This is an interesting, timely thread to stumble onto today. We have very high draft and have been experimenting with a key damper. Actually, the experiments were quite brief - install, ease it closed during the first burn, and immediately realize it will be used in only 2 positions - fully open when reloading and restarting the fire, and fully closed otherwise. On cold nights with it fully closed we are still pulling more than 0.15" w.c., and more if it is windy. Today with 35 degrees outside and a firebox full of coals and all dampers fully closed it is pulling 0.10" w.c.
I've got a couple of pics to post, but in respect of earlier cautions on this thread wanted to note...
-this is an experiment, not a solution
-cautions/warning earlier in this thread fully respected and understood
-we have a safety cover that we are using at night and when leaving the house
-we are starting with a clean flue
How clean? Here's what came out of 32' on the last cleaning:
So we have a barometric damper installed in addition to the key damper. Starting from the stove we then have the draft gauge, next the key damper, and then the barometric damper.
Does it make a difference? Yes, of course. With the barometric set at 0.10" w.c., the key damper fully closed, and a dying fire in the firebox we have 0.08" w.c. of draft, which is the lowest I've seen the draft without the stove door open.
Here's the safety lid installed. Still some airflow at the hinge, but nothing like the full 6"
The point of the exercise is to see if the difference between 0.08" and 0.15" w.c. results in enough fuel savings in milder weather to merit seeking additional draft mitigation measures beyond the fully-closed key damper.
