[5.4.2] 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 accomplished by using the ST-10
inlet sampling tube. If the tube is shorter than the width of
the air duct, install the end plug into the inlet tube as shown
in
Figure 4
and support the end opposite the duct detector.
Install the inlet tube as follows:
1. Drill a
3
/
4
˝ hole in the duct directly opposite the hole
already drilled for the inlet tube.
2. Slide the inlet tube with the flange into the centermost
housing bushing. Position the tube so that the arrows
point into the air flow. Secure the tube flange to the
housing bushing with 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
˝
conduit fitting supplied. Make sure that the holes on
both of the air inlet tubes are lined up and facing into
the air flow.
Figure 4. Air duct detector inlet sampling tube:
INLET
TUBE
END
PLUG
AIR HOLES
ARROWS
MUST FACE
INTO AIR FLOW
AIR FLOW DIRECTION
FLANGE
H0108-00
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 5. Tube mounting configurations with varying air flow direction:
H0109-00
4. Trim the end of the tube protruding through the duct so
that 1˝ to 2˝ of the tube extend outside the duct. Plug
this end with the end plug and tape closed any holes in
the protruding section of the tube. Be sure to seal the
duct when the tube protrudes.
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
electrical tape to close off some of the sampling holes so
that there is a total of 10 to 12 holes spaced as evenly as
possible across the width of the duct.
Air currents inside the duct may cause excessive vibra-
tion, especially when the longer sampling tubes are used.
In these cases a 3˝ floor flange (available at most plumb-
ing supply stores) may be used to fasten the sampling tube
to the other side of the duct. When using the flange/con-
nector mounting technique, drill a 1˝ to 1
1
/
4
˝ hole where
the flange will be used.
D400-13-00
4
I56-0555-010R
