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The MAXIMUM vertical system length must be less than 12 m (< 12
m!). If it is desirable to mount part of the flue horizontally, the 12-
metre
vertical system length can be converted to the horizontal.
Horizontal elements create considerable resistance, which is 1.5 times
greater than in the case of a vertical element.
•
1 metre horizontally = 1.5 vertically.
•
A maximum of ½ of the system may run horizontally.
The same method of calculation applies to bends:
•
45° bend = 1.5 m
•
90° bend = 2 m
•
Wall/roof duct = 1.5 m
Calculation example:
For a Fera connected to a concentric flue, the calculation example is
as follows:
The first metre (0,7) must be vertical (always), then a 90° bend to
the rear, then 50 cm horizontally, then another 90° bend upwards.
The flue then extends for 1 metre upwards to a roof duct.
•
1 metre vertical
= 1 metre
•
90° bend
= 2 metres
•
0.5 metres horizontal = 0.5*1.5 = 0.75 metres
•
90° bend
= 2 metres
•
1 metre vertical
= 1 metre
•
Roof duct
= 1.5 metres +
Total length
= 8.25 metres
As this is less than 12 metres, the appliance will function. It must be
expressly pointed out that the length must be kept to a minimum in
order to produce the best flames.
11
1.4
Restrictor plate
In some installation chimney draught may be stronger than strictly
necessary. In these circumstances it is desirable to restrict draught in
order to achieve a calmer and higher flame movement. This can be
adjusted by using a restrictor plate.
Use the following chart to find out which position of the restrictor plate
we recommend to achieve the best possible flame movement.
Restrictor plate
3 4
R1
2
1
length flue duct
12
restriction
100%
80%
60%
40%
20%
0%
9 10
7 8
5 6
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