Bosch FAS-420-TP2 - Page 58

58 en | Planning Aspiration smoke detector LSN improved
2020.04 | 6.1 | F.01U.029.275 Operation guide Bosch Sicherheitssysteme GmbH
Air sampling openings
Pipe
shape
1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 18 20 21 24 32
I 0.5
0
0.6
6
0.7
5
0.8
0
0.8
3
0.8
5
0.8
7
0.8
8
0.9
0
0.9
0
0.9
1
0.9
2
0.9
2
U 0.5
0
0.6
6
0.7
5
0.8
0
0.8
3
0.8
5
0.8
7
0.8
8
0.9
0
0.9
0
M 0.5
0
0.6
6
0.7
5
0.8
0
0.8
3
0.8
5
0.8
7
2 x U 0.5
0
0.6
6
0.7
5
0.8
0
0.8
3
0.8
5
4 x U 0.5
0
0.6
6
0.7
5
0.8
0
Table4.2: Factors for increasing the sensitivity (acceleration opening corresponds to one air sampling opening)
Air sampling openings
Pipe
shape
1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 18 20 21 24 32
I 0.3
3
0.5
0
0.6
0
0.6
6
0.7
1
0.7
5
0.7
7
0.8
0
0.8
1
0.8
3
0.8
4
0.8
5
0.8
6
U 0.3
3
0.5
0
0.6
0
0.6
6
0.7
1
0.7
5
0.7
7
0.8
0
0.8
1
0.8
3
M 0.3
3
0.5
0
0.6
0
0.6
6
0.7
1
0.7
5
0.7
7
2 x U 0.3
3
0.5
0
0.6
0
0.6
6
0.7
1
0.7
5
4 x U 0.3
3
0.5
0
0.6
0
0.6
6
Table4.3: Factors for increasing the sensitivity (acceleration opening corresponds to two air sampling openings)
Example:
A class B double U-pipe system with 24 air sampling openings is planned. According to EN
54‑20 or ISO 7240-20 , 24 openings are permitted in class B at a sensitivity of 0.25% LT/m. In
order to decrease the transport time, an acceleration opening the same size as the last air
sampling opening is to be used. According to 1. Option: increasing the sensitivity, page 57 , the
necessary sensitivity of the detector module in this case is 0.25 % LT/m * 0.85 = 0.1875 % LT/
m.
2. Option: reducing the number of air sampling openings
Reduced sensitivity at the air sampling openings can be offset by reducing the number of air
sampling openings. A distinction must be made regarding whether the cross-section of an
acceleration opening is smaller or the same as:
– the cross-section of the last air sampling opening of a branch
– the doubled cross-section of the last air sampling opening of a branch