# Secondary air modification complete, here's hoping I smoke less!



## HaTaX (Jan 28, 2013)

I've got a 1984 NightWatch made by Minnesota Stove Works (Company is defunct now, was around over 120 years prior to '84), and it's an old smoke dragon style insert. The only saving grace it had was a smoke shelf over the flue where some nice secondary burn would occur occasionally. I think where the primary air came in, it traveled along the channels for the firebrick to the back and that's why I would see it now and then back there prior to the mod.

I started this about 2 weeks ago where I setup a ladder style air supply and originally had the secondary air coming through the primary draft opening. This was just to see how it did as a proof of concept, and it worked quite well except I didn't have good control over the burn overall. Starting from cold was a bit of a fight, and once it was going it was difficult to throttle back. Basically you had to somewhat babysit it and I'm going to assume it was because of how much the primary draft was affected by my modification. If you'd like to see some pictures of how the secondary air worked in my proof of concept setup, there are some pictures in this thread: https://www.hearth.com/talk/threads...ve-slammer-install-looking-for-advice.103780/

To finalize it, I drilled a 7/8" hole just above and to the side of the primary controls, and used 2 x 7/8" SAE washers to get the required thickness between the pipe fittings. The outside washer and elbow are sealed with furnace cement, and from there it goes into a 45 degree street elbow in the firebox.

During this process I realized the left and right side are not symmetrical and it makes sense to me now, many of these units were shipped with non-glass front doors and the air controls were on the doors in that case. You can see where one firebrick is removed from each side, and they just knocked a hole in there and welded a section of flat steel to hold the draft and air plate on. Heck, the air plates themselves are even very different from right to left side, makes me wonder if it was just spare parts to put it together or if they were going for a swirl effect or something.

Anyway, the rest of the pipe is 1/2" black pipe and the air holes are 3/32" and 5/32" depending on where they're at. I figure if I've got too many, I can just fill them with a little weld in there but I doubt I've got too few.  Spacing of holes are 1" on center, and each section of ladder is 18.5" long, so there's about 54 holes total.  I also drilled a few on the back side of the pipe that is facing upwards on the back 2 pipes, these are aimed at the existing smoke shelf to provide some direct air in that area.

Once the cement sets up I'll fire this beast up tomorrow and see how it does! I'm kind of anxious to see how it performs with a proper air flow and I'm hoping I'll be able to regulate the burn a little better now.

The second week of February I'll be installing a full chimney liner for this as well, currently it's a slammer install and I know that needs to be resolved ASAP. Hoping that I'll be able to get a little more heat from it after that is completed. Eventually this thing will be replaced with a Blaze King Princess Insert, most likely before the next winter season. We'll see how it does with it's new pipes before making a decision.


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## pen (Jan 28, 2013)

You are lucky to have glass to be able to view the results!  I'm looking forward to seeing some flamage in there. 

Also, there's a good chance you created a whole new stove there.  Look for new parts of the stove to be your hottest areas. 

pen


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## HaTaX (Jan 28, 2013)

Hopefully I'll get some decent pictures tonight or tomorrow from it! There's a few pictures of the rough draft version producing some nice secondaries in the linked thread, not sure how much those will change overall with putting the primary air controls back to the way they were originally.

Right now there's candles inside the firebox with the flame just below the pipe where it enters, just trying to give it a little heat to help it with the curing process. Then I'll do one little fire before going nuts with it, just trying to make sure I cure the cement properly.

When I had it running with the rough draft version I noticed my stove top temps were higher throughout the middle of the burn, about 550-600. I used my IR on different areas, but the hottest area seemed to be middle of the top, about 6" back from the front of the stove. Normally the hottest area is a little further back closer to the outlet, I'm guessing the baffle and brick I added are bringing that heat a bit more forward on the top plate. If anyone is curious, firebox dimensions are 22" deep x 22.5" wide x 14" tall so I'd say I've got about a 3.2 cf firebox taking into account the smoke shelf displaces some of the available space and the fact that I normally don't use the front 4" of space to keep glass clean and it's then beyond the firebrick.

The stove is built like a tank, top and bottom plates are 5/16" and the side is one big solid piece of 1/4" steel, bottom is completely covered in firebrick and about 3/4 of the way up the sides is lined with firebrick. I've had stove top temps up to 700-750 before with no ill effects, at least nothing I could see warped or deformed, I'm assuming this thing can take a little bit of a beating. (Unlike some of the newer cast stoves I looked at, cast for some reason scares me above 600) And hell, if I kill it, it's just an excuse to get the Blaze King Princess a little earlier.


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## ScotO (Jan 28, 2013)

I hope that pipe holds up for you.  Black iron will take a beating in that kind of heat.  Most secondary tubes are made from stainless steel for this reason.  But I am anxious for your experiment to commence!  If this works out and the pipes don't last, you can build the same setup out of stainless steel and get many years out of it.  Keep us posted.....


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## Motor7 (Jan 28, 2013)

Most don't have the nads to cut and retrofit their stoves....


