Figure 3. Installation of foam gaskets over sampling
tube bushings:
H0107-00
[5.4] Sampling Tube Installation for Ducts Greater
Than 1
1
⁄
2
Feet Wide
The sampling tube is identified by a series of air inlet holes
on the tube. A plastic tube is included for ducts up to 18
in width. All other lengths must be purchased separately.
Order the correct length, as specified in Table 1, for width
of the duct where it will be installed. It is recommended
that the sampling tube length extend at least two-thirds
across the duct width for optimal performance. The
exhaust tube is molded onto the base of the duct housing,
and the A2440-00 Exhaust Tube Extension is available as
an accessory in those cases where the molded exhaust port
does not extend at least 2 inches into the duct.
The sampling tube is always installed with the air inlet
holes facing into the air flow. To assist proper installation,
the tube’s mounting flange is marked with an arrow. Make
sure the sampling tube is mounted so that the arrow points
into the air flow (see Figure 4). Figure 5 shows the various
combinations of tube mounting configurations with respect
to air flow. Mounting the detector housing in a vertical ori-
entation is acceptable, provided that the air flows directly
into the sampling tube holes as indicated in Figure 4.
Table 1. Sampling tubes recommended for different
duct widths:
Outside Duct Width Sampling Tube Recommended*
1 to 2 ft. ST-1.5
2 to 4 ft. ST-3
4 to 8 ft. ST-5
8 to 12 ft. ST-10
*Must extend a minimum of two-thirds the duct width.
[5.4.1] Installation For Ducts Greater Than 1
1
⁄
2
Feet
But Less Than 8 Feet Wide
1.
If the tube is longer than the width of the air duct,
drill
a
3
⁄
4
” hole in the duct opposite the hole already cut for
the sampling tube. Make sure the hole is
1
” to
2
” below
the inlet hole on the opposite side of the duct to allow
moisture drainage away from the detector.
If the tube is
shorter than the width of the air duct,
install the end cap
into the sampling tube as shown in Figure 4. Sampling
tubes over 3 ft. long must be supported at the end oppo-
site the duct smoke detector.
2. Slide the tube into the housing bushing that meets the
air flow first. Position the tube so that the arrows point
into the air flow.
3. Secure the tube flange to the housing bushing with two
#6 self-tapping screws.
4. For tubes longer than the width of the air duct, the tube
should extend out of the opposite side of the duct. If
there are more than 2 holes in the section of the tube
extending out of the duct, select a different length using
Table 1. Otherwise, trim the end of the tube protruding
through the duct so that 1” to 2” of the tube extend out-
side the duct. Plug this end with the end cap and tape
closed any holes in the protruding section of the tube.
Be sure to seal the duct where the tube protrudes.
NOTE:
The sampling tube end cap is critical to the proper
operation of the duct smoke detector. The end cap
is needed to create the proper air flow to the sensor
of the duct smoke detector.
Figure 4. Air duct detector sampling tube:
H0108-02
Figure 5. Tube mounting configurations with varying
air flow direction:
AIR FLOW
DIRECTION
DETECTOR
HOUSING
DOTS INDICATE POSITION OF
SAMPLING TUBE HOLES
AIR FLOW
DIRECTION
DETECTOR
HOUSING
SAMPLING
TUBE
EXHAUST
TUBE
AIR FLOW
DIRECTION
EXHAUST
TUBE
SAMPLING
TUBE
SAMPLING
TUBE
EXHAUST
TUBE
DETECTOR
HOUSING
AIR FLOW
DIRECTION
DETECTOR
HOUSING
A.
B.
C.
D.
HORIZONTAL MOUNTING OF HOUSING
VERTICAL MOUNTING OF HOUSING
WARNING
In no case should more than 2 air inlet holes be cut off the
tube. There must be a minimum of 10 holes in the tube
exposed to the air stream.
D100-68-00 3 I56-1684-06R
SCREW HOLES FOR
ATTACHING HOUSING
TO DUCT WORK.
SAMPLING
TUBE
END CAP
AIR HOLES
ARROW
MUST FACE
INTO AIR FLOW
AIR FLOW DIRECTION
FLANGE
NOTE: Only metal sampling tubes may be used on ori-
entations C and D.
H0109-01
Archived Document
