6.14 Grounding Systems
Separate equipment ground conductors. Comply with
NFPA 70, Article 250, for types, sizes, and quantities of
equipment grounding conductors, unless specific types,
larger sizes, or more conductors than required by NFPA
General. Grounding systems shall be designed to
70 are indicated.
coordinate with the specific type and size of the electrical
distribution system, including the following applicable
Install insulated equipment grounding conductor with
generic types of grounding systems, or grounding
circuit conductors for the following items, in addition
components:
to those required by NEC:
Feeders and branch circuits
Lighting circuits
Receptacle circuits
Single-phase motor and appliance branch circuits
Three-phase motor and appliance branch circuits
Flexible raceway runs
Metal clad cable runs
Busway Supply Circuits. Install insulated equipment
grounding conductor from the grounding bus in the
switchgear, switchboard, or distribution panel to
equipment grounding bar terminal on busway.
Separately Derived Grounds. Good practice dictates
that, in order to minimize extraneous "noise" on certain
systems, particularly those in which harmonics are
generated, the specific system grounds shall be separated
prior to grounding at the service grounding electrode
or counterpoise.
Isolated Grounds. Isolated grounds are applied where the
equipment served may be particularly sensitive to external
interference from sources generating third harmonics and
higher. In these instances the grounds, beginning from
the panelboard ground and the grounding conductor
from the raceway to the grounding terminal at the
receptacle or outlet box, shall be electrically isolated from
the main grounding system. The isolated grounds shall
terminate at a common ground or counterpoise.
Metzenbaum Courthouse, Cleveland, OH
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6.14 Grounding Systems
Revised March 2005 PBS-P100
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