Still confused!

After reading an article about cat stoves I'm a little perplexed about flue temps and cat light off. So if running the IS with flames what's the cat doing at that time, cleaning up what the secondarys are missing?
The articled stated your flue temp should go up when cat is engaged, (strickly a cat stove i believe), the only time I've seen that with the IS was when the flames went out otherwise the flue temp acts like a regular stove.
Dont fully understand the correlation between the two functions.

 

My flue temps go down when I engage the cat.

I engage the cat at ~400⁰ on the cat thermometer, at the top of the stove.

Flue temps go down, due to gasses being burned by the cat, heating the stove higher, less heat going up the flu.

That's my understanding, FWIW

 

Yes the cat will clean up the remaining fuel.
I've had the IS for 8 winters and the flue temps decreased every time I enaged the catalytic converter.

 

The time or 2 that the flue temp went up was when i reduced the air too quick and flames went out, i must of gave the cat a boatload of smoke to burn, IDK for sure.
Otherwise my flue temps go down when cat is first engaged and slowy creep up while reducing the air.
Maybe i read the article wrong.

 

Yes, when there are flames in the firebox and the bypass is closed, the cat. will burn up any particulates that made it past the firebox. Perhaps think of it as a ratio: if the firebox has no flames, the cat. is burning 100% of the particulates. If there is some flame, the firebox may be burning something like 50% of the particulates and the cat. the other 50%. If the firebox is very active with flame, especially those violet / blue gas flames up high in the firebox then the firebox is burning perhaps 90% of the particulates and the cat. the last 10%.

As to the flue temps. changing when the cat. is engaged and has 'lit off', it is not as simple what the flue temps. might do. It depends on how hot the cat. is but also how much air is passing through the firebox and cat. on the way to the flue. If the draft is damped way down, say to 2 notches or so, and the cat. is very hot, the flue temps. will probably go down because there is so little air carrying the heat from the cat. to the flue. If you open the draft somewhat and the cat. temps. go down, it <may> cause the flue temps. to actually go up because while the gasses passing through the cat. are somewhat cooler, there is a lot more of this gas getting all the way out to the flue. It also depends on where you measure the temp. in the flue because the temp. of the flue goes down dramatically all the way from the stove top to the flue entrance. On my own stove, it is several hundred degrees and my temp. probe is located just before the flue itself so I am measuring it as the last point in the house.

I would suggest not taking cat. temps vs. flue temps. as any kind of a rule and certainly not to focus on the flue temps. Just open the bypass, open the draft, load and light the stove and wait until the entire firebox is well engaged in the fire, with plenty of active flame and begin the cat. cycle. Do that by closing the draft to around 1/4 open and closing the bypass. Wait to see that the cat. 'lit off' by watching the cat. temp. to see it rise significantly, something like several hundred degrees or more and after something like 20- 30 minutes, adjust the stove to produce the heat you need for your house. I believe you have something other than an Ideal Steel so I cannot help you with specific draft recommendations but the basic flavor is what I am trying to describe. It sounds like you read the article fine but I do not think that what the article states is any kind of hard and fast rule and actually only one way a burn may go and it depends on the inside and especially outside temps. (a very cold outside temp. will cause all chimneys to draft quite a bit more than when it is only chilly outside), the wood you are burning and several other variables. It is tough to describe the interaction of the firebox, catalytic combustor and final flue temps. with one hard, written- down rule IME.

I can make a graph of my stove through loading and starting, then the entire cat. burn and then the solid fuel burn to the end of the fire if it might help you. I believe it is easier to see on a graph especially with a little explanation to go along with it.

 

BDF, thanks for the detailed explanation and the offer of a graph but i think i got it for the most part, little bit of anal analyzing on my part.
My stove is an ideal steel, only had it for 4 weeks or so i am a neophyte.

 

So, I think I know what you mean by this, but can you elaborate and spell it out so I can fact check my guesstimate please?

 

OK but the offer is open if and when you might want it.

The level 'anal' is in the eyes of the beholder (Easy Boys!). I have been studying the.... I guess I would call it science of burning wood for upwards of 30 years, continue to do so and am still learning about it. A lot of things only work because of what some might call minutiae. I guess it depends on what level an idividual decides to view something from- on the one hand, it is a metal box full of wood and fire. On the other hand, it is a finely tuned device to fully reduce a carbon fuel to another state in the most efficient and least polluting way possible. Both are correct so in the end, it is the observer's point of view that makes the difference. Similar to the way any car engine can be viewed: spark, fuel and off it goes. Or suck, squeeze, bang, blow is also correct. But to some, it is the science of chemistry and mechanical conversion with endless details that all require careful study, tweaking and interleaving to behave properly. Today's automotive engines are far more efficient than the engines of even 20 years ago, never mind 50 years ago which some view as the golden age of autos. On some level, it is rubbing steel on rocks, on some other level, it is honing a razor to an amazing edge using both technology, knowledge and skill..... and the observer gets to pick which applies in any conversation. The really amazing part is that people can use the same device / technology / science on so many different levels at any time, it depends on how deep you look into a subject. My goal has always been to understand the journey and possibly improve on it as an end user- my fires are cleaner and more efficient than they were 30 years ago and that is what works for me.

