cat stoves and burn times at high temps (500+ degrees)

[rmcfall]

I've been burning my new Keystone for about 2 1/2 months and have enjoyed the benefits of both the soapstone and the catalytic combuster (i.e., sustained burns at higher temps). I seem to recall a prior post about catalytic stove users getting all day burns at 600 degree temps. While I have managed to get burns at 500+ degrees for 4 or 5 hours, the stove top temperature drops (although slowly) down to 250 or so after that. I am just wondering how some managed to get 600 degree temps for an extended burn? At 600 I eat through the wood pretty fast.

 

[ozarkjeep]

I wonder too.

observations from mine.

I think I normally wait too long to engage the combustor ( it will light earlier than I anticipate)

also, the temp climbs after its engaged and the air intake is reduced...

I have the same questions and thoughts as you here

I cant get a sustained 6+ hour burn from mine with surface temps over 500

they might peak at 900+ but will go below 300 too in that time frame.

 

[elkimmeg]

I's not just the cat combustors Its the thermatically controled secondary air that self adjust to control the burn time. When I engage my cat combustir there
is little rise in temps What it does is to try to hold the setting at the time of engaging the cat. After the initial engagement if the temp is tool low 500 and I want more heat I can crack open the primary air and get it to hols 600 /650 for about 6 hours fully loaded. I loose an hour or so length doing this but I want heat its freaking cold and been real windy

Last night for instance 71 in downstairs zone loaded the stove up about 1030 Engaged the Cat at 11 and went to bed stove top tem at the time was 600.
Woke up at 700 stove temp 500 zone temp at 69 Just loaded it up again This is the first time I have really filled it up all other times loose l splits just dropped in

Temp at bed time 12 degrees temp at 700 8 one of our warner days recently. IT might make it into the 20's today

 

[Mo Heat]

It seems to me like there are too many variables to say much with certainty, but to me, using the stove-top temp to control the stove, especially if it's soapstone that changes temps rather slowly, is like using shadows to tell the time of day. By the time you open the primary air and get things going hotter, a couple splits are burned up and the stove-top temp is maybe just starting to change.

The species of wood, the size of each split, and your loading technique can all play improtant rolls (as I'm sure you know) in extending a burn, but there are only so many BTU's in a load. The better or harder the wood, the more BTU's, of course. What wood are you burning? Can you get higher BTU wood? Is your wood good and dry? Wet wood really sacrifices BTU's in burning.

I like to use my cat probe thermometer to control my stove. It's digital and reports instant temperature changes with the cat. I then just try to keep the cat temp around 1100*F so that any smoke that goes through there experiences both the catalyst and a temperature capable of combusting it.

Since I don't load my stove full, I just put in a few splits at a time, I don't do a lot of extended, one-load, burns. Two or three splits burns about 2 or 3 hours for me. In fact, my rule of thumb is about an hour per (big) split. Most of my stove is either double walled or a remote corner of the firebox, but I'd estimate my temps are only around 400*F, but that's enough to keep a large room warm if the convection blower is on high.

Sorry. I guess this isn't much help. BTW: are you pretty happy with your soapstone stove selection? Any other complaints besides extended burn times? Is the cat function (preheating, reengaging, etc.) more trouble than you expected?

 

[Todd]

I've been burning my new Keystone for about 2 1/2 months and have enjoyed the benefits of both the soapstone and the catalytic combuster (i.e., sustained burns at higher temps). I seem to recall a prior post about catalytic stove users getting all day burns at 600 degree temps. While I have managed to get burns at 500+ degrees for 4 or 5 hours, the stove top temperature drops (although slowly) down to 250 or so after that. I am just wondering how some managed to get 600 degree temps for an extended burn? At 600 I eat through the wood pretty fast.

With a steel or iron stove you will see those 600-700 stove top temps. With soapstone it can be done but like you say, it will eat through some wood. 500 for 4-5 hours sounds about right. Then it will drop from there. You will get a good 8 hours of usable heat from that stove.

