New Chiminee Frei Oeko plus 75 x 57 F+ smokes

Good day Hertwek. We have already consulted the chimney sweep as well. The chimney draws really well, I believe there are vortices forming at the top of the firebox, which makes it possible for smoke gases to escape despite good draft.

Hello Tsäme! It is also possible that the vents pull more than the chimney and thus pull the air down through the chimney. Try turning off the vents and give it a try?? Best regards from Dämmunsinn