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## HaTaX (Jan 29, 2013)

Heh, thank you sir for the nod to my nads, the boys need a little affirmation from time to time. :D

Just put a new door gasket on it, wow was the old one *bad*.  I noticed it today while I was checking the candles and letting the fixtures cool a little between heat on them, there was cold air just pouring out around the doors and I knew that was going to make draft control difficult at best...  Grabbed a gasket kit and a few other things from Menards and I latched the front doors a little over an hour ago so it should be good for a small fire here shortly. While I was at it I added a section of gasket between the two doors where there was none previously, while dry fitting it a dollar bill still wouldn't pass near the center so I figured it was safe to add,  that closed up the last of the cold air the doors were leaking.

On another note while I was at Menards I grabbed 2 packs of these to try out: http://www.menards.com/main/heating-cooling/fuel/wood-fuel-blocks/p-1712204-c-6855.htm  They're $5 for a package that weighs 38 lbs, not sure how they'll do yet but they looked to be cheap and decent as they use no glue and are safe for airtight stove use.  They look a little easier to light off and might be nice to toss in at the front of a large split load, no clue yet.  I'm sure I'll figure out something they're good for, and if not, off to the neighbors for their open fireplaces...


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## HaTaX (Jan 29, 2013)

Scotty Overkill said:


> I hope that pipe holds up for you. Black iron will take a beating in that kind of heat. Most secondary tubes are made from stainless steel for this reason. But I am anxious for your experiment to commence! If this works out and the pipes don't last, you can build the same setup out of stainless steel and get many years out of it. Keep us posted.....


 
I'm a little apprehensive on the lifespan of the black pipe as well, but some others have had theirs in a furnace over 2 seasons with no serious degradation, so these pipes might just outlive the stove.  If things do work out though, I am completely with you on the SS solution.  Ideally I'd use factory looking draft spin knobs on the outside with the SS inside sealed to the opening, that eliminates the gate valves, looks better, and should give me back a little more space inside the firebox since I'd be fabricating it all from scratch.  Hmmm, I'd have to bug my neighbor for his TIG welder...


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## HaTaX (Jan 29, 2013)

Well I started a fire up last night around midnight and fell asleep next to it for a bit.  Getting it going was a royal PITA as temps have gone up here and we recently got some rain / ice / snow and I had to work that humidity out of the chimney before I had a nice draft. (Will be so nice when I get my liner in)

After drying the flue out for about an hour it was drafting nicely and I was able to get it into a groove. I used just one mid sized split and a few of the gren heat bricks. Trying to keep the top temps from getting too high as I wanted it to get to about 350 degrees top temp and then let it cool before the AM to help cure the cement and gasket seal.

When I woke up I took a few pictures and a video and went to bed. I was really surprised though at the overall performance of it though! Normally I can't damp the primary air more then at least 2 revolutions of the spinners, but I left it at about 1/2 of a turn open on the primary and opened the secondary air all the way up and it was happy as could be there. I was producing nice secondaries with a small amount of flames on the bricks / log, and it was sustaining itself.  I think I actually captured two pictures that have the "ghost" flames present. (Almost see through / very faint glow that look like a sheet of fire)

Big change from how it used to behave, there was really no low to mid throttle on this thing, it was HOT or it had no fire in it. Some of this could be from the leaky gasket before, no real way to limit the air intake when it was leaking that bad, but I do know that a nice 350-400 degree top temp for the evening was perfect when it's not very cold outside.

Also as a bonus, today about 6 hours later I found about 5 coals that were still hot, and zero blackened coal chunks. Probably the gren heat bricks at work there, but normally I find 10 or so pieces of black coal that didn't get burned in the morning, this time it was all just white ash.

I'll try attaching this video in here as a link, I'd rather not go through the trouble of putting it on youtube.  It's just a short 20 second video of the flames in action. Let me know if the link does / doesn't work for you all: http://forward-thinking.net/SecondaryFlameVid.mov


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## HaTaX (Jan 29, 2013)

Well, now I'm gonna get cooked out of my house... I am currently running pretty hot (500-600 top temp) to finish the cure and see how it does with a little more wood in there. With just 5 medium sized splits I have no problem reaching 600 top temp, seems better then before!

I'm able to almost fully close the primary air draft, I can go as far down as 1/2 turn open from a complete close on both sides and the secondaries will sustain themselves no problem. Any lower then that and I think I'd start losing too much heat from the coals, maybe I could get it to 1/4 turn on both sides with some tinkering and timing.

Smoke difference is amazing, I threw some wood & bricks in there and headed outside to take the ice off the driveway before it gets very cold this eve. While I was out there it was doing it's smoke dragon thing and it looked like a small house fire on my block. :D After I went in, I opened up the secondaries and started reducing the primary air. I took a picture of my chimney about 10 minutes later when the top temp was 450, it's attached below.

Other pictures are just gratuitous shots of the secondaries as best as I could capture them (I need to play with my camera settings). I grabbed a few videos as well, but it was really a trip to see almost zero flames on the bottom, yet there's a very alive fireball rolling around in the top of the stove. I even saw quite a bit of combustion occurring above my pipes between the baffle I made and the top of the stove on the way to the outlet, that surprised me and I know I'm getting good heat from that fire up there.  You can kind of see it in the HotSecondary2 picture, it was hard to get in a picture but I've got some videos that show it clearly.


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## Motor7 (Jan 29, 2013)

Hatax it looks like you did very well. I think Schedule 80 pipe will hold up pretty good, if not it's way cheaper then SS pipe. My Hearthstone only has one secondary. Looking at it I think I can add another one without cutting any new holes. Also my shop stove, an old Buck copy really needs secondary's, so this summer I am going to do some mods to it and add a waste oil drip. Good job and keep us posted on the longevity..........


