# home built secondary burn chamber



## JeffHK454 (Sep 28, 2006)

With some fab skills could you add a chamber to older style wood furnace to improve emissions?

JH


----------



## MS-310 (Sep 28, 2006)

To a non boiler wood stove or a boiler type wood stove???


----------



## JeffHK454 (Sep 28, 2006)

Non-boiler wood furnace. 

From what I've seen in photos both here and on the net the secondary burn occurs when the smoke travels through a heated plate with slots/holes, I'm sure That I've over simplified this but I going by photos over the net.

Could you not divide the firebox with plate about 6" from the roof to create a secondary chamber? 

If I'm nuts let me know!

Pics of the internals of non-catalytic high efficiency stoves/furnaces and boilers would be very helpful.

Thanks, Jeff


----------



## Rspike (Sep 28, 2006)

Hey JeffHK454 , i just caught your PM. I'm sure you could build one to work on your unit. Stove company's do many test and arangments to get there design just right and to do the best job. Some secondary burn chambers are tubes and some are plate baffles. Here are some in my EPA stove that i had posted on another thread here. The big thing about secondary burn chambers is all the smoke and un burned gasses that go up the stack are turned into free heat for you. normally secondary burn chambers run at temps of up to 1100° the better one are made of stainless steel to take the extra heat. You'll need to line most of your fire box with refractory bricks ( stove bricks ) to keep the heat to a higher temp inside your fire box. The secondary burn chamber will need it own air supply so it not just a baffle sitting there. I post some pic and add some links.


----------



## Rspike (Sep 28, 2006)

http://chimneysweeponline.com/hocats.htm Here is a web page showing a cut of a stove with a secondary burn chamber. http://www.adamsstove.com/wood/pacific/pacific.htm another good read http://www.thefarm.org/charities/i4at/surv/woodburn.htm http://www.alternateheatingsystems.com/woodgasification.htm That should get you started.


----------



## JeffHK454 (Sep 28, 2006)

Rspike said:


> Hey JeffHK454 , i just caught your PM. I'm sure you could build one to work on your unit. Stove company's do many test and arangments to get there design just right and to do the best job. Some secondary burn chambers are tubes and some are plate baffles. Here are some in my EPA stove that i had posted on another thread here. The big thing about secondary burn chambers is all the smoke and un burned gasses that go up the stack are turned into free heat for you. normally secondary burn chambers run at temps of up to 1100° the better one are made of stainless steel to take the extra heat. You'll need to line most of your fire box with refractory bricks ( stove bricks ) to keep the heat to a higher temp inside your fire box. The secondary burn chamber will need it own air supply so it not just a baffle sitting there. I post some pic and add some links.




Thanks much for the info and pics, I was watching the "smoking boiler" thread which made me think about improving my current set-up. 

I could add the fire bricks and fab/install the plate but the secondary feed air is still unclear,it lets air in up high above the chamber plate? Is it a "tunable" type vent that you set by looking at the fire and making adjustments?

Thanks, Jeff

I did some reading on one of the links and it looks like the secondary feed air is going to be the stumbling block. How I can add controlled and heated air for the secondary burn is getting complicated, if anything I've learned a little!


----------



## laynes69 (Sep 29, 2006)

I have thought of the same thing you are fora long time. I have a forced draft option for my wood furnace, Its a US Stove Hotblast Wood/coal Furnace. My forced draft blower is on the back of the furnace right under the flame baffle. It goes into the stove, then from there its pushed through a piece of channel, which blows the air out the sides. I was thinking about adapting 2 pieces of heavy pipe one on each end, and drilling alot of holes in the pipe. Then run the pipes right under the baffle and have the holes facing the fire. This way you always get more secondary air to the fire. By the time the air goes through these tubes, it comes out hot, which then is easier to ignite the smoke. When the fan kicks on it pushes heated air directly on the fire. Now for coal this would do no good, but for wood, it would really help. These 2 tubes wouldn't take up any room in the firebox. I think it would work, and I have 1 1/2 OD 1/4 wall tubing, which would stand up to the heat. This would direct heated oxygen above the flames, which would help to re-ignite the gasses. I have also thought of putting a piece of steel on the baffle so when the smoke rises, it doesn't go apast the baffle right away, and keeps it there a little longer to be burned. These were just some ideas I have thought of. I have already rebuilt the inside of my furnace, its around 20 years old.


----------



## JeffHK454 (Sep 29, 2006)

I Have a two part plate that I plan on installing that will hopefully slow the escape of smoke and improve the burn efficiency. The flue opening on my furnace is in the top rear of the fire box and makes for a very straight shot out , the plate will divert the smoke back toward the front of the stove for a longer trip out. I might also angle the plate down in the front to create a "pocket" in the rear of the stove further slowing the exit of gases. 

