Catalyst protection with cold gasses - follow up question

[rashomon]

I want to understand this and found what is probably my answer but it's too vague for my understanding.

I allow my GreenMountain60 to burn out every night with the bypass closed and want to either
1) Make sure doing this isn't shortening the life of my catalyst and therefore the bypass should be opened at night, or,
2) Since colder gasses are okay at the end of the burn than in the morning when I start my fire it's okay to close the bypass early so long as I have a good fire going.

This question was asked in 2018 here - https://www.hearth.com/talk/threads/prolonging-catalyst-lifespan.170785/post-2292342

Although the question is more about possible heat shock to a cold catalyst. BKVP posted with some knowledge about moisture and says to look at burn charts, but I can't find the burn charts he's referring to. I imagine his statement "first stage of combustion...boiling water out of fuel..no measurable moisture at end of burn." is the answer, but wanted to follow up about this burn chart. He mentions "We need "catalyst conversion" to begin before we shove 100% of gases thru the combustor"-- to clarify he means "closing the bypass", correct? I don't know if he actually means there is a way to shove less than 100% of gases using a particular stove. (yeah, I'm probably reading into this)

 

[begreen]

Yes. Get the combustor up to temperature before closing the bypass.

 

[stoveliker]

And colder gases going through a colder (already inactive) cat at the end of a burn are fine too. There is no need to open the bypass when you let the stove go cold and the cat drops out of the active range.

 

[mellow]

Condor has a good website on cats and answers many questions: https://www.woodstovecombustors.com/

 

[barnaclebob]

Its temp shocks that you want to avoid. Dont sent hot air through a cold combustor or cold air through a hot one. As a fire dies down the combustor looses temp gradually which is fin.

 

[rashomon]

Thanks! It was the explanation that the concern is regarding thermal shock which is the issue.

For some reason I thought another issue would be creasote buildup which in my mind could happen at the end of the burn cycle when the temp falls to the inactive range and wood starts to smolder. Is that not a concern?

 

[stoveliker]

No, at the end of a burn, (almost) no creosote is produced.

 

[rashomon]

Great! I'll stop worrying then!

 

[mellow]

Thanks! It was the explanation that the concern is regarding thermal shock which is the issue.

For some reason I thought another issue would be creasote buildup which in my mind could happen at the end of the burn cycle when the temp falls to the inactive range and wood starts to smolder. Is that not a concern?

Creosote production through the night?

Help me conceptualize what is happening throughout an overnight burn. I understand with these EPA stoves, a hot fire is necessary to burn as much of the gases/particulate produced by a given firebox load of wood to maximize heat production and minimize environmental pollution. From what I can...

www.hearth.com