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## HaTaX (Jan 30, 2013)

Thanks for the kind words!  Just packed the box full with 3 large splits and a few mediums on top to pack it full, placed on a nice sized bed of coals that was just coming down.  Let it run with the primaries opened 2 turns and once the top temp got past 400 I tightened it down to almost 1/4 turn.  Spiked to 450 and has now settled in at 425 top temp with the secondaries roaring, still getting some decent log flames, but the majority of the flame volume is at the top.  It's kinda weird, at first 2-4 secondary holes come to life with small flames around them, then within 15 minutes there's 15-20 of them going.  I'm going to time this burn and see what I can get from it, I'm expecting at least 8 hours I'll still have decent coals.

If nothing else, it's a neat show while they're active.


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## HaTaX (Jan 30, 2013)

Geez, guess I can damp it down further if I can keep the fire from going out.  With just some dancing flames in there the top temp is 600 now,  doesn't look to be nearly enough flame for that, but the IR agrees.  If I lean down and look at the top I can see flames burning on the front section of the box where the air from the secondaries spills upwards,  guess there's a fresh supply of air for the smoke that's in that area now!

It's only 30 outside, 600 degree top is going to have my wife asking why it's 80 degrees in the house when she wakes up... Hehehe


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## begreen (Jan 30, 2013)

Looks like a good improvement. Nice job. You will have fun getting used to the new config and tuning it in. It's pretty common to leave the secondary air open and reduce the primary until the flames get minimal and lazy. As long as there's no smoke coming from the chimney, it's burning well.

So what's next? Rerouting the side air up and over the glass for an airwash?


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## HaTaX (Jan 30, 2013)

Well, I got a 10-11 hour burn out of it last night and now there are about 2 or 3 slightly smaller then fist sized coals in there still glowing along and top temps are just under 200.  Little colder then I'd like, but still pretty good stuff!  Not sure of the smoke levels out of the chimney last night, I couldn't see much of anything when I put the chimney between me and the moon and normally I'd see some haze whisping around so I think that's a good sign.

Next steps? Heh I actually started thinking last night "Hmmm, pretty sure there's enough room up there for a cat still, how much headache would that cause me?"  But then I stopped myself,  installing a cat would be fun, but a bit more $$ then I think I want to invest in it. (And time, that wouldn't be a 2 hour project)  There's actually an airwash system in there that keeps the lower 3/4 of the glass pretty clean, the primary drafts have a plate to divert air to the glass.  During the early testing I found out that they are actually functional as my glass was pretty nasty after just one or two loads in there, I had the plates removed so I could run the black pipe in through the primary air drafts.  One thing I am looking into though is improving the baffle area, maybe go with a full length plate in there or some other trickery to button up that area.  As it is, if the box is full of smoke and you open the doors too quick, you'll get some smoke rollout which never used to happen.  Pretty sure that's because the smoke plate is now extended about another 6" from where it used to stop, not an issue really more so a learning curve thing.

I'm sure I'll figure this "new" beast out over the next week or two, and I bet the liner will change the behavior yet again.


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## TX-L (Feb 1, 2013)

I love old stove mods.  I recently bought the baffle, secondary tube, and bypass components for a Lopi Liberty, am going to put them in an old Lopi 520 sometime this winter.  I'll try to take pictures before, during, and after the project; and share them on here.


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## valley ranch (Feb 2, 2013)

Looks pretty good, are you happy with the size of the air entry? Looks like 3/4".


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## HaTaX (Feb 10, 2013)

I've been away for a bit, had an ice fishing trip up at lake of the woods this last weekend and have been playing catch up.

Before I left I ordered up 2 ACS Powders and a 1 gallon of the ACS spray to help with my creosote glaze, TSP and a wire brush were gonna take a while to clean that mess.  So I crawled up on the roof friday evening and coated the flue nicely with the powder.  Probably did more then 4-6 squirts, and I may need a second application depending on how this goes.  There's some wet snow forecasted here the next few days so I thought it would be best to run the hot burns through it tonight and while it snows.  The ACS had about 48 hours to sit with no heat, and tonight it will get a nice hot burn while I douse every load that goes in with the ACS spray.  Hopefully this will break the glaze down enough I can remove it myself.

All this to prepare for the liner that I ordered on friday from Dynamitebuys (great people there BTW),  I went with the DuraLiner rigid product with a flex connector through the damper.  It will be so nice to get rid of the slammer install, I'm looking forward to chimney cleanings taking far less time as well.

The inlet pipes are 1/2" on each side, which seems adequate but 3/4" might have netted me a little better secondary performance.  You really do want the air to travel through the pipes as slowly as possible to gather as much heat as possible before exiting one of the holes.  When it's going full rip, I can almost shut down the primaries, ideally you should be able to shut them down completely, so I guess that says I'm just a little short on pipe size.  If you've got the space, screw it and go with 1" 

Still very happy with it!  When I just started the fire top down, the primaries were active within 15 minutes or so, didn't take long at all for them to get up to temp with the fire next to them.  If anyone has a little spare time and has one of these old smoke dragons in service, I think it's a great mod to breath some extra life into them.


