Add-on catalytic combustor

[pgmr]

I have a pre-epa airtight insert (Alpiner-not sure if that's a brand or model name) and am considering installing an add-on catalyst. The insert no longer has the metal surround and I've run a ss flex liner directly to it's 8" outlet and insulated between the 15" chimney tiles and ss liner w/vermiculite. The flue pipe is easily accessed and it's got a great draw now.

I have a pretty good idea of the benefits of a catalyst (longer burn times, more heat from stove, cleaner emissons). My concerns are listed below:

1) Does an add-on really deliver on those benefits?

2) Is it a pain to remove the section of pipe containing the catalyst damper each time the liner is cleaned? Right now, I just sweep everything from top down into the stove. How do you contain the sweeping mess - bag taped to end of flue pipe?

3) Is the combustor replaceable or does it require replacing the entire unit?

Comments from those who have or have used these add-on catalysts is appreciated.

 

[Eric Johnson]

I've got an add-on. Before I bought it, Craig Issod said that for my application (inside boiler) I could expect something like a 10% gain in efficiency and up to a 50% reduction in smoke. After using it for half a season, I'd say that's about right.

I don't like fooling around with black stove pipe, but the cat comes in its own section and is no harder to remove than any other section of black pipe. You still have to line up the screw holes when you put it back together, LOL. Theoretically at least, you should need to clean your chimney a lot less frequently if the cat is doing its job. In my case, I get zero creosote, but I got little to none before installing the cat, so take that observation for what it's worth. My main concern has always been smoke. I did notice that one night when I forgot to engage the cat, I had very few coals the next morning while when the cat is engaged, I usually have a nice bed.

It looks to me like you can just replace the cat element. But never having tried it, I don't know. The one I have is pressed inside a welded steel collar with some sort of filler between the cat element and the steel strapping. It's either asbestos or some kind of mica- or vermiculite-based sheet. It might or might not be tricky to get a new element back in there, but I'm guessing it's possible. I expect to get 2 heating seasons out of mine since it's rated for 12,000 hours. I use mine 24/7 for the entire heating season, which would be 14,000 hours over two years.

I took it out and cleaned it a couple of weeks ago, more out of curiosity than anything, and after being used for 3 months, it shows no signs of degradation or wear (i.e., no cracks or other flaws). I have a manual cast iron damper between the boiler outlet and the cat, which is always engaged when the cat is being used and keeps my blower from jamming it up too quickly with fly ash. In my limited experience, it goes about two months before needing to be vacuumed off to get rid of the dust.

In short, I think it was $200 well spent. Others may have a different perspective.