P/N 315-049708FA-4
4
2) To minimize the impact of air turbulence and stratification
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 8741, 8742 or 8743 duct smoke 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.
7) To prevent false alarms, the duct detector should not be
mounted in areas of extreme high or low temperatures,
in areas where high humidity exists, or in areas where
the duct may contain gases or excessive dust.
Duct Preparation
The 8741, 8742 and 8743 Housings come with an installation
kit that contains the following items:
• Short return (outlet) sampling tube
• Stopper
• Two #12 x
3
/
4
” sheet metal screws
• Mounting template (packaged separately)
Remove mounting template from the installation kit. Remove
paper backing from the mounting template and affix it to the
duct at the desired location. Using the template as a guide,
drill (2) mounting holes, 3/32" (2.5mm) for the #12 X
3
/
4
”
sheet metal screws packaged in the installation kit. Drill or
