Keystone Cat Going - Gone Bad

[leeave96]

I ordered a new catalyist combuster for my Keystone today. It is under warranty and the only charge is shipping - yippie & horray for Woodstock customer service!!

We have been in a semi-shoulder season around here for about 6 weeks, sometimes temps dipping in the 30's and lower 40's, but warming-up nicely during the afternoon and have only been burning the Keystone to knock off the chill and even then go for days with no fire.

When building these shoulder season fires, we have been turning the damper down for a smaller cat only driven heat vs full flames and glowing cat. We noticed that the combuster was not lighting off very well and not glowing at all (I know it doesn't have to glow to be working). I talked to Woodstock, they said to vacuum/brush it off and see how it does. Did that, burned it for another couple of weeks watching the combuster, stove top temps and visible smoke coming out of the chimney. Also noticed the cat crumbled a bit when I lightly brushed it off - not good.

This weekend was a bit chilly, and since I was home for both days, I had a good opportunity to check the cat a little closer. Sure enough, smoke out the chimney, no orange - no matter the damper settings and stove top temps not making it over 400 degrees - flames or no flames.

Bottom line - cat combuster is not working, so I called Woodstock today and a new cat is on the way.

We are about done for the year for burning, but it will be good to get a new cat in place for next fall.

BTW, the new combustor will be the stainless steel model.

Thanks!
Bill

 

[begreen]

Good to hear that it is covered by warranty. How old was the dead cat? How many cords of wood would you estimate went through it?

 

[Todd]

Strange that the cat went bad in only your first year. Did Woodstock say what could of caused this? If it is crumbling it sounds like thermo shock. Maybe engaging too soon with less than dry wood?

Woodstock is really good with their cat warranty. The new steel cats are resistant to thermo shock and should last longer. The new stainless scoop will help protect the cat as well. It's good to see them constantly improving their stoves.

 

[North of 60]

I think damp wood has been the culprit. I am just finishing year 5 and have no reason to contemplate a new cat. Nothing has changed the stoves characteristics to do any different.
Sorry to hear about your dead CAT. :red:

 

[leeave96]

I can't explain the cat failing. We have good wood, the crumbling of the cat is pretty minor, just some flakes here and there. It's hard to see how flames could get into the cat as it is recessed so far back in the stove and our burning is generally to get flames wicking the underside of the scoop.

I think I've hit 700 stove top one time and that was peak and temps settled out lower. A high temperature for us is usually 600 to 650. We typically cruise between 450 and 550.

I don't recall me or anyone else in our family burning a super cedar with the cat engaged, but reflecting back, the cat's demise was around the time I started using them.

Maybe we've done something wrong, but I'm pretty retentive when it comes to taking care of burning this stove. I offered to pay for the new cat - but Woodstock said no - it's under warranty; another reason to buy from them.

On the other hand, it is dissapointing too that I need to replace this cat. I paid a lot of $$$'s for this stove and to have to replace a part after one burning season bugs me a little bit - even if I am the problem. I am looking forward to burning the Englander 30 this fall to get a feel for these non-cat/secondary burn stoves to see how they compare. The Keystone ain't going anywhere, but if we like the way the Englander works and holds-up, we may upgrade that install in a few years to a PE Alderlea as I really like the looks of them and the positive stuff I'm reading about the stoves.

Bill

 

[leeave96]

Good to hear that it is covered by warranty. How old was the dead cat? How many cords of wood would you estimate went through it?

About 3 cords of mostly oak and locust with a bit of maple and pine mixed-in.

Thanks!
Bill

 

[North of 60]

Good to hear that it is covered by warranty. How old was the dead cat? How many cords of wood would you estimate went through it?

About 3 cords of mostly oak and locust with a bit of maple and pine mixed-in.

Thanks!
Bill

35+ cords of pine and spruce for the sudie chem ceramic catalyst in my Princess. You super cedars should NOT be a factor in your results. Engaged or not.
Good luck on your next one.

 

[leeave96]

35+ cords of pine and spruce for the sudie chem ceramic catalyst in my Princess. You super cedars should NOT be a factor in your results. Engaged or not.
Good luck on your next one.

