Osburn OB01151 - Manual (Page 6)

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1.2 Venting Requirements
The flue is a critical component to a satisfactory installation. Your Osburn insert will attain its best
performance if installed with a chimney that generates its own draft. The minimum requirement of a
flue will be the installation of a flue connector (the liner must conform to UL1777 chimney liners)
from the insert into the first flue tile of the chimney (USA), see Figure 2.3 , or a continuous stainless
steel liner (the liner must conform to the Class 3 requirements of CAN/ULC-S635) directly
connected to the flue outlet (Canada), see Figure 2.2. A continuous 6" (152mm) stainless steel liner
from the top of the chimney is the optimum system and will provide the best performance, as well as
compensate for poor draft situations caused by large cross-sectional chimneys. The insert will not
work without a positive seal in the chimney.
Chimneys constructed outside of the home, on an exterior wall, should be avoided if possible,
especially in colder climates. Outside chimneys may not draw as well and may downdraft due to the
difficulty in heating them up to operating temperature. Cooler chimneys will result in increased
creosoting, less draft, and poorer performance. Draft is proportional to overall chimney height as
well as to stack temperature. Draft can be increased by increasing chimney height, and by reducing
heat loss from the chimney through an insulated liner.
Ensure that all joints in the flue systems are tightly sealed, since any leaks will result in reduced
performance as well as a possible safety hazard.