For max BTU's try reloading when you have about a 2" coal bed and rake the coals in halves toward each side. This will leave a small valley or dip in the middle, so when you reload it gives more air circulation to the splits in the back. This technique works well in my Fireview and after engaging the cat my stove top climbs to 600, then settles back to 550 or so, then slowly drops over a 8 hr burn down to 250-300. A few times she went up to 700, so I shut down the air til she droped.

For a longer burn try raking all the coals forward towards the glass and the fire will burn from front to back. It will take longer for the rear splits to take off and your stove top temps will be cooler but more even over a longer time.

 

[rmcfall]

It seems to me like there are too many variables to say much with certainty, but to me, using the stove-top temp to control the stove, especially if it's soapstone that changes temps rather slowly, is like using shadows to tell the time of day. By the time you open the primary air and get things going hotter, a couple splits are burned up and the stove-top temp is maybe just starting to change.

The species of wood, the size of each split, and your loading technique can all play improtant rolls (as I'm sure you know) in extending a burn, but there are only so many BTU's in a load. The better or harder the wood, the more BTU's, of course. What wood are you burning? Can you get higher BTU wood? Is your wood good and dry? Wet wood really sacrifices BTU's in burning.

I like to use my cat probe thermometer to control my stove. It's digital and reports instant temperature changes with the cat. I then just try to keep the cat temp around 1100*F so that any smoke that goes through there experiences both the catalyst and a temperature capable of combusting it.

Since I don't load my stove full, I just put in a few splits at a time, I don't do a lot of extended, one-load, burns. Two or three splits burns about 2 or 3 hours for me. In fact, my rule of thumb is about an hour per (big) split. Most of my stove is either double walled or a remote corner of the firebox, but I'd estimate my temps are only around 400*F, but that's enough to keep a large room warm if the convection blower is on high.

Sorry. I guess this isn't much help. BTW: are you pretty happy with your soapstone stove selection? Any other complaints besides extended burn times? Is the cat function (preheating, reengaging, etc.) more trouble than you expected?

Where did you find your digital cat probe thermometer? I may have to get one of these to play around with, although I don't find it difficult to know when to engage the cat with this stove. Having not used a cat stove before, I wasn't sure what to expect. However, there really isn't much to it. I also find that I don't have to wait near as long as I thought I would to engage the cat. I can usually engage the cat pretty quickly and it will glow red hot. Usually I wait about 15 minutes or so, but if the stove is good and hot I don't have to wait at all and the cat will glow red hot right away. I took the cat out a week ago to clean it off and it looked good as new. So far I've been burning mostly oak that is good and dry.

I really have no complaints about this stove, except for I wish it was larger. The Fireview is a little bigger than the Keystone, but I wish Woodstock made a LARGE stove. I've got cathedral ceilings in the area with the stove and a lot of area overall that I am trying to heat, so I suppose I may need a second stove at some point in the future. That said, the Keystone keeps my open living/dining/family room heated, which is about 1500 square feet and the family room is very large with cathedral ceilings. I wish more heat made its way into the bedrooms down the hall off the open area, but that would be asking a lot of a stove this size, or probably any stove at all. I've got my house set up with different zones, so the heat never kicks on in the 1500 sq. foot area where the stove is. The stove keeps this area in the 68-74 degree range, depending on the stage of the burn cycle and where the temp is being taken. I wish the heat never kicked on in the bedrooms, but the stove can't be blamed for that since it isn't sized to heat that much area. I do wonder if a second stove at the other end of my open kitchen/dining/living area would generate enough extra heat to reach the bedrooms without overheating the main living space.

As far as the extended burn times, I am learning that I can damp the air down much more than I have been. Today I loaded the stove up at 10:30AM and turned the air down halfway between 0 and 1. The cat glowed red hot and the temp reached just over 500. When I got home at around 8:30 the stove top temp read 300 degrees and I had LARGE coals that turned red hot when I reloaded. Now I don't know how long the stove stayed at 400-500 degree temps, but this weekend when I am around I will find out. Nonetheless, I thought coming home to a 300 degree stove after 10 hours was pretty good, especially considering this thing has such a small firebox. Oh yeah, and the glass didn't get dirty, except for a little fly ash. One thing about this stove that is much different from my previous stove is that the stove can really be damped down. Zero on the air control actually seems like 0.

