Is a barometric damper beneficial on a wood furnace?

Hello all, I did some work to my Daka 621 wood furnace by installing a homemade secondary burn on it. Nothing fancy, just some black pipe with slots in it. Seems to be working great as I can see the smoke and gasses on fire even when I open the door. The reason I installed this is because I wanted to get a cleaner more efficient burn. Wood is becoming more valuable even though I CSS it all myself but I want to prolong my inventory (3+ years of course!) as long as I can. May even sell some if the price is right! My problem is that while I am getting more heat from the furnace, my burn times are not as long as I'd like or am used to. I am tossing around the idea of adding a barometric damper to the stove pipe to give me a more even and lower draft as I have plenty of draft with an old two story house. The wood furnace is in the basement, so without measuring the chimney, I'm guessing around 30 feet of chimney. It is lined with 6" stainless steel liner as well. Again, there is no problem with enough draft once everything is up to temp. For those not familiar with The Daka stoves they have what is called an automatic damper on it already to allow fresh air into the firebox. It opens up to allow more air into the firebox when cold, and closes down the air flow when the firebox is hot. I'm ultimately wondering if the barometric damper will allow too much cool air into the chimney, thus cooling the chimney off and possibly forming creosote? Of course with the secondary burn system installed, hopefully I wont have as much smoke and gasses in order to form creosote. Kinda curious what other have found out using barometric dampers. There is a company in northern Minnesota called Lamppa Manufacturing that makes Kuuma wood burning furnaces. Researching this company is what got me thinking some of these ideas. I should add that the operators manual for the Daka 621 says a barometric damper is optional and may be used to maintain no more than .06" water column updraft.

 

If you have a 30' chimney I can almost guarantee you have draft over -0.10" WC...probably a good bit more actually.
Yes a baro will help lower that...get a manometer to keep an eye on on exactly what your draft is too...the Dwyer Mark II Model 25 is a good one that is fairly cheap.
Yes the baro cools the chimney...that's how it works...it lets in just enough cool air to keep the draft at wherever it is set to do so. If you are burning good dry wood, and your furnace's intake control is doing its job, then you should not have a creosote problem...going to doublewall stove pipe can help too, if you do have a bit of an issue...hopefully your chimney liner is insulated?
I've heard of people with 30-40' chimneys that actually had to have 2 dampers!
Just FYI, I have been running baro's on my furnaces for 10-12 years now...no issues.

 

Thank you for the response! Makes sense... and cents! I'm curious to see what my draft actually is. The SS chimney liner itself is not insulated. Just a flexible 6" SS pipe shoved inside the previous chimney which still has the 8" clay liner. There is some vermiculite between the SS and the clay which I suppose gives it some insulation.

 

Better that nothing...barely. The problem with vermiculite is there is no way to guarantee that the liner is centered in it, and if there is any lil hole the vermiculite just flows right through it...you think you liner is insulated and turns out its all in some random cavity somewhere. Ceramic insulation blanket/wrap is what you want.
Its good the clay liner is still there, but way too often those old chimneys (even the newer ones) weren't built with proper CTC and you have no way to know for sure...and if there is damage to the clay, or missing grout, that's even scarier.
For me and my household, I sleep better knowing I have a quality SS liner with proper insulation on it (my clay liner was gone, so I had no choice anyways)

 

Interesting. I've not heard of ceramic insulation. I need to get out more! I've been thinking of overhauling my chimney some day. I'd like to hook the clean up door up again so I don't have to take the stove pipe off to clean out the creosote when I sweep it. The door is at the bottom of the chimney on the side. The company that came and relined it with SS "forgot" to put a hole in the bottom of the liner for the clean out. Now if you open the door you get a pile of vermiculite and the joy of trying to close the door with product flowing out of it. I've thought about draining all the vermiculite out and cutting a hole in the liner and using mortar to make a "tunnel" to the SS liner. However, you have me thinking again...maybe if I drain all the vermiculite out I can wrap the SS liner with ceramic insulation? How much of a process is that? The old clay liner is 8", and the newer SS liner is 6", that gives you 1 inch of room for insulation. Then you have to shove that down the hole and hope the insulation sticks to the SS and slides on the clay. May take some more research on my part.

