New catalysts - not as tall, will they fit and work OK?

[Graphite]

Hi - I have an Elmira Stove Works Fireview 1100 (as far as I can tell ) 6" stovepipe and single brick catalysts one either side.
My new bricks from Condar arrived today. CC-308s
They are not as robustly wrapped as the originals and do not have the wire mesh at the bottom for protection (or catching broken brick 🤷‍♀️) - but look big enough to span the gap in the cat slots...


Tops


Cat undersides


Cats from end view.

Old one external dims 2 3/4" wide, 7 1/2" long 3" deep, cat brick 2" deep - 25 cells per sq inch
New one external dims 2 3/8" wide, 7 1/4" long 2" deep - 16 cells per sq inch

So any ideas - or do I need to contact the supplier before I use them?

Many thanks...

 

[begreen]

That's a big differerence. Does the replacement cover the opening underneath it or does it drop through it? If the fit is too sloppy then flue gases will leak around them. And the 1/3d reduction in depth mean less exposed surface area.

 

[Graphite]

The catalyst bricks are the same depth 2" - but obviously the surface area on the new ones is much lower at 16 cpsi as opposed to 25 cpsi on the old ones. I'm pretty sure the slightly smaller new ones will still sit on the support ledge OK...
I have done a lot of work with automotive catalysts at 200 - 600 cpsi - a different world 😂

 

[Ashful]

The change in total surface area will cause amount of unburned fuel and temperature to be different between the two, but if it's the only available replacement and it fills the hole, I'd run with it. Since you're an automotive guy, you already know how temperature will spike around any exhaust leak, to the point of removing metal. I can't imagine the problem is nearly as acute with wood stove combustors, but all the same, I'd want to be sure the LxW is sufficient to minimize blow-by.

How does this combustor mount in the stove? Is the chamber/holder all metal, or refractory? If a metal chamber, then most wrap the combustor in interam gasket, before installing.

 

[Graphite]

The replacement parts I have are wrapped in cat support mat and then with a thin stainless wrap around that...

It may be that the washcoat materials are better than what they used 'back in the day' when my original parts were supplied? 🤷‍♀️
I know cat manufacturers are always looking to lower the costs and the washcoat formulations are a huge part of that with all those precious metals in there!

 

[Ashful]

There is a new washcoat, first available around 2018, which BK started making standard a year or two ago. It's more expensive, and I doubt many are using it, but yeah... things are always changing.

Even with the expanding gasket between ceramic and metal can, most still use interam gasket between the can and stove, if mounting hole is all metal. Check your user manual to see if you need it, mine uses 1/16" thick x 2" wide, available from most stove shops. It's similar to the gasket used between ceramic and the can on your combustor, and keeps the can from bulging out even more as that gasket expands against it. It's throw-away stuff, replaced each time you remove and re-install the combustor.

 

[Graphite]

Doesn't seem to be any major critical thing - only thing is that my new ones are an inch shorter on the can and do not have the mesh screen at the bottom...

 

[Ashful]

Doesn't really show much, but looks very similar to the mounting of my old Jotul Firelight 12 updraft stoves. In that stove, the cat was captured within a refractory chamber, so no interam gasket was used.

 

[Graphite]

I gave up and just installed them anyway - seems OK - I only have an IR thermometer (up to 220 °C) to measure temps with but I'm sure they are higher than before and it looks a cleaner burn...