High-draft cat burn

It was cool and windy today, and I took a few notes. Our PH is on a 32’ chimney, it has the modified damper, and has a pipe damper. I loaded it (not stuffed full) with Red Oak and Red Maple. Once it got going I closed the bypass, and about 10 minutes later I started closing the dampers. The firebox flames went out - usually we get backpuffs withon 15 minutes, but the draft extra strong, so I left it alone.
At 9:06 it was STT 545, probe at 600, firebox dark. I fully closed the dampers. You could hear a hum from the cat burn.

 

15 minutes later it was STT 615, and climbing, and the probe was down to 520. There was a strong hum going on. Given how fast the temp was climbing while all farmers were fully closed I bailed on the full-cat burn and gave the firebox some air.

 

Another 40 minutes later I had STT 510 and probe at 400, secondaries rolling, and the hum was gone.



In another half hour it was STT 450 and probe 350. Draft controls back to fully closed.
And then another hour later, STT 360 and probe 200.

 

Flamestead my chimney is only 24 BUT draft is crazy. I chicken out on cat only burns all the time

 

I’d love to find a sweet spot - I think less wood in the firebox and fewer coals at reload. But the weather, wind, house temp, etc are always giving me a different combo to play with.

 

I don't understand why your stt temp rose, but your probe temp fell when you were in the cat burn...? (Right before you bailed on the cat burn...) I thought if you were in cat mode your probe would have risen....

 

I agree. I think it happened this way because I cut the airflow right as I took the first reading. Maybe why?

 

I hear that! Sorry if I'm 9 years late on this thread!

 

So, does it reliably work to pull out on a cat that is super hot? I don't know why, but I've hesitated to do that, instead opting to close the intake air further. This generally will stall the cat, or at least all flames, and then I can regulate down to something less face-melting. But I haven't tried bypassing a very hot cat. Skeered, I guess!

 

Don’t bypass a hot cat! I think these guys are actually opening the intakes to create a flame in the box in hopes of consuming some fuel that would otherwise be burned by the cat.

 

Yes, I’m adding air, not bypassing. With the firebox black nearly all the combustion takes place at the cat, and the glass front of the stove isn’t radiating much heat. With flame in the firebox there is less to combust at the cat, more of the stove mass is being heated, and the heat from the glass is considerable. The net effect is the stovetop temp drops.

 

So if you're running in cat mode, and the cat still is still hot, you shouldn't disengage the cat (which is bypassing it, correct)? Does it hurt the cat, is that the reason? What if timing wise you need to add more wood? (I understand you're not getting the most out of the wood and your stove....) If you're running in cat mode so cat is hot, and you disengage it, won't it cool down similar to if it was engaged and just burnt out of fuel?

If you have the stove in cat mode, and it has gotten to the end of the burn and temps are falling and the cat is still engaged (you're away from home for example)...does this harm anything or cause any issues?

 

There’s no cat mode. The cat is always doing work once you close the bypass on a hot fire. Only open the bypass when opening the loading door and while warming up a cold stove. The stove is designed to have that bypass closed for the whole burn. Some stoves, like my my BK especially, can be damaged by running a hot fire with the bypass open not to mention the waste of fuel and pollution.

 

We've got to get our Absolute Steel in. Since they say it's a "hybrid", I wonder if it is somehow different, or if it too can be harmed by not running with the bypass closed?

 

I betcha the instructions tell you to leave the cat engaged. Woodstock is pretty proud of their high efficiency and low emissions. They wouldn't want you to bypass the very device that allows them to burn so well. The feds wouldn't either.

Sure, life or death, we would all do what we had to but keeping the cat working as designed is a win win.

 

The hybrid refers to the two types of clean burn technology, secondary burning, and catalytic burning. Both types in one stove provide the best of both worlds, where the secondary burn technology provides great high heat for somewhat shorter burn periods and catalytic stoves provide excellent long burns at a lower heat setting.

Having the bypass open past the initial cold-start phase is risking damage to the stove materials and is also a danger for chimney fires. Overfiring is the cause of many house fires, especially when using poorly seasoned wood. Like Highbeam said, the stove is made to have the bypass closed once the fire is engaged and the wood is charred.

 

My Ideal Steel has a great book that came with the stove, explains very well how to run the stove. You are correct, bypass is always closed except on start up and reload.

 

Thanks Highbeam , Oldhippie and oldspark. I will read the manual, haven't gotten to that yet... Glad you said that running it without the cat engaged could be harmful to the stove. I definitely don't want to hurt the stove, overfire or have a chimney fire.

But I'm not too worried about if the feds like it or not....

Sorry Flamestead, didn't mean to derail your thread.... I have been reading through the posts in this thread trying to get ahold of what's going on and the concepts....

 

No

No worries - great discussion!

 

Flamestead, any more burn issues like the one you started this thread with?