, but I wasn't sure about what to do.

Thank you for your ingenuity and willingness to share your findings and great work!


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