Adding secondary burn to this unique stove

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AtomicDog

Member
Aug 21, 2014
51
East TN
If you look at the pic of the stove you can get an idea of the room above the tubes. 1.5in or so. I've been so focused on what to do that I haven't really thought about how to do it. Drilling those tubes from inside the stove is a challenge at best. I can only see three of the four tubes. I'll have to use an angle drill and mirror to get that first one. Still a lot more fun than just buying a new stove. I'll probably install a thermocouple between two of the tubes since I don't have a window. I should be able to detect the secondary burn that way.
 

bholler

Chimney sweep
Staff member
Jan 14, 2014
27,120
central pa
I like your plans and they will probably improve the efficiency of the stove quite a bit. But honestly insulating the basement walls will make far more impact.
 

Blazzinghot

Burning Hunk
Dec 5, 2019
238
New Plymouth, Idaho
I would think that putting in new tubes would be easier under the used to be air tubes. The work could be done without cutting off the top of the stove. But I don't know the distance from the bottom of the inside of the fire box to the now existing air tubes. I have a couple of times been able to put in secondary air tubes without cutting off the lid. Others on this forum have also done it by using black stove pipe.

You could build the whole system and then slip in in through the door and then have a hole drilled for the intake for secondary air and weld the unit in place. And you don't have to think round you can use square tubing. Here is a method I used without cutting the stove that worked real well for me see picture. I brought in two secondary air burners using rectangular tubing.

Inside Secondary Burners.jpg Doors Open .jpg
 

AtomicDog

Member
Aug 21, 2014
51
East TN
I have a lot of room to work with. This would also allow me to keep my blower, have the intake lower, and a longer path for the air to heat up. Looks like I can fabricate everything ahead of time. Worst case this just becomes a firebox for my next BBQ smoker build.
 

AtomicDog

Member
Aug 21, 2014
51
East TN
I'll insulate the basement walls, but that's a huge summertime project. The basement is my workshop, so every wall has cabinets, work benches or shelves. Almost the entire basement is under ground. The only wall that isn't is the one with the stove, and its the end of the house. I guess I need to look at options. I like the durability of block walls.
 

bholler

Chimney sweep
Staff member
Jan 14, 2014
27,120
central pa
I'll insulate the basement walls, but that's a huge summertime project. The basement is my workshop, so every wall has cabinets, work benches or shelves. Almost the entire basement is under ground. The only wall that isn't is the one with the stove, and its the end of the house. I guess I need to look at options. I like the durability of block walls.
Under ground is just as bad. That ground eats up lots of BTUs as well.
 

Blazzinghot

Burning Hunk
Dec 5, 2019
238
New Plymouth, Idaho
AtomicDog, Just a couple more suggestions before you start grinding and welding is make sure you have a way to install the baffle above the new secondary burners as you are designing it. The Lopi woods stoves used to use bricks for the baffle above the burner but whatever you use also watch your clearances so your fire can wrap around the baffle and go up the flue so you don't have smoke coming out the door every time you open it. Have fun.
 
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MR. GLO

Feeling the Heat
Jan 26, 2021
263
Massachusetts
AtomicDog, Just a couple more suggestions before you start grinding and welding is make sure you have a way to install the baffle above the new secondary burners as you are designing it. The Lopi woods stoves used to use bricks for the baffle above the burner but whatever you use also watch your clearances so your fire can wrap around the baffle and go up the flue so you don't have smoke coming out the door every time you open it. Have fun.
Would insulation be OK to add? By installing, so it sits on top of the baffle?
 

Blazzinghot

Burning Hunk
Dec 5, 2019
238
New Plymouth, Idaho
MR. GLO, Some of the newer stoves are using stainless steel baffles with insulation blanket on top. Some use ceramic boards with insulation blanket on top and others bricks. Some of the older stoves were using 1/2 steel plating but the would warp over time. Then there is me who has tried Hardie panel but it does get brittle over time. So now I use stainless steel when I can get it from the recycle yard.
 

MR. GLO

Feeling the Heat
Jan 26, 2021
263
Massachusetts
Thanks. I was going to use stainless steel too but wondering if it's OK or worth putting a blanket on top. If so just lay it on top?
 

