MECHANICAL INSTALLATION
LOCATION PREREQUISITES
This guideline contains general information on duct smoke detector
installation, but does not preclude the NFPA and/or ICC
documents listed.
N
o responsibility
is assumed
for
the
improper instal
lation of the
duct detectors. To determine the correct
installation position for an SM-501 Series duct smoke detector, the
following factors must be considered.
1.
A uniform non-turbulent (laminar) airflow between 500 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 stratification on
performance, a duct smoke detector should be located as far as
possible downstream from any obstruction (i.e. deflector plates,
elbows, dampers, etc.). In all situations, confirmation of velocity and
pressure differential within specifications is required.
The pressure differential between the input sampling
(high pressure) tube and exhaust (low pressure) tube
for the SM-501 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.
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.
SAMPLING TUBE ASSEMBLY
Sampling tubes are to be ordered separately in one of four standard
lengths.
STS-1.0
For duct widths of 6” to 1.0’
STS-2.5
For duct widths of 1.0’ to 3.0’
STS-5.0
For duct widths of 3.0’ to 5.0’
STS-10.0
For duct widths of 5.0’ to 10.0’
FAST TUBE
Sectional Tube for duct widths up to 8.0’
Standard sampling tubes are steel tubes with air intake holes drilled
the entire length of the tube. FAST Tubes are a recognized plastic with
an open slot along the length. These tubes can be cut to length and
must span at least 80% of the duct width (spanning the entire width is
suggested).
Sampling tubes over 3ft must be supported on the opposite side of the
duct. To ensure correct operation of the sampling tube, the red end cap
(red stopper in installation kit) must be inserted in the end of the air
intake. For custom duct widths, always use the next longest standard size
and cut down to the exact requirement.
Once the airflow direction has been determined, insert the inlet and
exhaust tubes into the sampling tube connectors fitted to the back of
the duct smoke detector which are equipped with set screws. These
connectors will allow the tubes to be correctly orientated and secured
by tightening the set screw. Ensure air intake sampling tube is positioned
so that the inlet holes (or FAST Tube slot) directly face the airflow.
DUCT PREPARATION
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 (4) mounting holes
(3/32” diam.) for the # 12 X 1/2” sheet metal screws packaged in the
installation kit. Drill or punch (2) 1 3/8” holes for inlet sampling and
exhaust tubes, using the template as a guide. Clean all holes.
MOUNTING
After securing the sampling and exhaust tubes to the duct smoke unit,
(or initially placing the tubes through the 1 3/8” holes drilled or punched
in the HVAC duct to accept the inlet sampling and exhaust tubes and
then attaching them to the duct unit), hold the duct unit assembly in
position and use (4) # 12 X 1/2” sheet metal screws (packaged in the
installation kit) to secure the duct smoke detector to the HVAC duct
sheet metal.
AIR SAMPLING VERIFICATION
To ensure correct operation of the duct unit use a Magnehelic differential
pressure gauge, Dwyer 2000 or 4000 Series (or equivalent) to determine
the differential pressure between the inlet (high side) and exhaust (low
side) tubes. The differential pressure between the two tubes should be
greater than 0.01 inches of water and less than 1.2 inches of water.
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150303
Specifications subject to change without notice. | INST APD0191 D140113 | USA 150303 | Page 3 of 7
12700 Stowe Drive, Suite 100, Poway, CA 92064 | Ph: (858) 578.7887 & (888) GO.IN
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SM-501 – Installation
