Planning For Forced Airflow - Bosch FAS-420-TM Operation Manual

52 en | Planning
Limiting values
Double U-pipe system
Ø of air sampling openings in
mm
a
Punch diameter of the aspiration reducing film sheet
3.9

Planning for forced airflow

Monitoring the air-conditioning ducts
Air-conditioning units are broken down into low and high-speed units (see table below). The
details provided in this chapter apply only to low-speed units. There are no adequate
empirical values available for high-speed units. Hence, smoke trials must be executed for air-
conditioning ducts with flow speeds above 10 m/s, in order to determine optimal response
behavior.
Air-conditioning
Flow speed
ducts
Duct cross-section
Difference pressures along
the flow direction
The speed distribution in an air-conditioning duct appears as follows:
Figure 3.15 Speed distribution in an air-conditioning duct
F.01U.088.878 | 4.1 | 2010.11
Min. distance FAS-420-TM – last T-fitting
Max. distance FAS-420-TM – last T-fitting
Max. branch length
Max. total pipe length per pipe system
– Pipe Ø 25 mm
– Additional pipe Ø 12 mm
Max. total pipe length per pipe system for a fan voltage
< 10.5 V
– Pipe Ø 25 mm
– Additional pipe Ø 12 mm
Max. number of air sampling openings (n) per pipe
system
Min. distance between 2 air sampling openings
Max. distance between 2 air sampling openings
a
Low-speed units
Maximum 6 to 10 m/s
Large
Low
v
4
v
3
v
2
v
1
Operation Guide
FAS-420-TM Aspirating Smoke Detector
Number of air sampling openings
4
4.4
High-speed units
> 10 m/s
Small
High
1
1
V - V
1 4
v v v v
1 > 2 > 3 > 4
2 m
20 m
12.5 m
50 m
8 x 3 m
40 m
8 x 3 m
8 units
0.1 m
4 m
8
3.0
Air-conditioning duct
Flow speed
Bosch Sicherheitssysteme GmbH