I'm also going to line the sides with fire brick to increase the inside temperatures. 

I'm not going to do anything that's not reversible.

I have also considered a home brew forced draft but this is something that only works during the "heating" cycle and you still end up with a smoldering fire. 

I'm also in the process of making a fire monitoring system which uses both a fire box and flue probe to keep me informed of temperatures that are too low or too high. This little system will have a central "logic" box to trigger alerts when the fire is cooling and needs to be fed or if a very high flue temp signals a potential chimney fire. 

Just some ideas , Jeff

I also have a US Stove 1600M that heats like a mother but needs help with efficiency.


----------



## laynes69 (Sep 29, 2006)

With the forced draft you always have fresh air entering the rear of the firebox which aids in the combustion. Whether its running or not. It really helps. I also have a single baffle, with the exit at the rear. So its a straight shot like yours. I do have firebrick. The only thing is the furnace may not be made for the excess heat, the gases burn at very high temps. If you have luck with your design, send a pic, and let me know how it works. I've been looking for ways to improve mine.


----------



## JeffHK454 (Sep 29, 2006)

laynes69 said:


> With the forced draft you always have fresh air entering the rear of the firebox which aids in the combustion. Whether its running or not. It really helps. I also have a single baffle, with the exit at the rear. So its a straight shot like yours. I do have firebrick. The only thing is the furnace may not be made for the excess heat, the gases burn at very high temps. If you have luck with your design, send a pic, and let me know how it works. I've been looking for ways to improve mine.




The forced draft is always running , do you manually turn it on when you build a fire? They sold a kit for mine but it was switched with the thermostat that turns the blower on. 

I'm also not shooting for 1100 deg. with my modifications, just more than the 325-375 I get now. From what I've read on the net any controlled temp range from 400-500 is very good for a non-high efficiency wood burner. 

I also have fire brick on the top and down the sides at a 30 degree but I would like to add vertical rows down both sides. 

I also looked at the US Stove site for the make-up of the Hot Blast forced draft kit but the pic is so tiny I can't even rip off there idea. 

JH

The draft kit is electric, correct ?


----------



## laynes69 (Sep 29, 2006)

I set the forced kit at lets say 74 degrees, and I set the gas furnace at 68 degrees. If the house needs heat, the thermostat on the forced draft kicks on and loads the fire with air, it gets hot, the furnace blower kicks on and the house is warm. When the house hits 74, the forced draft shuts off. For the forced draft to get air, there is a damper on the fan itself. It stays open so even if the forced draft shuts off, air still enters that 2 1/2 inch hole and helps feed the fire. Its a squirrel cage fan. I never got any cresote accumulation at all in the chimney last year. And in the dead of winter when the wood furnace is running, there is no smoke 15 minutes after loading. It did drop the burn time down to 6 to 8 hours, but burns alot hotter and cleaner. I load 4 to 5 logs at 9:30 pm open the dampers for about 20 minutes then shut it down, I do keep the ash drawer damper open, and I keep the damper on the forced draft kit open. That way I dont starve the fire and 5:30 am the furnace is full of red hot coals, throw on wood and away I go. The forced draft kit has a relay, limit control and a junk thermostat. I put a programmable digital thermostat on mine.


----------



## JeffHK454 (Sep 29, 2006)

Thanks for the clarification.

When I bought my furnace the sales guy was uninformed about the forced draft kit for my model so I shied away from it but I might rethink it.

It sounds like it does as advertised.

JH


----------



## laynes69 (Sep 29, 2006)

One other thing, I hear it works good with hard coal or soft coal. So if you ever decide to burn coal it would help you there too. I burned some hard coal last year and I was first told to turn it off when burning coal, but im gonna try it this year.


----------



## JeffHK454 (Sep 29, 2006)

Whats the going rate on coal and where do get it? 

I've burned it in fires while camping/offroading in Kentucky and Tennessee but have no experience with it as home heating fuel. We would gather a couple 
5gal buckets of it and dump it on a active wood fire for something different.

I actually like the smell it gives off.?

JH


----------



## laynes69 (Sep 29, 2006)

I get it around here ashland county from the amish. Last year is was 185.00 a ton picked up, Not sure of it this year. The hard coal I get has no smoke, no odor whatsoever. Burns well over 12 to 14 hours very hot! If it was washed, you could touch it all day and stay clean as could be. Hard coal is extremely difficult to get going, but once its lit, its hard to go out. If you burned hard coal your neighbors would never have a clue you were burning anything. Also there is no need to sweep your chimney, because it burns so clean. Its close to 90% carbon.


----------



## edc (Oct 20, 2008)

I would like to improve my summeraire furnace as well. Would a stainless barbeque burner work for the air tubes?

Thanks


----------



## laynes69 (Oct 20, 2008)

Nope, You would melt them in two.


