System Sensor D2 - Manual (Page 3)

width of the duct. If there are more than 2 holes in the section of the
tube extending out of the duct, select a shorter tube using Table 1. Oth-
erwise, trim the tube to leave approximately 1-2 inches extending out-
side the duct. Plug the end with the end cap and tape closed any holes
in the protruding section of the tube. Be sure to seal the duct where the
tube protrudes.
fIgURE 4:
DETECTOR 3 /
4
˝
HOLE
12˝
1 /
4
˝
2˝
H0215-00
NOTE: Air currents inside the duct may cause excessive vibration, especially
when the longer sampling tubes are used. In these cases, a 3 inch 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 mounting
technique, drill a 1 to 1
1 ⁄
4
inch hole where the flange will be used.
[6.3] MODIfICATIONS Of SAMPLINg TUBES
There may be applications where duct widths are not what is specified for the
installation. In such cases, it is permissible to modify a sampling tube that is
longer than necessary to span the duct width.
Use a 0.193 inch diameter (#10) drill and add the appropriate 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 in-
tended as a permanent substitute for ordering the correct length tubes.
[6.4] REMOTE SAMPLINg TUBE INSTALLATION
The detector arrangement can also incorporate the remote mounting of the
sampling tube and/or exhaust tube. In this case both the detector, sampling
tube and exhaust tube (if included) should be rigidly mounted to withstand
the pressure and vibrations caused by the air velocity. The location of the
detector’s sampling tube should be such that there is uniform airflow in the
cross section area.
The pressure differential across the sampling and exhaust ports in the detec-
tor housing shall be verified to be between .01 and 1.11 inches of water. Do
so by measuring the pressure difference between the inlet and outlet ports
on the detector housing using a manometer as described in Section 10.4.4 of
this manual.
[7] MEASUREMENT TESTS
[7.1] AIR fLOw
The D2 is designed to operate over an extended air speed range of 100 to
4000 FPM. To verify sufficient sampling of ducted air, turn the air handler on
and use a manometer to measure the differential pressure between the two
sampling tubes. The differential pressure should measure at least 0.01 inches
of water and no more than 1.11 inches of water. Because most commercially
available manometers cannot accurately measure very low pressure differen-
tials, applications with less than 500 FPM of duct air speed may require one
of the following: 1) the use of a current-sourcing pressure transmitter (Dwyer
Series 607) per Section 7.2; or 2) the use of aerosol smoke per section 10.4.4.
[7.2] LOw fLOw AIR fLOw TEST USINg DwyER SERIES 607 DIf-
fERENTIAL PRESSURE TRANSMITTER
Verify the air speed of the duct using an anemometer. Air speed must be at
least 100 FPM. Wire the Dwyer transmitter as shown in Figure 5. Connect the
leads of the meter to either side of the 1000Ω resistor. Allow unit to warm up
for 15 seconds. With both HIGH and LOW pressure ports open to ambient air,
measure and record the voltage drop across the 1000Ω resistor (measurement
1), 4.00 volts is typical. Using flexible tubing and rubber stoppers, connect the
HIGH side of the transmitter to the sampling tube of the duct smoke detec-
[6] SAMPLINg TUBE INSTALLATION
[6.1] SAMPLINg TUBE SELECTION
The sampling tube must be purchased separately. Order the correct length,
as specified in Table 1, for width of the duct where it will be installed. It is
recommended that the sampling tube length extend at least
2 /
3
across the duct
width for optimal performance.
TABLE 1. SAMPLINg TUBES RECOMMENDED fOR
DIffERENT DUCT wIDThS:
Outside Duct Width
Sampling Tube
Recommended*
Up to 1 ft. DST1
1 to 2 ft. DST1.5
2 to 4 ft. DST3
4 to 8 ft. DST5
8 to 12 ft. DST10 (2-piece)
*Must extend a minimum of 2 /
3
the duct width
The sampling tube is always installed with the air inlet holes facing into the
air flow. To assist proper installation, the tube’s connector is marked with an
arrow. Make sure the sampling tube is mounted so that the arrow points into
the airflow as shown in Figure 3. 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 3. The sampling tube and exhaust tube
can be mounted in either housing connection as long as the exhaust tube is
mounted downstream from the sampling tube.
fIgURE 3. AIR DUCT DETECTOR SAMPLINg TUBE:
SAMPLING TUBE ENDCAP
ARROW MUST FACE
INTO AIR FLOW
AIR FLOW
DIRECTION
H0551-00
CAUTION: The sampling tube end cap, included with the detector, is criti-
cal to proper operation of the duct smoke detector. The end cap is needed to
create the proper air flow to the sensor of the duct smoke detector. Once any
sampling tube length adjustments are made, plug the end of the sampling tube
with the provided end cap.
A plastic exhaust tube is included with the unit to be installed if needed. In-
stall into the housing connection that is downstream from the sampling tube
connection. The exhaust tube can be installed from the front of the detector
or the back. A longer 1 foot exhaust tube, model ETX is available as an acces-
sory in cases where the molded exhaust tube does not extend at least 2 inches
into the duct.
[6.2] SAMPLINg TUBE INSTALLATION
1. For tubes shorter than the width of the duct, slide the sampling tube,
with installed end cap, into the housing connection that meets the air-
flow first. Position the tube so that the arrow points into the airflow as
shown in Figure 3. Per NFPA sampling tubes over 3 feet long should be
supported at the end opposite of the duct detector. In ducts wider than 8
feet, work must be performed inside the duct to couple the other section
of the sampling tube to the section already installed using the
1 /
2
inch
conduit fitting supplied. Make sure that the holes on both sections of the
air inlet sampling tube are lined up and facing into the airflow.
2. For tubes longer than the width of the air duct, the tube should extend
out of the opposite side of the duct. Drill a 3 /
4
inch hole in the duct op-
posite the hole already cut for the sampling tube. Ensure that the sam-
pling tube is angled downward from the duct smoke detector to allow for
moisture drainage away from the detector. The sampling tube should be
angled at least 1/4” downward for every 12” of duct width per Figure 4.
There should be 10 to 12 holes spaced as evenly as possible across the
SS-300-014 3 I56-3050-004R