Backpuffing with a CAT ?

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raygard

Member
Nov 5, 2011
88
Columbia, MD
Hello All,

Vermont Castings Cat, griddle on top for top loading. Burning dry wood (old wood pallets kept inside for years and ripped up with a circular saw). Burning hot 600 to 650 degrees. Engage the cat after it is running smooth and after about half an hour i'm starting to get backpuffing. Air is 3/4 on, sometimes I go to full, yet I am getting back puffing. Now I know and have experienced that if you choke the air it'll backpuff yet my questions is if the CAT in this thing is partially clogged could that be causing the backpuffing. It's driving me crazy at present.

Thanks a bunch

Ray
 

Patapsco Mike

Feeling the Heat
Jun 3, 2008
277
Maryland
All I know is my VC Dutchwest was a backpuffing machine. It did it when it was new, it did it after a few years, it did it every time I choked the air down too fast.

WHOOOOOMP! beep beep beep beep beep (the smoke alarm)
 

Gark

Minister of Fire
Jan 27, 2007
808
SW Michigan
Easy to inspect cat , download user manual to see how if you don't have it. Also check that primary air shutter door opens and closes when you turn air handle front and back. I solved backpuffing by improving draft - could your flue be partially clogged? What model VC stove?
 

BrowningBAR

Minister of Fire
Jul 22, 2008
7,609
San Tan Valley, AZ
rayg said:
Hello All,

Vermont Castings Cat, griddle on top for top loading. Burning dry wood (old wood pallets kept inside for years and ripped up with a circular saw). Burning hot 600 to 650 degrees. Engage the cat after it is running smooth and after about half an hour i'm starting to get backpuffing. Air is 3/4 on, sometimes I go to full, yet I am getting back puffing. Now I know and have experienced that if you choke the air it'll backpuff yet my questions is if the CAT in this thing is partially clogged could that be causing the backpuffing. It's driving me crazy at present.

Thanks a bunch

Ray

Are you running a 6" or 8" liner? Or is the chimney not lined?
 

BrowningBAR

Minister of Fire
Jul 22, 2008
7,609
San Tan Valley, AZ
Gark said:
Easy to inspect cat , download user manual to see how if you don't have it. Also check that primary air shutter door opens and closes when you turn air handle front and back. I solved backpuffing by improving draft - could your flue be partially clogged? What model VC stove?
Based on his previous posts he is using a Vermont Castings Encore 2550.
 

raygard

Member
Nov 5, 2011
88
Columbia, MD
Correct its the Encore 2550. I'm running a 6" SS liner down a 24' brick chimney, liner is insulated and sealed at the top. It comes straight out the back of the stove for 12" and then "T" and then straight up. I just cleaned the chimney last weekend and I the air handle seems to be working as advertised. Is it possible for the cat to become clogged enough with soot and stuff to affect the draft, thereby causing backpuffing?

I'll recheck the chimney clean and will knock out the internal plate out of the stove and drag out the CAT and suck it clean

Cheers

Ray
 

raybonz

Minister of Fire
Feb 5, 2008
6,208
Carver, MA.
rayg said:
Hello All,

Vermont Castings Cat, griddle on top for top loading. Burning dry wood (old wood pallets kept inside for years and ripped up with a circular saw). Burning hot 600 to 650 degrees. Engage the cat after it is running smooth and after about half an hour i'm starting to get backpuffing. Air is 3/4 on, sometimes I go to full, yet I am getting back puffing. Now I know and have experienced that if you choke the air it'll backpuff yet my questions is if the CAT in this thing is partially clogged could that be causing the backpuffing. It's driving me crazy at present.

Thanks a bunch

Ray
Hi Ray,
I owned a CDW and the 1st year I burned pallets and yes they made the stove backpuff.. The problem with pallet wood is it tends to be thin compared to split firewood so they all try to burn at the same time.. The result is a very hot stove that goes into a backpuff mode when you try to reduce the air. I feel this caused by large amount of smoke that suddenly ignites which makes the stove puff then it starts smouldering again then ignites then it puffs.. It's a constant cycle and after the 1st year I gave up on pallets.. If you burn dry hardwood splits (try larger splits) the backpuffs will be greatly reduced.. I feel this problem would occur in any cat stove because the cat ignites the smoke which in large volume is more than it can exhaust when the gasses expand.. Try mixing in the pallet wood with splits and it should get better.. It's hard to explain the backpuff cycle as i understand it and I hope this helps..

