White sky - smoke! Failing cat?

[Ashful]

I noticed a few weeks back that my chimney seems to be emitting black smoke any time the cat probe was reading below 700F. Above 700F, it would seem all I got was white steam. I'm using the new Condar SteelCat for one year now, which the tech at Condar told me was still a little experimental for them.

I hesitated to call Condar, since I wasn't sure if this was my imagination, or if maybe this is normal.

A few weeks have gone by since that observation, and this morning I noticed black smoke out the chimney with the cat probe at 814F.



I ran it up to 1000F, and now no smoke.

Failing cat? It's never been above 1800F, to my knowledge.

 

[BrowningBAR]

I would chalk it up to weather at this point. Temps are around 50 degrees right now, really humid, and thick fog. Drafts kind of suck. See what happens later this week when the highs dip back down into the 30s.

 

[Woody Stover]

Any recent change in the quality of the fuel? Not as dry?

 

[Todd]

I wouldn't doubt its a bad cat, we saw problems with those steel cats last year and the manufactures even got involved and have made some changes.

I'd keep a close eye on it for another week and if it doesn't get any better call in the warranty on it.

 

[rideau]

I agree with Todd. Had to replace my cat, the newer cat has been improved. The cat should be burning all the flue gases once it is engaged...you should never have black smoke. At the very least, your cat has become less efficient. Were you running a typical cat fire when you observed this, or did you have a really roaring fire going, where maybe you were putting way more flue gases through the cat than it could handle? Unless the latter, I'd call in the warranty on the cat.

 

[Wood Duck]

In cool humid weather you will possibly see the water vapor in the exhaust. There is always water vapor because water is one of the products of combustion. Sometimes there isn't enough water to see, but in the right atmospheric conditions you can see it. Water vapor will look white, not black, so the black smoke is another problem.

 

[Ashful]

Thanks, guys! To answer the questions posed...

Weather was warm and humid, and I have not been paying attention to what the weather was the various other times I noticed this problem. All I noticed was a lower cat temp, and if I ran open for a while to drive up the cat temp, I could usually make it go away.

Yep... recent change for the worse in my fuel. I dug into a new stack starting New Years day, which is younger than the previous, although I was seeing at least some of the same behavior toward the end of the previous stack. The previous stack was about 12 months old, and what I'm burning now is likely 9 - 10 months old. All stacked in double rows outdoors, top-covered only. Not ideal, but we all start somewhere...

I do believe this is black smoke. I have often seen white water vapor, and in fact got there this morning by running the cat up to 1000F. What I'm not sure of is how much is normal, or if my eyes are playing tricks on me, making it look worse due to the snow-white sky we had this morning.

I think I'll wait until temps drop in a few days (cold forecast ahead), and do some testing to see if the behavior changes. I had it in my head that this cat has become less reactive than it was when new, and now playing with a brand new SteelCat in the second F12, I again notice how much more reactive the new cat seems to be. I've seen one or two other posters mention that the SteelCats can be almost hyperactive when new, so I'm just not sure if this is normal "settling in", or if this thing is dying an early death.

 

[Backwoods Savage]

Because of the fuel problem I would certainly hesitate calling about a warranty. One just cannot expect good results with questionable fuel, no matter what stove or what circumstance.

 

[Ashful]

I agree, which is why I haven't taken the fact that the cat has become a little difficult to light off as any sign of a failure. However, I think that seeing black smoke out the chimney when the cat probe is reading a solid 814F is a different thing. If the cat is up to temp, it should be burning those gasses, no? Wet wood would be cause for not getting up to temp, but I think only depletion of the catalyst could explain why it fails to burn at a temperature over 800F.

That was my thinking, anyway...

 

[AbuJas]

The variables that have been mentioned are certainly thought provoking, but the fact that the flue gases are still emitted over the cat's expected reburn temp is a problem. The cat could have gotten overly contaminated by the low quility fuel or other burned items in the stove(plastic, chemicals, etc), and thus simply needs to be further exposed to higher temperatures to burn it off, or you may need to renew the cat in a vinegar and boiling water solution in a non-reactive metal pan.

 

[rideau]

The PH cat is really long. I couldn't find anything in the house big enough to clean it in except the BATHTUB. Do you have any idea how much vinegar it would take to fill a bathtub deep enough to clean a cat? Hopefully the Jotul cat is more square....

 

[Ashful]

The cat could have gotten overly contaminated by the low quility fuel or other burned items in the stove(plastic, chemicals, etc), and thus simply needs to be further exposed to higher temperatures to burn it off, or you may need to renew the cat in a vinegar and boiling water solution in a non-reactive metal pan.

This is a brand new cat with only 3 months of shoulder-season burning on it, and nothing other than good clean cord wood and the occasional SuperCedar or plain newsprint for starting has ever been burned in this stove as long as I've had it. The "low quality fuel" to which Dennis was referring was the fact that my wood supply is not yet mature. I'm burning stuff I split and stacked as recently as last April (9 months old, now).

