Planning For Forced Airflow - Bosch FCS-320-TM Operation Manual

50 en | Planning
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
ducts
The speed distribution in an air-conditioning duct appears as follows:
Figure 3.15 Speed distribution in an air-conditioning duct
Aspiration
To achieve optimal detection results, the pipe system should be organized into the areas v
to v
Installation location of the pipe system
The exhaust duct should be selected as the installation location of the pipe system, as far as
possible away from the sound dampers, air baffles and bends. The distance from obstacles of
this kind should be at least three times the smallest duct diameter.
If it is absolutely essential to install the pipe system directly behind air baffles, sound
dampers or bends; the main speed ranges must be monitored (see Figure 3.16/Figure 3.17).
F.01U.130.928 | 1.0 | 2009.11
Flow speed
Duct cross-section
Difference pressures along
the flow direction
v
4
v
3
v
2
v
1
3
Number of air sampling openings
4
a 4.4
Low-speed units
Maximum 6 to 10 m/s
Large
Low
1
v v v v
1 > 2 > 3 > 4
Operation Guide
FCS-320-TM Aspirating Smoke Detector
8
3.0
High-speed units
> 10 m/s
Small
Large
1 air-conditioning duct
V - V Flow speed
1 4
Bosch Sicherheitssysteme GmbH
1