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## Ehouse (Feb 10, 2013)

I just got a Hearthstone Harvest for next to nothing.  picking it up this week.  The cat is gone, so rather than replace it, I'd like to try adding some tubes.  This thread and the one on the Hearthstone 1 give me hope.

Ehouse


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## valley ranch (Feb 11, 2013)

Ha Tax, You did a nice job. Been wanting to do this to my Centennial for years, maybe I'll get to it this year. I think about it each time I build a fire. Have a good day.


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## HaTaX (Feb 11, 2013)

Thanks guys, glad it gave a little inspiration to try it out yourselves!  I really thought I'd have to babysit it a lot more often, but I've found if I want less heat I just pack the box with less wood and have shorter times between reloads.  Easier to regulate the heat output that way then messing with the gate valves and primaries constantly.

So this way my primary air adjustments are always between 1/2 turn to 2 turns open, and secondaries are fully open unless top temps are under 250-300.  Anything below those temps and having secondaries open seems to just prolong the warmup.  One exception to the rule, when I'm starting from cold, I build up larger logs on bottom to small splits and starting pellets at the top.  I start the fire top down with some cardboard and it seems to really heat the secondary area up quickly, in this case I just open them up from the start and it's over 350 or so in about 15-20 minutes.  Then I damp down primaries and they pretty much sit wherever I've set them till I let it get to a low coal state.

After running it the last few days and trying to not spend much time messing with it, I'm very happy with how it runs after the modification.  I was outside shoveling yesterday after I had just thrown some fresh logs on the fire.  When I was outside I first smelled that smoky wood smell and saw some smoke out of the chimney.  Within 20 minutes the smoke was nearly gone completely and I could still smell the faint whiff of wood burning.  Made me very happy I didn't have to mess with it, just load and go, I was probably just being anal retentive before wanting to watch / tweak it. If it keeps up running like this I'll be hard pressed to come up with a reason to replace it...  

On another note, looks like the ACS powder is doing it's thing as the top half of the flue has gone from a shiny black surface to a velvety brown.  Since the fire was very very low I decided to dump a little more powder down there and I'll torch it up again this evening.  Hopefully after a week or two of this regimen I'll be able to brush out the glaze and get it all cleaned up nicely before my liner shows up.


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## Corey (Feb 11, 2013)

Looks like you're getting it dialed in. One thing to play around with is the balance of primary to secondary air. Too much primary air wafts the flames through the firebox so fast, they don't have time to transfer heat...too little and you get a smoky cold fire which may not put enough heat into the secondaries. Once the secondaries do light off, too little secondary air can allow unburned gasses/smoke up the flue, too much air in the secondaries cools the burn tubes off. But once you hit it and get 'dialed in' it's amazing how little flame/fire is needed to keep the burn clean and the stove top at or over 600ºF.

I love peeping inside the stove to find the secondaries and top baffle glowing orange hot while just the wisps of translucent blue-purple flame waft around up there and the stack just has some heat ripples rising out with no visible smoke at all.


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## new england tommy (Feb 11, 2013)

Motor7 said:


> Most don't have the nads to cut and retrofit their stoves....


 
We should do this!


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## HaTaX (Feb 12, 2013)

Sure is fun to watch the secondaries in action, I didn't expect to get much using these Gren-Heat bricks but they really do go through a long gassing out period when the stove is hot enough. Lately I've been mixing one or two wood splits in to get the fire going with these, but once it's to life I can feed it bricks all day long with no problems. Tonight the top temp was 250 and I moved the coals around and put 5 more on top of the coals. 10 minutes later I brought the air down to 1/2 turn open and the whole top of the box is engulfed in flames. 

I always thought all the 'bricks' were bad news in wood stoves but these things really work well and are cheap. I'm going to try to stick to them as much as possible until the end of this burning season, they should keep creosote build up to a minimum and I won't need to even think about humidity content.


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## HaTaX (Feb 12, 2013)

Well, I'm still learning apparently!  Threw 4 of the gren-heat bricks on a medium sized bed of coals, stove top was ~200F, I let it get going with the primaries wide open for about 20 minutes.  At this point the secondaries had been going for a few minutes and were covering the baffles pretty well so I decided to go all the way down to 1/4 open on the primaries and left the secondaries wide open.

Result?  Secondaries are still active almost 5 hours later but have been quite small after the primary air was reduced.  I figured they would go out honestly, and every time I've gone to check on it they're still dancing around in a 10" area but have been moving around from left, center, and right.  Stove top is deceiving at ~300F as the blower is on low and the house is staying at 71 degrees upstairs (outside temp is 35F).  So looking at the thermometer would tell me that it's not burning hot enough, but without the fire raging I don't get as much heat up at the top plate.  Outside all I can see is heat distortion from the chimney, not even a faint wisp of smoke.

So when burning very low I have to keep an eye on the flame much more so then the thermometer, looks like the added baffles and bricks are keeping that heat where it needs to be!

Watch, I'll put the liner on and have to re-learn this thing all over again...


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## pen (Feb 12, 2013)

Is the air from that blower going over the thermometer and lowering it's reading?


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## HaTaX (Feb 12, 2013)

It is blowing over it, but where its sitting it doesn't get much of a breeze there.  I figure the thing is only accurate to about 50F anyway and that's what I've seen comparing it to my IR gun.  I situated it so it sits in front of the flue and the air is blown around that, and actually even with the blower going full bore I've not seen it get outside of 50F off.  (Got worried one time when I was running ~700F according to it and the blower was on high... Never saw any glowing and IR said it was closer to 750F,  didn't seem to bother it in the slightest.)


