System Sensor DH400ACDCIHT - Manual (Page 3)

[4.3] Secure The Detector Housing To The Duct
Remove the duct housing cover. Slide the foam gaskets over
the tube bushings as shown in Figure 2. Make sure the two
small holes in the gaskets line up with the two base mount-
ing holes. Put one 5/16-inch O-ring over each of the two
#10 sheet metal screws. Use the two sheet metal screws to
screw the detector housing to the duct. CAUTION: Do not
overtighten the screws.
Figure 2. Installation of foam gaskets over sampling
tube bushings:
SCREW HOLES FOR ATTACHING
DETECTOR HOUSING TO DUCT
FOAM GASKETS
EXHAUST TUBE
(EXTENSION BUSHING)
DUCT DETECTOR
HOUSING
O-RINGS
MOUNTING
SCREWS
INLET SAMPLING
TUBE BUSHING
H0238-00
Figure 3. Speed nut mounting location:
HOLE B
HOLE A
DUCT
WALL
SPEED
NUT
H0116-00
[4.4] Install The Inlet
The inlet tube (shown in Figure 4) is identified by a series
of air inlet holes on the tube. This tube must be purchased
separately. Order the correct length, as specified in Table 1,
for width of the duct where it will be installed. The exhaust
tube is molded into the base of the duct housing, and the
A2440-00 Exhaust Tube Extension is available as an acces-
sory in those cases where the molded exhaust port does not
extend at least 2 inches into the duct.
The inlet tube is always installed in the centermost hous-
ing bushing, with air inlet holes facing into the air flow.
To assist proper installation, the tube’s mounting flange is
marked with arrows. Make sure the inlet tube is mounted
so that the arrows point into the air flow. Figure 5 shows
the various combinations of tube mounting configurations
with respect to air flow.
Mounting the detector housing in a vertical orientation
is acceptable, provided that the air flows directly into the
sampling tube holes as indicated in Figure 4.
Table 1. Inlet tubes required for different duct
widths:
Outside Duct Width Inlet Tube Required
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
[4.4.1] Installation For Ducts Less Than 8 Feet Wide
1. If the 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 tube is shorter than
the width of the air duct, install the end plug into the
inlet tube as shown in Figure 4. Sampling tubes over 3
ft. long must be supported at the end opposite the duct
detector.
2. Slide the tube into the centermost housing bushing.
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 inches 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.
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.
[4.4.2] 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.
D400-64-00 3 I56-991-08R