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Is your “pipe” temp the surface of the stove pipe temperature, and the “out” temp the flue gas temperature? Also how are you measuring the cat temp?

You have a single wall stove pipe on this stove correct?
Sorry, meant to include those details:

1. "Pipe" is surface thermometer on single-wall pipe. Yes, you can do 30+ hours with single wall when the outdoor temp is 40F or below, BKVP is exercising an abundance of caution when he tells you double-wall is needed. Double wall is better for lower burning, no doubt, but single works well enough for reliable 24 hour burns in all weather, on this stove with a very straight shot of 15 feet.

2. Cat temp is eyeballed off un-labeled BK gauge, knowing the inactive/active crossing is 500F, and then eyeballing the remaining increments against this thermometer:

And yes, if it wasn't clear... this stove has about 5-6 feet of single wall followed by about 9-10 feet of blanket-wrapped smooth wall liner, somewhere near 15 feet total from memory, although I should really measure it before being too confident in those numbers. It may be as short as 13 feet, or as long as 16 feet, total.

Awesome. Thanks for the clarification.

I just got my Auber up and running. I notice the cat goes active on my stove around 330 degrees flue temp. Maybe because it’s a newer cat?

My chimney is about 23’ of vertical run, and 30” of horizontal run.

I just got my Auber up and running. I notice the cat goes active on my stove around 330 degrees flue temp. Maybe because it’s a newer cat?
Your 330F probe is roughly equivalent to my 160F surface, if past experiments by others are to be believed.
My chimney is about 23’ of vertical run, and 30” of horizontal run.
I have a second Ashford with 6 feet of double wall into 30 feet of blanket-wrapped smooth-wall liner, the double wall being equipped with both a probe thermometer and Magnehelic. It's my primary stove, where I run about 7 cords per year. I will repeat this experiment on that stove at some point soon, which will give better data resolution, although the cat presently installed has a LOT of miles on it.

I measured the stove pipe surface temp a few times, and it was very close to half the flue temp. So it seems like what people say is true about that.

I ran a little experiment on one of my BK Ashfords last night. Learned / confirmed I could only expect about 24 hours active cat on a short 15 chimney when the temperature was > 50F outside on a 4-year old combustor, which is still miles beyond any other similar size stove on the market, but short of what it can do with good draft in January.

The experiment was run with only a 75% wood load, as it was 50F outside and this 3 cu.ft. stove is only heating something like 1200 sq.ft., depending on how you count it. So, when I say "24 hours for a full load", I mean I measured 18 hours on a 75% load of wood.

I initially pushed for a longer burn, turning the dial below my usual 24 hour setting, and using only 25% of a full load in 10 hours. Impressive, but the warm weather, short chimney, and 4-year old combustor were all conspiring to push me toward a cat stall, so I increased the air at the 10 hour mark. You will see this reflected in the 100F jump in cat temp at that point in the graph.

Summary point 1: I think my combustor is doing fine after 4 years, now into its 5th season, and after roughly 12 cords.
Summary point 2: You need to have an ideal setup to push toward 30 hours... and 15 feet of pipe at 50F outdoor temperature is not ideal. But hitting 24 hours is easy, even under poor conditions.

View attachment 299953

In the future, I'll try the same on my other stove, which sets under 30 feet of insulated pipe and is straddling a cat with more than 30 cords on it over the last 4+ years. I may also repeat the above on the short pipe stove, but in colder weather, seeing if this old cat can still hit the 30 - 36 hour times it did when new.
“years” is a terrible way to quantify the condition of your catalyst. My spare unused catalyst on the shelf is also a few years old but has no hours of use.

Perhaps an approximation of hours would be more useful. Like the manufacturer rates them.

“years” is a terrible way to quantify the condition of your catalyst. My spare unused catalyst on the shelf is also a few years old but has no hours of use.

Perhaps an approximation of hours would be more useful. Like the manufacturer rates them.
That's really all you got from that post, Highbeam? Picking on my tracking method?

Fair enough, but you know I don't have an hour meter on either stove! I'm pretty sure I gave this previously, but to keep it together with this data, here's the rough hours:

I run the steelcat used in the graph above at ~8.3 hours per cubic foot consumed, so 12 cords = roughly 12,700 hours.

