19.5 hour burn time achieved

[BC_Josh]

I just got a 19.5 hour burn time in my Sirocco 20,2 Blaze King woodstove. I was amazed that it achieved this, even with split fir in it (I also have some larch for cold snaps saved up). I did pack the firebox nice and full on that burn, yet with pretty good airflow between pieces. It seems like smaller pieces are better for achieving this; seems like the surface area is needed for the longer burn times. I let it burn hot for 25 min's first, then turned down the thermostat from 6 o'clock position (full) down to 4:30 position, then after about five min's down to the 3 o'clock position where I left it. I went out after lunch for a whole day, stayed out, had dinner out, went to a super long movie, then a slice of pizza, came home, went to bed and got up in the morning to my surprise, still lots of glowing embers in the stove! Raked them and put more wood on it for another fire this morning. Just so happy with the performance of this stove.

Mind you, it is still pretty mild out, just getting to freezing temps outside finally (I'm in the interior rainforest area of south eastern British Columbia, Canada) so I'm not sure how long of a burn time I'll be getting when it gets colder, but still... pretty darn great. I remember growing up and my dad would get up in the middle of the night to feed our wood furnace (a Valley Comfort stove) to keep us all warm.

Any other Blaze King owners or any long, low burn stove owners out there want to chime in with any tips, stories or other info? Anyone else got a Blaze King with a number 20 after the model name? Chinook, Sirocco, etc?
~BC Josh P.S.: enjoy the pic I added. It's from this morning, with a low temp fire going off of yesterday's embers.

 

[Ashful]

Nice work, Josh! Yes, 10 hours per cubic foot is very achievable with a BK on a good chimney setup. I have done over 30 hours of active cat many, many times on one of my two Ashford 30's, and I think my record was roughly 36 hours before the cat probe thermometer needle clearly fell into inactive territory.

What's impressive about your feat is you're doing it on a much lower BTU wood. All of my long burns were on oak of one variety or another, or perhaps hickory.

Now, if you really want to impress yourself when it gets cold out, rip a few loads with the thermostat wide open. I've proven many times over that I can rip thru a full load of oak in 4-5 hours, or stretch it beyond 30 hours, all with the simple turn of a knob. Gotta love that range!

 

[moresnow]

I am more impressed with the schedule you had out and about that day! Fun day, good eats, by the sound of it.
I run the same exact stove in my house. Same results.
Let us know when you get a 24hr round. It can be done. I've done it. Good times...

 

[BC_Josh]

Nice work, Josh! Yes, 10 hours per cubic foot is very achievable with a BK on a good chimney setup. I have done over 30 hours of active cat many, many times on one of my two Ashford 30's, and I think my record was roughly 36 hours before the cat probe thermometer needle clearly fell into inactive territory.

What's impressive about your feat is you're doing it on a much lower BTU wood. All of my long burns were on oak of one variety or another, or perhaps hickory.

Now, if you really want to impress yourself when it gets cold out, rip a few loads with the thermostat wide open. I've proven many times over that I can rip thru a full load of oak in 4-5 hours, or stretch it beyond 30 hours, all with the simple turn of a knob. Gotta love that range!

Yes, I was surprised that I used fir and got the long burn time. I might've had pieces that had more dense heart wood than outer wood, just by chance, but I'm not sure. It's good to know that BK stoves actually live up to their claims.

I'm cautious about burning for more than a half hour, or so, with the thermostat wide open. Can't that run the risk of warping some of the steel plate in the stove?.... I notice when I get it going really hot, the needle on the catalytic thermometer is at about the end of the white band/zone, and almost at the end of its range. I've heard you have to get a stove up to 2,000 F before it'll warp, though. I don't have a flue thermometer. Are those a good idea to have, or necessary?

 

[BC_Josh]

I am more impressed with the schedule you had out and about that day! Fun day, good eats, by the sound of it.
I run the same exact stove in my house. Same results.
Let us know when you get a 24hr round. It can be done. I've done it. Good times...

Yes, fun day for sure. Went to the swimming pool before dinner and the movie.

I have some larch firewood as well, and that should be able to get me over 20 hrs burn time.

I've learned that it's all in the loading. I split the wood pretty small(ish) and I feel that it helps with this stove to have plenty of surface area for the low burn.

:^) Josh

 

[moresnow]

Yes, I was surprised that I used fir and got the long burn time. I might've had pieces that had more dense heart wood than outer wood, just by chance, but I'm not sure. It's good to know that BK stoves actually live up to their claims.