I don't think 9-months seasoned walnut or maple (okay... maybe an occasional oak split) should kill a cat... should it?

 

[jharkin]

I wouldn't doubt its a bad cat, we saw problems with those steel cats last year and the manufactures even got involved and have made some changes.

I'd keep a close eye on it for another week and if it doesn't get any better call in the warranty on it.

This makes me wonder about mine. I bought a steelcat 3 years ago and I too see a lot more creosote in the chimney at the end of season than I would expect and smell some smokey odor outdoors, even though I am getting good catalyst temps between 1100-1600 for most of the burn cycle.

I have not seen any significant amount of black smoke though.

 

[clemsonfor]

I agree, which is why I haven't taken the fact that the cat has become a little difficult to light off as any sign of a failure. However, I think that seeing black smoke out the chimney when the cat probe is reading a solid 814F is a different thing. If the cat is up to temp, it should be burning those gasses, no? Wet wood would be cause for not getting up to temp, but I think only depletion of the catalyst could explain why it fails to burn at a temperature over 800F.

That was my thinking, anyway...

no you can be burning 35% wood and still get your cat to 1500f once the moisture is all cooked out. 800F is easy to obtain. Mine is really boderline active in that range. But i guess its all how your stove is designed etc how hot your cats read?

 

[jharkin]

In my experience I always assumed if it didn't shoot up to 1000+ after engaging I was having a stall. On a big load when its active its almost impossible to keep the cat temp below 1100-1200 until the off gassing ends.

But Ive smelled smoky odor in the yard even over 1000F on the probe which makes me wonder....

 

[pgmr]

Another possibility is that some smoke is getting around the catalyst rather than through it. If your bypass is not sealing well or the catalyst is not sealed around it's perimeter, then some of the exhaust gases will bypass the catalyst.

I was having the same symptoms and while doing some maintenance recently, discovered that the cat chamber bolts had worked a bit loose. There was evidence of exhaust bypassing the cat between the stove body and the seal around the catalyst chamber. Stove now requires the primary air control to be open a little more to maintain the same amount of flame in the firebox, which I am assuming means I've fixed the unintended bypass.

 

[Ashful]

Another possibility is that some smoke is getting around the catalyst rather than through it.

Yes, I forgot to mention this, but I do suspect it's a possibility. My bypass door action on this stove is not quite as tight as the other stove, although I do suspect not much smoke can get thru the bypass door gasket, either way. I should try adjusting my bypass door, or even replacing the gasket, before bothering Condar.

In my experience I always assumed if it didn't shoot up to 1000+ after engaging I was having a stall. On a big load when its active its almost impossible to keep the cat temp below 1100-1200 until the off gassing ends.

But Ive smelled smoky odor in the yard even over 1000F on the probe which makes me wonder....

You can smell smokey odor, even when the cat is working flawlessly, I think. More importantly, you should not need to get a cat to 1000+ to get it to function, and if you do need to do so, it's a sign your catalyst is depleted. You will get purely mechanical non-catalytic reburn at those temperatures, no catalyst needed.

no you can be burning 35% wood and still get your cat to 1500f once the moisture is all cooked out. 800F is easy to obtain. Mine is really boderline active in that range. But i guess its all how your stove is designed etc how hot your cats read?

Agreed, clemsonfor... but I think you missed the point I was making. I was saying that if I'm already running at 800F, and was able to easily drive it up over 1000F, the moisture had already been baked out, and the cat should be doing its job.

I wouldn't doubt its a bad cat, we saw problems with those steel cats last year and the manufactures even got involved and have made some changes.

I recall hearing the same, but the question is... which manufacturers? This catalyst was made last year, and I think it was new technology to Condar at the time, although I know a few others have been making steel catalysts a little longer.

 

[jharkin]

You can smell smokey odor, even when the cat is working flawlessly, I think. More importantly, you should not need to get a cat to 1000+ to get it to function, and if you do need to do so, it's a sign your catalyst is depleted. You will get purely mechanical non-catalytic reburn at those temperatures, no catalyst needed.

Oh sorry I guess I wasn't clear... I know that when it lites off properly I close the bypass at 500 probe temp and the temperature will immediately start climbing and usually doesn't level off until it hits 1100+. Once the cat activates the heat of combustion inside the cat chamber drives the temps up that high.

If I close at 500 and it only rises to 700 or 800 that is a stall and will usually be accompanied by smoke dragon plumes out of the stack.

 

[clemsonfor]

I can close my bypass when the probe say 500, 700 or even 800, if i have not charred the wood well enough it will stall it. temp is not the only thing.

 

[Ashful]

Interesting. What do each of you mean when you say it is "stalled"? What do you see? Sometimes I'll do a full burn cycle with the cat holding 550F the entire time.

 

[clemsonfor]

what you just described to me is what i consider a stall.

