Swapping to a steel cat in the Blaze King

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Highbeam

Minister of Fire
Hearth Supporter
Dec 28, 2006
20,935
Mt. Rainier Foothills, WA
After three years of burning with only annual cleanings of the flue and door adjustements I have noticed that the stove, with its original ceramic cat, was almost constantly emitting a stream of blue smoke. Especially bad during the first 3-5 hours of the cycle. This is not normal and in this age of burn bans and green energy I wanted to attain that clean burn that cat stoves are supposed to be very good at.

I test my wood and it is softwood over two years old and moisture below 13%.

So I managed to acquire a SS cat element. The steel cats are what is now OEM on most stoves and is supposed to go active at much lower temperatures to start eating smoke sooner. It also has a ton more surface area which to me means more catalyst in contact with the smoke so it should do better at eating it. They are more resistant to thermal shock and the only drawback I could find is slightly higher cost and a higher likelihood of clogging due to ash. Honestly, I have never had anything accumulate in my cat, I think the BK design prevents this issue.

In preparation for the swap I used a sooteater brush system on my all vertical 12 foot flue which is over 4 feet of double wall and 8 feet of class A. I discovered that you can reach into the bypass hole and lift the bypass plate to expose the trough behind the cat and vacuum every dang bit of flue debris without wasting time and effort removing the flue from the stove. Try it, you can lift up that bypass plate towards the stove top and reach a finger in there to touch the back of the cat.

I was a little afraid of prying the cat out. The new one comes with an expanding gasket that might make the old one a tight fit. Manual says to pry out with screwdriver so that's what I did. It pried right out a little at a time on opposite corners. It was stuck in there but easily came out. No popping loose, very slow. The ceramic cat looked fine with cracks and held together nicely. It's a fairly stout piece. The back of the cat had weird aluminum foil looking shrapnel peeling off of it. Hmmmm, maybe I was loosing catalyst from the substrate. Oh and with the cat out of the way I could double check that all debris is vacuumed from the cat chamber, it was.

The new cat comes with new gasket which is wrapped with masking tape to hold it on. The steel cats also come with masking tape across the face and back of the cat which I cut off. It is important to leave the perimeter tape in place since shoving the new cat in requires the new gasket to be firmly held in place. The new cat was a tight fit. It is very important to evenly push the cat into the frame or it could bind. Slow and even working all around. That's it. Start a fire.

This cat works differently. My old cat got plenty hot and was still glowing but it was just letting smoke by. The steelcat is dark until you flop the bypass and then it instantly begins to glow orange. It was odd, closing the bypass actually caused the fire to pick up and burn more briskly. Perhaps the cat burning actually increased draft? It's pretty warm here so I wasn't able to burn a full load but I can say that within 30 minutes of lighting the fire that the emissions would have passed the 20% burn ban smoke opacity test which would NOT have happened with the old ceramic cat. It was still evident that I was burning but within the first hour, and after turning down the thermostat, the emissions were clear.

Main reason for this thread was to show that changing cats is REALLY easy with simple hand tools and not very expensive when you consider the benefits of a cat. Second is to show some of the differences between a steel and ceramic cat.
 

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Here are a couple more photos of the thing installed and glowing. A guy could almost adjust the bypass through the cat opening.
 

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Appears that the new cat has much smaller holes. Could the addition of surface area be part of the "cleaner" burn you are seeing with the new cat? It will be interesting to know if the smaller holes create any type of plugging issue.
 
Appears that the new cat has much smaller holes. Could the addition of surface area be part of the "cleaner" burn you are seeing with the new cat? It will be interesting to know if the smaller holes create any type of plugging issue.

Yes, smaller holes and many many more of them like double the amount which means way more catalyst touching the smoke. The metal cell walls are very thin though so perhaps this doesn't add up to a restriction until/unless it clogs with ash. Plugging cats do not seem to be an issue with any BK stove, even the ones with OEM steel cats. Easy to check and you can bet I'm watching for it.
 
Yeah, looks like the catalyst is peeling off the ceramic in that second pic. I think that is caused by running the cat at 1800+ for extended periods. That cat is only a couple years old, right? How often were you running with the meter needle around the top of the silver arrow dial marking?
 
I'll be interested to see how the steel cat performs long term. I've read a few posts from BK users about fly ash plugging up the steel cats. I may buy a spare for next season, I've been leaning towards the ceramic up to this point.
 
