A. Installation for Ducts Less Than 8 Feet Wide
1.
If the inlet tube is longer than the width of the air duct,
drill a 3/4-inch hole in the duct directly opposite the
hole already cut for the inlet tube.
If the inlet tube is shorter than the width of the air duct,
install the end cap into the inlet tube as shown in Figure
3.
2. Slide the inlet tube into the bushing located in the center
of the duct housing. Position the tube so that the arrows
point into the air flow.
3. Secure the tube flange to the housing bushing with the
two #6 self-tapping screws.
4. For tubes longer than the width of the air duct, the tube
should extend through the opposite side of the duct. If
there are more than 2 holes in the section of the tube
extending from the duct, select a different tube length
using Table 1. Otherwise, trim the end of the tube pro-
truding through the duct so that 1 to 2 inches of the tube
extends outside the duct. Plug this end with the tube
end plug and tape closed any holes in the protruding
section of the tube. Be sure to seal the duct when the
tube protrudes.
5. Any inlet tube over 3 feet long must be supported on the
opposite side of the duct detector 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.
B. Installation for Ducts More Than 8 Feet Wide
NOTE:
To install inlet tubes in ducts more than 8 feet
wide, work must be performed inside the air duct.
Sampling of air in ducts wider than 8 feet is accom-
plished by using the ST-10 inlet sampling tube.
AIR FLOW
DIRECTION
DETECTOR
HOUSING
DOTS INDICATE POSITION OF
SAMPLING TUBE HOLES
AIR FLOW
DIRECTION
DETECTOR
HOUSING
INLET
TUBE
EXHAUST
TUBE
AIR FLOW
DIRECTION
EXHAUST
TUBE
INLET
TUBE
INLET
TUBE
EXHAUST
TUBE
DETECTOR
HOUSING
AIR FLOW
DIRECTION
EXHAUST
TUBE
INLET
TUBE
DETECTOR
HOUSING
A.
B.
C.
D.
HORIZONTAL MOUNTING OF HOUSING
VERTICAL MOUNTING OF HOUSING
Figure 4. Tube mounting configurations with varying air flow direction and orientation of detector housing.
Vertical as well as horizontal mounting is acceptable.
H0109-00
Install the inlet tube as follows:
1. Drill a 3/4-inch hole in the duct directly opposite the
hole already drilled for the inlet tube.
2. Slide the inlet tube into the bushing located in the center
of the duct housing. Position the tube so that the arrows
point into the air flow. Secure the tube flange to the
housing bushing with the two #6 self-tapping screws.
3. From inside the duct, couple the other section of the
inlet tube to the section already installed using the 1/2-
inch conduit fitting supplied. Make sure that the holes
on both of the air inlet tubes are lined up facing the
direction of air flow.
4. Trim the end of the tube protruding through the duct so
that 1 to 2 inches of the tube extends outside the duct.
Plug this end with the tube end plug and tape closed any
holes in the protruding section of the tube. Be sure to
seal the duct when the tube protrudes.
5. Any tube (over 3 feet long) that doesn’t protrude through
the duct (on the side opposite the housing) must be sup-
ported by other means.
NOTE:
An alternate method to using the ST-10 is to use
two ST-5 inlet tubes. Remove the flange from one
of the tubes and install as described above. After
the installation, use electrician’s tape to close off
some of the sampling holes so that there are a total
of 12 holes spaced as evenly as possible across the
width of the duct.
NOTE:
Air currents inside the duct may cause excessive
vibration. This vibration can slowly open the
seal around the tube and permit air to escape. To
prevent this from occurring, a 3-inch floor flange,
D500-07-00
4
I56-432-11R
