Installed the damper at noon today. 1:20 AM and am running a load I started at 8:30 PM. Damper completely closed (which means draft reduced by 80% and air completely closed. Active slow secondaries for over 4 hours with stovetop at 420 and flue at 600. For me a big improvement. Flue had been running at 800. Sometime between 12:30 and 1:20 the secondaries disappeared. I wasn't watching so I don't know when. Noticeably more heat radiating into the room, less heat lost up the flue. Still have a ridiculous draft, but much better.
I've never measured the flue, but about 28 feet, based on a height of the house (30 feet) and chimney coming out at peak, extending 3 feet above peak. Perhaps just as significantly, we are at the extreme south end of a long lake, high on a hill overlooking the lake, exposed to the prevailing westerly and northerly winds. Flue is (obviously, since it is at the peak) in the center of the house and is therefore warm, as well. My Fireview had a rear exhaust, and that extra 90 degree turn seems to have decreased draft a lot more than the flue damper does. I had a healthy draft with the Fireview, but not like this.
I had a pretty wicked draft when I had the princess, I thought the 90 might be a problem but it seems it makes it just right, only under certain conditions does it get roaring and I have to turn it down quickly.
