Baxi Megaflo System HE IE Series Installation & Servicing Instructions Manual page 35

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Fig. 17
9.2 Determining Permissible Lengths
In the graph the solid line diagonal represents the relationship between the concentric flue assembly (and any extensions) and the
60Ø exhaust (and any extensions or additional bends).
Example 1 - Not Permissible
Example 1 Flue Lengths - Not Permissible
If, for instance, a concentric length of 5 metres was required and the 60Ø exhaust needed to be 6 metres the graph shows that this combination
would NOT be permissible as the intersection point would be above the solid diagonal line.
Example 2 - Flue Lengths OK
Example 2 Flue Lengths - OK
Where both lengths have been determined they can be applied to the graph to check that the installation is permissible. For example, if it was
known that 2 metres of concentric flue and 4 metres of 60Ø exhaust were required, the values could be applied to the graph as shown in Example 2
. As the point of intersection of the dotted lines is below the solid diagonal line, the combination of lengths is shown to be acceptable.
Example 3 - Flue Lengths OK
Example 3 Flue Lengths - OK
In the example shown, assume that the concentric part of the flue needs to be 2.3 metres long. Find the position of '2.3' on the horizontal axis of the
graph and then project upwards to the solid diagonal line. This is represented by the vertical thick dotted line. Where this dotted line intersects with
the solid diagonal line on the graph, project across to the vertical axis. As can be seen this corresponds with 6 metres. Therefore, the total
equivalent length of the 60Ø exhaust can be up to 6 metres. Any elbow equivalencies must be accounted for i.e. 93° elbows are equal to 1 metre,