Chimney cleaning and optimal burning

[SD Golden]

I just got around to cleaning my chimney after a busy spring, it was done for the 1st time in December and had burned mostly non-stop from then through mid March. Out of the 24' of exposed class A (I can't build an enclosure around it at this time) I got about 1.5-2" of black, light crusty creosote in the bottom of a 5 gallon pail overall after cleaning with a soot eater, which seems to do just ok of a job. I did notice there is some small spots that it appears a glaze type creosote is forming that the soot eater won't even begin to remove. Is this excessive? The stove is a Blaze King Sirocco 30, I typically burn in as high as I can without overheating the cat, but do have to turn it back about half way with a full load of wood. Once every week or 2 I will leave it in bypass for a while and let it roll for an hour or so to get everything good and toasty. I got the blaze king for the low, long burn times, but that inevitably leads to creosote. I considered removing the catalyst and using a creosote remover log of some sort to help clean the chimney of that glaze, then a couple fires after to remove any residual before reinstalling it, is this acceptable for a cat stove? Anybody have any tips on burning methods to take advantage of the catalyst stove while reducing cresote?

 

[moresnow]

Is this excessive?

With the length of your pipe and the duration of burn time between cleaning I am not surprised to hear your result. I see some of the same residue when cleaning, as well as some shiny glaze near the top occasionally. We use the Sooteater also. BK stove. 15 foot of pipe. Interestingly I've noticed some the shiny glaze ending up in the stove over the coarse of the summer.
We run the stove 24/7. We shut it down for a cleaning approximately once a month. More or less to reassure myself things are looking reasonable. Telescoping double wall connector pipe seems to have reduced the amount of residue compared to the single wall I started with. Guessing you will get a few more comments. Should be interesting.

Running wide open for a hour with the bypass open sounds excessive to me. May want a @BKVP opinion on that.

 

[Highbeam]

I believe that you need to go back and read the manual. You’re doing some things wrong. First, you do not need to and can’t monitor cat temperature with factory equipment other than for when to engage the cat. Second, do not leave the bypass open after your cat meter indicates “active”. The one hour burn out is done with the cat engaged. You’ll melt your retainers if you leave the bypass open!

24’ of exterior class a will generate some build up. Your wood quality probably has more to do with it than anything.

With that tall of a stack and running hot a lot you are a candidate for cat clogging since you’re on a 30 box. Keep an eye on it.

 

[jetsam]

The thermostat will monitor firebox temperature and keep the cat safe. You can burn on high all the time if you really want to (but if you want that, you probably should have got a cheap tube stove). There is no reading on the cat probe that means that the cat is too hot.

Don't burn with the bypass open unless you are bringing the cat up to temperature.. Some stoves can actually be damaged this way, not sure if yours is one of them.

You are also getting the opposite of the effect you wanted by burning with the bypass open. The open bypass is sending all the unburned creosote-forming organics up the flue at lower temperatures instead of burning it in the cat and raising the temperature of the flue gasses. (It's also a waste of wood, for the same reasons.)

Don't use any kind of creosote log or chemical in the stove.

If you want less creosote, quit burning with the bypass open, and use drier wood.

If drier wood is not an option, look into insulating the flue, and/or sweep more often.

 

[SD Golden]

I have run it with the bypass open to raise the flue temp vs it being run through the cat since the stove flows better with it open, which I have verified the higher flue temps with an infrared thermometer. I have been directed in the past to run hotter or a hot fire weekly to heat up the flue to prevent buildup, thus my running it open and heating up the chimney. I don't like to run the cat at the upper end of the temp range on the thermometer, and certainly not above. The fact remains that running your catalyst too hot (that threshold is debated) will reduce its life as it degrades the precious metals within the catalyst. I do hope to build an insulated enclosure around the vertical stack but due to a few reasons, I am not able to at this time. Thanks for the replies.

 

[jetsam]

Any time the cat is above 500°, you are going to have a cooler flue with the cat disengaged than you would have at the same burn rate with the cat engaged (possible exception for low burn rates with the fans on high, I guess).

