Determining Permissible Lengths - P.d.k. - Baxi MULTIFIT Flue Systems Fittings Manual

© Baxi Heating UK Ltd 2011

Determining Permissible Lengths - P.D.K.

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
If, for instance, a concentric length of 5 metres was required and the 60Ø
exhaust needed to be 11 metres the graph shows that this combination
would NOT be permissible as the intersection point would be above both
solid diagonal lines A & B.
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 both solid diagonal lines, the
combination of lengths is shown to be acceptable.
Example 3 - Flue Lengths OK
In the example shown, assume that the concentric part of the flue needs to
be 2 metres long. Find the position of '2' 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 (line B). Therefore, the total equivalent
length of the 60Ø exhaust can be up to 6 metres (models in group B
below). Any bend equivalencies must be accounted for i.e. 93° bends are
equal to 1 metre, each 45° bend to 0.5 metres.
Graph Line A is suitable for
Graph Line B is suitable for
page 14
Combi 24 Models
System 12,15,18,24 Models
Combi 28,33,40 Models
System 28,32 Models