For example after a full load has burned down and i have nothing but coals, not really much that is still smoking to run the cat but just coals and maybe some charcoal, i may still read anywhere from 400-600 depending upon how hot i ran that load. Anyway i will stiff them up and rake foward and have plenty of coals to start a new load, it will combust and start burning almost instantly. I load with whatever and maybe put a stick or 2 of kindling infront of the NS load. I can be at 600 as soon as i shut the door after getting those coals glowing and now with the door shut i can be 700+ in a feew minutes. This is my probe temp. If i shut the bypass i will never get very hot and just stay there. This seems to cause me to burn in lingo, not sure if cat is engaged or not and will be more smokey, but if i get it say 800F at least with some good char and then close bypass i will go easy about 1100F to 1800F depending upon load (species, MC, and amount). Getting these faster first temps i beleive i am burning clean. Other wise its what i call a "stall" not sure this is the true deffinition?

As to what i see, i see wood actively burning with good flames but little char, shut bypass they will slowly die back sometimes to nothing and the load may even go out if i shut it to early and not enough coals to keep it going, as well as little heat output. Not sure all cat stoves do this but i have noticed that if i do it this way it can run the whole load but sometimes its more smokey and the smoke will not clear. I dont like to do this though.

 

[jharkin]

Interesting. What do each of you mean when you say it is "stalled"? What do you see? Sometimes I'll do a full burn cycle with the cat holding 550F the entire time.

Something must not be right with your setup Joful.. Even the first year I had my stove burning marginal wood (25%+) I didn't see such low temps. I suspect you were in smoke dragon mode. The next time you see such low temps go look outside, let us know if you see clouds of smoke billowing from the stack.

Stalled means that the catalytic reaction did not innate a burn. Once it lights off I beleive the heat of the flame inside the catalytic chamber becomes self sustaining and drives the temps up fast, as I almost never see temps under 1000 except for the coaling stage of the cycle, even with the primary air shut. Generally on a big load the routine is something like:

• Bypass open, air open reload
• Load is fully charred, stovetop temp over 500

• Close bypass
• Cat probe hits 500 within a minute if I timed it right
• over 1-2 minutes cat probe rapidly rises 550 .. 600.. 650... up to about 1100

• Now I start cutting the air down in stages
• While I am dialing down the air the cat temp will keep rising and eventually settle in at cruising temp, anywhere from 1100-1300 depending on load, weather, etc

• the cruising temp will hold for anything from an hour to 6+ depending on load size
  • On a really big load on a cold strong draft day the cat temp may spike as high as 1700 at times
• Once the off gassing phase ends the cat temp will quite suddenly start dropping from the cruise temp down to about 800
• Over the next few hours as the coaling stage the cat temp will slowly decline from 800 down to 500 and eventually go cold

 

[jharkin]

what you just described to me is what i consider a stall.

For example after a full load has burned down and i have nothing but coals, not really much that is still smoking to run the cat but just coals and maybe some charcoal, i may still read anywhere from 400-600 depending upon how hot i ran that load. Anyway i will stiff them up and rake foward and have plenty of coals to start a new load, it will combust and start burning almost instantly. I load with whatever and maybe put a stick or 2 of kindling infront of the NS load. I can be at 600 as soon as i shut the door after getting those coals glowing and now with the door shut i can be 700+ in a feew minutes. This is my probe temp. If i shut the bypass i will never get very hot and just stay there. This seems to cause me to burn in lingo, not sure if cat is engaged or not and will be more smokey, but if i get it say 800F at least with some good char and then close bypass i will go easy about 1100F to 1800F depending upon load (species, MC, and amount). Getting these faster first temps i beleive i am burning clean. Other wise its what i call a "stall" not sure this is the true deffinition?

As to what i see, i see wood actively burning with good flames but little char, shut bypass they will slowly die back sometimes to nothing and the load may even go out if i shut it to early and not enough coals to keep it going, as well as little heat output. Not sure all cat stoves do this but i have noticed that if i do it this way it can run the whole load but sometimes its more smokey and the smoke will not clear. I dont like to do this though.

This is the exact same behavior I see and Ive seen other cat stove owners report.. When you see it sit at 800 there will be a lot of smoke out of the stack. In that case, reopening the bypass and let the load char another 10-15 minutes and try again usually gets a good light off.

 

[clemsonfor]

This is the exact same behavior I see and Ive seen other cat stove owners report.. When you see it sit at 800 there will be a lot of smoke out of the stack. In that case, reopening the bypass and let the load char another 10-15 minutes and try again usually gets a good light off.

Which is what i do, sometimes i can just open the air up all the way if i have already shut it down and get the cat back active.

 

[Ashful]

So we have come full circle, as what I see is what I described in my initial post above. I see smoke at temps if 500 - 800F, but according to all the cat combustir literature, a ceramic cat should ignite at 500F, and a SteelCat even lower than this.

Like you, I also often run the cat up to 1000-1500F, but this involves leaving the stove in bypass a little longer after loading so the stovetop exceeds 500F before closing the bypass damper. The literature suggests life should be good, if you get the cat to 500F.