If your stove flows better with the bypass open, your cat is clogged. Hit both sides, especially the back, with a shopvac. Make sure there's not a big pile of sweepings on the ledge behind the cat.

 

[BKVP]

I have run it with the bypass open to raise the flue temp vs it being run through the cat since the stove flows better with it open, which I have verified the higher flue temps with an infrared thermometer. I have been directed in the past to run hotter or a hot fire weekly to heat up the flue to prevent buildup, thus my running it open and heating up the chimney. I don't like to run the cat at the upper end of the temp range on the thermometer, and certainly not above. The fact remains that running your catalyst too hot (that threshold is debated) will reduce its life as it degrades the precious metals within the catalyst. I do hope to build an insulated enclosure around the vertical stack but due to a few reasons, I am not able to at this time. Thanks for the replies.

There is no debate on threshold temperatures. There are 3 components to a combustor:
1) Substrate...ceramic, reticulated foam (looks like a loofa) ceramic and metallic.

2) Washcoat....a proprietary application that increases surface area and acts as carrier for precious metals.

3) Frame....the often metal frame is needed to control expansion and contraction. Also, offers way to apply expanding gasket for sealing in stove housing.

Prior to washcoat being applied, surface of substrate looks smooth under microscopic view. Once washcoat is applied, it takes on appearance of an English muffin. This is where so much surface area comes from.

When the washcoat reaches 1600F, the washcoat goes from alpha alumina to gamma alumina, flattens-out in appearance and loses critical surface area needed for effective emissions control.

Under great stack effect due difference between inside and outside temps, the chimney will pull more air in from the source. CFM increases, cat gets hotter and if it repeatedly hits 1600F, the cat is toast.

In some cases, ceramic cats, this can be evident by seeing cracks (there are also natural cracks from expansion and contraction), crumbling and total collapsing of the substrate. In metallic cats, the washcoat is identical and although the substrate may not fail, the washcoat still has same temperature threshold. It will just flatten-out and peel away.

There is no exception to the washcoats acceptable max temp. There are various companies touting "new" materials of substrate that can tolerate higher temps. The materials are not new, even in the stove industry and it's the washcoat that must be protected.

 

[SD Golden]

There is no debate on threshold temperatures. There are 3 components to a combustor:
1) Substrate...ceramic, reticulated foam (looks like a loofa) ceramic and metallic.

2) Washcoat....a proprietary application that increases surface area and acts as carrier for precious metals.

3) Frame....the often metal frame is needed to control expansion and contraction. Also, offers way to apply expanding gasket for sealing in stove housing.

Prior to washcoat being applied, surface of substrate looks smooth under microscopic view. Once washcoat is applied, it takes on appearance of an English muffin. This is where so much surface area comes from.

When the washcoat reaches 1600F, the washcoat goes from alpha alumina to gamma alumina, flattens-out in appearance and loses critical surface area needed for effective emissions control.

Under great stack effect due difference between inside and outside temps, the chimney will pull more air in from the source. CFM increases, cat gets hotter and if it repeatedly hits 1600F, the cat is toast.

In some cases, ceramic cats, this can be evident by seeing cracks (there are also natural cracks from expansion and contraction), crumbling and total collapsing of the substrate. In metallic cats, the washcoat is identical and although the substrate may not fail, the washcoat still has same temperature threshold. It will just flatten-out and peel away.

There is no exception to the washcoats acceptable max temp. There are various companies touting "new" materials of substrate that can tolerate higher temps. The materials are not new, even in the stove industry and it's the washcoat that must be protected.

I maybe misspoke, I agree with this but I question the ability to run the stove on high without the catalyst reaching these temperatures was my intent. If I leave it on the upper 1/3 of the range on the thermostat with a full load, the thermometer will easily go beyond the range shown on the thermostat.

 

[jetsam]

I maybe misspoke, I agree with this but I question the ability to run the stove on high without the catalyst reaching these temperatures was my intent. If I leave it on the upper 1/3 of the range on the thermostat with a full load, the thermometer will easily go beyond the range shown on the thermostat.