Ray
 

Gark

Minister of Fire
Jan 27, 2007
808
SW Michigan
+1 on what Raybonz wrote since the other items are OK. Too much wood surface outgassing at once caused by burning lotsa small pieces. FWIW, there is a way to blow out the cat without removing the lower fireback (the plate held in by 2 steel wedges). Remove the hood, use a 90 degree bend attachment on the hose hooked to the "blow" side of your portable vacuum. Only do this with a nearly-full dirt-catcher bag in the vacuum, to avoid too much wind cracking the cat. Careful not to bump the refractory with the vacuum, it is fragile.
 

BrowningBAR

Minister of Fire
Jul 22, 2008
7,609
San Tan Valley, AZ
rayg said:
Correct its the Encore 2550. I'm running a 6" SS liner down a 24' brick chimney, liner is insulated and sealed at the top. It comes straight out the back of the stove for 12" and then "T" and then straight up. I just cleaned the chimney last weekend and I the air handle seems to be working as advertised. Is it possible for the cat to become clogged enough with soot and stuff to affect the draft, thereby causing backpuffing?

I'll recheck the chimney clean and will knock out the internal plate out of the stove and drag out the CAT and suck it clean

Cheers

Ray

That seems doubtful. Has back-puffing been an issue in the passed? If not, could it be an issue with mild outside temps causing a problem with your draft? I am very interested in this issue as I am leaning towards buying a second VC cat stove and I am trying to detail out all the potential issues these stoves have and how to avoid them.

I am running a 6" liner with an Encore 0028 with about the same length chimney (maybe a foot or two shorter). No hint at back-puffing no matter what the outside climate might be.
 

BrowningBAR

Minister of Fire
Jul 22, 2008
7,609
San Tan Valley, AZ
raybonz said:
rayg said:
Hello All,

Vermont Castings Cat, griddle on top for top loading. Burning dry wood (old wood pallets kept inside for years and ripped up with a circular saw). Burning hot 600 to 650 degrees. Engage the cat after it is running smooth and after about half an hour i'm starting to get backpuffing. Air is 3/4 on, sometimes I go to full, yet I am getting back puffing. Now I know and have experienced that if you choke the air it'll backpuff yet my questions is if the CAT in this thing is partially clogged could that be causing the backpuffing. It's driving me crazy at present.

Thanks a bunch

Ray
Hi Ray,
I owned a CDW and the 1st year I burned pallets and yes they made the stove backpuff.. The problem with pallet wood is it tends to be thin compared to split firewood so they all try to burn at the same time.. The result is a very hot stove that goes into a backpuff mode when you try to reduce the air. I feel this caused by large amount of smoke that suddenly ignites which makes the stove puff then it starts smouldering again then ignites then it puffs.. It's a constant cycle and after the 1st year I gave up on pallets.. If you burn dry hardwood splits (try larger splits) the backpuffs will be greatly reduced.. I feel this problem would occur in any cat stove because the cat ignites the smoke which in large volume is more than it can exhaust when the gasses expand.. Try mixing in the pallet wood with splits and it should get better.. It's hard to explain the backpuff cycle as i understand it and I hope this helps..

Ray
Interesting. Thanks for posting that.
 

Wade A.

Feeling the Heat
Nov 4, 2010
360
South
I once had a VC Dutchwest Cat stove and yeah, it back puffed a plenty. It really freaked me out the first couple of times, as I had no ideas about what was happening. After awhile I just learned to accept it. Not sure I ever managed to reduce it. My set up was not ideal. In those days, lacking any better information like you can find here, I had the 6" connector basically stuffed up into the throat of the flue. I know now this no doubt contributed by constricting the flow of hot gases and allowing an influx of of air. Not to mention it was an unsafe install in general. Well, live and learn, and hopefully never the hard way!

All that said, I'd be more attuned to outside temp differentials and lack of draft in general. How many hours do you have on your CAT element? Might consider replacing that if you're not getting full combustion, alllowing gases to accumulate. Blockage could be the reason and you might want to pop the top and have a look around.

I had the Jotul "breathing" like a locomotive the other night. I think it was a combination of wamer ouside temps and the wood stacked just right inside the firebox. Every 6 seconds or so I saw a "flash" and a woosh inside the stove....not enough to push out any smoke. It was kind of cool to watch. Guess I can vouch for my door gasket now.
 

raybonz

Minister of Fire
Feb 5, 2008
6,208
Carver, MA.
BrowningBAR said:
raybonz said:
rayg said:
Hello All,

Vermont Castings Cat, griddle on top for top loading. Burning dry wood (old wood pallets kept inside for years and ripped up with a circular saw). Burning hot 600 to 650 degrees. Engage the cat after it is running smooth and after about half an hour i'm starting to get backpuffing. Air is 3/4 on, sometimes I go to full, yet I am getting back puffing. Now I know and have experienced that if you choke the air it'll backpuff yet my questions is if the CAT in this thing is partially clogged could that be causing the backpuffing. It's driving me crazy at present.