I totally agree. Whatever went wrong with it could have been our fault, but I'm not sure what we could have done differently. When we install the new one, we'll be burning the same wood, same burning style. If the new one fails - then I'll totally take the blame - maybe get a pellet stove...

Bill

 

[henkmeuzelaar]

35+ cords of pine and spruce for the sudie chem ceramic catalyst in my Princess. You super cedars should NOT be a factor in your results. Engaged or not.
Good luck on your next one.

I totally agree. Whatever went wrong with it could have been our fault, but I'm not sure what we could have done differently. When we install the new one, we'll be burning the same wood, same burning style. If the new one fails - then I'll totally take the blame - maybe get a pellet stove...

Bill

Since you appear to be a careful wood burner, my guess is that you simply got a "lemon" cat.

Nonetheless, the things to watch out for in order to maximize a woodstove cat's operating life are:

(1) to avoid "coking" or "slagging" the surface up by regularly trying to activate the cat at too low a temperature. Only a calibrated thermometer probe placed immediately downstream of the cat can be trusted to show the correct temperature.

(2) to avoid "poisoning" the platinum and/or palladium catalyst with compounds such as sulfur or nitrogen. Sulfur and nitrogen are both abundant in certain types of composite wood constructed with bone glue as well as all other organic matter such as food left-overs. Even thoroughly decomposed ("rotted") or fungus-covered wood can be expected to be high in both sulfur and nitrogen. Moreover, the ink of newspapers or magazines, as well as certain types of wood paint are likely to be rich in nitrogen compounds.

Not saying that you must be burning any of these materials. However, potentially it could take only one kid who wants to see how well this or that old plastic toy burns to seriously poison a cat....

Henk

 

[Todd]

Did you take the cat out and inspect it? What did it look like on the exhaust side? When I clean my Keystone cat I like to remove the scoop and stick one of those air cans inside the box and blow it through the cells. I think this technique is a little more thorough than just brushing or vacuuming the front side. Could there be some build up on that other side? Might even be worth it to run a pipe cleaner through each cell or do a 50/50 vinegar/water bath just to see if you can bring it back to life before replacing it with a new one.

 

[Backwoods Savage]

For sure, extremely rare for a cat to go bad that soon. Naturally fuel is the first thing to look at and especially burning oak. I've always said that oak needs 3 years after being split before burning it. Even if you let the stove get to 250 stove top or above and wait 15 minutes before engaging the cat, that oak can still have lots of moisture in it and that will kill a cat fast. I hope this is not the reason but thought I'd just throw it out. But as stated, it is extremely rare. I really hope the new cats take care of these problems and I've heard some good things about them. For sure our next cat will be the steel cat.

 

[rtljr]

The cat on our Keystone showed slight hairline fractures after the first year of 24/7 burning. At the beginning of the second season, I noticed that it was harder to get the cat to glow. All was fine during my post-Christmas cleaning as the cat only exhibited the same hairline cracks. At the end of the season when I removed the cat there was some crumbling on the top but the bottom was severely crumbled. It appeared to be damage from flame impingement. The two stove operators (my wife and I) had resorted to running in non-bypass mode longer to try to get the cat to light off so we likely damaged the poor critter.

I took the cat to the August open house and showed it to Mike H. He said that we could eke some more life out of it and said that it was OK to keep using it while we waited for the stainless steel replacement. The stove continued to perform poorly but once the stainless steel cat arrived and I installed it well, WOW! The new cat lights off easily, heat output is greater, and we burned at least a half cord less this season despite colder temperatures.

The stove performs like it did when new and Woodstock supplied the replacement at no charge; outstanding customer service yet again from Woodstock. In addition to the Keystone we own the Mini Franklin for our master bedroom. When the new stove comes out we will be buying that and reassigning the Keystone to a future three-season room.

 

[leeave96]

Did you take the cat out and inspect it? What did it look like on the exhaust side? When I clean my Keystone cat I like to remove the scoop and stick one of those air cans inside the box and blow it through the cells. I think this technique is a little more thorough than just brushing or vacuuming the front side. Could there be some build up on that other side? Might even be worth it to run a pipe cleaner through each cell or do a 50/50 vinegar/water bath just to see if you can bring it back to life before replacing it with a new one.