----------



## edc (Oct 20, 2008)

Bummer, How about cast iron BBQ burner? I've seen those available.


----------



## Moddoo (Oct 20, 2008)

I modified mine last year, it works very well.
here is a sketch.
The blue are fire bricks added to increase the flame travel distance.
The red is iron pipe added to allow air to preheat before entering the chamber through holes drilled into it.
I'll post some pics later tonight.


----------



## Moddoo (Oct 20, 2008)

here goes.
it is tough to get pics inside the firebox











here's a couple action shots


----------



## HARRY BARKER (Oct 20, 2008)

Moddoo said:


> here goes.
> it is tough to get pics inside the firebox
> 
> 
> ...




sweet!! that looks like it works good


----------



## hotrod1950f1 (Oct 20, 2008)

Moodoo am I seeing what you are doing in your stove correctly. Are you injecting hot air above you fire in the main burn chamber. Also how are you forcing the air through the pipe. Thanks

Joe


----------



## Moddoo (Oct 21, 2008)

hotrod1950f1 said:


> Moodoo am I seeing what you are doing in your stove correctly. Are you injecting hot air above you fire in the main burn chamber. Also how are you forcing the air through the pipe. Thanks
> 
> Joe



Basically, yes.
The secondary air is coming from the optional forced draft port in the back.
this port is in the center of the back of the furnace. It enters a preheat chamber, before entering the firebox below the grate in the back.

This is where I attached my new pipe.

I am not using a blower for the air.

It is sucked into the stove by the draft..

I very rarely have any smoke coming out, and have regular 12 hour burn times in the winter.

We use the gas furnace only when we are out of town.

I went through about 5 1/2 cords heating my 1958, 2000 sq ft rambler. with the original single pane windows and insulation.

She likes the house at 75*! LOL


----------



## edc (Oct 21, 2008)

That is beautiful! Nice work!:agree2:


----------



## hotrod1950f1 (Oct 21, 2008)

What is everyone using to adhere replaced and/or additional firebrick in there stove. I have a Royall add on stove built circa 1980 and I am just trying to make it as efficient as possible.


----------



## 046 (Oct 21, 2008)

modoo... nice job! 

looks very simple to inplement


----------



## edc (Oct 21, 2008)

What size pipe is that? and what size holes did you drill? Seems to be perfect!


----------



## Moddoo (Oct 21, 2008)

Thanks for the kind words guys.
I just had to do something after seeing all of these fancy "new" stoves out there!

The pipe is 1" coming in and Tees to 3/4" if I remember right.
The holes are 3/16" I believe.
I drilled approximately enough holes to equal the area of the inlet pipe.

The extra couplings and such are a product of available lengths at menards, and being able to assemble/fit everything in the firebox.

My firebrick is also from menards. mine are all gravity adhered. 
adding the extra bricks and roof, really helped keep the box temps up for the secondary burn.


----------



## 046 (Oct 21, 2008)

what material are you using for the top shelve? 

is the air intake regulated in any way? just by drilled orifice size? 

would like to fab one for my insert before cold sets in....


----------



## Moddoo (Oct 21, 2008)

046 said:


> what material are you using for the top shelve?
> 
> is the air intake regulated in any way? just by drilled orifice size?
> 
> would like to fab one for my insert before cold sets in....



The shelf is 4 fire bricks.
I "mitered" them to fit together and on top of the 2 on the sides.
I have to say that I got lucky with the dimensions there.

The secondary air can be reduced by screwing a reducing fitting on the outside 1 1/2" pipe (that is the size of the original fitting for the optional forced draft blower) But, there is no need for it with the way mine is set up.


----------



## edc (Oct 21, 2008)

Thanks Moddo, you just saved me at least 5 cords of hauling, cutting, splitting...You are the man!


----------



## 046 (Oct 21, 2008)

thanks for clarifying... any chance you can take a few pic's of the shelve setup, showing fire brick? 



Moddoo said:


> The shelf is 4 fire bricks.
> I "mitered" them to fit together and on top of the 2 on the sides.
> I have to say that I got lucky with the dimensions there.
> 
> The secondary air can be reduced by screwing a reducing fitting on the outside 1 1/2" pipe (that is the size of the original fitting for the optional forced draft blower) But, there is no need for it with the way mine is set up.


----------



## jburner (Jan 1, 2009)

*Reburn tubes*

Moddo - Thanks for the nice pics and making the bold move. I was just going to do the same with my furnace and I hadn't seen anyone who had done it before. Thanks. Looks like it works good too! 

Are those tubes just plain old cast iron? I'm going to try doing all 3/4" using two holes in the front of the furnace coming off of the forced air blower baffle. The only question I had was, are firebricks absolutely necessary? The walls on my furnace are angled / \ like this above where firebricks normally sit on the bottom, so stacking bricks is impossible up the sides. I do have a "secondary heat exchanger", but I'd like to burn up those gases before going out the chimney, anything to get more heat out of my wood. 