 

You'll be tight with an 8" flue, but it is doable if the clay is in decent alignment and don't have a bunch of mortar sticking out of the joints. The insulation gets a SS mesh sock pulled over it so it has a little protection...that should come with the liner kit.
Installing insulation on the liner is pretty easy...there are lots of videos on it.
What I did on mine was to add a short section of flex liner to the bottom of the tee (where is comes through the basement wall) so that it reaches down to the cleanout door...I have a SS cap that I put on the bottom of the liner and then a couple bricks to slide under the cap to hold it up in place. The place I bought the liner kit from crimped the bottom of the tee so that I could slide the liner up on there like that. I did not insulate that bottom section of the liner, just from the bottom of the tee up.

Its good that the installer "forgot" to put a hole in the bottom of the liner...that can really affect your draft, and could be a real fire hazard.

 

years ago I had a uss coal/wood furnace with that auto draft unit on it. I called it an automatic overfire unit as it wood stick wide open all the time. That could be why you are seeing shorter burn times. I had a baro on it as well , about 25 ft of flue similar to yours liner down the the flue but the clay fire tubes were busted out to get liner down and vermeculite poured in around it. it worked to a limited extent. never quite trusted it. max burn times were about 3.5-4 hours a load . If the very old dragon that was there prior would have been in better shape- that would have been better. It was cracked in several areas and leaked like sieve. hence replacing it. and the liner made the Ins. co. happy. I didn't seem to have much problem with creosote, fuel was 15-20% at room temp on fresh split face ( important part here is checking your fuel for moisture at room temp and on fresh split face). As to the baro, it worked to hold the draft around .06 or so - although I really could not tell much difference with it or with out it. didn't do squat for burn time on that set up. pulled that out put a freestanding stove and new flue (Class A) on main floor much better and less wood used. If I not mistaken the Daka is also a wood or coal unit- works much better with coal as that is what it was primarily designed for.

 

Yes, the Daka will burn coal as well. Although I believe you need a coal grate installed for it to work properly. I've never tried it as I wouldn't know where the closest place to buy coal is in my neck of the woods (SW Minnesota). Plus I really enjoy CSS firewood , so that's what I burn.

 

Hey mn would you be willing to post some pics of your retrofit I am trying to add secondary burn to an old smoke dragon from the 80’s. Thanks in advance

 

Nate oehlbeck ,I'll see if I can load some pics here. First time uploading pics to this site. This is what it looked like assembled. I just used black pipe. I think it was 1" in size and I cut some slots every 1" where I wanted the heated oxygen to come out. I have no idea if this is too many slots or not enough. Nothing scientific about this! I did weld shut the ends of the pipe as you can see they are a little "whiter" than the rest of the pipe. I waited to tack those three "arms" to the intake pipe until I had it inside the stove as my stove already has a baffle in it but it is starting to warp a little. If this idea bears fruit, and I get the ambition, I'll cut out the old baffle and replace with a heavier one, and probably use stainless steel pipe. We will have to see how this holds up.

Here is what the front of my stove looks like. You can kinda see where the outline of the firebox is. I bought a new 1.25" hole saw and drilled a hole just off to the side of the door. I did not put a valve on it to control the amount of secondary air to it...yet anyways. I figured if this project doesn't work, I can just put a 1" pipe cap on it and tear it out next summer when I get time. Or leave it in as it doesn't take up much room in the firebox.

Once I got it inside I put "legs" to help hold it up in the two opposite corners, and tack welded the three "arms" to the intake pipe. My baffle (or false ceiling), is starting to show its age and is sagging a little bit. I tried to take a hydraulic jack and straighten it out, but didn't have too good of luck with that. As you can see if you look close, the three "arms" don't meet up perfectly to the intake pipe. It's not "purdy lookin", but hopefully its functional.