Yes, I took the cat out on the advice of Woodstock for a thorough cleaning. The cat was grey in color as I recall. There were hairline cracks, but nothing that alarmed me. When I lightly brushed it and vaccumed it, a little bit of the cat crumbled, but not more than a 16th or 8th of an inch on a few honeycombs - again, didn't really concern me other than to signal that I need to handle the cat carefully. BTW, nothing was stopped-up either. One nice thing about the Keystone is how well you can see the cat. If it has some fly ash on it, you can usually see it without taking it out.

Thanks!
Bill

 

[leeave96]

(2) to avoid "poisoning" the platinum and/or palladium catalyst with compounds such as sulfur or nitrogen. Sulfur and nitrogen are both abundant in certain types of composite wood constructed with bone glue as well as all other organic matter such as food left-overs. Even thoroughly decomposed ("rotted") or fungus-covered wood can be expected to be high in both sulfur and nitrogen. Moreover, the ink of newspapers or magazines, as well as certain types of wood paint are likely to be rich in nitrogen compounds.

Not saying that you must be burning any of these materials. However, potentially it could take only one kid who wants to see how well this or that old plastic toy burns to seriously poison a cat....

Henk

Henk,

You may be onto something. I have what I call some "punky" wood that I have in my shoulder season pile. It is from rounds that I split and the center was pretty much rotten/shreadded wood. It's dry, but about half of it is not solid. This is the first I've ever heard that burning rotten wood would cause damage to a cat. All of the wood I cut and season is dead to start with. When I say dead, I mean it hasn't had a leaf on it for years! Sometimes the trunks of these trees will have a bit of punky center. I cut it, split it and burn it (not that much of it) when I don't need a super hot fire.

Thanks,
Bill

 

[Woody Stover]

It's hard to see how flames could get into the cat as it is recessed so far back in the stove

As you may remember, I've been getting some smoke when there's flame in the box; The combustor doesn't seem to be burning left-over smoke. I've not had the chance to remove and clean the combustor yet, and haven't had a chance to pick up some pipe cleaners to clean it. I'll be looking closely for any damage such as flaking or peeling.
I've mentioned before that sometimes I get some smoke/gas igniting behind the baffle screen, directly under the combustor. I mean to ask Woodstock if that is considered "flame impingement" and could damage the combustor, but haven't found the time yet to do it. I don't think it's anything to worry about; It's not a super-hot flame slamming into the face of the combustor. Any other Keystone or Fireview burners seen this flame inside the scoop/screen? If so, has installing the new stainless scoop eliminated the flame under the combustor?
After I clean and inspect the combustor, I think I'll go ahead and order a steel cat and stainless scoop and do some experimenting.
I wonder if cat failure has been a frequent problem in the Keystones, and this is the reason they've moved to the stainless combustors? Or are they just looking for better performance?

 

[henkmeuzelaar]

It's hard to see how flames could get into the cat as it is recessed so far back in the stove

As you may remember, I've been getting some smoke when there's flame in the box; The combustor doesn't seem to be burning left-over smoke. I've not had the chance to remove and clean the combustor yet, and haven't had a chance to pick up some pipe cleaners to clean it. I'll be looking closely for any damage such as flaking or peeling.
I've mentioned before that sometimes I get some smoke/gas igniting behind the baffle screen, directly under the combustor. I mean to ask Woodstock if that is considered "flame impingement" and could damage the combustor, but haven't found the time yet to do it. I don't think it's anything to worry about; It's not a super-hot flame slamming into the face of the combustor. Any other Keystone or Fireview burners seen this flame inside the scoop/screen? If so, has installing the new stainless scoop eliminated the flame under the combustor?
After I clean and inspect the combustor, I think I'll go ahead and order a steel cat and stainless scoop and do some experimenting.
I wonder if cat failure has been a frequent problem in the Keystones, and this is the reason they've moved to the stainless combustors? Or are they just looking for better performance?

Fascinating observations! Apparently, there is too much distance (or rather air volume) between the baffle screen and the catalyst. Although I do agree with you that superhot flame impingement is probably not to blame (after all, the ceramic substrate of the cat can withstand extreme temperatures) I would not rule out that the "slamming" itself may have a lot to do with the damage.