Yeah, looks like the catalyst is peeling off the ceramic in that second pic. I think that is caused by running the cat at 1800+ for extended periods. That cat is only a couple years old, right? How often were you running with the meter needle around the top of the silver arrow dial marking?

This is the third full season on that OEM ceramic cat. It still glows and the probe meter happily climbs to the top of the active range. By all accounts it is performing well except for blue flue smoke. There is no way to know how hot the cat gets on a BK, the gauge has no numbers and the manual does not instruct you to operate based on "how" active the cat is. Even if you did know how hot the cat was or cared, I don't know how you would cool it. Probably with each fire the ceramic cat caused the needle to run to the top of the active range.

The steel cat did not seem to cause the meter to climb as high and being new it is probably more active than the old.

You know there is a reason that industry is switching to a more expensive steel cat. They wouldn't spend extra money for less performance.
 
This is the third full season on that OEM ceramic cat. It still glows and the probe meter happily climbs to the top of the active range. By all accounts it is performing well except for blue flue smoke.

Would this qualify as a warranty issue for the cat?
 
Would this qualify as a warranty issue for the cat?

I find the smoking cat to be defective at reducing the emissions rate to the 2.4 specified.
 
Yeah, looks like the catalyst is peeling off the ceramic in that second pic. I think that is caused by running the cat at 1800+ for extended periods. That cat is only a couple years old, right? How often were you running with the meter needle around the top of the silver arrow dial marking?
Our stoves are engineered to not allow 1,800 temps...of course this can be influenced by excessive draft of thermostat modifications. (Not allowed!)
 
I find the smoking cat to be defective at reducing the emissions rate to the 2.4 specified.

If I remember right when I browsed the EPA Method 28 the 2.4 is calculated from the "Weighted Average Emission Rate" of the 4 burn rates tested. That number is also from dimensional lumber used doing the testing not the cord wood we're burning. While your burn may start off smokey I'd bet the overall emissions rate would be similar to the EPA test results if we could test our stoves using the same method.

If the Princess has been tested with the ceramic and steel cat I'd like to see the test differences. I'd imagine it's only been tested with the ceramic since that was the catalyst used when the stove was developed? ;hm

I have always found from day one my stove will smoke a little early in the burn if I have flames in the box, once the flames go out(pretty typical for the stat setting I run after 30 minutes or so) the stack is smoke free for the rest of the burn.
 
If I remember right when I browsed the EPA Method 28 the 2.4 is calculated from the "Weighted Average Emission Rate" of the 4 burn rates tested. That number is also from dimensional lumber used doing the testing not the cord wood we're burning. While your burn may start off smokey I'd bet the overall emissions rate would be similar to the EPA test results if we could test our stoves using the same method.

If the Princess has been tested with the ceramic and steel cat I'd like to see the test differences. I'd imagine it's only been tested with the ceramic since that was the catalyst used when the stove was developed? ;hm

I have always found from day one my stove will smoke a little early in the burn if I have flames in the box, once the flames go out(pretty typical for the stat setting I run after 30 minutes or so) the stack is smoke free for the rest of the burn.
It's actually more complicated that just the result of the four (or more) runs. Firebox size plays a role in the equation and also determines size of test fuel. Then there is the weighting which is skewed towards the low and medium Low test results. This is done to reflect how consumers use solid fuel appliances. Steel cats (Dura foil...not that crap diesel foil some on line company sells) does go active quicker than ceramic. However, ceramic stay active longer (approx. 10%). Both work equally well in most applications.
 
Has this completely solved the smoke problem Highbeam?
 
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Has this completely solved the smoke problem Highbeam?

It was 78 degrees yesterday so I was unable to run another test burn. Hopefully tonight but we are about to enter a stretch of warm weather that might limit me to partial loads every few days.
 
49F here right now., heading down to 44F tonight. Smokem if ya gottem.
 
Has this completely solved the smoke problem Highbeam?

Loaded a 3/4 full load last night of regular sized splits. Stove was stone cold. Within 20 minutes the probe gauge said active so I flopped the bypass and the steelcat instantly switched from black to orange. It's really cool to watch how quickly the steelcat gets orange. Within 30 minutes I was smoke free and cruising at 50% stat setting. No smoke ever returned for the rest of the burn. So yes, smoke is reduced to "normal" levels IMO.

I can only hope that the cat maintains this level of performance for many years. Is it just a new cat? Would smoke have gone to zero with a new ceramic cat? Maybe.
 
Hope it works much better for you. What brand steel cat did you end up getting.
 
Hope it works much better for you. What brand steel cat did you end up getting.

