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Graph Line F is suitable for Performa 9, 12, 15, 18 SL HE
Graph Line G is suitable for Performa 21,24 SL HE
20
F
18
16
14
12
G
10
8
6
4
2
0
0
1
2
Concentric 60/100 Flue (metres)
Example 1
Flue Lengths - Not Permissible
20
F
18
16
14
12
G
10
8
6
4
2
0
0
Example 3
Flue Lengths - OK
60Ø Exhaust
Y
Concentric 60/100 Flue
Fig. 17
Additional Accessories
A - 93° Elbow
B - 45° Elbow (Pair)
C - 1 metre 60Ø Extension
© Baxi Heating UK Ltd 2008
20
F
18
16
14
12
G
10
8
6
4
2
0
0
1
3
Concentric 60/100 Flue (metres)
Example 2
Flue Lengths - OK
1
2
Concentric 60/100 Flue (metres)
X
Support
Bracket
Extension
5117381
5117382
Fig. 18
5117380
3.9.1
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
2
3
If, for instance, a concentric length of 2.5 metres was
required and the 60Ø exhaust needed to be 16
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
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 1 metre
of concentric flue and 6 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
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
3
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 5.5 metres.
Therefore, the total equivalent length of the 60Ø
exhaust can be up to 5.5 metres. Any elbow
equivalences must be accounted for i.e. 93° elbows
are equal to 1 metre, each 45° elbow to 0.5 metres.
Flue Length - Worked Example
Potterton Performa 24 SL HE
93° Elbow
In Fig. 18 opposite an additional 93° elbow has been
included in the 60Ø exhaust. with 2 x 1metre
extensions which have been cut to 0.25metres and
fitted. The waste is discarded.
To calculate total length:-
2 x 0.25 metre Lengths =
Concentric Flue
1 x 93° Elbow =
Total 60Ø Exhaust =
After consulting the table in Example 3 it can be
determined that the concentric flue could be up to
approximately 6.25 metres long.
Determining Permissible Lengths
0.5 metres
1 metre
1.5 metres
19
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