This Keystone is also built solid. It is small in size, but I believe it weighs 430 lbs. The stove is tight and seems like a well crafted piece of the furniture. The air control lever itself is impressive, being a solid piece of cast-iron. Again, I don't have any real complaints about this stove. I was just surprised to hear about Elk's stove getting such hot temps for an extended time. I believe his stove has a much larger firebox than the Keystone though... Given the small firebox of the Keystone and the burn times I am getting with the stove damped down more, I imagine the soapstone helps to accomplish a similar effect (i.e., relatively constant temp over extended period of time) as his stove's thermostat controlled air intake.

 

[rmcfall]

I've been burning my new Keystone for about 2 1/2 months and have enjoyed the benefits of both the soapstone and the catalytic combuster (i.e., sustained burns at higher temps). I seem to recall a prior post about catalytic stove users getting all day burns at 600 degree temps. While I have managed to get burns at 500+ degrees for 4 or 5 hours, the stove top temperature drops (although slowly) down to 250 or so after that. I am just wondering how some managed to get 600 degree temps for an extended burn? At 600 I eat through the wood pretty fast.

With a steel or iron stove you will see those 600-700 stove top temps. With soapstone it can be done but like you say, it will eat through some wood. 500 for 4-5 hours sounds about right. Then it will drop from there. You will get a good 8 hours of usable heat from that stove.

For max BTU's try reloading when you have about a 2" coal bed and rake the coals in halves toward each side. This will leave a small valley or dip in the middle, so when you reload it gives more air circulation to the splits in the back. This technique works well in my Fireview and after engaging the cat my stove top climbs to 600, then settles back to 550 or so, then slowly drops over a 8 hr burn down to 250-300. A few times she went up to 700, so I shut down the air til she droped.

For a longer burn try raking all the coals forward towards the glass and the fire will burn from front to back. It will take longer for the rear splits to take off and your stove top temps will be cooler but more even over a longer time.

Good tips about raking the coal bed. How about that sale Woodstock is having right now? Almost makes me want to get another one!

 

[Todd]

You can get a probe thermometer from Woodstock. But I don't think you really need one. I have one, and made the mistake of engaging too soon because I was going off the probe temp which was only taking about 5 minutes. I was trying to squeak out every bit of efficiency I could and thought the probe would help. I ended up with cracks in my combustor, probably from thermo shock. Sure the temp was there, but you still need to wait 10-20 minutes to drive out moisture and get the wood good and chared. Good thing Woodstock has a 2 year replacement warranty on cats. They sent me a free one, even paid shipping.

I know what you mean about the air setting. I put 3 pencile marks between 0 and 1 and I usually run mine around 1/4. Sometimes I have to put it at 0 for really cold nights. Heck, I might even need a pipe damper because the draft is so good.

That is a great sale they are having! $600 off! I paid $2449 including shipping last year for my Fireview. Now they are only $2000.

 

[Mo Heat]

They sent me a free one, even paid shipping.

Wow. That's impressive... and convenient.

I know what you mean about preheating each and every new load. It's important, and I do it religiously, even though the cat is up to temp on the probe read-out, you've got to make sure the new load isn't going to shock your cat. If I've got a good bed of coals, this is only about 5 minutes, by then, the splits are usually charred and flaming, giving off heat instead of consuming it.

I like knowing the cat temp at reload time. I figure it helps minimized the chance of thermal shock to the cat compared to say if my cat was still over 1000*F (or higher). It's an easy way to create a margin of safety.

After a load has been burning a while, I allow the cat temp to drop to about 800*F, I disengage, open the door, and throw in two or three splits. I let them get rolling and reengaging the cat. By then, the cat temp is around 700 - 750*F and quickly climbs back over 1000*F. I feel like this keeps the entire stove cycling within a minimum thermal range and puts out enough heat to warm the 900 sq ft room it's in to aroung 70*F, which is right where I like it.

