Progress Hybrid damper questions

[John Lehet]

Is there a way to shut off the secondary air in this stove? I would much prefer a true cat stove control unless I really needed a ton of heat.

Aside from the secondary air being designed in, I’m not positive the cat doesn’t get overwhelmed by lots of smoke from a near full firebox this size without flame. I don’t burn it smoldering very often at all. Maybe my opinion on this is just biased by my installer (a sweep who is a Woodstock geek, working in the area local to the shop) and some other stuff I’ve read. Including the manual, which has the “night burning mode” suggested at the first big mark short of closed. I shut it down way more than that (ideally if I can get minimal secondaries at the top of the stove).

My sense of the intent of the design of the stove is that in general the flames do most of the burning work, and the cat cleans up whatever gets past them and then in the early coaling stage or any smoldering later into coaling. It seems to want to burn generally pretty hot and fast and put that heat into the stone. It seems pretty far from a pure cat stove in that regard, though with the ability to hold coals and keep heat in the stone I think overall it works out about the same.

My situation might be influenced by my very strong chimney draw. I don’t get long fires like a Blaze King or maybe even a Fireview at all, but the end result is a long period of heating and an easy reload on hot coals.

I might be completely wrong and there are people completely happy and getting good results running this stove more often without flame!

 

[tsh2002]

Aside from the secondary air being designed in, I’m not positive the cat doesn’t get overwhelmed by lots of smoke from a near full firebox this size without flame. I don’t burn it smoldering very often at all. Maybe my opinion on this is just biased by my installer (a sweep who is a Woodstock geek, working in the area local to the shop) and some other stuff I’ve read. Including the manual, which has the “night burning mode” suggested at the first big mark short of closed. I shut it down way more than that (ideally if I can get minimal secondaries at the top of the stove).

My sense of the intent of the design of the stove is that in general the flames do most of the burning work, and the cat cleans up whatever gets past them and then in the early coaling stage or any smoldering later into coaling. It seems to want to burn generally pretty hot and fast and put that heat into the stone. It seems pretty far from a pure cat stove in that regard, though with the ability to hold coals and keep heat in the stone I think overall it works out about the same.

My situation might be influenced by my very strong chimney draw. I don’t get long fires like a Blaze King or maybe even a Fireview at all, but the end result is a long period of heating and an easy reload on hot coals.

That would make sense to me too. I have seen issues with low smoldering fires as well with extra creosote buildup in my flue with my BK, so when I start a new load in either stove, I open the damper up all the way with the bypass open (usually when the temp is below where that cat would be active), and give it about 15-20 minutes to get a decent fire going or when the stovetop temp reaches 350 or so, then damper it down and and close the bypass. Based on my research and experience, this will burn off any residual moisture and get things heated up and cat active. Since doing this the flue has stayed clean. I also don't try to open the damper past halfway with the bypass closed either, in order not to push smoke past it too quickly.

Compared to the BK, the PH definitely does not burn as low (damper all the way "closed") and doesn't get the long burn times that the BK can do. Even at the lowest damper setting, the PH still has a fair amount of airflow from my experience, but like you said that also provides more heat for the burn cycle and I think that helps keep the secondaries active. I too have a tall stack since the PH is in the basement.

 

[Todd]

I’m not an wood stove engineer but the cat in the PH is just about twice the size of the Fireview cat and the firebox is only about 1 cu ft larger so I’m assuming the PH cat could handle a full smoldering load. I just thought it would be interesting to see how it would perform as a true cat stove and if it could be dialed down for a lower BTU output and longer burn. I think it would be nice if you could switch those secondaries on and off but I doubt the EPA test methods would allow it.

 

[John Lehet]

I’m also definitely not a woodstove engineer, but I wonder if on account of the secondary air if there is in general greater volume and velocity of exhaust gas going through the cat and so the cat has a tougher job. I’d imagine that if exhaust is going faster there is less dwell time of smoke over metal. On the other hand exhaust gas might be hotter and have more oxygen in it to support catalytic reaction. No idea, just tossing out complexity.