Just imagine the kind of momentary air velocities one can get when the mix of gases reignites. Then imagine such micro-puffs happening time and again during the height of the burn cycle. Finally, remember that the manufacturers of these cats always warn the user not to use high speed air flows for cleaning, as this may easily dislodge and carry off the catalyst particles, leading to severe loss of activity....

So, yes, I think you may indeed be right that the new steel versions of the cat are being substituted to help solve the problem. Because of the way the catalyst can be sintered to the steel surface, these cats should be much less sensitive to mechanical damage.

Henk

 

[Todd]

It's hard to see how flames could get into the cat as it is recessed so far back in the stove

As you may remember, I've been getting some smoke when there's flame in the box; The combustor doesn't seem to be burning left-over smoke. I've not had the chance to remove and clean the combustor yet, and haven't had a chance to pick up some pipe cleaners to clean it. I'll be looking closely for any damage such as flaking or peeling.
I've mentioned before that sometimes I get some smoke/gas igniting behind the baffle screen, directly under the combustor. I mean to ask Woodstock if that is considered "flame impingement" and could damage the combustor, but haven't found the time yet to do it. I don't think it's anything to worry about; It's not a super-hot flame slamming into the face of the combustor. Any other Keystone or Fireview burners seen this flame inside the scoop/screen? If so, has installing the new stainless scoop eliminated the flame under the combustor?
After I clean and inspect the combustor, I think I'll go ahead and order a steel cat and stainless scoop and do some experimenting.
I wonder if cat failure has been a frequent problem in the Keystones, and this is the reason they've moved to the stainless combustors? Or are they just looking for better performance?

Fascinating observations! Apparently, there is too much distance (or rather air volume) between the baffle screen and the catalyst. Although I do agree with you that superhot flame impingement is probably not to blame (after all, the ceramic substrate of the cat can withstand extreme temperatures) I would not rule out that the "slamming" itself may have a lot to do with the damage.

Just imagine the kind of momentary air velocities one can get when the mix of gases reignites. Then imagine such micro-puffs happening time and again during the height of the burn cycle. Finally, remember that the manufacturers of these cats always warn the user not to use high speed air flows for cleaning, as this may easily dislodge and carry off the catalyst particles, leading to severe loss of activity....

So, yes, I think you may indeed be right that the new steel versions of the cat are being substituted to help solve the problem. Because of the way the catalyst can be sintered to the steel surface, these cats should be much less sensitive to mechanical damage.

Henk

I've seen this as well but always thought it was ok since it wasn't a direct flame being sucked up through the cat cells. The new scoop in the Fireview wraps around the sides unlike the old one and I didn't notice any flame bursts after I installed it.

 

[3fordasho]

I have two Fireviews, one installed in 2007 and the 2nd in 2009. The first cat went 2 seasons before crumbling to pieces- I attribute the early failure due to not ideally seasoned wood. Wood is much better now, much of it 2-3 years seasoned and it then spends the entire summer in a wood shed before the next burning season. A recent inspection/cleaning of the replacement cat shows quite a bit of hairline cracking and a bit of crumbling on the exit side. The original cat in the newer stove also shows the hairline cracking, but I have not pulled it for cleaning to see if it's going to start crumbling. I expect to call Woodstock soon to discuss the issue and hope for replacements - I hope the new steel cats are going to hold up better for me. I never get excessive fly ash or other build up on the cat, just the cracking issue.

 

[leeave96]

It's hard to see how flames could get into the cat as it is recessed so far back in the stove

As you may remember, I've been getting some smoke when there's flame in the box; The combustor doesn't seem to be burning left-over smoke. I've not had the chance to remove and clean the combustor yet, and haven't had a chance to pick up some pipe cleaners to clean it. I'll be looking closely for any damage such as flaking or peeling.
I've mentioned before that sometimes I get some smoke/gas igniting behind the baffle screen, directly under the combustor. I mean to ask Woodstock if that is considered "flame impingement" and could damage the combustor, but haven't found the time yet to do it. I don't think it's anything to worry about; It's not a super-hot flame slamming into the face of the combustor. Any other Keystone or Fireview burners seen this flame inside the scoop/screen? If so, has installing the new stainless scoop eliminated the flame under the combustor?
After I clean and inspect the combustor, I think I'll go ahead and order a steel cat and stainless scoop and do some experimenting.
I wonder if cat failure has been a frequent problem in the Keystones, and this is the reason they've moved to the stainless combustors? Or are they just looking for better performance?

