Confusing Draft Issue with Cold Stove

[learnin to burn]

I'm not sure what's going on but I know I have issues I have been working on solving. I mentioned in an earlier thread about smoke coming into the room when I reload my stove and on start up unless I do a top down fire and the flames gong right up the flue, otherwise the stove runs great.

Blaze King King stove - wall thimble 44 inches on center above the stove - into a 7x7 clay lined masonry chimney - chimney height 20 ft above stove - Flex King liner with insulation to be installed this week. OAK to be installed also.

Past few days have been warm so I haven't been burning. I left the damper open intentionally to provide more air to bun the coals down for clean out. I had no smoke odor at all during this time. Cleaned the stove out tonight and closed the damper. 1/2 hour later I went to the basement to turn a light out I forgot when I came up initially. I got half way down the stairs and could smell the flue odor through out the room. I opened the damper and went back upstairs. checked again 15 minutes later and the smell was gone.

Why would there be a difference in the draft with the damper closed vs open? (closed = reversed draft - open = normal draft)
I'm stumped

 

[EatenByLimestone]

With your damper closed, the chimney can't draft as well as the house can. Your house became the chimney. When you opened the damper the situation corrected itself.

Matt

 

[LLigetfa]

With your damper closed, the chimney can't draft as well as the house can. Your house became the chimney. When you opened the damper the situation corrected itself.

Matt

+1
Opening the damper allows warm room air to service the chimney and maintain the draft. Without the air to heat the chimney, it becomes a cold shaft of air that reverses.