Going with a non OEM cat

Rob_Red

Member
Feb 2, 2021
105
Southern New England
Hey all, I stumbled across a ceramic cat the is the same dimensions as my steel cat. It got my gears turning because my steel combuster has very small holes and likes to plug up quickly with powdery fly ash. This ceramic aftermarket version has bigger holes for the gasses to pass through so it seems it would be less prone to plugging up. Are the ceramic cats inferior in any way? Would I be doing a bad thing by putting a different style of cat than factory in my stove?
 

Highbeam

Minister of Fire
Dec 28, 2006
18,759
Mt. Rainier Foothills, WA
Anyone ever try this?
My stove was purchased new with a ceramic cat but they make both ceramic and steel replacements. I’ve tried both and prefer the ceramic. Either will work, I don’t think it matters that much unless you’re having cloggage problems.
 
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Highbeam

Minister of Fire
Dec 28, 2006
18,759
Mt. Rainier Foothills, WA
May I ask why you prefer the ceramic?
In my experience, with my stove being used for full time heat 9 months per year, ceramic is significantly cheaper, lasts longer before dying (we could say just as long to keep people happy but my steel was much less time), less likely to clog which is a big problem for many folks, and the larger holes offer less restriction to flow so better draft.

The alleged benefit of “faster” light off of steel makes zero significant difference in the real world. In the emissions testing world it probably matters more. Manufacturers also like steel because they don’t chip, crack, or break leading to complaints. Really though, once you have dry fuel and a tight door seal your ceramic cat looks like new all the way until it stops working from old age.

If price was the same then it would be a harder choice but it definitely is not. These cats only last 10-12k hours so you'll be buying lots of them unless you're just a part time heater.
 
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Highbeam

Minister of Fire
Dec 28, 2006
18,759
Mt. Rainier Foothills, WA
I wonder why they don't make the steel cats with the same size cell holes as the ceramics? Or if it would be cheaper if they did due to less surface area covered in those precious metals.
 

begreen

Mooderator
Staff member
Nov 18, 2005
87,290
South Puget Sound, WA
I wonder why they don't make the steel cats with the same size cell holes as the ceramics? Or if it would be cheaper if they did due to less surface area covered in those precious metals.
Probably because the performance characteristics would be close to the same, making the sales point less compelling.
 

Highbeam

Minister of Fire
Dec 28, 2006
18,759
Mt. Rainier Foothills, WA
Probably because the performance characteristics would be close to the same, making the sales point less compelling.
Supposedly, the steel cats "light off" or go active 50 degrees or some other small amount sooner due to the very low thermal mass of the thin steel cell walls and/or the additional catalyst surface area exposed to smoke from having a zillion tiny cells. The thick ceramic cell walls take longer to heat up and achieve active capabilities. Emissions testing is important at the front end of the fuel charge.

So if you made a steel cat with the same number of cells as the thick wall ceramic cells, each cell would be slightly larger but total surface area much smaller than the current steel cats so less precious metals and cheaper to make/sell.

I guess it depends on what makes the steel cats perform slightly better for early emissions reductions in the lab. Is it the steel's additional surface area with the additional catalyst or is it the thin walls with the rapid heat up to the active temperature?

There is at least one brand with a very large celled cat on the market. I forget if it was steel or ceramic but I'm guessing steel. Cat cloggage is much more common that it should be. Cheaper cats are more likely to be replaced when they wear out which helps everybody.
 

MTASH

Burning Hunk
Dec 24, 2018
164
Montana
As someone who operates with barely adequate draft, I would really like to know what the flow difference is between the steel and ceramic. I will probably get one more season out of my steel, but if ceramic really is that much better I'd consider switching now.
 

Highbeam

Minister of Fire
Dec 28, 2006
18,759
Mt. Rainier Foothills, WA
As someone who operates with barely adequate draft, I would really like to know what the flow difference is between the steel and ceramic. I will probably get one more season out of my steel, but if ceramic really is that much better I'd consider switching now.
Since you don’t engage the cat until the stove is hot and door is closed, the draft resistance shouldn’t matter much until/unless the steel cat clogs. Then it’s pretty obvious.

If you’re one of the people pulling their hair out over smoke smells “leaking” from the stove then moving to a freer flowing cat is worth a try.

Draft strength is pretty important on these high efficiency stoves during startup and when opening the loading door. When they are cruising on low, the air inlet to the stove is very small so the velocity of smoke through the cat is very low.
 

MTASH

Burning Hunk
Dec 24, 2018
164
Montana
Since you don’t engage the cat until the stove is hot and door is closed, the draft resistance shouldn’t matter much until/unless the steel cat clogs. Then it’s pretty obvious.

If you’re one of the people pulling their hair out over smoke smells “leaking” from the stove then moving to a freer flowing cat is worth a try.

Draft strength is pretty important on these high efficiency stoves during startup and when opening the loading door. When they are cruising on low, the air inlet to the stove is very small so the velocity of smoke through the cat is very low.
I have had issues with ash clogging when burning Aspen. But that's not my primary wood type so not really that important in the grand scheme. I'm more interested in the effects in a draft sensitive stove such as my Ashford. Even though velocity is slow while cruising, every little bit could help it seems.
 
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