I don't know, whatever the BK dealer sells as OEM. It has no name.
 
There is no way to know how hot the cat gets on a BK, the gauge has no numbers and the manual does not instruct you to operate based on "how" active the cat is. Even if you did know how hot the cat was or cared, I don't know how you would cool it. Probably with each fire the ceramic cat caused the needle to run to the top of the active range. The steel cat did not seem to cause the meter to climb as high and being new it is probably more active than the old. You know there is a reason that industry is switching to a more expensive steel cat. They wouldn't spend extra money for less performance.
Even with no numbers on the dial, you can tell how hot the cat is running by looking at it. I like to see the cat a medium-orange, where I can still see the structure of the cat. If you look at your '005.jpg' pic, you can see the structure on the right side of the cat. I don't like to see the cat as hot as on the left side of that pic, where the cat is more yellow than orange, and the structure of the cat isn't visible.
You've often said that in your opinion the cat meter's only use is to tell you when the cat is active so that you know when to close the bypass, and that you don't care what the actual cat temp is. You seem to think that's true because BK orders their cat probes with no numbers on the dial. I think the reason they put the no-numbers probe on their stoves is to make it seem like cat stoves aren't as complicated to run as they really are. Their "10-yr. guarantee" makes it sound to the uninformed buyer as though the cat stove is foolproof and simple to run. That, I believe, is why manuals say nothing about operating the cat properly. Now, I don't claim to be a cat expert by any means, and really hadn't paid much attention to combustors until about 4 years ago, when I started running other cats besides the Dutchwest, and started burning dry wood. What I can say for sure is that the operator can control how active the cat gets by how much of the load he gets gassing when establishing a new load, and by how much air the smoldering load is given once the stove is cruising (flame in the box means less active cat, of course.) I became aware of this with the Buck 91, before I replaced some gaskets and got more control over the air entering the stove. I also became aware that different wood types gassed faster or slower and that had an effect on how active the cat got, given the same air settings and draft conditions. Since you peeled the catalyst off your original cat in 3 yrs, maybe you'll take a closer look at how your cat, and cat stove, operate.
As for why they went to steel cats, I think part of the reason is their durability in the face of operators that have no clue about the operation or maintenance of a stove (I'm guessing that's why BKVP is always harping on door gasket maintenance...thermal shock?) The steelies don't crack from thermal shock. Maybe the catalyst is less likely to peel off the metal than the ceramic as well, I don't know. Replacing all these cats under warranty has got to be eating into these stove makers' bottom line.
Our stoves are engineered to not allow 1,800 temps...of course this can be influenced by excessive draft of thermostat modifications. (Not allowed!)
Highbeam has a 12' stack so it shouldn't be over-drafting. Assuming he hasn't altered the thermostat, to what do you attribute the peeling of the catalyst shown in the pic? I was under the impression that only continuous heat in excess of 1800 can cause this kind of damage. I'll admit, positioning of the probe will affect temp readings. I have 2 different length probes for the Dutchwest; The one that is closer to the surface of the cat reads higher by 200 degrees. When in doubt, I judge temp by looking at the cat. I like to see a medium-orange glow. Bright orange, or orange-yellow is hotter than I like to see it. As has been said here, if you drive your car with it floored all the time, it will crap out pretty quick. ==c
I'm not familiar with your stoves so I'm not clear on what engineering you are using to prevent the cat from going high. If I went to Highbeam's house, crammed the stove full of small splits of that pitchy Douglas Fir fatwood, got a king-sized blaze going in the box to get a bunch of it gassing, then closed the bypass and adjusted the thermostat to feed the most air, just short of flaming the load, I bet I could send that cat well over 1800, engineering notwithstanding. ==c I'm sure that with a moderate thermostat setting, cat temps will stay well in hand. But if the stove isn't big enough to supply the needed heat at a low setting, the operator opens the air up for more heat. That's fine as long as there's flame in the box to eat some of the excess smoke, but if not, the cat may be going high. I don't think you can control the amount of flame in the box with the thermostat, can you? IMO, there's just no getting around the fact that cat stoves like to run low, and are easiest to run when the air is set low. My solution is to get plenty of stove so I get enough heat running it on low, most of the time. If I need to push the stove harder and open up the air, I may need to watch it more closely.
 
Has this completely solved the smoke problem Highbeam?
Once the cat is lit, you see zero smoke, unless you are running a lot of air through the stove. Like I always say, the cats like to run low. ==c
Would this qualify as a warranty issue for the cat?
He's playing it cagey...doesn't say if he called in the warranty or not. ==c
What brand steel cat did you end up getting.
I think the Woodstock and BK steelies are Sud-Chemie.
 