Thanks a bunch

Ray
Hi Ray,
I owned a CDW and the 1st year I burned pallets and yes they made the stove backpuff.. The problem with pallet wood is it tends to be thin compared to split firewood so they all try to burn at the same time.. The result is a very hot stove that goes into a backpuff mode when you try to reduce the air. I feel this caused by large amount of smoke that suddenly ignites which makes the stove puff then it starts smouldering again then ignites then it puffs.. It's a constant cycle and after the 1st year I gave up on pallets.. If you burn dry hardwood splits (try larger splits) the backpuffs will be greatly reduced.. I feel this problem would occur in any cat stove because the cat ignites the smoke which in large volume is more than it can exhaust when the gasses expand.. Try mixing in the pallet wood with splits and it should get better.. It's hard to explain the backpuff cycle as i understand it and I hope this helps..

Ray
Interesting. Thanks for posting that.
Glad that helped.. I seldom saw backpuffs if I ran dry medium to large splits so I attribute this to what I mentioned previously.. CDW got a bum rap because I think these stoves were a bit more susceptible to this situation due to the cat being located directly above the firebox.. It actually burned pretty well the last 4 years or so.. VC may have a similar situation..

Ray
 

BrowningBAR

Minister of Fire
Jul 22, 2008
7,609
San Tan Valley, AZ
raybonz said:
BrowningBAR said:
raybonz said:
rayg said:
Hello All,

Vermont Castings Cat, griddle on top for top loading. Burning dry wood (old wood pallets kept inside for years and ripped up with a circular saw). Burning hot 600 to 650 degrees. Engage the cat after it is running smooth and after about half an hour i'm starting to get backpuffing. Air is 3/4 on, sometimes I go to full, yet I am getting back puffing. Now I know and have experienced that if you choke the air it'll backpuff yet my questions is if the CAT in this thing is partially clogged could that be causing the backpuffing. It's driving me crazy at present.

Thanks a bunch

Ray
Hi Ray,
I owned a CDW and the 1st year I burned pallets and yes they made the stove backpuff.. The problem with pallet wood is it tends to be thin compared to split firewood so they all try to burn at the same time.. The result is a very hot stove that goes into a backpuff mode when you try to reduce the air. I feel this caused by large amount of smoke that suddenly ignites which makes the stove puff then it starts smouldering again then ignites then it puffs.. It's a constant cycle and after the 1st year I gave up on pallets.. If you burn dry hardwood splits (try larger splits) the backpuffs will be greatly reduced.. I feel this problem would occur in any cat stove because the cat ignites the smoke which in large volume is more than it can exhaust when the gasses expand.. Try mixing in the pallet wood with splits and it should get better.. It's hard to explain the backpuff cycle as i understand it and I hope this helps..

Ray
Interesting. Thanks for posting that.
Glad that helped.. I seldom saw backpuffs if I ran dry medium to large splits so I attribute this to what I mentioned previously.. CDW got a bum rap because I think these stoves were a bit more susceptible to this situation due to the cat being located directly above the firebox.. It actually burned pretty well the last 4 years or so.. VC may have a similar situation..

Ray

I've noticed a lot of back puffing issues came from VC stoves not using liners.
 

raybonz

Minister of Fire
Feb 5, 2008
6,208
Carver, MA.
BrowningBAR said:
raybonz said:
BrowningBAR said:
raybonz said:
rayg said:
Hello All,

Vermont Castings Cat, griddle on top for top loading. Burning dry wood (old wood pallets kept inside for years and ripped up with a circular saw). Burning hot 600 to 650 degrees. Engage the cat after it is running smooth and after about half an hour i'm starting to get backpuffing. Air is 3/4 on, sometimes I go to full, yet I am getting back puffing. Now I know and have experienced that if you choke the air it'll backpuff yet my questions is if the CAT in this thing is partially clogged could that be causing the backpuffing. It's driving me crazy at present.