I'm cautious about burning for more than a half hour, or so, with the thermostat wide open. Can't that run the risk of warping some of the steel plate in the stove?.... I notice when I get it going really hot, the needle on the catalytic thermometer is at about the end of the white band/zone, and almost at the end of its range. I've heard you have to get a stove up to 2,000 F before it'll warp, though. I don't have a flue thermometer. Are those a good idea to have, or necessary?

Burning hot occasionally is actually recommended.
I'd guess a large percent of users are dialing the stat back/down prior to the recommended 30 min. Whatever works best for each setup.
Your stat settings sounds like mine. Your elevation is 800' above mine. What do you have for venting? Curious.

 

[tabner]

Fellow 20 box owner here. I easily get 12 hours between reloads. Sometimes actually have an issue with too long of a burn. yesterday I loaded the stove at 8:30am, and last night around 8:30pm i had the thermostat on high with the blower going trying to burn through the coaling phase quicker in order to load up before bed. What are most peoples' views on a hot reload in a BK? Like a full bed of hot coals? I think on some of the Hybrid/Non-Cat stoves that can be a little risky due to a big off-gassing happening quickly? Are the BK's mostly able to control it? I was a little scared to do a full reload of Oak last night with a big hot coal bed.

 

[BC_Josh]

Burning hot occasionally is actually recommended.
I'd guess a large percent of users are dialing the stat back/down prior to the recommended 30 min. Whatever works best for each setup.
Your stat settings sounds like mine. Your elevation is 800' above mine. What do you have for venting? Curious.

Yes, I make sure to burn hot for 25 min's before I turn down the thermostat setting (the manual says to do so, for 20 to 30 min's). The fellow who installed the stove told me to burn hot a few hours per/week to avoid creosote buildup. I also like how it burns off much of the glass stains so I can see the fire better.

 

[BC_Josh]

Fellow 20 box owner here. I easily get 12 hours between reloads. Sometimes actually have an issue with too long of a burn. yesterday I loaded the stove at 8:30am, and last night around 8:30pm i had the thermostat on high with the blower going trying to burn through the coaling phase quicker in order to load up before bed. What are most peoples' views on a hot reload in a BK? Like a full bed of hot coals? I think on some of the Hybrid/Non-Cat stoves that can be a little risky due to a big off-gassing happening quickly? Are the BK's mostly able to control it? I was a little scared to do a full reload of Oak last night with a big hot coal bed.

BK recommends raking hot coals towards the front of the box (I think they just mean to make a flat bed of coals), then putting more wood on it to relight the stove, then shutting the door just to the latch, so there is a crack open. I don't think it's a problem at all, as long as you remember to turn off the bypass if it's already in the active zone. These stoves are built to reload hot.

As long as your load gets a good blaze on for 20 to 30 min's then you should be fine to turn down the heat and go for another slow burn.

Like the pic with your cat watching the fire, by the way. You'll have to train your cat to turn off the bypass. 😺🔥

 

[BC_Josh]

What do you have for venting? Curious.

I have a furnace fan that brings in cool air from the basement (might also bring in air from the air intake from outside as well) and distributes it around the house through the furnace vents. Also, when I'm lighting a fire, I open the door which is not far from my stove. Of course, I close it again once the fire starts a-blazin'.

 

[neverstop]

what flue temperatures do these stoves run at when you get 20+ hr burn times?

 

[tabner]

what flue temperatures do these stoves run at when you get 20+ hr burn times?

i'm between 300 and 400 for most of the burn cycle.

 

[moresnow]

Fellow 20 box owner here. I easily get 12 hours between reloads. Sometimes actually have an issue with too long of a burn. yesterday I loaded the stove at 8:30am, and last night around 8:30pm i had the thermostat on high with the blower going trying to burn through the coaling phase quicker in order to load up before bed. What are most peoples' views on a hot reload in a BK? Like a full bed of hot coals? I think on some of the Hybrid/Non-Cat stoves that can be a little risky due to a big off-gassing happening quickly? Are the BK's mostly able to control it? I was a little scared to do a full reload of Oak last night with a big hot coal bed.

View attachment 318348

Load her up. If it starts to burn to intensely, turn it down. Excessive off gassing is a mute topic unless you have a failed seal somewhere. My experience.

Gotta laugh at trying to burn down your load after 12hrs in a 1.8cu/ft stove. Hell of a problem to have. Enjoy.

You may know this but. A single small split tossed on the coal bed will help reduce the pile when run wide open. Food for thought.

 

[tabner]

Load her up. If it starts to burn to intensely, turn it down. Excessive off gassing is a mute topic unless you have a failed seal somewhere. My experience.

Gotta laugh at trying to burn down your load after 12hrs in a 1.8cu/ft stove. Hell of a problem to have. Enjoy.

You may know this but. A single small split tossed on the coal bed will help reduce the pile when run wide open. Food for thought.

