Enerzone Euromax EP00070 Installation And Operation Manual page 87

Instead, if the installation consisted of a horizontal vent coming out at
the back of the stove on a total distance of 4 feet, followed by a tee
and a 6-foot vertical rise, it would be acceptable. The termination is
within the allowable configuration zone on the chart since it would
have at least one foot of vertical rise for each foot of horizontal run.
Furthermore, the total vertical rise is at least 3-feet high.
WARNING: To reduce the risk of smoke spillage there should
always be at least one foot of vertical rise for each foot of
horizontal run. In all cases, at least 3 feet of vertical rise is
needed.
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Euromax Pellet Stove Installation and Operation Manual