Custom Search
|
|
|
||
 MIL-HDBK-1012/3
(5) With junction boxes and inserts level with the
floor and sealed to prevent the entry of moisture; and to
interface with wall outlets using a properly bonded and grounded
metallic conduit.
e) Cellular floor systems, unlike duct or trench
systems serve as a structural floor. The modules are composed of
a rolled top and a flat bottom and may be obtained in either
steel or concrete construction. Cellular floor planing must be
coordinated with the structural engineer. Cellular floor modules
are available in two-, three-, or four-cell configurations.
Various widths and depths are available to provide the
connectivity required. The RCDD must know the area to be served
and the number and diameter of the distribution cables to
determine the size and number of cells.
f) In accordance with NFPA 70, Articles 300, 356, and
358 and EIA/TIA 569 , par. 4, cellular floor systems shall be
installed:
(1) On 1.2 m to 1.5 m (4 in. to 5 in.) centers
with 50 percent of the modules allocated to cells and the
remaining modules non-cell (cells are 5 cm (2 ft.) wide and non-
cells are 5 cm to 7.5 cm (2 in. to 3 in.) wide);
(2)
With preset inserts on 60 cm (24 in.) centers;
(3) So that distribution cells run the length of
the building to reduce feeder duct length; and
(4) Maintaining a maximum 40 percent fill ratio;
BICSI also recommends an additional 15 percent reduction in fill
for each 90-degree bend. Consequently, a 40 percent fill with
two 90-degree bends would be reduced to a 28 percent fill.
1.5.1.2
Ceiling Distribution System. Ceiling distribution
systems are an inexpensive alternative in areas where non-locking
suspended ceiling tiles are to be installed and where local codes
allow loose cables to be run within ceilings. Within the ceiling
the cables may be supported by trays, rings, or hooks suspended
from the ceiling or wall structure. A zone distribution system
may be desirable whereby cables are run from the closet in
conduit or tray to the center of the area to be served and
distributed from there to the workstations using a suspension
arrangement as described above. Where possible wall jacks should
be stubbed up into the false ceiling, using appropriately sized
EMT, as close to the zone distribution point as practical. Par.
1.5.1.3.c) and EIA/TIA 569, Table 4.4-1 provide assistance in
sizing conduit.
32
|
 
|
|
|
||