Thank you! That is reassuring. And yes, this thing impresses me every day.
I had read that about the single small split before, but I'd forgotten all about it. I'll give it a try!

 

[neverstop]

i'm between 300 and 400 for most of the burn cycle.

View attachment 318362

that's internal temp right? seems on the low side. how's the build up in the chimney running like this?

 

[tabner]

that's internal temp right? seems on the low side. how's the build up in the chimney running like this?

Yes, that's internal on a flue probe. Not sure about buildup, this will be my first full season with this stove. I'll let ya know in a few months.
My fuel is very dry, my chimney is lined and internal to the house, and I get very little visible smoke, I'm optimistic/expecting it to be pretty good.

 

[Tron]

that's internal temp right? seems on the low side. how's the build up in the chimney running like this?

Mine's the same, internal temperature on a double-walled pipe, not even into the orange zone.
Down here we don't need much heat, so my stove usually runs about as low as it'll do.
I clean the flue once a year, but usually only get a handful of creosote out of it, if that. So really nothing to worry about.

 

[Highbeam]

that's internal temp right? seems on the low side. how's the build up in the chimney running like this?

Mine's the same. Eerily almost exactly the same when running on low which of course the huge majority of burners do the huge majority of the time. 400 internal, same as 200 surface temperature if you're using single wall.

You can run them even lower with an active cat but I find that lower than 400 is risky. Risk of stalling the cat, black glass, creosote in the stack, but magical long burn times.

It's not just the low flue temperatures but the very low flow of flue gasses that means 400 at the stove will be pretty cold by the time those fumes make it to the chimney cap. A noncat pukes tons of very hot smoke up the stack, much lower efficiency but cleaner stack.

 

[Ashful]

I'm cautious about burning for more than a half hour, or so, with the thermostat wide open. Can't that run the risk of warping some of the steel plate in the stove?....

Only if your chimney is severely over-drafted. I burn mine totally wide open at least one load per week for most of the year, with no ill-effects, and BK promotes this ability as one of the big advantages of their thermostatic stove. But, if you are severely over-drafted, then it's a little harder on things, overall.

What is your total chimney height and configuration?

I don't have a flue thermometer. Are those a good idea to have, or necessary?

Yes, especially for cold starts. I usually close my bypass damper as soon as the flue probe hits 500F, which is waaaayyy before the cat needle ever hits active on an open chimney of any height. If you wait for your cat to reach active before closing the bypass, and your heated pipe draft is anywhere over .05"WC, you're wasting wood. Consistent and reliable light-offs can usually be achieved way before cat reaches active in bypass, but you need to know your flue temp to know when to close the bypass, if playing that game.

Yes, I make sure to burn hot for 25 min's before I turn down the thermostat setting (the manual says to do so, for 20 to 30 min's). The fellow who installed the stove told me to burn hot a few hours per/week to avoid creosote buildup. I also like how it burns off much of the glass stains so I can see the fire better.

This is good advice for the manufacturer to give, because they know many don't have properly dry wood, and this initial bake-out time helps to ensure that. But for several years and several dozens of cords now, I've shortened the time before turn down to about 10 minutes. In fact, as soon as cat needle reaches 12 o'clock, I start turning down. I'm burning hardwoods seasoned at least 3 years (usually 4 summers) under a roof, and put more wood thru just one of my BK30's than maybe anyone you'll meet here, and have observed no ill-effects yet. If you're not convinced your wood is dry, then staying with the longer time is probably best, but if your wood is well-dried then I'd experiment with less time to maximize your burn time and minimize cat temp spiking.

BK recommends raking hot coals towards the front of the box (I think they just mean to make a flat bed of coals), then putting more wood on it to relight the stove, then shutting the door just to the latch, so there is a crack open. I don't think it's a problem at all, as long as you remember to turn off the bypass if it's already in the active zone. These stoves are built to reload hot.

My reload procedure:

1. Open thermostat, open bypass damper, grab wood satchels, and head outside to fetch wood. This will give cat time to cool in bypass, while you're gettin your wood.
2. After fetching wood, open front door, grab your ash rake, plow the ash from front to back, then gingerly drag coals that come to the surface from back to front. Level the whole bed, with dead ash in back and live coals in front.
3. If coals are lively, just load wood and close the door. If coals are waning, make a trough or divot front and center in coal bed, and toss a lit quarter SuperCedar in before loading. Either way, close the door right after loading, no need to ever leave it open on a warm stove.
4. Run 5 minutes in bypass, or until cat reaches active or flue probe reaches 500F, then close bypass.
5, Run 10 minutes on high, or until cat probe needle reaches 12 o'clock.
6. Turn down thermostat to desired run point.