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## gzecc (Feb 13, 2013)

I'm no expert with the modifications you've made, however I am surprised it seems to be working so well without a liner hooked up (slammer). Once the liner is hooked up, I think you will have to re-learn, only for the better.


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## gzecc (Feb 13, 2013)

Its probably too short a time, but have you noticed a fuel usage change?


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## HaTaX (Feb 13, 2013)

I'm surprised as well that it works as well as it does, and it sounds funny but the primary reason I did this was to reduce the smoke output from it.  After cleaning the chimney out a few times and trying to keep it clean with hot burns, it seemed like no matter my burn habits on the stove I was ending up with a mess in the smoke chamber.  Not having a liner and it being installed in a slammer fashion I thought it would be much more difficult to manage, and I will say that on a cold start I need to leave just the primaries open for quite a bit.  I think most people start to damp down the air 20-30 minutes after getting the fire going, I have to wait about an hour from a dead cold start before the chimney has a healthy enough draw to maintain a lower burn.  Once it's going it's no problem and I can chuck some logs in every so often and I don't have to fiddle with air settings or anything, if it has burned down pretty far I just open the air up for 10-20 minutes and all is good.

One other reason I did it is that I had read most people saw a reduction in stack temps after installing secondary air.  I figured with a reduction in flue temps it would reduce the likely hood of a chimney fire, not eliminate cleanings but just that it would be a little bit safer.  That's one of the reasons I tried to block access to the flue with my baffles and firebricks,  I want to make sure that fire stays inside the box, flames leaping towards the damper isn't something I want to think about. 

I've noticed a fuel change only in how often I reload, I'm doing it far less now.  I should keep better track, but truthfully I did the mod because of the reasons listed above and the lower wood usage is just a bonus at this point.  It's not a huge difference, but the burn times have been extended by quite a bit so it must be having an effect.

An example of it's change though, last night I stuffed about 5 bricks and a log in there (about 1/3 of the capacity of the box) and brought the air down to 1/2 open at about 1am.  I just put a few more bricks in there 30 minutes ago and the large log I put in at 1am was still mostly intact in there and well into the coaling process.  Temps were 300 still and the added fuel took off in the amount of time it took for me to get a coffee.

I have never gotten burn times like this out of this stove, normally 6-8 hours was the max you could leave it if you didn't want to work to get it going again as you wouldn't have many coals left.  Also it used to leave quite a few 2-3" coal chunks that didn't get burned entirely and now it's burning down to almost complete ash.  I'm guessing the extra air from the secondary supply is helping the coals to burn down,  it's just nice to see the coals burn themselves down at the end of the cycle.


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## gzecc (Feb 14, 2013)

HaTaX said:


> I'm surprised as well that it works as well as it does, and it sounds funny but the primary reason I did this was to reduce the smoke output from it. After cleaning the chimney out a few times and trying to keep it clean with hot burns, it seemed like no matter my burn habits on the stove I was ending up with a mess in the smoke chamber. Not having a liner and it being installed in a slammer fashion I thought it would be much more difficult to manage, and I will say that on a cold start I need to leave just the primaries open for quite a bit. I think most people start to damp down the air 20-30 minutes after getting the fire going, I have to wait about an hour from a dead cold start before the chimney has a healthy enough draw to maintain a lower burn. Once it's going it's no problem and I can chuck some logs in every so often and I don't have to fiddle with air settings or anything, if it has burned down pretty far I just open the air up for 10-20 minutes and all is good.
> 
> One other reason I did it is that I had read most people saw a reduction in stack temps after installing secondary air. I figured with a reduction in flue temps it would reduce the likely hood of a chimney fire, not eliminate cleanings but just that it would be a little bit safer. That's one of the reasons I tried to block access to the flue with my baffles and firebricks, I want to make sure that fire stays inside the box, flames leaping towards the damper isn't something I want to think about.
> 
> ...


I'm wondering your climate. What state are you in?


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## HaTaX (Feb 14, 2013)

I'm in Minnesota and lately the weather has been really mild, yesterday we touched the 40s for a few hours.  Running in the shoulder season has always been tough for me,  damp it down too far and the chimney is a complete mess after just a few weeks, otherwise with a cleaner burn the thing heats us out of the house.  I'm hoping the liner will help out a bit with that, and I think I've figured out how to get a slow burn out of it now with the secondaries, so maybe this spring I'll be able to keep running it longer.

Really liking those bricks, about 80% of the fuel burned lately has been those and while they can be a pain if the stove gets cold, they burn completely and leave behind little ash.  Before all this (secondaries), I was removing ash every other day or every day depending on how I was burning.  I haven't removed any ash from it since I started it cold earlier this week, might be from the better burn during coaling, the bricks producing less ash, most likely a combination of the two.

Also, it hasn't ALL been daises and roses, now I need to be much more mindful of how I open the doors to keep smoke from rolling out and I never had to think about that before.  There used to be a space in the back corners where smoke could go around the baffle plate, and that space was covered with fire bricks to force the smoke to travel to the front and then towards the flue in the back.  The top baffle has a 8" or so space that's open in front between it and the glass, with that added baffle bringing the smoke shelf out an additional 6".  Not a huge deal, but a few times when I wasn't thinking about it I released a cloud into the house.