We've debated this quite a bit in the BK thread over the years.

I think the consensus is that you do want to keep it under 1600, but the built in cat probe does not provide you with an accurate idea of where 1600 might be (the last mark on the unlabeled BK probe that Condar makes for the Princess is at 1600° on the generic Condar version of the same probe, but they are apparently not very accurate on the high end). You'll also see that they drift... mine commonly drifts 200-600 degrees in a burning season, requiring a recalibration to room temp. (Pair of pliers, 5 minutes.)

Not sure that you have the same probe, but I wouldn't rely upon it to tell me where 1600 is. I haven't heard that anyone has stuck a calibrated thermocouple probe in there yet, but I'd love to hear their findings if they did.

Anyway, I certainly wouldn't let that cheapo coil thermometer stop me from using my stove on the burn rate I needed for that day.

You can also get within a couple hundred degrees of the surface temp of the cat using a mark 1 eyeball, which is probably better accuracy than the cat probe boasts.

 

[BKVP]

The bimetallic thermometer are indeed not highly accurate. Cat temps actually accelerate as the residence time increases. So turning down the air will result is increased residence time.

Luckily your stoves' thermostat will help prevent the excessive temps. I have thermocoupled my stove and in our lab we only use thermocouples to register cat temps.

91 companies rushed cat units to market between 1984 and 1988. Nearly all the cats failed, deservedly earning a poor reputation. Consumers were blamed for over firing the stoves, cat suppliers were blamed for poor product dependability, dealers were blamed for not educating users. The fact it the mfg's were to blame as they were reacting to Oregon State regulations for wood stoves. (EPA did not start until 1988 (phase 1).

If the stove design does not take this all into consideration, the cats will fail. There has to be a safeguard against excess temp (1600F).

 

[SD Golden]

Thanks for the info! I screenshotted that heat photo for reference come heating season.

If the stove design does not take this all into consideration, the cats will fail. There has to be a safeguard against excess temp (1600F).

Does the blaze king firebox design adequately safeguard against excessive temps?

 

[jetsam]

Yeah, that was his point. Run the stove according to the manual and the accurate, calibrated internal thermostat will regulate firebox temperature appropriately.

No babysitting needed for these stoves.

We have years of BK customer discussions archived here (all available to read if you're feeling masochistic). You will see very few people saying that they ran their BK hard and lunched the cat. Of those few I can recall, they all had three things in common: 1) Excessive draft 2) Unwillingness to address the excessive draft 3) Undersized stove for their space.

Any stove will run hotter than designed if you vent it at multiple times the designed flue gas pressure and run it flat out, though.

So with your 30' flue, I would recommend that you get a manometer and have a cheap damper ready to go for this winter, but beyond that, use the stove how you want to use the stove, and let the thermostat worry about internal temperatures.

 

[BKVP]

Thanks for the info! I screenshotted that heat photo for reference come heating season.
[QUOTE="BKVP, post: 2365425, member:

If the stove design does not take this all into consideration, the cats will fail. There has to be a safeguard against excess temp (1600F).

Does the blaze king firebox design adequately safeguard against excessive temps?[/QUOTE]
Yes.

 

[BKVP]

Yeah, that was his point. Run the stove according to the manual and the accurate, calibrated internal thermostat will regulate firebox temperature appropriately.

No babysitting needed for these stoves.

We have years of BK customer discussions archived here (all available to read if you're feeling masochistic). You will see very few people saying that they ran their BK hard and lunched the cat. Of those few I can recall, they all had three things in common: 1) Excessive draft 2) Unwillingness to address the excessive draft 3) Undersized stove for their space.

Any stove will run hotter than designed if you vent it at multiple times the designed flue gas pressure and run it flat out, though.

So with your 30' flue, I would recommend that you get a manometer and have a cheap damper ready to go for this winter, but beyond that, use the stove how you want to use the stove, and let the thermostat worry about internal temperatures.

