[5.1] Verify Duct Air Flow Direction And Velocity
Model DH400ACDCP detectors are designed to be used in
air handling systems having air velocities of 500 to 4000
feet per minute. Be sure to check engineering specifications
to ensure that the air velocity in the duct falls within these
parameters. If necessary, use a velocity meter to check the
air velocity in the duct.
[5.2] Drill The Mounting Holes
Remove the paper backing from the mounting template
supplied. Affix the template to the duct at the desired
mounting location. Make sure the template lies flat and
smooth on the duct. Center punch holes A and B. Drill the
holes as indicated on the template. Slide the two speed
nuts over the two small holes (hole A) next to the sampling
tube bushing holes (hole B) previously drilled in the duct.
(See
Figure 3
.)
[5.3] 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
mounting holes. Put one
5
/
16
˝ 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
[5.4] 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 ex-
haust tube is molded into the base of the duct housing, and
the A2440-00 Exhaust Tube Extension is available as an ac-
cessory in those cases where the molded exhaust port does
not extend at least 2˝ 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
[5.4.1] 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
˝ 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. Po-
sition 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 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 ex-
posed to the air stream.
D400-13-00
3
I56-0555-010R
