Technical Bulletin
SuperDuct Conventional Two-Wire Duct Smoke Detector
5
6 to 10 duct widths
1 duct
width
Bend or other
obstruction
Airflow
•
For detection of smoke in the supply air system, install
the duct smoke detector in the supply air duct at a point
downstream from the supply fan and air filters
•
For detection of smoke in the return air system, install the
duct smoke detector in the return air duct at a point before
the return air stream is diluted by outside air
•
Extend sampling tubes at least two-thirds across the width
of the HVAC duct with the air inlet holes pointed into the
direction of airflow
•
Support sampling tubes longer than 36 inches at the end
farthest from the detector to avoid excessive vibration
•
Upon installation, perform an air pressure differential test
to ensure the duct smoke detector is capable of sampling
the air stream
Installation sequence
The steps required to install the duct smoke detector are
described below. The order in which these steps are performed
may vary depending installation requirements.
1. Verify the duct airflow direction and velocity.
2. Drill the mounting holes using the drill template provided.
3. Assemble
the
detector.
4. Mount the detector on the HVAC duct.
5. Verify the detector pressure differential.
Installing the sampling tube from the front of
the detector
The sampling tube is normally installed from the rear, but it
can also be installed from the front of the detector as shown in
Figure 4. This method requires that you remove the detector
cover.
Note:
Sampling tubes are ordered separately.
Sampling tube
(fully assembled)
Detector
Sampling tube
connector
Figure 4: Sampling tube installed from the front
Supporting sampling tubes greater than 36
inches long
NFPA requirements state that sampling tubes must extend at
least two-thirds of the way into the duct and those that are
greater than 36 inches long must be supported at both ends. To
meet this requirement, drill a 3/4-inch hole on the opposite
side of the duct. Extend the sampling tube through the hole as
shown in Figure 5. Cut off the excess sampling tube and seal
the opening around the tube with an approved sealant.
Note:
For ducts greater than or equal to 36 inches, use the next
longest sampling tube available.
HVAC
duct
Sampling
tube
Exhaust tube
Plug
Detector
Sealant
Airflow
36
in
≥
Figure 5: Installation with sampling tubes longer than the width
of the duct
