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4.0 Sample Tubes
The sample tubes must extend across the width of the
duct. The three sizes of sample tubes are:
•
D344-1.5 (1.5 ft [0.46 m])
•
D344-3 (3 ft [0.91 m])
•
D344-5 (5 ft [1.52 m])
Sample tubes include an end plug that must be
installed in the narrow end of the tube (Figure 1).
Figure 1:
D344-1.5 Sample Tube
1 - Set screw
You can combine or cut sample tubes to make
different lengths. A sample tube can be a maximum
length of
10 ft (3 m) or a minimum length of 1 ft (0.3 m). For
example, you can join a 3 ft (1 m) and a 5 ft (1.5 m) to
make an 8 ft (2.4 m) sample tube.
To combine sample tubes:
1. Remove the roll pin and set screw from one of the
sample tubes.
2. Remove the end plug from the other sample tube.
3. Push the flared end over the sample tube you want
to lengthen.
4. Align the holes, insert the set screw, and reinstall
the end plug. For example, if you want a 7 ft (2 m)
sample tube, combine a 3 ft (1 m) sample tube and
a 5 ft (1.5 m) sample tube. Then cut 1 ft (0.3 m)
from the narrow end to get the necessary length.
Sample tubes must have at least 12
sample holes within the duct. Do not cut
sample
tube to less than 12 sample holes.
Sample tubes over 3 ft (1 m) must be supported at
the end opposite the duct detector. The support
hole should be 1 in. to 2 in. (2.5 cm to 5 cm) below
the entry hole to allow for possible moisture
drainage (Figure 2).
Bosch Security Systems, Inc. | 7/09 | F01U071685-06
2
1
2 - End plug
D340 | Installation Guide | 4.0
Figure 2:
Support Hole Position
1 - 1 in. to 2 in. (2.5 cm to 5 cm)
5. Seal the gap between duct and sample tube. You
can remove up to 6 in. (15 cm) from the D344-1.5
for 1 ft (0.3 m) duct installations.
When using the D344-1.5 in installations where the
duct width is between 12 in. (31 cm) and 18 in.
(46 cm), cover some of the sample holes. The
D344-1.5 has 19 sample holes, but only 12 are
required for normal installations. Depending on
the length, you might have to cover some of the
holes with duct tape. Use even spacing when
covering the sample holes to allow an even sample
across the width of the duct. Refer to Figure 3.
Figure 3:
D344-1.5 Sample Tube
1 - Place tape over these sample holes
Sample Tubes
1
1
3
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