Thanks a bunch

Ray
Hi Ray,
I owned a CDW and the 1st year I burned pallets and yes they made the stove backpuff.. The problem with pallet wood is it tends to be thin compared to split firewood so they all try to burn at the same time.. The result is a very hot stove that goes into a backpuff mode when you try to reduce the air. I feel this caused by large amount of smoke that suddenly ignites which makes the stove puff then it starts smouldering again then ignites then it puffs.. It's a constant cycle and after the 1st year I gave up on pallets.. If you burn dry hardwood splits (try larger splits) the backpuffs will be greatly reduced.. I feel this problem would occur in any cat stove because the cat ignites the smoke which in large volume is more than it can exhaust when the gasses expand.. Try mixing in the pallet wood with splits and it should get better.. It's hard to explain the backpuff cycle as i understand it and I hope this helps..

Ray
Interesting. Thanks for posting that.
Glad that helped.. I seldom saw backpuffs if I ran dry medium to large splits so I attribute this to what I mentioned previously.. CDW got a bum rap because I think these stoves were a bit more susceptible to this situation due to the cat being located directly above the firebox.. It actually burned pretty well the last 4 years or so.. VC may have a similar situation..

Ray

I've noticed a lot of back puffing issues came from VC stoves not using liners.
Liners tend to increase draft and more so if lined so based on that I say less backpuffing as the liner can better accomodate the exhaust.. Large amounts of smoke igniting at one time is more than can be pushed through the cat therefore it blows out of any fresh air intake it can find (the path of least resistance).. It makes sense if you think about it..

Ray
 

Diabel

Minister of Fire
Jan 11, 2008
2,611
Ottawa, ON
You are closing the air too fast and too far. Open it up a bit
and the problem will go away
 

raygard

Member
Nov 5, 2011
88
Columbia, MD
Hi Ray,
I owned a CDW and the 1st year I burned pallets and yes they made the stove backpuff.. The problem with pallet wood is it tends to be thin compared to split firewood so they all try to burn at the same time.. The result is a very hot stove that goes into a backpuff mode when you try to reduce the air. I feel this caused by large amount of smoke that suddenly ignites which makes the stove puff then it starts smouldering again then ignites then it puffs.. It's a constant cycle and after the 1st year I gave up on pallets.. If you burn dry hardwood splits (try larger splits) the backpuffs will be greatly reduced.. I feel this problem would occur in any cat stove because the cat ignites the smoke which in large volume is more than it can exhaust when the gasses expand.. Try mixing in the pallet wood with splits and it should get better.. It's hard to explain the backpuff cycle as i understand it and I hope this helps..

Ray
How interesting. I hadn't thought of the wood as off gassing to fast yet that would make sense on two fronts as I experiment. When I open the damper the problem stops and two when I have the cat engage at full air it doesn't do it and when the palletized wood burns down I can reduce the air back to almost nothing. I'll try mixing up the wood on the next fire and see what the result is.

I have been burning on this cat for 2 seasons now and this will be the third. Up until this point in time I have never had a problem with it. I will pop the inside out tommorow and take a peek at the cat and vacum out the little squares. Many Thanks for all you help, I'll keep you posted of what goes on

Ray
 

BrowningBAR

Minister of Fire
Jul 22, 2008
7,609
San Tan Valley, AZ
Diabel said:
You are closing the air too fast and too far. Open it up a bit
and the problem will go away

Which is probably another reason as to why I haven't had this issue as I always decrease my air in stages on all the stoves.
 

raybonz

Minister of Fire
Feb 5, 2008
6,208
Carver, MA.
rayg said:
Hi Ray,
I owned a CDW and the 1st year I burned pallets and yes they made the stove backpuff.. The problem with pallet wood is it tends to be thin compared to split firewood so they all try to burn at the same time.. The result is a very hot stove that goes into a backpuff mode when you try to reduce the air. I feel this caused by large amount of smoke that suddenly ignites which makes the stove puff then it starts smouldering again then ignites then it puffs.. It's a constant cycle and after the 1st year I gave up on pallets.. If you burn dry hardwood splits (try larger splits) the backpuffs will be greatly reduced.. I feel this problem would occur in any cat stove because the cat ignites the smoke which in large volume is more than it can exhaust when the gasses expand.. Try mixing in the pallet wood with splits and it should get better.. It's hard to explain the backpuff cycle as i understand it and I hope this helps..

Ray
How interesting. I hadn't thought of the wood as off gassing to fast yet that would make sense on two fronts as I experiment. When I open the damper the problem stops and two when I have the cat engage at full air it doesn't do it and when the palletized wood burns down I can reduce the air back to almost nothing. I'll try mixing up the wood on the next fire and see what the result is.

