Cat Question

[claybe]

On start up you want the cat to be "active" before you shut down the damper. I understand this. However, everyday I come home from work the stove is still producing heat and the cat is not "active". My question is: why do you have to wait until the cat is active to close the damper? Why can't you load it up, get the fire going, close the damper and let it rise to temp? Being new to the cat stove I guess I don't understand the physics behind the stove. It seems to me that if it can handle burning several hours in the non active temps with the damper shut, it could handle a few minutes of start up with it closed...I guess it has to do with difference in temps? Start up is hot and end of cycle is cool on the cat? If you start talking physics you will lose me... Please laymen terms

 

[rdust]

No physics involved in my answer. It's simply hard on the cat to not bring it up to light off temps before closing the bypass. Burning it with the bypass open will also allow some moisture to burn off before pushing it through the cat.

 

[WoodpileOCD]

My understanding is that at startup you have a huge amount of smoke pouring off of the wood and if the cat is not hot enough to ignite it, you are going to gunk up your cat pretty bad which would then cover up the catalyst material in and on the ceramic honeycomb. Do this long enough and the cat won't light even when it does get up to temp. At the end of the bburn cycle there is very little smoke being produced so directing the gases through the cat shouldn't be a problem. I'm sure some of the more knowledgable and experienced cat burners will be along to add to or correct my explanation but that's as simple as I can put it. Good question though.

 

[Jon1270]

I don't even have a cat stove, but I think Rusty basically has it. When you're down to coals and nonluminious (blue) flame, the combustion is already very clean and there's nothing for the cat to do, just as there's nothing for the secondaries to do in a non-cat stove. It's early in the burn cycle, when there's lots of smoke and bright flame, that combustion tends to be incomplete. Taking care of that is what the cat is for.

 

[mellow]

2 Good reads for new cat owners:

(broken link removed to http://www.woodstove.com/pages/pdffiles/Catalytic%20Combustor%20Tips.pdf)
http://www.woodstovecombustors.com/How_They_Work.html

 

[Machria]

My understanding is that at startup you have a huge amount of smoke pouring off of the wood and if the cat is not hot enough to ignite it, you are going to gunk up your cat pretty bad which would then cover up the catalyst material in and on the ceramic honeycomb. Do this long enough and the cat won't light even when it does get up to temp. At the end of the bburn cycle there is very little smoke being produced so directing the gases through the cat shouldn't be a problem. I'm sure some of the more knowledgable and experienced cat burners will be along to add to or correct my explanation but that's as simple as I can put it. Good question though.

Exacttly. You can do it (close the bypass immediately that is), but you are shortening the life of your cat, that's all. In addition, if I am around during the very end of my burn when there is a very small coalbed left, and the stove top is down to 150..... I'll open the bypass for the same reason, to put less "stress" (for lack of a better word) on the CAT.

 

[mellow]

IMHO opening the bypass to finish out the burn cycle is not needed, most of the particulate that the cat is going to reburn has already been out gassed, the coaling stage is really just heat.

 

[Machria]

IMHO opening the bypass to finish out the burn cycle is not needed, most of the particulate that the cat is going to reburn has already been out gassed, the coaling stage is really just heat.

Probably, but it doesn't hurt it either. This isn't a habbit, just if I happen to be going to work, and I see the stove is at it's last hour or two, and I'm leaving and not re-loading, I'll turn it, no biggie.