Is a catalyitic stove really more efficient since a cat looses its efficiency with age

[Fargo]

So as I am constantly thinking about wood stoves since my purchase, I am questioning the efficiency of catalytic stoves. I will preface by saying a lot of my research was done by chatgpt. So it could be completely wrong. But I have found that a cat can loose 10%-15% efficiency per year. I have also found that a stove with no cat or secondary burn may only be around 40%-50% efficient. So a stove like the BK Ashford 30.2 may start off at 83% efficient, but the stove itself might (my assumption) only be 50% efficient and the cat might be doing the other 33% of the work. If that is all true and the cat is loosing 10% efficiency over a 5 year period, a cat stove is only averaging 75.4% efficiency over that 5 year period. Or about the same as a clean non-cat like the Alderlea T6 (74%). (The 2 stoves I was considering). If my data is correct, it would seem to me, a cat should be replaced at a minimum of every 5 years to maintain efficiency.

What am I missing? If a cat looses 10% efficiency per year how is it more efficient than a non-cat, which as I understand does not suffer this type of loss. The break down looks something like this.

Given
Base stove efficiency = 50%
Catalyst adds = 33% when new
Total when new = 83%
Catalyst degrades 10% per year (multiplicative decay)

Summary: Efficiency Over 5 Years
Year Catalytic Efficiency Total Efficiency
0 33% 83%
1 29.7% 79.7%
2 26.73% 76.73%
3 24.06% 74.06%
4 21.65% 71.65%
5 19.49% 69.49%

Final Answers
Efficiency after 5 years: 69.5%
Average efficiency over the 5-year period: ≈75.4%

 

[EbS-P]

So as I am constantly thinking about wood stoves since my purchase, I am questioning the efficiency of catalytic stoves. I will preface by saying a lot of my research was done by chatgpt. So it could be completely wrong. But I have found that a cat can loose 10%-15% efficiency per year. I have also found that a stove with no cat or secondary burn may only be around 40%-50% efficient. So a stove like the BK Ashford 30.2 may start off at 83% efficient, but the stove itself might (my assumption) only be 50% efficient and the cat might be doing the other 33% of the work. If that is all true and the cat is loosing 10% efficiency over a 5 year period, a cat stove is only averaging 75.4% efficiency over that 5 year period. Or about the same as a clean non-cat like the Alderlea T6 (74%). (The 2 stoves I was considering). If my data is correct, it would seem to me, a cat should be replaced at a minimum of every 5 years to maintain efficiency.

What am I missing? If a cat looses 10% efficiency per year how is it more efficient than a non-cat, which as I understand does not suffer this type of loss. The break down looks something like this.

Given
Base stove efficiency = 50%
Catalyst adds = 33% when new
Total when new = 83%
Catalyst degrades 10% per year (multiplicative decay)

Summary: Efficiency Over 5 Years
Year Catalytic Efficiency Total Efficiency
0 33% 83%
1 29.7% 79.7%
2 26.73% 76.73%
3 24.06% 74.06%
4 21.65% 71.65%
5 19.49% 69.49%

Final Answers
Efficiency after 5 years: 69.5%
Average efficiency over the 5-year period: ≈75.4%

Life of the cat is roughly 10k hours. Do in a decade or 3 years. It doesn’t change the efficiency. The cat stoves are more efficient at lower operating temps. Burn less wood but you get replace a cat every 10k hours. They work well for some who don’t need lots of heat. Once you need to go to a 6-8 hour burn cycle the efficiency difference is less compared to a secondary burn stove.

The cat efficiency is just being measured how? Probably not the same way we measure stove efficiency.

 

[Fargo]

Life of the cat is roughly 10k hours. Do in a decade or 3 years. It doesn’t change the efficiency. ...

The cat efficiency is just being measured how? Probably not the same way we measure stove efficiency.