He's playing it cagey...doesn't say if he called in the warranty or not. ==c

His stove has a 10 year free replacement on the OE cat so I'm sure it's being replaced under warranty.
 
Even with no numbers on the dial, you can tell how hot the cat is running by looking at it. I like to see the cat a medium-orange, where I can still see the structure of the cat. If you look at your '005.jpg' pic, you can see the structure on the right side of the cat. I don't like to see the cat as hot as on the left side of that pic, where the cat is more yellow than orange, and the structure of the cat isn't visible.
You've often said that in your opinion the cat meter's only use is to tell you when the cat is active so that you know when to close the bypass, and that you don't care what the actual cat temp is. You seem to think that's true because BK orders their cat probes with no numbers on the dial. I think the reason they put the no-numbers probe on their stoves is to make it seem like cat stoves aren't as complicated to run as they really are. Their "10-yr. guarantee" makes it sound to the uninformed buyer as though the cat stove is foolproof and simple to run. That, I believe, is why manuals say nothing about operating the cat properly. Now, I don't claim to be a cat expert by any means, and really hadn't paid much attention to combustors until about 4 years ago, when I started running other cats besides the Dutchwest, and started burning dry wood. What I can say for sure is that the operator can control how active the cat gets by how much of the load he gets gassing when establishing a new load, and by how much air the smoldering load is given once the stove is cruising (flame in the box means less active cat, of course.) I became aware of this with the Buck 91, before I replaced some gaskets and got more control over the air entering the stove. I also became aware that different wood types gassed faster or slower and that had an effect on how active the cat got, given the same air settings and draft conditions. Since you peeled the catalyst off your original cat in 3 yrs, maybe you'll take a closer look at how your cat, and cat stove, operate.
As for why they went to steel cats, I think part of the reason is their durability in the face of operators that have no clue about the operation or maintenance of a stove (I'm guessing that's why BKVP is always harping on door gasket maintenance...thermal shock?) The steelies don't crack from thermal shock. Maybe the catalyst is less likely to peel off the metal than the ceramic as well, I don't know. Replacing all these cats under warranty has got to be eating into these stove makers' bottom line.
Highbeam has a 12' stack so it shouldn't be over-drafting. Assuming he hasn't altered the thermostat, to what do you attribute the peeling of the catalyst shown in the pic? I was under the impression that only continuous heat in excess of 1800 can cause this kind of damage. I'll admit, positioning of the probe will affect temp readings. I have 2 different length probes for the Dutchwest; The one that is closer to the surface of the cat reads higher by 200 degrees. When in doubt, I judge temp by looking at the cat. I like to see a medium-orange glow. Bright orange, or orange-yellow is hotter than I like to see it. As has been said here, if you drive your car with it floored all the time, it will crap out pretty quick. ==c
I'm not familiar with your stoves so I'm not clear on what engineering you are using to prevent the cat from going high. If I went to Highbeam's house, crammed the stove full of small splits of that pitchy Douglas Fir fatwood, got a king-sized blaze going in the box to get a bunch of it gassing, then closed the bypass and adjusted the thermostat to feed the most air, just short of flaming the load, I bet I could send that cat well over 1800, engineering notwithstanding. ==c I'm sure that with a moderate thermostat setting, cat temps will stay well in hand. But if the stove isn't big enough to supply the needed heat at a low setting, the operator opens the air up for more heat. That's fine as long as there's flame in the box to eat some of the excess smoke, but if not, the cat may be going high. I don't think you can control the amount of flame in the box with the thermostat, can you? IMO, there's just no getting around the fact that cat stoves like to run low, and are easiest to run when the air is set low. My solution is to get plenty of stove so I get enough heat running it on low, most of the time. If I need to push the stove harder and open up the air, I may need to watch it more closely.
I do not believe it has been confirmed the plating peeled. Second, we went to stainless because we did not want all our supply to come from a single supplier, which is very risky. Third, stainless substrates are more durable, but not the wash coat. Fouth, we still use ceramic in many models. Fifth, sorry there is no fifth point, instead,
How about, "way to go Highbeam! No smoke is the way to go." And we can move on.

Speaking of moving on, I will be in Sturbridge Mass., on Sunday & Monday. Any BK guys there want a free drink?

Chris
 
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Close! 1hr to the south and I'd be there. Have fun!
 
If you find yourself down there...send me a pm with contact number.
 
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