Where it is necessary to run communication cables
wall space of 1800 mm (6 feet) on all sides where splices
parallel to power cables, two separate systems must be
are to be racked. Manholes shall be provided with pulling
provided with separate manhole compartments. The
eyes, sumps and grounding provisions as necessary.
same holds true for normal and emergency power cables.
Stubs. Minimum of two spare stubs shall be provided
Ductbanks shall be spaced at least 300 mm (1 foot) apart.
(to maintain a square or rectangular ductbank) so that
Site entrance facilities including ductbanks and manholes
the manhole wall will not need to be disturbed when
must comply with requirements stated in Federal
a future extension is made. Stubs for communications
Information Processing Standard 175: Federal Building
manholes must be coordinated with GSA Federal
Standard for Telecommunication Pathways and Spaces
Technology Service.
(see also EIA/TIA [Electronic Industrial Association/
Telecommunication Industry Association] Standard
Handholes may be used for low voltage feeders (600V
568-A and related bulletins).
and below), branch circuits or communications circuits.
They must be not less than 1200 mm (4 feet) in depth,
Where redundant service is required (power,
1200 mm (4 feet) in length, and 1200 mm (4 feet) in
communications and/or life safety) systems alternate,
width with a standard manhole cover and sump of the
diverse paths and separation shall be maintained.
same type provided for manholes. Generally, at least four
Duct Sizes. Ducts shall be sized as required for the
racks shall be installed. Where more than two splices
number and size of cables. All ducts for medium voltage
occur (600V feeders only), a 1800 mm (6 feet) by 1800
services shall be a minimum of 100 mm (4 inch). Inner
mm (6 feet) by 1800 mm (6 feet) manhole shall be
ducts must be provided inside communication ducts
required.
wherever fiber optic cables will be used. A sufficient
Communications Service Coordination. The
number of spare ducts shall be included for planned
Telecommunications Design professional shall contact
future expansion; in addition, a minimum of 25 percent
the local telephone company and coordinate with the
spare ducts must be provided for unknown future
client agency to determine the size and location of the
expansion.
incoming service and to determine the enclosure and
pathway requirements for telecom systems. The Scope
Manholes. Manholes shall be spaced no farther than 150
of Services varies with each project; it includes as a
m (500 feet) apart for straight runs. The distance between
minimum the design of the infrastructure (pathway and
the service entrance and the first manhole shall not exceed
enclosure) and may include full design and specification
30 m (100 feet). Double manholes shall be used where
of the telecommunications system. The design
electric power and communication lines follow the same
professional shall contact the local telecommunications
route. Separate manholes shall be provided for low and
providers early in the project.
medium voltage systems. Manholes shall have clear
interior dimensions of no less than 1800 mm (6 feet) in
Provision shall also be made to provide cable television
depth, 1800 mm (6 feet) in length, and 1800 mm (6 feet)
(CATV) service to the facility. Typically, CATV service is
in width with an access opening at the top of not less
independent from other communications services.
than 750 mm (30 inches) in diameter. Medium voltage
manholes shall be sized in accordance with Utility
Company requirements. Manholes must have a minimum
179
ELECTRICAL
ENGINEERING
6.4
Utility Coordination
Revised March 2005 PBS-P100
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