[5.4.2] Installation For Ducts More Than 8 Feet Wide
NOTE:
To install sampling 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. 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 and support the end opposite the duct
smoke detector.
Install the inlet tube as follows:
1. Drill a
3
⁄
4
inch hole in the duct directly opposite the hole
already drilled 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 for moisture drainage.
2. Slide the sampling tube with the flange into the housing
bushing that meets the air flow first. Position the tube so
that the arrow points 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 sections of the
sampling tube to the section already installed using the
1⁄2 inch conduit fittings supplied. Make sure that the
holes on both of the air inlet tubes are lined up and fac-
ing into the air flow.
4. 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 cap 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 sampling 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 are a
total of 10 to 12 holes spaced as evenly as possible
across the width of the duct.
NOTE:
Air currents inside the duct may cause excessive
vibration, especially when the longer sampling
tubes are used. In these cases a 3” floor flange
(available at most plumbing supply stores) may be
used to fasten the sampling tube to the other side of
the duct. When using the flange/connector mount-
ing technique, drill a 1 inch to 1
1
⁄
4
inch hole where
the flange will be used.
[5.4.3] Modifications of Sampling Tubes
There may be applications where duct widths are not what
is specified for the installation. In such cases, it is permis-
sible to modify a sampling tube that is longer than neces-
sary to span the duct width.
Use a 0.193-inch diameter (#11) drill and add the appro-
priate number of holes so that the total number of holes
exposed to the air flow in the duct is 10 to 12. Space the
additional holes as evenly as possible over the length of the
tube.
NOTE:
This procedure should only be used as a temporary
fix. It is not intended as a permanent substitute for
ordering the correct length tubes.
[5.5] Install The Filters
To install the sampling tube filters, simply push the filters
into the sampling and exhaust tube holes, as shown in
Figure 6. If a metal sampling tube is used, install the filters
over the tube ends.
Figure 6. Sampling tube filter installation:
CAUTION
Filters require periodic cleaning or replacement, depend-
ing on the amount of dust and dirt accumulated. Visually
inspect the filters at least quarterly; inspect them more
often if the dust accumulation warrants it. See Section [6]
for more information. Replacement filters can be ordered
from System Sensor, 3825 Ohio Ave., St. Charles, IL 60174.
(Exhaust tube/intake tube filter P/N F36-09-11)
[5.6] Field Wiring
Installation Guidelines
All wiring must be installed in compliance with the
National Electrical Code and the local codes having juris-
diction. Proper wire gauges should be used. The conduc-
tors used to connect smoke detectors to control panels and
accessory devices should be color-coded to prevent wiring
mistakes. Improper connections can prevent a system from
responding properly in the event of a fire.
For signal wiring, (the wiring between interconnected
detectors or from detectors to auxiliary devices), it is usu-
ally recommended that single conductor wire be no smaller
than 18 gauge. The duct smoke detector terminals accom-
modate wire sizes up to 12 gauge. The last foot of conduit
should be flexible conduit (available in electrical supply
houses), which facilitates easier installation and puts less
strain on the conduit holes in the housing. Solid conduit
connections may be used if desired.
D100-68-00 4 I56-1684-06R
A78-2691-00
Archived Document