Most critical on cat stoves is a nice snug door gasket seal to prevent thermal shock. Another necessary design element in any wood stove.

 

[Highbeam]

Does the blaze king firebox design adequately safeguard against excessive temps?

Yes.[/QUOTE]

This single one word answer is very valuable. Of course there are a couple of assumptions such as that your draft must fall within spec and that your door gasket must be working.

The op might have missed it but the highest cat temps are often not at high thermostat settings.

Also, the cats wear out. Go ahead and experiment. You’ll need a new one every 12000 hours anyway. They are super easy to swap out.

 

[BKVP]

You may need one every 12,000 hours depending upon how you use your stove. If you burn on low burn rates, high burn rates, manufactured fuels versus cordwood.

There are many variables that determine cat lifespan. A year round, high volume burner may see a need to replace more often than another user that burns less often.

There is no question that cats diminish in there effectiveness with time, but the 12000 hour rule does not apply to all users.

Applied Ceramics has tried for years to have Condar remove that wording from their website and literature. They are the experts and clearly acknowledge that most cats have 9 lives and others have even more or less.

 

[Highbeam]

Of course 12000 hours of cat life does not “apply” to ALL users. Many cat stove operators don’t even know that they have a cat, engage it, or care about the smoke, drop in output, increase in flue deposits, etc of a dead or dying cat.

Most forum members, competent users, and even the other top tier cat stove manufacturer do know and have experienced that 12000 hours is the real world life expectation for acceptable performance. Woodstock tells us to only expect 12000-14000 hours per cat which is only 3 years of full time burning a measly 6 months per year. Bk doesn’t tell us anything really. I’m on a phone so can’t gather more data points but it’s certainly not just condar.

I propose that being honest about cat life expectancy is very important for the industry. Wouldn’t it be great to actually get 10 years of life from a cat being actually used for actual heating? That would be over 40,000 hours!

 

[jetsam]

It's an impossible topic because all of our performance measures are subjective.

"My cat has declining performance after 2 years", "I have burned full time with the same cat for 10 years and it still works okay"- both are interesting anecdotes, but neither one has any actual data it. How much exposed catalyst remains on the 10 year old cat versus the 2 year old cat? Where does "okay" end and "dead" begin?

Drives me crazy, but not so crazy that I'm setting up data collection and logging to figure it out for myself.

 

[Highbeam]

I admit there will be extremes. One guy demands excellent performance and the other is asleep at the wheel. It’s pretty obvious when your cat is dead if you’re paying attention.

 

[begreen]

It’s pretty obvious when your cat is dead if you’re paying attention.

Not everyone pays attention.

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[Highbeam]

Not everyone pays attention.

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That’s what I’m trying to say. I sure hope our brightest manufacturers aren’t depending on that. You know who will pay attention? The epa.

 

[jetsam]

I admit there will be extremes. One guy demands excellent performance and the other is asleep at the wheel. It’s pretty obvious when your cat is dead if you’re paying attention.

Well, our local technical expert on cats IS the guy who has been burning full time for a decade on one cat. Where's the line between dead and alive?

 

[BKVP]

A independent study commissioned by CHC and at the request of EPA, who were also involved in the study formation and condition, enjoined OMNI Environmental Labs to study cats that were in user stoves.

Mfg's provided large lists of consumers that owned cat stoves. That is the ONLY role the mfg's played in the study.

The upshot was that a cat that burned more than 3 cords per year, was 9.5 years old, burned 1 gr/h dirtier than it's certification value.

Additional cats were studied as well of various ages.

Study included emissions from untreated cats (no precious metals/washcoat), cat removed etc.

All wood heaters...All wood heaters....diminish in their ability to burn as clean as when new.

As a dear friend says..."Go out, look up". If you see smoke into a burn, something needs to be done.

 

[Highbeam]

As a dear friend says..."Go out, look up". If you see smoke into a burn, something needs to be done.

Cheers good friend. We all can agree to that!

If it takes 10 years then that’s just fine.