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## HaTaX (Feb 16, 2013)

The last two days here have been a bit more chilly and I've been able to open it up a little more, temps between 5-20F outside so it gave me a chance to run the stove around 650 yesterday without overheating the house. Upstairs stayed between 70-72, nothing but some ceiling fans and the blower to move the air around the house was needed. Sometimes I kick the low speed recirculating fan on the furnace on, but only when it's really cold outside, and there is an air return into the furnace in the same room as the stove about 2' down from the ceiling.

Another non-eventful 10 hour burn last night, loaded it up before 11PM and let it rip. This was a pretty full load as I knew I'd be sleeping as late as I could today, previously the longest I could let it go was about 8 hours if I wanted to start the next load off the coals. After 10 hours, the large oak split in the back still had its shape and was basically a huge coal. I think I put in about 6 of the bricks, 1 large split in back, and a few medium splits to fill in the gaps up front. It wasn't as packed as I could get it, but was much fuller then I have been loading it lately, everything with within the "firebrick" zone.

So I'm still amazed by the burn times I'm getting now, even if it is only 2-3 hours extra that's still 20% roughly and a great result for the time and $$ invested into the project. I also like that the coal burn down seems to be much better now, if I leave it alone I'm left with quarter sized hot coals underneath the ashes, before I would find about a half dozen larger coal pieces about half the size of a man's fist. (And those were not hot, just unburnt coals) A bonus that goes along with the more complete burns is that I'm not emptying ash nearly as often as I was, actually haven't emptied it at all this week and I've got about 1.5" of white ash in the bottom of the stove. Probably need to empty it this weekend, but it hasn't been causing any airflow issues so I've just left it as I know it does help the burning process.

Something I don't like, my glass gets much dirtier then before. Could be because I'm choking it down so far, making a lot more smoke than previously (to be burned of course), or just because the airflow dynamics in the box are considerably different now. The baffle plate that I added brings the smoke further forward in the box before heading towards the flue outlet, that probably doesn't help either. Stock air deflectors seemed like a poor attempt at an airwash anyway, they're just bent in a manner to encourage the air to move across the glass. (You can see them in my first post in this thread)

I've been thinking about making an airwash system for it now... Basically take the deflector plates off the primary draft and replace them with a steel box that can be fastened using the existing bolt that connects to the deflector plate. So this steel box would pick up the inlet air where it normally comes in, and I would channel it to the top front of the firebox to a square channel with holes pointed downward across the glass. I could use black pipe again, but I'm not sure that would be any easier then the square stock and I'll need to fabricate a pick up box anyway. Not completely sold on doing this as I think I've got something good going currently and I don't want to mess it up... The glass somewhat cleans itself in a really hot burn, but it's also far away from the fire most of the time so it's not getting the same intense heat, the top half of the glass is always pretty grimy after 2-3 burns.

Anyone added or modified an airwash system on their stove? Looking for some pointers and things to watch out for... This air channel would need to be considerably larger then the secondary supply, but as it is I never open the draft knobs more than 3 turns open and they will open up to 10+ turns if I wanted. (Never opened them that far for a length of time, I fear what I would end up with for temps with a full load in there...) Honestly the dirty glass doesn't bother me too much, but it would be nice to clean the glass once a week and still be able to see the entire fire. I just don't want to end up with a stubborn stove that has to be babied until it's going full bore.

I'll take some pictures of what a load up at night looks like and what I'm left with in the morning in the next few days, they always tell the story better than my TLDR posts.


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## Corey (Feb 16, 2013)

Ditto on just about everything you observed!  Funny I find myself saying 'yep - noticed that', 'yep saw that too', 'yep, me too' every time I read your posts after adding the air.  On the glass I've noticed my old smoke dragon, the smoke would basically go right up the stack, while the new baffle/tubes almost seem to set up a 'rolling air current' where the smoke goes up, hits the baffle, gets burned, shoots forward, hits the glass, some goes up the stack, some goes down the glass and hits the base of the fire again.  This doesn't happen all the time, but definitely see it on occasion.  Sometimes I notice a bit of smoke on the glass from this, but nothing a hot burn won't take care of.

Adding an air wash is even easier than the secondaries, IMHO.  You just need a bar above the glass to distribute air, and you can grab air right from the front of the stove.  You actually want cool air so it sinks down and 'washes' the glass.


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## HaTaX (Feb 16, 2013)

It's nice to hear some affirmation that I'm not alone in what I've experienced!  Honestly I don't have much of a baseline as this is the first stove I've "owned",  but have run many others over the years here and there and I only became a homeowner about 9 years ago and this one came with the place.  At first I thought I was being optimistic about my results because I had put some time into it and I didn't want to see failure, now I'm feeling like I got the placebo and that I shouldn't be able to get such a change in burn behavior from a 30 year old stove.

I did end up moving the baffle plate in the front a little bit,  basically I created a little tunnel in the middle and placed the metal baffle on top instead of being on the bottom.  Here's two pictures that show a fairly cold start where you can see the 'tunnel'.  There's 3 holes on the top of each secondary tube and one of those is centered to provide air to the tunnel.