I don't know how the efficiency is measured, but surely they loose efficiency. They are made with materials that wear out and degrade. A used cat with 5000 hours won't work as well as a new cat, right???. Something must changed as the hours add on. Otherwise there would be no need to replace them. Unless you're saying a cat either works at 100% or it doesn't work at all. That would be a different scenario. But from my research, it appears a cat will loose its efficiency as it gets used up. So maybe the question is how much efficiency is lost at 10,000 hours? Is that when the cat is completely drained out and not doing anything? Is that closer to 50% loss of efficiency, or is it closer to 30% loss and your at the break even point of a non-cat? It seems to me a catalytic converter is a consumable item that wears out and looses its efficiency as it breaks down the materials. If so, the efficiency of the stove would have to be affected. So unless I'm completely wrong in my thinking, a cat stove will decrease in its efficiency as the cat breaks down. So its efficiency is kind of a decreasing number. Where a non-cat, with a secondary burner will have a more stable efficiency level through out its life. Sure the tubes or baffle can also wear out. And at that point they are not efficient and need replacing as well. But I think they are more durable will not suffer from loss of efficiency until completely gone. It seems to me the secondary burners either work or they don't. Otherwise, it would seem we would be replacing them as part or regular maintenance as well.

So I guess the question I am trying to figure out is how does the loss in the efficiency of the cat, or secondaries, affect the overall efficiency of the entire stove.

Note: I understand, the scenario I am trying to measure would require both stoves to be running at their optimal efficiency levels through out the test period (say 10,000 hours) The comfort of low and slow vs hot and fast could certainly affect efficiency as the secondary burner would likely drop out of its efficiency zone sooner as the firebox cools off. But lets assume, for the sake of argument, we are keeping both stoves warm enough during the entire 10,000 hours that both are maintaining optimal efficiency. How does loss of efficiency affect each stove.

In short, which is more efficient, a good quality catalytic stove with 9000 hours or a good quality non-cat, but secondary burner stove with 9000 hours?

 

[John Lehet]

Personally, I think chatGPT can draw itself a pixel bridge and go jump off of it. When we don’t have to worry about it spouting nonsense, maybe I will use it, but I’d rather not.

It’s like the cat in your car. It works, until it fails. When it fails, you replace it. I think what people see as the cats get older is that it’s harder to get them to light, takes slightly higher temperatures. So in that regard, you do lose a tiny bit of efficiency because you have to burn the fire longer without the cat. Like a non-cat stove. You can clean the cat, rinse it in vinegar in the case of my stove, to restore it, periodically, but eventually you get to a point where it’s hard to get it to light off at all.

I’ve been burning a non cat stove for the last 17 years, and before that I also had a non cat stove for some years. About 28 years ago I had a cat stove that worked very well, and then for a few years I had a very badly designed cat stove (Vermont Castings), which kind of soured me on catalytic stoves.

From my research, modern well designed cat stoves are much better than the early generation of catalytic stoves. I am replacing my stove with a hybrid stove, which features both secondary burning when the temp is high enough, and then uses the cat when the temps are lower. My current (non cat) stove needs to keep the temp higher all the time, so that often means burning a hot fire and then letting it go out. With this stove I don’t have to worry about the cat wearing out, but I’m definitely burning at lower efficiency and with less flexibility. Also catalytic stoves (with a bigger fireboxes) are better for burning overnight. This is something I want to do, since I live in a cold climate.

I fully expect that my new hybrid stove will give me more heat using less wood (which means less work). I also expect I will have to replace the cat after some winters. In the case of my incoming stove, that’s very easy and costs $200. I will have saved at least $200 worth of wood and had an easier and more comfortable time of it. Others may well want to avoid a cat, as I have for the last many years. Lucky we have many choices.

 

[Fargo]

I hear you on chatgpt. I take everything it says with caution. That is why I mentioned it was the source of my info. So I'm totally open to being wrong here. Infact, since I just ordered a Blazeking Ashford 30.2, I hope I am wrong about the cat loosing its efficiency. But it made sense to me. So I had to pursue the idea.

I see what your saying in regards to the cat. As long as its lighting up its doing something. I could even understand if a failing cat just means higher temps to light. So I guess the real question is, does a cat actually loose its efficiency or does it just get harder to light until it just doesn't work any more. Thanks for your thoughts.