Sometimes if the temperature outside is warm, but there is still enough chill in the house to justify a small fire - say first thing in the morning and the stove is cold, I will get some smoke build-up and sometimes a tad of spillage either through the open door or on a rare occasion, out the damper opening at the rear of the stove. I chalk that up to less draft due to warm outside air temps. It doesn't take but a few seconds/minutes for that to clear and I am good.

As to flame impingement, I don't buy that as a cause of the catalyst failing or even the ceramic. The catalyst is designed to ignite smoke and burn it, i.e. fire/flames, and of course the secondary light show that goes on from time to time - driven by the cat lighting off the smoke just like a secondary burn tube in a non-cat stove. The ceramic is baked in the first place at what ought to be a high temperature just to make the thing from the get go. Maybe the glowing cat is much hotter than the ceramic baking , but I wouldn't think it would hurt it - but maybe it does and the stainless steel will cure that problem. I can tell you this - my cat is the hottest when it is a smoldering burn, the cat glowing bright orange, no flames in the firebox and the stove top temp approaching 700 degrees. If that ruins the cat, then I need to rethink the merit of having a cat stove in the first place.

Also, with regard to stalling the cat or plugging the micro-substrait pores, I should think that you could engage the cat full time and allow the stove to get up to temperature and when the temps reach, stove top, 200-250 degrees, the cat would have to light off - IF there is enough air for combustion. If there is any clogging, once the cat lights off and starts glowing orange, any creosote on the cat would have to burn off. The only reason I see for bypassing the cat is to allow more draft to get your fire going - sort of like a choke on a lawn mower when starting. The other reason is to let steam boil off the wood if you throw in a snow covered piece or one that has been setting the rain.

It may be that the stainless steel structure may be the majic bullet. For heavens sake, the stove is a holding vessel for an live fire in it. To somehow direct the user to limit the flames - short of warping metal, to save something inside the stove seems like a design flaw or unnecessary limitation. I am hopeful the new SS cat will allow me to burn my stove safely and hot - not dance around with saving the cat instead of maximizing the heat from the stove.

I say burn the Woodstocks stoves up to 700 degrees with as much flame as necessary to get there, keep a safe stove pipe temperature and these are your stoves limits - not the cat. Of course the other limit is do you really want to open every window and door in your house, strip of most all clothing while maintaining 90 degree plus room temperatures I'd say from there, damper down and enjoy the stove and the view of the fire.

I ought to have my SS cat in a few days and I'll give it a try. I am also excited about burning the Englander 30 later this year to see how that beast handles flame impingement, 700 plus stove top temps and long clean secondary burns.

Bill

 

[Todd]

I remember a discussion with Woodstock about potassium in the fly ash being the real cat killer. I don't remember all the details but I'm thinking this new scoop/steel cat combination will eliminate much of the potassium damage. Wonder if some woods have different potassium levels than others?

 

[Backwoods Savage]

Todd, they did talk quite a bit about potassium last year when we were there but it sounded as if more experimenting might be in order.

On the cats, those hairline cracks won't hurt and even a little bit of crumbling won't hurt but too much and then it has to be replaced.

On cleaning the cat, I've never seen where we would need pipe cleaners or anything else to clean them. I simply use an old paint brush. Just brush it lightly on both sides and put it back in. The only thing we've ever had is some very light fly ash.

 

[Woody Stover]

("rotted") or fungus-covered wood can be expected to be high in both sulfur and nitrogen.

Henk,
You may be onto something. I have what I call some "punky" wood that I have in my shoulder season pile. It is from rounds that I split and the center was pretty much rotten/shreadded wood. It's dry, but about half of it is not solid. This is the first I've ever heard that burning rotten wood would cause damage to a cat. All of the wood I cut and season is dead to start with. When I say dead, I mean it hasn't had a leaf on it for years! Sometimes the trunks of these trees will have a bit of punky center.

I'm definitely gonna try to find out more about this. I, too, cut mostly dead wood. Not usually as punky as what you're describing, though. I guess I could use the punky stuff on the bottom, punk down, for cold starts or reloads, and burn off the punk when the bypass is open...