I have been burning on this cat for 2 seasons now and this will be the third. Up until this point in time I have never had a problem with it. I will pop the inside out tommorow and take a peek at the cat and vacum out the little squares. Many Thanks for all you help, I'll keep you posted of what goes on

Ray
Good luck Ray! Try to get some dry hardwood splits of decent size and let us know if it makes a difference.. It's also important that you have a good draft with a cat stove or any epa stove for that matter.. Back in the late 80's when I bought that cat stove there was no forum or anyone to help so I lived with the backpuffs plus I was burning green wood.. Back then everyone did even the manual said it was OK to burn green wood lol.. Now I know they were very wrong.. Hearth.com is a Godsend for any wood burner especially for someone new to epa stoves..

Ray
 

JV_Thimble

Feeling the Heat
Sep 28, 2010
313
South-Central MI
I experienced this problem for the first time today and it scared me a bit. Griddle temp 600 F with CAT engaged and CAT temp at 1500.
Backed off the air and CAT temp went up to 1750. Set air to minimum and CAT temp went up to 1800 with backpuffing. Yikes. I know you guys are saying to open up the air a bit to stop the backpuffing, but at those temps I'm very hesitant. Was thinking I'd have to shut off my air supply at the OAK instead...

Dry wood with mostly larger pieces, and lined/insulated flue.
 

raygard

Member
Nov 5, 2011
88
Columbia, MD
Well, it seams that the problem was with the palletized wood. Started burning with "normal" wood from my pile and haven't experienced a backpuff since. Although in order to make the Encore sweat a little I have found that loading it up with palettized wood, switch the damper to CAT and having the air set halfway or lower, will make the stove puff. Open the air all the way up, or put "normal" wood in and there is no problem.

Many Thanks for the assist.

Ray
 

raybonz

Minister of Fire
Feb 5, 2008
6,208
Carver, MA.
rayg said:
Well, it seams that the problem was with the palletized wood. Started burning with "normal" wood from my pile and haven't experienced a backpuff since. Although in order to make the Encore sweat a little I have found that loading it up with palettized wood, switch the damper to CAT and having the air set halfway or lower, will make the stove puff. Open the air all the way up, or put "normal" wood in and there is no problem.

Many Thanks for the assist.

Ray
Glad to hear that Ray! I had the feeling the loads of pallet wood were the culprit.. Dry cordwood works much better and is much more controllable and pallets are good for mixing in with small amounts or for starting a fire..

Ray
 

greythorn3

Minister of Fire
Oct 8, 2007
1,002
Alaska
wheelordie.com
Funny to find this, as i got the back puffing tonight! cat blaze king princess, burning pallets! dang things. was stumped cause i just cleaned my chimney last month and its -6f out.. guess its the pallets. did it when i just realoaded it, i engauged the cat right away as it was 500f stovetop already from earlier pallets in the night. very interesting.
 

greythorn3

Minister of Fire
Oct 8, 2007
1,002
Alaska
wheelordie.com
boy im not sure thats it! cant figure it out, always had great draft, the cap looks clear, got 4 sticks of class a 5' total 20 feet plus 6 feet of double wall black pipe. been burnng this chimnet for a couple years, new stove this year bk cat princess.. i think it has something to do with this stove. cleaned the chimney last month, been burning pallet wood since.

-7f last night, and the problem started then, on reload, i reloaded it a little early to go to bed. and smoke started coming out the pipe joints came out more when i had the stove door cracked tho. chimney was 250f or so.

about to go back to my non cat king.

could to many ashes have any effect on the princess?
 

raybonz

Minister of Fire
Feb 5, 2008
6,208
Carver, MA.
greythorn3 said:
Funny to find this, as i got the back puffing tonight! cat blaze king princess, burning pallets! dang things. was stumped cause i just cleaned my chimney last month and its -6f out.. guess its the pallets. did it when i just realoaded it, i engauged the cat right away as it was 500f stovetop already from earlier pallets in the night. very interesting.
Grey read the entire thread as I shed light on the pallet thing from my exprience over 20 yrs. ago.. Cat stoves will do this in certain situations..

Good luck!

Ray
 

greythorn3

Minister of Fire
Oct 8, 2007
1,002
Alaska
wheelordie.com
raybonz said:
greythorn3 said:
Funny to find this, as i got the back puffing tonight! cat blaze king princess, burning pallets! dang things. was stumped cause i just cleaned my chimney last month and its -6f out.. guess its the pallets. did it when i just realoaded it, i engauged the cat right away as it was 500f stovetop already from earlier pallets in the night. very interesting.
Grey read the entire thread as I shed light on the pallet thing from my exprience over 20 yrs. ago.. Cat stoves will do this in certain situations..

Good luck!

Ray
even with the cat not engauged??
 
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