SpaceBus

Minister of Fire
Nov 18, 2018
6,450
Downeast Maine
I think an insulation blanket would only help. Lining the firebox with some form of refractory will also help things out.
 
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AtomicDog

Member
Aug 21, 2014
51
East TN
Blazzinghot, 20 inches from the bottom to the existing tubes.

My plan was to put the insulation between the tubes and the top of the stove, which would become the baffle. I suppose I could cut this out and replace it with stainless if the .250 steel wouldn't hold up.
 

Blazzinghot

Burning Hunk
Dec 5, 2019
238
New Plymouth, Idaho
Mr. Glow yes SpaceBus is correct. I try to remember that secondary air needs to be hot. The newer stoves have the stainless steel and the insulated blanket some others have a ceramic board with insulation on top.

AtomicDog, You want to have the baffle as close as possible to the secondary burn tubes as possible so the heat radiates off the baffle on them. Secondary combustion starts at about 1200 degrees.

In my mind I would think it would be better to have the baffle with the insulated blanket right on top of the secondary air tubes. The idea is to get those tubes nice and hot. I would put the secondary air tubes just blow the upper camber with baffle and insulation to allow a couple of inches on the front end toward the door for air to pass up into the top chamber. That is if you still plan to put the flue on the top which I think is a good idea. If you leave the top air pipes open the heat can swirl around them better and you will have some good hot air blowing out through them with the fan. Hope this makes sense. If you need a diagram let me know but at the same time I want you to dream and built this stove your way as this is half the fun. If you have other questions I will do my best to help. There are other members of this forum who have put in secondary burn tubes so hope they can share their experience.
 

snobuilder

Member
Dec 16, 2021
126
WI
Mr. Glow yes SpaceBus is correct. I try to remember that secondary air needs to be hot. The newer stoves have the stainless steel and the insulated blanket some others have a ceramic board with insulation on top.

AtomicDog, You want to have the baffle as close as possible to the secondary burn tubes as possible so the heat radiates off the baffle on them. Secondary combustion starts at about 1200 degrees.

In my mind I would think it would be better to have the baffle with the insulated blanket right on top of the secondary air tubes. The idea is to get those tubes nice and hot. I would put the secondary air tubes just blow the upper camber with baffle and insulation to allow a couple of inches on the front end toward the door for air to pass up into the top chamber. That is if you still plan to put the flue on the top which I think is a good idea. If you leave the top air pipes open the heat can swirl around them better and you will have some good hot air blowing out through them with the fan. Hope this makes sense. If you need a diagram let me know but at the same time I want you to dream and built this stove your way as this is half the fun. If you have other questions I will do my best to help. There are other members of this forum who have put in secondary burn tubes so hope they can share their experience.
In bold /red. This is very refreshing to read on this mostly helpful website. I am following this thread as I added a controlled secondary burn tube array to my DAKA wood furnace. It shows signs of catching a secondary burn but I think the temps aren't high enough through the entire burn cycle. I will be adding a ceramic insulating panel above the tubes .
 

Blazzinghot

Burning Hunk
Dec 5, 2019
238
New Plymouth, Idaho
snobuilder, I am still learning about wood stoves so had to look up what a DAKA wood furnace to see what it looked like. I found an older none EPA picture of one. Yes, it would be hard to get a good secondary burn with out a baffle and insulation of some kind. If you study the wood stoves today most bring in the secondary air from the bottom back of the stove as the fire torches the back wall of the stove or furnace. This way the air gets heated before it gets to the secondary burn tubes. Hope you get DAKA secondary burn working.
 
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snobuilder

Member
Dec 16, 2021
126
WI
snobuilder, I am still learning about wood stoves so had to look up what a DAKA wood furnace to see what it looked like. I found an older none EPA picture of one. Yes, it would be hard to get a good secondary burn with out a baffle and insulation of some kind. If you study the wood stoves today most bring in the secondary air from the bottom back of the stove as the fire torches the back wall of the stove or furnace. This way the air gets heated before it gets to the secondary burn tubes. Hope you get DAKA secondary burn working.