Here is another view. The rod in top/middle goes to the back of the stove and opens a bypass door for the smoke to go out the back rather than coming towards the front by the door. The angle iron that the "legs" sit on hold the firebrick in place. I believe the firebrick is around 8" deep. Under the firebrick is a grate which is overtop the ash pan.

Here it is in action. Hard to see in a picture, but once it gets up to temp, the smoke does start on fire! Even with the door open. At least for the first 10-15 seconds anyway.

 

So this is what I tried I’m on rev 1.
I think it’s working but it’s rather finicky and I notice that I still get some smoke although definitely a reduction I’m hoping to redo soon and get more air.
Bullard is a local kind of company that kinda copied some of the big guys. I think the air coming in the side is not enough to feed also the only one main large second burner down the middle isn’t quite ideal.
Have you noticed a large reduction in smoke or creosote ? So far.

 

I added a baffle with a bypass made of fire brick as well to aid in keeping the heat in the burn box.
But I think

 

I have not checked the chimney for creosote yet as I have to shut the stove down. And its cold outside. And I don't want to run the furnace to get the temp caught back up. However, once the stove is cool, I can take the stove pipe off chimney and stick a mirror inside the chimney pipe to get a good look. My guess is there is some as I didn't start the season with the barometric damper installed. Then I went the cheap route and installed the cheaper foreign built damper that did not work the best with my high draft issues. The damper weight would go over center and allow too much air I did finally get the higher quality damper and it seems to be working much better now, but I have only had it for 3-4 weeks. I do still get some smoke, but it is usually after I load the stove with wood. Still learning on this thing as it runs quite a bit different from what it did before.

 

Looks good. The secondary combustion inside looks good too. I know with mine so far, I have to run it warmer than I have in previous seasons in order to get the secondary air warm enough to ignite the smoke/gases. I'm not sure if down the middle, front to back is better, or if side to side is better.

 

No no don’t take anything apart. I was merely curious.
I burned in the house I grew up in so running this unit Is definitely a growing pain I get some combustion I’m sure I am actually hoping to modify my doors to add some small glass pieces to do some visual observation.
I’m currently burning 6-700 degrees with chimney temps around 3-400 thought about putting a damper in myself. Had one on my coal stove

 

Update. Stove ran great last year with the good barometric damper, but I am still getting a little more draft (.08"WC) than what is recomended (.06"WC) when everything is warmed up. I don't have enough area to add a second barometric damper, but might be able to squeeze a manual damper in somewhere. Where is the best place to add the manual damper? I've heard that it needs to go between baro and chimney, so that if there is a chimney fire, you can close the air off. I don't have any concerns anymore about a chimney fire, as the chimney was the cleanest it has ever been after last years burning with the baro installed. Thoughts?

 

I'd put it between the furnace and the existing baro.
If you have a chimney fire, that manual damper isn't gonna stop it anyways!
Keep your chimney clean, burn only dry (under 20%) wood, and don't let the fire smolder, you should never have a chimney fire.

 

My thoughts as well. Plus that is where I have the most room. Thanks for the reply!

 

Hey Mn I actually swapped out stoves for a larger furnace a Clayton 1602m they seem pretty close to Daka.
I’m getting amazing heat but short burn times did the baro really bring up burn times I’m looking at appx 21 feet straight chimney up so I believe I’m drafting hard and trying to cut air down to slow it is only resulting in sooty burns
Thanks in advance

 

With the amount of heat that generation of wood furnaces put up the flue, and that height, I guarantee you are over drafting.
As for the "sooty burns", is the wood dry...I mean really dry, as in under 20% MC on the inside?
Unfortunately with those old school wood furnaces, there is just no such thing as "low n slow"...just gotta let the big dog eat, they'll make some heat though!