Wood still burning quickly.....

Nope, my stove pipes out the basement wall, near ground level. Then goes up about 25ft.
Its a bad picture, but this was on my old phone and it had problems at only 2 degrees outside. I do not use the brick chimney. That might go away when I remodel my 92 year old house.

 

That temp is middle of winter not now, it was low teens this week.

 

I run 12 hour burns down to about 0F then I switch to 8 hours. I've done 24 hours in shoulder season with dimensional oak.

 

Some stoves are just not capable of a 12 hour burn.

Doesn't mean that it doesn't have a few coals left after 12 hours, but that is not the equivalent of a 12 hour burn.

 

Si

Size of the stove is a big contributing factor, I could get 12 hours burns but not interested in the creosote it would produce.

 

I would look into if the secondary air supply goes thru those 5 air inlet holes.
If those 5 holes only supply air to the air wash and primary air and you block them off the chimney will just suck air thru the secondary supply.
Some stoves have separate supply sources.
With a really tall chimney that sucks like mad you might have to also block the secondaries supply ( if the key damper doesn't work - it should)
A key damper should work well on 25 feet of chimney.

Sometimes you can find the secondaries input source by closing the key damper too far too soon on a real smoky fire start.
If the back puff spills out the 5 input holes it's a shared supply. If it drafts back thru the secondary tubes and comes out somewhere else you now know you have a double air supply.

 

I found info where it has two sources of air, on the bottom and in front above the door.

 

I believe that all stove manuals prohibit key dampers now not because it isn’t a great idea but because it allows the operator to defeat all of those emissions controls. Noncats especially must run hot to make low emissions, so the manufacturer takes away the ability to run them a little cooler.

I would have no problems installing a key damper in a woodstove flue to regain control.