Not sure how to post pictures, but I'll try to learn and put some up. Hoping it will work. . .

Oh, and if I read your post right, you put 8 holes in the tubes based on the size of the hole coming into the furnace. 1.5" / 3/16" is my math correct?


----------



## kees53 (Jun 13, 2010)

*it is somewhat late*

Hi All


The pictures of this topic on page 1 where I see the plate with holes, what I need is what kind of steel do I need to make it lasting longer with this high heat.

I have burnd this winter with a tryout, it works, and now I want to make the plate so that heat will warmup the secondary air properly, so that the combusting of smoke starts sooner and easy.

thanks.


----------



## ronsetoe (Jun 15, 2010)

kees53 said:


> Hi All
> 
> 
> The pictures of this topic on page 1 where I see the plate with holes, what I need is what kind of steel do I need to make it lasting longer with this high heat.
> ...



I am not understanding the question? When I installed my tubes I used cast iron with fire brick above the tubes. Mine enter the front of the furnace through the bottom and turn up the rear and back towards the top. What furnace are you trying to modify? Shoot some pics and we might be able to help. Welcome from overseas!


----------



## kees53 (Jun 16, 2010)

*Hi There*

Wel again a new message, this site loosed it after try to post it because it ask again for the password, nasty.

Here are the pictures, I have put firebrick in it, fermaculite on top for refection of heat, and above that another plate to make the pad for the smoke longer.

als I have put in a window airwash, who works fine, but after some months it get dirty, and also a tube in the back, but this don,t give enough heat air for secondairy combustion.

Somewhere on this site there are pictures of vlame plate with holes in it, this way I tryed but I have see your attemt what is very good indeed, I wil also first try the tubes.

nice done.


pictures.






inside






thanks.


----------



## romulus (Jun 16, 2010)

*Exchange of ideas needed*

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. 

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. - Thanks


----------



## ronsetoe (Jun 16, 2010)

kees are you getting the air heated up enough with you design? This is what I designed my secondary burn tube after for my furnace. I used cast and it worked well. It is a good 4 page read with plenty of pictures for ideas.
http://nepacrossroads.com/about2066.html#p13410
good luck


----------



## kees53 (Jun 17, 2010)

*Hi There*

Hi 

I have calculated the pad of the air, it has 1.6 sq feet x 2 so for preheat alswel for heat, tubes of 2 inch you get then 6 feet x 2, then you have a real afterburn with very low emissions.

I go make a vlame-plate from hollow square pipe welded togehter, so I have a very long pad, 3.2 sq feet meter for the afterheater alone so I am there already with a vertical airsupply pipe.


Thanks for for the link I wil for sure studie it.


regards


----------



## kees53 (Oct 26, 2014)

Hi All

It is a time ago that I was here! I have done some things with the stove like a 4 tubes in it and more heat exchange, however it get difficult
to go secondairy, I have thick fire bricks yellow ones and I think the fire itslef is to cool.

I hear that primairy has to be shut off with wood, is this right? I think it is a combination of air get in it.

here some pictures of different tryouts.





















and the old one 6 months ago






The firebrick get black from smoke and burn clean, however a big part of it does not give the idea of to cool
fire.

I have seen stoves use not firebrick but ceramic plate in it. A idea how to insulate burnchamber best? this
is still problem.

regards

kees


----------



## blades (Oct 27, 2014)

laynes69 said:


> I have thought of the same thing you are fora long time. I have a forced draft option for my wood furnace, Its a US Stove Hotblast Wood/coal Furnace. My forced draft blower is on the back of the furnace right under the flame baffle. It goes into the stove, then from there its pushed through a piece of channel, which blows the air out the sides. I was thinking about adapting 2 pieces of heavy pipe one on each end, and drilling alot of holes in the pipe. Then run the pipes right under the baffle and have the holes facing the fire. This way you always get more secondary air to the fire. By the time the air goes through these tubes, it comes out hot, which then is easier to ignite the smoke. When the fan kicks on it pushes heated air directly on the fire. Now for coal this would do no good, but for wood, it would really help. These 2 tubes wouldn't take up any room in the firebox. I think it would work, and I have 1 1/2 OD 1/4 wall tubing, which would stand up to the heat. This would direct heated oxygen above the flames, which would help to re-ignite the gasses. I have also thought of putting a piece of steel on the baffle so when the smoke rises, it doesn't go apast the baffle right away, and keeps it there a little longer to be burned. These were just some ideas I have thought of. I have already rebuilt the inside of my furnace, its around 20 years old.


This has been done although I do not not know if the information is in the archives do to the hacking that went on - around 5 years ago was when it was posted.


----------

