S4-34760_Venturi-Air Duct Kit
6
4188-971_issue 1_07/09_duct sensor kit
2.2 Calculation of upstream and downstream distances
Air duct with circular cross-section
Air duct with rectangular cross-section
d
h
=
2 x H x B
H + B
d
h
= D
B
H
D
In order to prevent incorrect measurements the air through the duct detector should be in the same direction as
the air flow through the duct. For applications with a detector mounting close to reducing dampers and
regulating flaps, filter units or bends, the following minimum distances must be observed:
upstream
Î
at least 3 x the nominal diameter of the air duct
downstream
Î
at least 5 x the nominal diameter of the air duct
Fig. 3: Air duct detector after a bend in the duct system and downstream from an air intake (Example)
www.acornfiresecurity.com
www.acornfiresecurity.com
