So after a long battle with my super 27 overdrafting, and the dealer here and replacing my chimney cap, I think a draft damper would be my next step. I have a 18' straight up Excel chimney with double wall stove pipe. After a recent long term power outage I found the stove difficult to control without the blower. After a re-load at 200F stove top, once the secondaries caught and the draft completely shut at 400F The stove would soar too 875F and a stove probe temp of 1275F with 3/4 load of white birch. I noticed since it was dark and no electricity that the stove collar ring was starting to glow red. Obviously not a good sign, But not much I could do about it. So anyway, my question is I was told that the Excel damper can either be used fully open or fully shut and not partially closed. Is this true and does anyone have any experience using a damper on a Super 27 or T5?