Back Puffing

[AppalachianStan]

I have checked some of the wood by re splitting them and then checked with moisture meter. There at 20% But I have tried eco blocks on hot coals and it still take time to get it to 1000*. I have 4 packs of them now. I used the eco block to see if they would do better then my wood. I have had my stove to 1350* but stove pipe was at 250*

 

[Ashful]

Are you following the procedure I outline above, or is your procedure different. The "I am closing around 400* on the cat probe," statement made me think you're doing things much differently.

I forgot to add, although I think I said it before: I have two identical cat stoves, one on a 15' chimney, the other on 27' of chimney. The one on the tall chimney must be run pretty close to 0% primary air, to keep stovetop temps in check. However, the one on the shorter chimney can never be run on 0% primary air, without backpuffing. We must keep the air open maybe 10% on that stove, but since the draft is low, stovetop temps stay in the 400's.

 

[AppalachianStan]

No. I was trying to get stove to 800* before I closed the by pass with the prime air open to the end of the burn. Last 3 loads I have closed down the by pass and the prime air at 400*. It will only back puff at temps of 1000* or more on both ways I have tried.

 

[Ashful]

No. I was trying to get stove to 800* before I closed the by pass with the prime air open to the end of the burn. Last 3 loads I have closed down the by pass and the prime air at 400*. It will only back puff at temps of 1000* or more on both ways I have tried.

I'm having trouble following you. 800 F before closing the bypass? Are you talking stove-top or catalyst temp?

Can you describe exactly what's happening, in order? It's really not possible to piece together what's happening, from all of these various temps you've named, without the context of time, and where exactly you're measuring each temperature.

 

[Woody Stover]

Got my first long burn today at 9 hours. I closed down the bypass and the prime air at 600* to get this burn. But it started back puffing. I was wrong it does not start at the end of the burn. It starts at the peak of the burn all ways at 1000* are higher then it stop as the temp goes down. Still waiting on delivery on the chimney pipe.

9 hrs, that's a pretty decent burn. Good deal.

1. Do you get all the wood cherried like a cig. Are just some?
2. How long should it take to get up to temp?
3. What should be the ideal temp to get the stove before closing down?
4. How do I get the temps to 1000* on the cat probe with out it back puffing and keeping the temp until it peaks?

If you have "all the wood cherried," you are creating a lot of smoke. If you close the bypass and cut all the air, that can create the flash ignitions of the smoke in the box and cause a backpuff. After you close the bypass, try cutting the air in steps, as Joful suggests in #6 below. I load the Buck 91 full, but have the coals piled front to back in the center. The wood I've loaded close to the center is burning well, but the wood on the sides isn't burning. I have to do this because if I get too much wood gassing, the cat can get too hot (1800+.) Like Joful says, on a good burn I get 1500 probe temps for the first two or three hours, with the surface thermo on the stove front at 400-500.
I agree with Joful, 400 cat probe temp sounds low to be trying for a cat light-off. My Buck manual says 700-900, and the newer App 52 manual says 500-700. Once I close the bypass and cut the air in steps, if I see the cat probe climbing even without much flame in the box, I know the cat is burning smoke. I generally want 900+ on the Buck probe before I close the bypass and start cutting the air in steps. If I close the bypass with lower probe temps, I risk a "crash," where the cat won't light off. Then I would have to open the bypass and air to heat up the stove more, and try again.
With your wood not as dry as it could be, the amount of time it takes you to get the stove up to temp might be longer. Some of these cat stoves can be a little tricky to run (not my Keystone, ) but dry wood sure simplifies everything.

I'm not familiar with the operating instructions on the Appalachian 52, but this sounds awful early to me. Normal procedure (on reload of an already warm stove) is as follows:

1. Open bypass.
2. Load wood. A few smaller pieces (3") on bottom to get load going, larger stuff (4" - 6") on top.
3. Burn with bypass open until stovetop hits 500 - 600 F, or flue temp hits 500 - 600 F on outside of single-wall.
4. Close bypass.
5. Wait 5 - 15 minutes for cat to reach cruising temperature (~1000F).
6. Lower primary air in 3 - 4 increments (1/2, 1/4, 1/8, closed).
7. Verify cat probe temp stays well above 500 F (1000 - 1500 F is typical).

Doing this, I typically have stove-top temps 350 - 400 F, and cat probe temps of 1500 F for the first several hours of the burn.

 

[AppalachianStan]

I'm having trouble following you. 800 F before closing the bypass? Are you talking stove-top or catalyst temp?

I am talking about at start up on the cat probe.

Can you describe exactly what's happening, in order? It's really not possible to piece together what's happening, from all of these various temps you've named, without the context of time, and where exactly you're measuring each temperature.

I'll try.
1. Cold stove start up. just like you said. Get cat probe to 800* closed down the bypass with prime air open 100%. I get a 4 to 5 hour burn by doing this. But I would let it burn its cycle.
2. On a re load I would close down the bypass at 400*.
3. Now to get a 9 hour burn I will close down both the bypass and prime air at 800*.
4.My chimney stove pipe has not been over 250* (on the chimney Gage) with the cat probe getting to 1350*
5. Any way I do it if I close down the bypass with the prime at 100% open I have no fire in the firebox?
6.To get the temps to 800* I have to leave the door open and the bypass. Once at 800* close the door if I close the bypass fire goes out and firebox fills up with smoke. This is with Prime open or close.
7. This temp are on the cat probe.