Originally I moved it around because I thought having the brick facing the intense portion of the fire was best, but in the end that tunnel ends up being far more functional then I had anticipated.  As the fire gets going that is the first place I see secondary action, and as the flames get larger they eventually ignite the gases that are up in the very top of the firebox resting near the top plate.  If I get down and look at the ceiling of the firebox it is covered in a blue ghost flame early on in the burn when there's a lot of smoke and the temps are getting hot enough for secondary ignition. 

On the very front tube I tried to place them roughly in a ^ formation so that in the middle the air is pointing slightly forward and down and at the sides mostly pointing downward.  This ends up creating a curtain of flames that roll around the end of the baffle and then back towards the flue.  Not sure if the positioning of the holes is really that important, but I was trying to create an airflow that would encourage the smoke to be pulled back into the fire.

Hmmm, don't tell me that the airwash is easier or I'll be busting out the welder today!   I'd reuse the draft controls on the box and could make it so I could go back to stock easily enough.  Just need a "capture box" for the inside of the stove, and then channel it above the doors.  It's nice that the firebox is big enough to make these mods without seriously restricting the size load I can fit in there.

Seriously debating replacing the stove now, one thing I really like is that this thing can throw massive amounts of heat if needed and that it sits out so far onto the hearth for no electric power heating situations. (Don't get them often, but it is important to me living in this state)  We had -15 to -20F nights about a month ago and I was able to keep the upstairs around 68-70, entire heating area is about 2500sq ft with it equally split upstairs and downstairs.  If I had pushed it harder it could probably get even warmer, but it uses quite a bit of fuel beyond 2 turns open on the primary air.


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## HaTaX (Feb 17, 2013)

Okay, here's a few pictures of my loading at 12:30AM last night (followed by pumping about 6oz of ACS all over the firebox while avoiding the secondary tubes).  Then what was left when I went to get it started a little after 10AM today,  the patch of coals is about 8-10" in diameter and the stove top was about 250F.

1 or 2 small splits brings the heat back up quick and the secondaries come to life within 15-20 minutes after loading it in the AM.  I'm noticing that the top of the stove doesn't get nearly as hot in the coaling phase, but the area where the burn actually happens is still very hot.  (tubes read 524F when I opened the doors)

The load at 12:30AM wasn't huge, there were 8 or so bricks in there with one split in the front to aid in the take off.  Temps last night were 5-10F so I had it opened a little more then the last few days. (3/4 turns open vs 1/2 on the primary drafts)

Not bad for a ~10 hour burn out of an old smoke dragon!  Before the secondaries most I could scrape out of it was about 8 hours and many times I had cold coals in the box after a night burn.  Now everything is white ash, and there is plenty of hot coals to make the restart easier.

Now that I'm getting used to how it runs, I find myself tending to it far less.  I think I was just being OCD with how it worked and behaved, checking on it every hour or so...


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## sesmith (Feb 23, 2013)

Nice job!  You did a similar design to what I did a few years ago on my older stove.  I can tell you that the black pipe will be fine.  Neat to see the pics through the glass front as mine doesn't have any viewing to see the results.  I had similar results as you do...less smoke, better performance, and less fuel use.

If you REALLY want to make the smoke go away...I later added an add-on cat converter box to the top of the stove with a steelcat in it.  Works great.  Between that and the secondaries, there really is no smoke.  I can also dial it way down in the shoulder season weather and get 24 hr. burns out of it at a very low rate...cat working most of the burn.

We don't use our stove much anymore since we replaced our heating system with a GSHP, but it's nice to visit this forum now and then and see people improving these old stoves still.


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## HaTaX (Mar 2, 2013)

Temps are supposed to be flirting with single digits tonight so I thought I'd fire it up for the weekend. I dumped a little more ACS powder down as well so I thought a good hot fire would be helpful as well.

I thought about building a block off plate for the top portion that could accept a cat, but it seemed like a lot of work to get a bypass in there and everything else.  Unfortunately I don't have the space above it to really utilize a cat well other then using it to keep the flue clean...  Get this, my neighbors actually have said they miss the wood smell as it's much harder to smell it now. (And when really rolling along the exhaust takes on a very odd 'vaporized' wood smell)

Took off nice and easy with the basement door cracked, went about 4 hours on the small load and then I loaded it up with the bricks.  45 minutes later temps are at 800F on the top and here's a picture of the fire at those temps.  Totally worth the modification just for the hypnotizing flame show. :D


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## PapaDave (Mar 5, 2013)

HaTax, I've got a question.
How in the world did you get the crossover pieces threaded?


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## HaTaX (Mar 5, 2013)

Yeah, that part was a little tricky as I decided early on I didn't want to mess around with having a bunch of unions on there,  they'd add quite a bit of weight that may encourage sagging and also it would make it harder to get a plate to fit flush over the burn tubes.

I tightened one side's close nipple into the "T" as tightly as possible,  then twisted the other side around until it was snugged down as far as it would go.  Then I covered the threads of the not connected nipple in furnace cement and threaded it into the "T" by backing it out of the other one.  I kept a strap between the two burner tubes while I backed it out of one set of threads and into the others to make sure it stayed as close & tight as possible.  After that was all done I used some additional cement to seal both ends of threads on that particular nipple.  For the furthest back burn tube (I'll call it #1 for now, #3 would be the front most tube) the left hand side nipple was cemented, the nipple between #2 & #3 is cemented on the right side. 