16424304339529054313124183559626.jpg 16424305092977494359008065787023.jpg 16424306777918543109498874274750.jpg 16424308129123887004901648915112.jpg
 

Blazzinghot

Burning Hunk
Dec 5, 2019
238
New Plymouth, Idaho
snowbuilder, looks like you used stainless steel tubing for your secondary air tubes correct? That is a very interesting set up you have. It is always nice to see what others are doing to improve their wood stoves. Thanks for the pictures. I certainly agree that is one very big white spot on the back of your stove you might consider a 1/2 steel shield inside the stove to protect the back wall. you certainly have plenty of heat to warm up the secondary air so it should work. Keep us posted on if your secondary burners become more effective.
 

snobuilder

Member
Dec 16, 2021
126
WI
snowbuilder, looks like you used stainless steel tubing for your secondary air tubes correct? That is a very interesting set up you have. It is always nice to see what others are doing to improve their wood stoves. Thanks for the pictures. I certainly agree that is one very big white spot on the back of your stove you might consider a 1/2 steel shield inside the stove to protect the back wall. you certainly have plenty of heat to warm up the secondary air so it should work. Keep us posted on if your secondary burners become more effective.
Tubes are 1/2" black pipe that threads in if replacement is needed.

I actually run this stove extremely low most of the time. After using my new IR thermometer and realized this I cranked it up today to get the afterburners to fire. The Rutland stove pipe gage which was around 150 went into the burn zone .

Back wall of stove is getting new fire brick and I will see if I can add more height to it. Like another layer sideways.
 

Blazzinghot

Burning Hunk
Dec 5, 2019
238
New Plymouth, Idaho
snobuilder, Thanks for the explanation. How are you able to tell if the secondary burners are working? Have you tried to put a flame via a match or lighter to see if the secondary air tubes are pulling in air at the inlet? I am sure you have been checking the smoke coming out of the top of the chimney. Keep us posted on your progress.
 

snobuilder

Member
Dec 16, 2021
126
WI
snobuilder, Thanks for the explanation. How are you able to tell if the secondary burners are working? Have you tried to put a flame via a match or lighter to see if the secondary air tubes are pulling in air at the inlet? I am sure you have been checking the smoke coming out of the top of the chimney. Keep us posted on your progress.
No smoke at chimney top. Without glass door, I open door after checking chimney top and will see a clean burn going on at and around the tubes. One issue I'm noticing is the stove is fairly tall inside so the secondary burn isn't as affective once the pile burns down.
I do get a convective draw into the square tube at the floor but am also trying out a small low speed fan to add a little boost.
 
Last edited:

bholler

Chimney sweep
Staff member
Jan 14, 2014
27,120
central pa
No smoke at chimney top. Without glass door, I open door after checking chimney top and will see a clean burn going on at and around the tubes. One issue I'm noticing is the stove is fairly tall inside so the secondary burn isn't as affective once the pile burns down.
I do get a convective draw into the square tube at the floor but am also trying out a small low speed fan to add a little boost.
Put a baffle in not a fan forced secondary air is asking for trouble
 

Blazzinghot

Burning Hunk
Dec 5, 2019
238
New Plymouth, Idaho
snobuilder, Did you already install the baffle as you mentioned in one of your posts? If you have a good draft on the chimney and a good air tight stove it should pull in plenty of secondary air without a blower fan. It depends on how many air holes you drilled and what size they are. I built one stove for my shop and did not drill enough holes in the secondary burn tubes and it was a real pain drilling holes after the fact.
 

snobuilder

Member
Dec 16, 2021
126
WI
Its a work in progress and is my everyday stove. Next addition will be the ceramic insulation panel above the tubes when it gets here.
I don't mean to hijack the thread on the OP, just posted some pics of my similar mod.
 

bholler

Chimney sweep
Staff member
Jan 14, 2014
27,120
central pa
Its a work in progress and is my everyday stove. Next addition will be the ceramic insulation panel above the tubes when it gets here.
I don't mean to hijack the thread on the OP, just posted some pics of my similar mod.
I don't see it as hijacking. Your experience with your setup is applicable for them.