Circuit and System Grounding
250.32 Buildings or Structures Supplied with
This subsection added a new requirement
and it reads:
(B) Grounded Systems.
(2) Grounded (neutral) Conductor. Where
(1) an equipment grounding conductor is not run with the supply
to the building or structure, and (2) there are no continuous
metallic paths bonded to the grounding system in both buildings
or structures involved, and (3) ground-fault protection of equipment
has not been installed on the common ac service, the grounded
circuit conductor run with the supply to the building or structure
shall be connected to the building or structure disconnecting
means and to the grounding electrode(s) and shall be used for
grounding or bonding of equipment, structures, or frames required
to be grounded or bonded.
The size of the grounded conductor shall
not be smaller than the larger of:
(1) That required by 220.22 (maximum unbalanced neutral load),
(2) That required by 250.122 (equipment grounding conductor size).
changes to this section should make it much easier to understand
the grounding and bonding requirements contained in Article 250.
The most significant change includes the explanation that, in
order to clear a fault, the fault current must have an effective
low-impedance ground-fault current path back to the grounded (neutral)
terminal at the power supply.
an equipment grounding conductor is not run to a separate building
or structure, the grounded (neutral) conductor must be used to
provide the effective fault current path required to clear any
line-to-case faults in addition to carrying any unbalanced neutral