Catalytic stove - does it have to damped down?

[kallanreed]

I just got a new Blaze King Boxer 24 and I'm not quite sure how to use it. Specifically I'm trying to understand the primary job of the catalyst.
I follow the instructions and get a good fire going, wait until temps are in active range before closing bypass, let it burn with the air control fully opened. That's all great, but unfortunately, that's where the instructions stop and where the 95% of the operation time begins,

I have a few questions that hours of perusing this forum haven't entirely cleared up.
1) Do I _have_ to damp down the fire once the cat engages? How far?

Everything I've been reading/watching seems to show people damping down to almost nothing once the stove is hot. That's great, but when I try that in my big, drafty house, it doesn't seem to keep the place warm. Should I stop caring about how damping down and just set the air control to "it's nice in the house?"

2) What's the main purpose of the catalyst? Should I be thinking of it as a heat source, or is it mainly to allow the fire to be damped down without loading the chimney up with gunk?

Initially, I thought the point was it basically was the heat source that a smoldering fire fed. In practice, that doesn't seem to be the case. Sure, it gets crazy hot, but there's just not a lot of mass there so it's not particularly good at actually heating a large room. I'm thinking how a small space heater would get hot, but not have enough power to heat a large room.

In that case, it seems like the burning/smoldering wood is the main source of heat, in which case, the primary job of the cat is to keep the exhaust scrubbed and the flue clean. Does that sound right?

3) Flames or no? Or does it not matter and what I should focus on is "room is the temperature I want"?

Intuitively, damping down the fire make it release less energy so it can't heat as well. So there has to be a contention between effeciency and warmth. It sounds like I don't want a roaring fire for a few reasons. A roaring fire may be hot, but it also inefficient and may be dirty. Hot temps, make for more draft and more gets past the cat without reacting. Hot flames are just bad for the cat generally.

Am I overthinking this? Do I just put wood it in, follow the startup directions and turn the air control to "I'm comfy"?

 

[mellow]

This old video from BK is still relevant for your questions:

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[kborndale]

The big advantage of a cat stove is the ability to burn low and slow. It can give off a little bit of heat for a long time. In a large, drafty house burning low and slow may not produce enough heat so you need to keep it turned up to keep the house warm which unfortunately takes away the advantage of a cat stove.

 

[kallanreed]

This old video from BK is still relevant for your questions:

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Good ol' John and Vanessa! I have watched that one, and it is really great for understanding the basics. The part where my questions start is when she "lowers it to about half" for a "steady burn". What's the goal there? Just to lower the burn rate, I'm assuming. But why half and not 3/4 or 1/4? What should I be aiming for?

Re: large and drafty == keep it turned up. It's normally pretty mild where I live, so low and slow will probably be fine for most of the time, but when it gets down into the 20s (F), this house just wasn't insulated for that cold. It's not my primary heat source, either, although the electric heats gets $$$$ really fast when it's that cold.

 

[stoveliker]

I just got a new Blaze King Boxer 24 and I'm not quite sure how to use it. Specifically I'm trying to understand the primary job of the catalyst.
I follow the instructions and get a good fire going, wait until temps are in active range before closing bypass, let it burn with the air control fully opened. That's all great, but unfortunately, that's where the instructions stop and where the 95% of the operation time begins,

I have a few questions that hours of perusing this forum haven't entirely cleared up.
1) Do I _have_ to damp down the fire once the cat engages? How far?

No, you don't have to. Folks on here in Fairbanks run mostly wide open certain times of the year.

Everything I've been reading/watching seems to show people damping down to almost nothing once the stove is hot. That's great, but when I try that in my big, drafty house, it doesn't seem to keep the place warm. Should I stop caring about how damping down and just set the air control to "it's nice in the house?"

Yes, set it to what heat output you want.

2) What's the main purpose of the catalyst? Should I be thinking of it as a heat source, or is it mainly to allow the fire to be damped down without loading the chimney up with gunk?

Both: keep the chimney clean *at settings* (of low heat output) where other stoves would gunk up the chimney.
At such settings there is not a lot of heat from the firebox (running in "black box mode"), but the main (but not only) heat source when running lowest is the cat. Running at its lowest it can run really low: the same heat output as three and a half 1.5 kW plug in electric heaters (for a 30 firebox, so yours likely even a bit less). (This only works as low as that if your chimney provides draft to spec.)

Initially, I thought the point was it basically was the heat source that a smoldering fire fed. In practice, that doesn't seem to be the case. Sure, it gets crazy hot, but there's just not a lot of mass there so it's not particularly good at actually heating a large room. I'm thinking how a small space heater would get hot, but not have enough power to heat a large room.

You are thinking correctly here.

In that case, it seems like the burning/smoldering wood is the main source of heat, in which case, the primary job of the cat is to keep the exhaust scrubbed and the flue clean. Does that sound right?