The beta3 cat is run at roughly double that rate, so its ~30 cords = roughly 15,900 hours, by that estimation method. Accuracy can be debated, I do believe actual hours on the beta3 is more like 17,500 (~10% higher), based on the months of full/part time burning per year.

In this regard, if anyone uses a fan to move air when the stove is hot, one can easily count the hrs by adding a (wifi) plug that measures the energy used (and knowing the energy consumption of the fan) or the hrs directly.

I switch on my (inline duct) fan within an hour after the cat is active - and likely an hour or so after it falls out of being active if I don't reload. Last year I ran it about 2000 hrs. So my cat was used about 2000 hrs last season. I hope it'll last at least 6 yrs if this was a standard winter.

I tried earlier to keep notes of how long the cat was active, to track its life, but that was impossible (without a proper lab journal...). This was an easy solution. At the end of the season, I just look at how many kWhs consumed, divide by 26 W (fan at full speed), and voila, the hrs of active cat used roll out.

Just a thought.

Ashful
Ha ha, you guys are awesome. That’s a whole new level of wood heating. Just when I was beginning to think the blaze king set and forget operations made it relatively boring you expose the science

@BKVP , how did that slab wood work out for you? I’m getting a sawmill delivered today and thinking too much bark ( mostly Doug fir) but curious if you burned any that you had yet

That's really all you got from that post, Highbeam? Picking on my tracking method?

Fair enough, but you know I don't have an hour meter on either stove! I'm pretty sure I gave this previously, but to keep it together with this data, here's the rough hours:

I run the steelcat used in the graph above at ~8.3 hours per cubic foot consumed, so 12 cords = roughly 12,700 hours.

The beta3 cat is run at roughly double that rate, so its ~30 cords = roughly 15,900 hours, by that estimation method. Accuracy can be debated, I do believe actual hours on the beta3 is more like 17,500 (~10% higher), based on the months of full/part time burning per year.
Yeah, you’re a scientist type so you know about garbage in = garbage out. Once I get tripped up on a catastrophic error it’s really hard to trick myself into thinking the rest of the data is valid. 😀

@BKVP , how did that slab wood work out for you? I’m getting a sawmill delivered today and thinking too much bark ( mostly Doug fir) but curious if you burned any that you had yet

A sawmill in eatonville? Nice!

Nealm66
Yeah, you’re a scientist type so you know about garbage in = garbage out. Once I get tripped up on a catastrophic error it’s really hard to trick myself into thinking the rest of the data is valid. 😀
Well, here's the real question: Can you pick out a failing cat from data like this? Or does it always come down to the cleanliness of the chimney at the end of the year? You have a method of spotting a bad cat, the aforementioned goo oozing down the outside of your chimney. But what about the rest of us, never seeing anything so severe?

I ask, because I'm not sure I've ever been able to name the moment when a cat fails in a BK. My jotuls would eat them, overfire them until the cat came out looking like a potato chip. But other than a little surface rust on the band/can, the ceramic cat in my Ashford looks almost like the day I installed it in 2018, and it still lights off nearly the same as it ever did. When do I call it "done"?

These photos were taken last week, it's been used thru four seasons. Note this is the ceramic beta3 cat, not the same stove used in the graph above, but I'd bet it generates a similar graph.

A sawmill in eatonville? Nice!
There’s actually quite a few around but none with trailers that I know of. It doesn’t really add up financially on my end with my logging and tree service but I really love making boards. Might burn the scraps even if they’re really hard on the cat after seeing how easy it was to replace.

Highbeam and Diabel
Might burn the scraps even if they’re really hard on the cat after seeing how easy it was to replace.
Hey, if you haven't already done it, order yourself 10 feet of 2" x 1/16" interam gasket. The shipping will cost as much as the gasket (unless you found a better source than me), but you'll want to have this on-hand for sweeping the pipe, or any other time you need to pull the cat. My cat uses 30", so 10 feet gets me four sweepings, or one year for two stoves, since I often pull the cat once mid-season to vacuum ash off it.

When you install, just wrap gasket around combustor, and then wrap 2" painters tape tight around that. The tape vaporizes during first use, but makes sliding the thing into the hole much easier.

I see some for about \$5 per foot. Does that sound about right?