 

Well sure but I am not quite following what you want me to expand on. ??? Put simply, what is 'this' from the last few posts? Happy to elaborate but not quite sure what you would like me to elaborate on?

 

I was referring to the below quote:

Specifically the "entire cat. burn and then the solid fuel burn" part. The separation into two "burns" is what I would like information/clarification on.

 

With many people not having cat probes i wonder if there is any good reason to have one.
I received my new condar probe and it seems to be a better gauge as the temps are more realistic but the cat is still pretty hot (close to 1600) with a STT of only 480.
What do other people see for cat temps at 500 degrees STT?
Maybe i do need a graph.

 

OK, I can expand on that.

I think of a wood fire, at least one in a cat. stove, as a three- part burn. The first part is starting the fire all the way to when the entire fuel load comes up to a pretty high temp.. This is the part where there are a lot of flames, all yellow, and it is pretty inefficient and there is no secondary burn because the firebox / cat. are not yet hot enough. The second stage is when the fuel is involved and the firebox is either black and without any visible flames, or if pushed harder the firebox has though purple / blue / violet 'waffling' flames which are the combustible gasses burning. If the firebox is black, then the cat. is burning those gasses and will be at the highest temp. of the entire burn cycle. Finally, after all the moisture and almost all gasses and particulate matter has been consumed, the solid part of the wood burns. This is the coaling part of the burn cycle and typically puts out a lot less heat and requires at least some air to come from under the coals or they will actually 'go out' which is why there is charcoal left after a fire.

These phases are pretty fixed, especially the first part. The second and third phases can be combined in something such as a pot bellied stove but in an airtight cat. stove they are very distinct. By the way, this is something that really mangles the concept of burn time because it results in very different heat outputs for each phase given a fixed draft setting. Which leads to the real question of burn time- the coals are still burning albeit with very little heat output but can last for literally days. So is the burn time of the stove days? Not as I regard burn time because the stove is no longer putting out sufficient heat to actually carry the building it is in but in a technical sense, absolutely.

Burning wood can be as complex or as simple as you want to perceive it to be. On one hand, it is a 'box of burning wood' and nothing more. Certainly just filling the firebox with splits and setting them on fire works. Or one can view it more closely and see the phases and changes in how the wood actually burns, as well viewing efficiency and stove emissions. Finally, there is some chemistry and a bit of physics happening and all of that can be tweaked and improved to increase the stove's output, the stove's efficiency and the cleanliness of the actual burn. Different people see different things in the same stove (or car, or hydroelectric dam, etc., etc.) and really everyone is basically correct. Depends on how anyone chooses to look at that 'box of fire'. And nothing beyond basically burning wood in a box is required, those of us who chase efficiency, observe the nuances of a stove are doing so just because we are interested and like to do so. None of the extra effort is ever required and I believe the great majority of wood burners are just not interested in the minutia, and that is perfectly fine IMO. Just as it is with, say, autos- most people just use a car with little to no interest in how it works and again, that is absolutely fine and sufficient. Others look at the same auto and combustion phases, intricate timing of different events, the complexity of chassis geometry and so forth. ???

 

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Maybe it would help to draw a picture of the stove parts that generate heat (firebox, 2ndary air, cat) and where that heat goes (stove body, flue).

 

Woodstock has nice drawings of there stoves on their site and manual, i been reading all sorts of different ways people are running their cat stoves, it can get confusing at times.

 

you are not kidding…. I think you sent the back puffing saga out to my stove…. I’m pulling my hair out
Now.

 

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Conceptual pictures. Not necessarily the way a stove is made.

 

Burn it how you need to heat your space. I haven’t looked at temps on my BK in years. I set it where I need it to be for the heat I need/want.

Cat will last 3 years-ish no matter what so burn it how you need.

 

Was it raining there. Really humid/warm?
Turn the air up

 

Might have that screen name for more than one reason, eh?!

 

No… it’s been about 0* and dry. I have to keep some flame in the stove… otherwise it will backdraft… the other night it even shot sparks out of the lid…. The dogs were less than impressed.