Secondary burn upgrade

Arborist Forum

Help Support Arborist Forum:

This site may earn a commission from merchant affiliate links, including eBay, Amazon, and others.

Mustang71

Addicted to ArboristSite
AS Supporting Member.
Joined
Sep 30, 2016
Messages
2,339
Reaction score
2,430
Location
Somerset NY
Ok so I have a daka furnace and I have been looking at adding a secondary burn to it with some black iron pipe. Looks easy on google. I have all the tools and access to whatever material I need.

Im looking for longer cleaner burn times. I added a baro but it lowered my fire box temp a lot and made the chimney dirty so what about secondary burn.

Is it as simple as adding some black pipe with holes in it below the plate under the flue?

Any opinion for improving my furnace would be great. It heats fine but I would like more efficiency if possible.
 
@Mustang71 it is not nearly as simple as adding piping and air, I have done it on my OWB with fairly good success but it is time consuming and frustrating. I believe I have some threads on here about all I've done, check them out and I will certainly offer any advice I can. PM anytime.
 
Is it as simple as adding some black pipe with holes in it below the plate under the flue?

I don't think so.
 
@NSMaple1 , you are completely correct, getting the fire box lined, getting the holes in the tubes in exactly the correct orientation, getting the air flows balanced right (which by the way changes with different MC wood), lining the plate AKA baffle, all play huge rolls in this. I know it can be done because I have done it, but its no simple task. Once it works right though it saves a lot of wood and cuts the smoke to almost nothing, as you can see in my avatar, thats roughly five minutes into a fresh load.
 
I dont get much smoke after the fire is rolling but the burn times are poor. I figured there would be some fire bricks added I have already added some along the back of the furnace because it was getting to hot. I dont want to burn my house down. It looked online like people just added secondary burn tubes and away they went.
 
You'll need firebrick to not only keep the firebox hotter, but also to protect the steel. If the firebox hits secondary temperatures for an extended period that's alot of stress on exposed steel. Stainless will take the repeated hot cycles much better than mild steel. You need oxygen, temperature and time. The other issue, you need the right balance between primary and secondary air. It's doable, but not a throw together and work kind of thing.
 
I have done a lot of searching and it seems like a good amount of people have done it to their furnace. I have no view of the flames so it would be hard to figure out what's going on and I have a 900$ furnace so idk how well it would hold up to the secondary burn...

But I'm still tempted to add a secondary burn tube. The research continues...
 
If I reload my furnace once it has reached peak air to combustion ratio, where it's basically slow burning and not violent, then I can get a decent burn time with a 200 degree air temp. The issue is that's 2 loads of wood in less than an hour. From what I have read is that with secondary burn you can cut down the primary air and heat off the smoke by re igniting it. So to me that sounds like one load of wood with less air makes a longer cleaner burn time.
 
If you are accustom to choking a stove down to smolder for long "burn" embers you'll be disappointed.
Secondary burn has the capability to INCREASE efficiency but the constant intake of air by its nature can only shorten the burn(smolder) time.
If burn time is a major concern for anyone out there, this is not for you. Stay with your current creosote creator and smolder all day long...

Back to secondary burn:
Fabricating an effective rack or grid system to hold a shelf of fire brick then positioning the secondary burn tube is going to be the big challenge.
Stoves using combinations of steel and iron often have air flow inside the baffle to cool and keep from warping.
The old Jotul 118 and 601 had air from the door intake directed upwards to the lip of the S baffle. Proportioning the normal intake air High/Low is genius.
 
I run my primary full open. The primary air on a daka is a spring loaded damper that closes as the spring heats up so if you dont run it wide open it closes way to early, produces no heat, and puts the fire out. It's a poor design that is claimed to be for efficiency. I only close it between burn cycles to keep the furnace warm and the coals going.

I have a baffle below the flue so I could fire brick that and hang the secondary off of it. I already fire bricked the back of the furnace because it started to warp and now it doesn't discolor the paint.
 
@Mustang71 you will need to brick all the walls below the baffle for sure in order to get enough heat to lite the secondarys, you will also need to make at least one pass through the box with incoming secondary air prior to your outlet holes in order to preheat that air. I also recommend individual control for primary and secondary air. It can be done but will take some thought and a lot of messing around to tune it. you will also really want to get a glass viewing port int the door so that you can see waht is happening. A word of caution too, if your flow path for the gasses force them towards the door before they go over baffle be ready for the door to warp once you get secondary, until I lined my door with brick and another plate the exterior surface temp would peak around 800
 
Sell your stove to fund a used Blaze King? I never thought adding secondaries could be so difficult. But, I never thought much about it due to having my Princess.

Good Luck!
 
I'm not getting rid of it until I'm ready to spend the money on a real nice one. I was exploring the idea of secondary burn because it seemed like a cool project but I know a lot of furnaces dont have secondary burn so whatever.
 
Seen MENARDS had the shelters furnace at a good price . I bought the Drolet from there a few years ago been happy with it . I was going to retro fit my old furnace after seeing how hot the new ones burn might be a big safety issue .
 
I had looked at the drolet a few times now and I like it. Hopefully by the time I'm ready to upgrade there will be a lot more furnaces like it. I think this will be my 5th winter burning wood so after buying the furnace and the saws and whatever else I bought, I think I'm going to use my current system for a while longer and try to save money burning wood.
 
Secondary burn is easy, I have done 2 different stoves now, so highly unlikely I got lucky twice. I used 1"x2" steel RHS for the secondary burn intake pipes and 3/4x3/4 drilled stainless for the secondary burn tubes themselves x2. I drilled 2x 3/4 holes into the back of the stove. I then ran 2 intakes up the back, middle of the stove. Then one goes left and the other goes right to the side of the stove itself. Then both come forward to the front of the stove with the ends capped, about 2.5" from the top of the stove. The 3/4 burn tubes then link the left and right pipes, they also support the fire bricks that sit on top of the whole setup and form the new baffle. My stove had fire bricks on the floor but i also added them to the sides as well.
All you are trying to do is get the heat in the fire box then add super heated air to the smoke and gasses while they are still in the fire box.
When my stove is up to temp and I shut down the primary air the top of the box explodes into tumbling flames with the wood only having minor flames.
So to turn the heat up I turn the stove down :)
The stainless pipes have a 1/8 hole every 1 1/4
 
I modded my Yukon furnace for better secondary air (they have a factory SA system of sorts) got it to get better secondary burn...sometimes...but it made the furnace very finicky, with a tendency to back puff (back fire). Like has been said already...its not as simple as it seems! I'd run it as is and just save up for a factory tube burner furnace (like the Drolet)
Oh, and black iron pipe doesn't hold up to secondary burn temps very well...that's what I started out with, and after a couple months it had a nice sag in the middle...had to go to stainless pipe $$$
 

Latest posts

Back
Top