I see some for about \$5 per foot. Does that sound about right?
Holy crap! I was going to reply I usually pay under \$3/foot, but then thought I should see if the price from my usual supplier (Woodman's Parts Plus) had changed.

Yes, indeed... now they get \$6.25/ft. I'm not going to waste time hunting old emails, but I'm pretty sure my last two orders were both \$2.79/ft. Not sure who I can thank for that, it's a new world.

I guess if you found it for \$5/ft, I should be asking for your supplier and ordering some!

Well, here's the real question: Can you pick out a failing cat from data like this? Or does it always come down to the cleanliness of the chimney at the end of the year? You have a method of spotting a bad cat, the aforementioned goo oozing down the outside of your chimney. But what about the rest of us, never seeing anything so severe?

I ask, because I'm not sure I've ever been able to name the moment when a cat fails in a BK. My jotuls would eat them, overfire them until the cat came out looking like a potato chip. But other than a little surface rust on the band/can, the ceramic cat in my Ashford looks almost like the day I installed it in 2018, and it still lights off nearly the same as it ever did. When do I call it "done"?

These photos were taken last week, it's been used thru four seasons. Note this is the ceramic beta3 cat, not the same stove used in the graph above, but I'd bet it generates a similar graph.

View attachment 300001 View attachment 300002 View attachment 300000
Cat failure is certainly not physically apparent when looking at the catalyst in my experience with the BKs. It’s about smoke mostly. Go outside, look at the emissions.

Dropping heat output along with rising fuel consumption is another clue but that smoke is more conclusive.

It’s never been about chimney accumulations or gunk on the glass for me.

If you buy a new cat does it come with a gasket?

My chimney has a cleanout outside. And I usually remove the stove pipe when I clean the chimney. The only reason I’d be taking the cat out is to replace it.

Highbeam
I see some for about \$5 per foot. Does that sound about right?
I can’t think of any reason to remove the catalyst until it’s time for replacement. I’ve never bought any of this gasket since new cats come with it.

Cat stoves just don’t have to be so complicated to operate.

I can’t think of any reason to remove the catalyst until it’s time for replacement. I’ve never bought any of this gasket since new cats come with it.

Cat stoves just don’t have to be so complicated to operate.
I was just about to ask. “Should I remove and brush the cat?” I did a very thorough chimney and stove cleaning yesterday. I have never removed the cat in three yrs (part time burning). I do have additional gasket. The cat works fine and does not look plugged or anything.
When I cleaned the chimney part (up to the tee) was done via the bypass entry. I vacuumed all around the bypass door. Would any of the falling ash end up on the other side of the cat? That needs to be cleaned?

I think it depends on the vendor whether the gasket comes with it. I may be wrong though.

I take my stove pipe off as well. Vacuum the front and the back of the cat, and all around the space there near the bypass. No need to take it out. (Careful though if I bump it a bit too hard from behind, it can slide out very easily).

Ashful
my current catalyst probe has the majority of the writing smudged off, it probably doesn’t need to be replaced but I would like to replace it. Is their an off brand that would work the same. I see Amazon has a few for around \$30. Thoughts or suggestions.

I have purchased and received cat's both with and without the gasket. The last steelcat I bought was listed "with", but actually arrived without.

But I like to remove the cat 1x to 2x per year:

1. To sweep the chimney. A lot of what comes down the pipe accumulates behind the cat, in a BK 30. Without removing the cat, it would be hard to clean completely around the bypass door gasket.

2. To vacuum fly ash that tends to accumulate on and in the combustor during the season. I often (but not always) do this once at mid-season.

Diabel
So far the shop vac has been able to reach behind and around the cat here. But I did get me some gasket - always good to be able to put a cat back when it's mid-winter.

Highbeam
So far the shop vac has been able to reach behind and around the cat here.
I did my first year sweeping with cat in place, it's definitely possible. Then someone here mentioned how much easier it was to get in there to clean everything with it removed, and I was converted. Give it a try next time, just for kicks, and I bet you'll join the faith! Or not, nothing lost but \$12.50 in gasket material, at \$5/ft.

Also, always nice to just get the thing on the floor in front of you for a good inspection and vacuuming, or make sure you can see thru all the channels. I guess that could also be done in-situ with a flashlight up thru the bypass and some contortion exercises, but it has just become part of my routine to remove it now.

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