Both: low heat from the wood, more from the cat. But small surface area from which it radiates, so a low output. And it keeps the chimney clean when smoldering at low output, which non-cat stoves can't at such burning mode.

3) Flames or no? Or does it not matter and what I should focus on is "room is the temperature I want"?

Set the thermostat to the heat output that you want is all you need to do.

Intuitively, damping down the fire make it release less energy so it can't heat as well. So there has to be a contention between effeciency and warmth. It sounds like I don't want a roaring fire for a few reasons. A roaring fire may be hot, but it also inefficient and may be dirty. Hot temps, make for more draft and more gets past the cat without reacting. Hot flames are just bad for the cat generally.

BKVP (vice pres of BK) has said on here that the efficiency of a BK does not change much going from lowest to highest setting.
The cat will still clean the exhaust of a roaring fire - even if there is less to clean because the fire itself burns more complete at such settings.

Am I overthinking this? Do I just put wood it in, follow the startup directions and turn the air control to "I'm comfy"?

Yes, put wood in, "char" the load until all is nice and black, then dial down (or not) to the heat output setting you want. If you dial down more than 20% or so on the dial range, do so in steps with 10 minute or so pauses in between.

 

[kallanreed]

No, you don't have to. Folks on here in Fairbanks run mostly wide open certain times of the year.

Yes, set it to what heat output you want.

Both: keep the chimney clean *at settings* (of low heat output) where other stoves would gunk up the chimney.
At such settings there is not a lot of heat from the firebox (running in "black box mode"), but the main (but not only) heat source when running lowest is the cat. Running at its lowest it can run really low: the same heat output as three and a half 1.5 kW plug in electric heaters (for a 30 firebox, so yours likely even a bit less). (This only works as low as that if your chimney provides draft to spec.)

You are thinking correctly here.

Both: low heat from the wood, more from the cat. But small surface area from which it radiates, so a low output. And it keeps the chimney clean when smoldering at low output, which non-cat stoves can't at such burning mode.

Set the thermostat to the heat output that you want is all you need to do.

BKVP (vice pres of BK) has said on here that the efficiency of a BK does not change much going from lowest to highest setting.
The cat will still clean the exhaust of a roaring fire - even if there is less to clean because the fire itself burns more complete at such settings.

Yes, put wood in, "char" the load until all is nice and black, then dial down (or not) to the heat output setting you want. If you dial down more than 20% or so on the dial range, do so in steps with 10 minute or so pauses in between.

Thank you for the detailed reply! That really helps reduce some of my "I'm going to break it" anxiety.

 

[begreen]

Everything I've been reading/watching seems to show people damping down to almost nothing once the stove is hot.

That is for a secondary tube stove running a large load. It doesn't apply to the Boxer which is thermostatically regulated. Set the thermostat to a comfortable operating temp and leave it.

 

[reaperman1]

I also have a Boxer and found out very quickly that this stove doesnt put out much radiant heat. The way it was designed, it traps most of the heat between the stove and the stoves outer casing. When I have a good fire going I can actually place my bare hand on the sides and even the top of the stove, except in the very top center over the catalyst. Try that on any other wood stove and your skin would be gone! IMO, BK should have cut some holes in the outer casing to let the heat escape rather than trapping it inside. The only radiant heat comes from the front door and glass. Which is only 1/6th of the firebox. With all of this said, you need to run the blower if equipped. Without the blower, the stove is just another fireplace.

 

[stoveliker]

I think those remarks are exactly right: as far as I know, the Boxer is a BK insert that was put into a freestanding frame. A blower is then quite needed to get the heat out.

(I note that my Chinook does have a convection deck that convects out quite a lot of air, as well as holes in the side panels.)

 

[BKVP]

A couple of points of clarification.

Yes, the BX24 uses the same firebox as the SC/AF 25 series.
It is not mobile home approved because it cannot connect directly to fresh air
It is a great convective heater and great for shoulder seasons.
During colder weather, use the blowers and move a lot more heat into the room.
Regardless of whether you have low and slow or hot and fast, the thermostat still provides the advantage of even heat output.
Adding methods to release more heat can be considered but it will change clearances.

BKVP

 

[Ashful]

The big advantage of a cat stove is the ability to burn low and slow. It can give off a little bit of heat for a long time. In a large, drafty house burning low and slow may not produce enough heat so you need to keep it turned up to keep the house warm which unfortunately takes away the advantage of a cat stove.

As one who might own the oldest "large drafty house" on this forum, I'll have to disagree with this. You are right that while burning low and slow, you are not taking advantage of one of the primary advantages of cat stoves. But, no matter how big and how drafty the house, there will always be countless hundreds of hours per year of low and slow burning, which we call "shoulder season".

Yes, I run at least one of my two cat stoves full-bore at least one load per day, in our coldest weather, but I also still take advantage of its low burn capability when it's not so blistering cold out. Comparatively, the hours of cool weather when I'm taking advantage of "low and slow" are much greater than the hours of very cold weather when I'm running it like a non-cat.