 

[Ashful]

Cool. Headed out to split wood today! Will respond tonight. In the meantime... Stay warm!

 

[Woody Stover]

if I close down the bypass with the prime at 100% open I have no fire in the firebox

When the bypass is closed, that's a more restrictive path so less air is moving through the stove. Now, with a fresh load in my stove and the bypass closed, I can cut the air to about 1/4 open and still have flame in the box. Not a lot, but some. If I opened the air even half way (bypass closed) there would be big flame and I would over-fire the stove before long. All the wood I'm burning now has had two or three years in the stack, so it doesn't need as much air to flame up as your not-as-dry wood does. But the fact that the bio-bricks didn't burn a lot hotter for you brings me back to the draft question. I'm interested to see what happens when you get the additional 3' of chimney up there. I'm thinking that with the additional draft, closing the bypass won't snuff the flame completely, as the increased draft will be pulling more combustion air into the box. It's good to be able to run some flame in the box if you want with the bypass closed. On the Buck I can see a definite drop in the cat temp when some flame is burning some of the smoke. I can also get the stove surface temp up higher, quicker, running a little flame in the box. These aren't huge differences, but they are definitely there....and sometimes you just want to see a little flame.

 

[Woody Stover]

With the Buck 91 on a freshly burned-in load, I've got flame unless the air is totally cut. With just a little air, the flame is intermittently on the wood, or floating above it.

 

[Ashful]

I'm with woody at this point. You've checked your wood, and confirmed it has acceptable MC. You burned with bio bricks, and got the same result. Only three options left:

1. Operator error: Seems we've already flushed that out.
2. Insufficient draft: Likely.
3. Malfunctioning stove: Dead mouse carcass plugging one of the intake plenums?

 

[AppalachianStan]

3. Malfunctioning stove: Dead mouse carcass plugging one of the intake plenums?

Mark this off the list. The prime air intake and maybe top of glass is the only air that comes into the stove firebox.
At the top of the glass looks like some type of air wash but not sure.

 

[Ashful]

Well, you know your next task, then! Up on the roof top, click, click, click! Down thru the chimney...

 

[AppalachianStan]

I was hoping the chimney I ordered would have came in today but it did not.

 

[AppalachianStan]

Just pick up the Chimney. Have it up Sat.

 

[mellow]

Checking in to see how the stove is operating now, no news is usually good news.

 

[Charles1981]

I posted this in the VC encore burning thread, but no one has confirmed this is back-puffing? I am 99% sure it is but if someone wanted to view this movie I made? I think the dancing flames are supposed to be normal but the flames going out for 5-10 seconds and then wooshing back into play is the back puffing? Anyway no smoke in the house but it is really pretty to watch....

Thanks for watching the boring video. Just wanting to confirm this IS backpuffing. There is a small poof at the start and then starting around the 30-35 second mark the stove builds up to a big one. My stove will do this depending on a number of variations. 20+mph winds, ash box too full, turning the secondary closed to quickly, sometimes it just happens for no particular reason. Never get smoke in the house though.... maybe once when it was 50mph winds and power was out and trees were coming down everywhere, but that is the only time.

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[mellow]

Yes that is back puffing, at worst case that is followed up with a puff of smoke being shot out of your air intake as the smoke ignites and causes an explosion. If you are not getting the smoke shot out then I wouldn't worry about it to much, just keep an eye on it and maybe add a tid bit of more incoming air to keep a little flame in the fire to help burn the smoke.

 

[AppalachianStan]

Mellow it has rain every Saturday since I got the Chimney and have been working late during the week. and it is suppose to rain tomorrow. Still need to get it up.

 

[AppalachianStan]

I posted this in the VC encore burning thread, but no one has confirmed this is back-puffing? I am 99% sure it is but if someone wanted to view this movie I made? I think the dancing flames are supposed to be normal but the flames going out for 5-10 seconds and then wooshing back into play is the back puffing? Anyway no smoke in the house but it is really pretty to watch....

Thanks for watching the boring video. Just wanting to confirm this IS backpuffing. There is a small poof at the start and then starting around the 30-35 second mark the stove builds up to a big one. My stove will do this depending on a number of variations. 20+mph winds, ash box too full, turning the secondary closed to quickly, sometimes it just happens for no particular reason. Never get smoke in the house though.... maybe once when it was 50mph winds and power was out and trees were coming down everywhere, but that is the only time.

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That is want my stove has been doing.

 

[Charles1981]

I don't get smoke in the house when this happens though. It is actually a really cool light show honestly.

If it was blowing smoke in my house though I would not be happy. And it only happens infrequently and only with the stove 100% closed. Usually if i open it a 1/4 turn it stops.

 

[AppalachianStan]

Just put on the 3' of chimney. Lets see what it will do later to night when the temp drops.

 

[raybonz]

Just put on the 3' of chimney. Lets see what it will do later to night when the temp drops.

Good luck Stan!

 

[AppalachianStan]

I am see a little more flue temps but on the cat probe is at 800* with air all the open and bypass closed after start up a hour ago.
Are there suppose be any flames in the firebox with the air all the way open?

 

[AppalachianStan]

Cat probe is at 900* flue at 250* every thing is closed and getting a smoke smell!

 

[AppalachianStan]

Okay at 1000* no back puffing. but you can smell a little smoke. What would cause that?