I'd agree that you may not need a cat probe thermometer, but personally, burning my stove the way I do, namely, by limiting my fuel loads to control heat output instead of filling the firebox and damping the primary air, which I only need do on rare occasion, I wouldn't feel comfortable burning without the cat probe since it allows me to precisely control the secondary burn rate within a narrow and nearly ideal temperature range (typically 1000 - 1400*F), and besides, I'd always be wondering what the temp was in there and it would drive me crazy. Now I just look, and know. To me, it's piece of mind... plus the gadget factor, I guess.

 

[rmcfall]

Hey Mo. You mentioned your cat thermometer is digital. Is the digital readout close to the stove? I am just wondering what keeps the thing from melting?

They sent me a free one, even paid shipping.

Wow. That's impressive... and convenient.

I know what you mean about preheating each and every new load. It's important, and I do it religiously, even though the cat is up to temp on the probe read-out, you've got to make sure the new load isn't going to shock your cat. If I've got a good bed of coals, this is only about 5 minutes, by then, the splits are usually charred and flaming, giving off heat instead of consuming it.

I like knowing the cat temp at reload time. I figure it helps minimized the chance of thermal shock to the cat compared to say if my cat was still over 1000*F (or higher). It's an easy way to create a margin of safety.

After a load has been burning a while, I allow the cat temp to drop to about 800*F, I disengage, open the door, and throw in two or three splits. I let them get rolling and reengaging the cat. By then, the cat temp is around 700 - 750*F and quickly climbs back over 1000*F. I feel like this keeps the entire stove cycling within a minimum thermal range and puts out enough heat to warm the 900 sq ft room it's in to aroung 70*F, which is right where I like it.

I'd agree that you may not need a cat probe thermometer, but personally, burning my stove the way I do, namely, by limiting my fuel loads to control heat output instead of filling the firebox and damping the primary air, which I only need do on rare occasion, I wouldn't feel comfortable burning without the cat probe since it allows me to precisely control the secondary burn rate within a narrow and nearly ideal temperature range (typically 1000 - 1400*F), and besides, I'd always be wondering what the temp was in there and it would drive me crazy. Now I just look, and know. To me, it's piece of mind... plus the gadget factor, I guess.

 

[elkimmeg]

rmcfall my second stove in my faqmilly room is 20 years old using a stove combustor.com combustor small firebox 1.25 cu ft I can get a decen burn time of 6hrs
griddle top temps above 450.
Maybe its also top loading where it is easier to stuff the fire box. Honestly I am not exagerating the burn times this is day after day of constant use

It might also be the extent I care for the stove. I disconnect it and blow it out with 125lbs compressed air before the start of the season the cat is cleanned up to 3 times before
and twice during the seaaon wood seasoned 2 years in advance I guess I'm a bit anal about squeezing every bit of heat out.

For those that have never experienced Cat Combustor preformance, eat my shorts. For those the diss cats take your head out of your a** long enough to take a deep breath
you have no idea from what you speak..

ETb everburn technology works intermittently as the temps rise above 1000 degrees required to burn smoke. I can burn particulates for hours as low as 380.

With wood seasoned stacked split and seasoned 2 years in advance, I can dial down the primary air to its lowest setting with the cat engaged and let thermoatically secondary air control
as long a burn as possible. I talking 500+ degrees for hours and hours

 

[rmcfall]

I hear what you are saying Elk and with some practice I think I will be able to get those burn times and temps as well. These past couple days I have damped the stove down a lot more than usual, and when I get home from work I still have 300 temps. I am realizing that with the cat I can get a strong glow with pretty much no flame at all. I had been giving the stove enough air to have at least a small consisent flame. However, I am learning that I can achieve that strong glow with the air cut back so much that the fire looks like it is just about out. Plus, when I look at the chimney there is hardly anything coming out so the combuster must be doing its thing. Granted, having no flame in the stove isn't that nice to look at, but when I am away at work who really cares...

