P/N 315-049708-5
Siemens Industry, Inc.
Building Technologies Division
4
MOUNTING THE AIR DUCT HOUSING
Location on Duct System
This guideline contains general information on duct smoke
detector installation, but does not preclude the NFPA
documents listed. Siemens Industry, Inc. assumes no
responsibility for improperly installed duct detectors. To
determine the correct installation position for an AD2 Series
duct smoke detector, the following factors must be consid-
ered.
1) A uniform non-turbulent (laminar) airflow between 100 ft/
min. to 4,000 ft/min. must be present in the HVAC duct.
To determine duct velocities, examine the engineering
specifications that define the expected velocities or use
an Alnor model 6000AP velocity meter (or equivalent).
2) To minimize the impact of air turbulence and stratifica-
tion on performance, a duct smoke detector should be
located as far as possible downstream from any obstruc-
tion (i.e. deflector plates, elbows, dampers, etc.). In all
situations, confirmation of velocity and pressure differen-
tial within specifications is required.
The pressure differential between the input sampling
(high pressure) tube and outlet (low pressure) tube for
the AD2 Series smoke duct detector should be greater
than 0.01 inches of water and less than 1.2 inches of
water.
3) Identify a code compliant location (supply or return side,
or both) for the installation of the duct unit that will
permit easy access for viewing and serviceability.
4) When installing on the return side, install duct units prior
to the air being exhausted from the building or diluted
with outside “fresh” air.
5) When installing duct smoke units downstream of filters,
fires occurring in the filters will be detected, but if the
filters become blocked, insufficient air flow through the
duct unit will prevent the correct operation of the duct
detector. Duct units installed in the supply air side may
monitor upstream equipment and/or filters.
6) Where possible, install duct detectors upstream of air
humidifiers and downstream of dehumidifiers.