 

[BC_Josh]

My reload procedure:

1. Open thermostat, open bypass damper, grab wood satchels, and head outside to fetch wood. This will give cat time to cool in bypass, while you're gettin your wood.
2. After fetching wood, open front door, grab your ash rake, plow the ash from front to back, then gingerly drag coals that come to the surface from back to front. Level the whole bed, with dead ash in back and live coals in front.
3. If coals are lively, just load wood and close the door. If coals are waning, make a trough or divot front and center in coal bed, and toss a lit quarter SuperCedar in before loading. Either way, close the door right after loading, no need to ever leave it open on a warm stove.
4. Run 5 minutes in bypass, or until cat reaches active or flue probe reaches 500F, then close bypass.
5, Run 10 minutes on high, or until cat probe needle reaches 12 o'clock.
6. Turn down thermostat to desired run point.

Thanks for all the info. Lots to remember. I do like, however, how a hot burn daily cleans some of the grime off the door glass...

 

[BC_Josh]

What is your total chimney height and configuration?

Hi Ashful, I currently have a bit of a cold, so I'll give an estimate. My chimney is about twenty feet high, goes straight up except for a bit of a jog (a couple of 30 degree elbows, I think) and out a metal roof a few feet (or so), with a cap on top. That's not tall enough for negative pressure buildup, right?

 

[Ashful]

You likely have a bit more than the maximum specified 0.06"WC draft, when that pipe warms up. My 30 footer was pulling 0.21"WC, roughly 3.5x the specified maximum allowable draft, and I have two 45 degree offsets in that setup.

My manometer and key damper rig has been photo'd and featured many times on this forum, including just recently. If you use the search function, I am sure you will find it. Might be worth considering for your setup, as well. Getting that draft dialed down is key to being able to run at wide-open throttle (WOT) without concerns of overfiring, overheating your chimney during bypass, or plugging the cat on long hot burns.

 

[tabner]

You likely have a bit more than the maximum specified 0.06"WC draft, when that pipe warms up. My 30 footer was pulling 0.21"WC, roughly 3.5x the specified maximum allowable draft, and I have two 45 degree offsets in that setup.

My manometer and key damper rig has been photo'd and featured many times on this forum, including just recently. If you use the search function, I am sure you will find it. Might be worth considering for your setup, as well. Getting that draft dialed down is key to being able to run at wide-open throttle (WOT) without concerns of overfiring, overheating your chimney during bypass, or plugging the cat on long hot burns.

When you run your stoves at WOT or close to it, what flue temps do you usually see? Or do you not monitor them?
As the weather gets colder here, i'm starting to run my stove at more of a medium/high range on the thermostat, and my flue temps are much higher. On low they hover in that 250 to 450 range. Running 4:00 or 5:00 range on my dial gives me flue temps approaching 600. I'm not worried from a safety perspective, but it just feels like any heat above 400 up the flue i'm wasting BTUs. Or is that just the side effect of running a hotter stove?
i have a Magnehelic and a damper (chimney is 26 feet, plus 2 feet off top of the stove), but it doesn't seem to effect the flue temps, still around 600 degrees. just wondering if that's standard for a hotter running stove, or if something is a little off.

 

[Ashful]

Good question. Let me get some numbers, rather than trusting my (admittedly untrustworthy) memory, and get back to you. Flue temps definitely run way hotter without the pipe damper, but as to exact numbers, let me get some fresh data when I have a chance to run wide open again.

I can say I have run over 100 but less than 1000 loads at WOT, with never any issue. The stove stabilizes at a reasonable burn rate, that probably gives me about 4-5 hours of active cat time at nearly constant temperature, not that I'm sitting there and watching it with a thermometer and stopwatch.

 

[Highbeam]

When you run your stoves at WOT or close to it, what flue temps do you usually see? Or do you not monitor them?
As the weather gets colder here, i'm starting to run my stove at more of a medium/high range on the thermostat, and my flue temps are much higher. On low they hover in that 250 to 450 range. Running 4:00 or 5:00 range on my dial gives me flue temps approaching 600. I'm not worried from a safety perspective, but it just feels like any heat above 400 up the flue i'm wasting BTUs. Or is that just the side effect of running a hotter stove?
i have a Magnehelic and a damper (chimney is 26 feet, plus 2 feet off top of the stove), but it doesn't seem to effect the flue temps, still around 600 degrees. just wondering if that's standard for a hotter running stove, or if something is a little off.

I'm on a princess, but at higher burn rates the flue temps go way up. I agree that efficiency goes down as burn rate goes up. Still though, is the efficiency at those high burn rates still as good as a noncat? Pretty close and most of the time we're down on low output.