I wasn't so sure about cat stoves before having this one. I had never used one before and I had read and heard all the negative things about them. I now can only wonder whether these people have ever had any experience with a cat stove before. I don't find operating one to be the least bit complicated or time consuming. And as far as maintenance, there is nothing difficult about taking the combuster out on occasion and vacuuming it off. It's a 10 minute job (if that) that is easy and doesn't take a rocket scientist. Figuring out how to pack different size splits into a stove requires more thought and effort.. That's how easy it is... Oh well...glad I took the leap and got a cat stove for myself.

 

[Roospike]

rmcfall my second stove in my faqmilly room is 20 years old using a stove combustor.com combustor small firebox 1.25 cu ft I can get a decen burn time of 6hrs
griddle top temps above 450.
Maybe its also top loading where it is easier to stuff the fire box. Honestly I am not exagerating the burn times this is day after day of constant use

It might also be the extent I care for the stove. I disconnect it and blow it out with 125lbs compressed air before the start of the season the cat is cleanned up to 3 times before
and twice during the seaaon wood seasoned 2 years in advance I guess I'm a bit anal about squeezing every bit of heat out.

For those that have never experienced Cat Combustor preformance, eat my shorts. For those the diss cats take your head out of your a** long enough to take a deep breath
you have no idea from what you speak..

ETb everburn technology works intermittently as the temps rise above 1000 degrees required to burn smoke. I can burn particulates for hours as low as 380.

With wood seasoned stacked split and seasoned 2 years in advance, I can dial down the primary air to its lowest setting with the cat engaged and let thermoatically secondary air control
as long a burn as possible. I talking 500+ degrees for hours and hours

Question Elk ......... From my understanding an inside fire box temp of 380° would give the stove surface about 180° . As great as 380° light off temp is ... isn't it kinda a moot point to home heating? How long is a wood stove firebox inside temp around 380° ?

I agree its great that emissions are starting to be reduced at that temp but were talking what 2-5 minutes as the temps increase. As the temps decrease the wood is in coal stage and very less likely if at all putting off emissions.

 

[Todd]

It doesn't matter much weather it's 380 or 500 light off. It doesn't take long to reach light off temps and you should wait longer anyway so you don't run the risk of thermo shocking the cat like I did this year. The great thing about a cat stove is that it doesn't need to maintain 1100 degrees for secondary combustion like a non cat, so it can be run with less air like the old smoke dragon air tights, but creates gobs of heat and longer burns with little or no smoke.

Also a non cat will send more heat up the chimney than a cat. I noticed about a 100 degree difference in pipe temps when I switched to my cat stove. Also a significant drop in firewood useage. I've gone through 3/4 of a cord less than this time last year. Me thinks that means higher efficiency.

 

[Mo Heat]

Hey Mo. You mentioned your cat thermometer is digital. Is the digital readout close to the stove? I am just wondering what keeps the thing from melting?

It's next to the stove. The WWL's side pedistals are like heat shields, it doesn't even get warm over there. You may not know that the digital readout box is only one of the two parts of the thermometer. The other is a braided copper conductor with the probe on one end and a terminal that plugs into the readout on the other. It transmits some sort of a signal from the probe, which is inserted into the back of the firebox all the way through the refractory can and into the cat combustion chamber, just downstream of the cat exhaust. I guess the probe is a thermopile, but I'm not really sure.

Here's a link to the Condar site and my thermometer. They've even added a photo of the WWL since I was here last.

(broken link removed to http://www.condar.com/digital.htm)

Here is a photo of my thermometer next to the stove.

 

[Mo Heat]

Here's another a bit closer up.

[edit: If you look closely to the right, you can see the 9-volt pig tail adapter from my 110V AC to 9V DC power converter that saves tons of batteries. A real must-have if you get one of these. I bought it at Radio Shack, but you can get them lots of places.]

 

[rmcfall]

thanks, Mo. I'll have to check those out.

Here's another a bit closer up.

[edit: If you look closely to the right, you can see the 9-volt pig tail adapter from my 110V AC to 9V DC power converter that saves tons of batteries. A real must-have if you get one of these. I bought it at Radio Shack, but you can get them lots of places.]