I would not rule out that the "slamming" itself may have a lot to do with the damage.
Just imagine the kind of momentary air velocities one can get when the mix of gases reignites.

The burning I'm seeing is more of a lazy burn under the combustor as opposed to an explosive ignition...

As to flame impingement, I don't buy that as a cause of the catalyst failing or even the ceramic. The catalyst is designed to ignite smoke and burn it, i.e. fire/flames, and of course the secondary light show that goes on from time to time - driven by the cat lighting off the smoke just like a secondary burn tube in a non-cat stove. The ceramic is baked in the first place at what ought to be a high temperature just to make the thing from the get go. Maybe the glowing cat is much hotter than the ceramic baking , but I wouldn't think it would hurt it - but maybe it does and the stainless steel will cure that problem. I can tell you this - my cat is the hottest when it is a smoldering burn, the cat glowing bright orange, no flames in the firebox and the stove top temp approaching 700 degrees. If that ruins the cat, then I need to rethink the merit of having a cat stove in the first place.

Good points...

Also, with regard to stalling the cat or plugging the micro-substrait pores, I should think that you could engage the cat full time and allow the stove to get up to temperature and when the temps reach, stove top, 200-250 degrees, the cat would have to light off - IF there is enough air for combustion. If there is any clogging, once the cat lights off and starts glowing orange, any creosote on the cat would have to burn off. The other reason is to let steam boil off the wood if you throw in a snow covered piece or one that has been setting the rain.

Hmmm, I though that you were supposed to avoid loading the cat with creosote because when you burn it off, ash remains and keeps the smoke from contacting the catalyst...
Getting some pipe cleaners today. Gonna burn tonight and I'd like to see if, with a clean combustor, the stove will burn all the smoke. Hard to believe the cat would be compromised after only a month or so of burning, but I was guilty of trying to see how soon I could engage as I played with the new stove; Maybe I ashed it up pretty bad...

To somehow direct the user to limit the flames - short of warping metal, to save something inside the stove seems like a design flaw or unnecessary limitation. I am hopeful the new SS cat will allow me to burn my stove safely and hot - not dance around with saving the cat instead of maximizing the heat from the stove.

Yep.

 

[leeave96]

Update: Received my new cat combuster today

Bad News: It's to warm to burn

The new combuster's stainless steel structure is very thin, almost looks like corrigated carboard cross-section. I hope this sucker works!

If it get's colder between now and next fall, I'll give it a try. I gather that flame impingement and thermal shock damaged are pretty much minimized with this stainless steel vs the ceramic - we'll see.

Bill

 

[Woody Stover]

I removed the cat from the 'stone tonight. My other cats are constantly preening themselves, but this one I have to clean. ;-)
I used pipe cleaners, which dislodged a bit of ash, then vacuumed lightly. No real damage that I could see. A little ceramic was broken along one edge, but that could have happened during assembly...or not.
So I reinstalled it and lit a load. I saw the same thing that I mentioned in my "Keystone stack smoking?" thread; After engaging, cat was glowing and I had flame in the box, but saw smoke coming out the stack. I didn't quite have 250 on the stove top. Then when it got to 250, even though the cat wasn't glowing very brightly, all of the smoke was getting burned. So my solution could be as simple as that; Make sure the stove top is at 250 before engaging. I don't understand why that should make a difference if the cat is glowing, but apparently it does.
Another interesting thing I've seen is that when I'm establishing a load, even though the bypass is open, I sometimes see the combustor glowing faintly, indicating (I think) that a small amount of smoke is being pulled through the cat. So what happens if you're trying to burn a little excess moisture off of some not-quite-seasoned wood? Could that cause damage to the combustor? If so, there's another reason to have "Dennis-dry" wood.

 

[Todd]

Woody,
How soon after you engaged did you look at your stack? Sometimes for me it can take 5 minutes or more til the stack goes smokeless. I also pay more attention to my stack temp than stove top when looking to engage. I think the majority of the time I engage with a stove top of about 200 but the internal stack temps are well within lite off range.

I have also seen the cat glow at times during bypass, and when I do It's usually because the box is engulfed in flame so I turn the air down some. No sense in sending all that heat up the flue.