If you look at the first page pictures "InsideLeft" & "InsideRight" you can see the cement fairly easily,  it's somewhat of a hack job, but it's held up just fine so far.  I'm not to worried about it leaking air as it should follow the path of least resistance, and there's holes no further then an inch or two away from that point.


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## PapaDave (Mar 5, 2013)

So, the left and right side "manifolds" could be put together, then you put the cross over into one side, and as you loosened from the first side, it would thread into the other.
I think I got it. I was wracking my feeble brain. I've done gas line plenty of times but never like that.


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## HaTaX (Mar 7, 2013)

Basically I started at the 90 degree elbow where the rack starts in the back of the stove and assembled it rung by rung outward until I got to the 3rd and last rung using that "back out" method on two of the connections out of all of them in the entire thing.

On another note, I wanted to get a slab of ceramic board or blanket to go across the entire top of the ladder. Looking around online I found a few places that had the board for about $30-50 in various densities. While I was out at Menards today cleaning out the last of the Gren-Heat bricks I saw they had the 25lb pail of castable refractory cement on clearance for $17, so I picked it up. Looks like its good to 2400F and I should be able to make a little cardboard cast of what I need and make up a slab or two. The biggest problem I have is that there's an area where I've only got about 1/4" of an inch clearance between the original welded in smoke baffle and the flat plane on the secondary ladder. I'll probably cast two different sections if it ends up being too thin, but at least with the castable stuff I can work around that clearance. Hopefully that will help keep the secondary temps up and it shouldn't take more than an hour or so of my time.

Still waiting for the liner to show up... I'm holding off on burning so I've got enough fuel to test out the new liner (hopefully by the end of the month).

EDIT:  Just a thought on the refractory... I've read that it should be reinforced using stainless steel needles, but those are a pain to get shipped in a small quantity with reasonable shipping.  I was thinking of getting some small stainless nails in place of them, if they're small enough think they would serve the same or similar purpose as the needles?  I would try to go with the thinnest nails possible as the needles look more like the shards left behind from drilling.


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## Corey (Mar 7, 2013)

For my baffle, I found a guy on ebay selling the faux brick lining kits for gas fireplaces. These are a light weight insulating ceramic board about 7/16" thick which really keeps the heat in (as you can see in my [url=https://www.hearth.com/talk/threads/burnin-orange-tonight.106714/]Burning Orange[/URL] post. He was doing a closeout at about $15 per kit, I don't know if similar deals are still around.

For the refractory, if you want SS reinforcement, you might hit the kitchen aisle and get a couple of stainless steel Brillo pads. Unwind them and chop up with a decent pair of utility shears. Seems like that would almost be ready-made reinforcing fibers. The down side is, stainless steel will conduct heat, so it will reduce the insulating properties of the baffle. I was thinking almost the opposite...mix in some vermiculite to increase the insulating properties. Ideally, this is an insulating piece it doesn't need much structural strength.


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## Spanky54 (Mar 16, 2013)

HaTaX said:


> I've got a 1984 NightWatch made by Minnesota Stove Works (Company is defunct now, was around over 120 years prior to '84), and it's an old smoke dragon style insert. The only saving grace it had was a smoke shelf over the flue where some nice secondary burn would occur occasionally. I think where the primary air came in, it traveled along the channels for the firebrick to the back and that's why I would see it now and then back there prior to the mod.
> 
> I started this about 2 weeks ago where I setup a ladder style air supply and originally had the secondary air coming through the primary draft opening. This was just to see how it did as a proof of concept, and it worked quite well except I didn't have good control over the burn overall. Starting from cold was a bit of a fight, and once it was going it was difficult to throttle back. Basically you had to somewhat babysit it and I'm going to assume it was because of how much the primary draft was affected by my modification. If you'd like to see some pictures of how the secondary air worked in my proof of concept setup, there are some pictures in this thread: https://www.hearth.com/talk/threads...ve-slammer-install-looking-for-advice.103780/
> 
> ...


 

 I like the idea!
I also did much the same to my wood furnace, by installing secondary burn tubes in it with black pipe. Mine comes in the front of the stove (1") and goes all the way to the back wall, up to the baffle I installed and back to the front, right down the center (just one for experimenting)
 I usually heat the flue temp to 250 degrees, then shut off the primary air completely, which shows the secondary tubes burning like a gas flame coming out of them. The stack temps drops a few degrees, but the fire stays good and hot. I now have NO smoke, so no creosode to deal with. I get longer burn times and a lot less ash to cleanout.

 My summer project will be to completely rebuild this unit, with all new metal where needed, now baffle with lava rock or fire brick on it to retain the heat (lava rock holds heat for a long time and works much the same as fire brick - cheaper too!) The I'm making the secondary intake out of 2" square tubing, entering in the back of the stove, up the back wall and along the sides, just under the baffle. I'm going to go with 3 tubes across to burn up the smoke, much like most EPA stoves I've seen. My fire box is lined with fire brick to hold the heat, and I should have a completely smoke free stove next season.
 Being from Minnesota, there's been a several nights -0, and it's amazing how warm a small flame can heat the house so warm by just burning the smoke (which burns hotter than the fire below it) and no smoke coming out of the chimney at all! A hell of a lot cheaper than buying a new stove too! Spanky


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