NETA Level III
This question is incorrect and somewhat misleading. Technically the scenario described is not legal for new installs anyway per NEC 250.32 (B)(1) BUT there is an exception made for old installs... but you still cant connect the neutral...
question reads,
Building A is supplied with 120/240 volt single-phase power from Building B on the same property. Building B is supplied from a three-wire with two ungrounded conductors and one neutral without any metallic water pipe or other metal equipment connections to the building or equipment ground fault protection installed. The neutral conductor must:
Your Answer: Not be connected to a grounding electrode in the second building
Correct Answer: Be bonded to the disconnect enclosure in the second building and connected to a grounding electrode
Help: NFPA 70-2017 Section 250.32(D) This is a misinterpretation of that code, that section of the code that DOES mention connecting the neutral only applies to things that meet 250.30(A)(1), Exception No. 2. IE a separately derived system that meets a slew of other exceptions
250.32 Buildings or Structures Supplied by a Feeder(s) or
Branch Circuit(s).
(A) Grounding Electrode. Building(s) or structure(s)
supplied by feeder(s) or branch circuit(s) shall have a grounding
electrode or grounding electrode system installed in
accordance with Part III of Article 250. The grounding electrode
conductor(s) shall be connected in accordance with
250.32(B) or (C). Where there is no existing grounding electrode,
the grounding electrode(s) required in 250.50 shall be
installed.
Exception: A grounding electrode shall not be required where only a
single branch circuit, including a multiwire branch circuit, supplies the
building or structure and the branch circuit includes an equipment
grounding conductor for grounding the normally non–current-carrying
metal parts of equipment.
(B) Grounded Systems.
(1) Supplied by a Feeder or Branch Circuit. An equipment
grounding conductor, as described in 250.118, shall be run
with the supply conductors and be connected to the building
or structure disconnecting means and to the grounding electrode(
s). The equipment grounding conductor shall be used
for grounding or bonding of equipment, structures, or frames
required to be grounded or bonded. The equipment grounding
conductor shall be sized in accordance with 250.122. Any
installed grounded conductor shall not be connected to the
equipment grounding conductor or to the grounding electrode(
s).
Exception No. 1: For installations made in compliance with previous
editions of this Code that permitted such connection, the grounded
conductor run with the supply to the building or structure shall be
permitted to serve as the ground-fault return path if all of the following
requirements continue to be met:
(1) An equipment grounding conductor is not run with the supply to
the building or structure.
(2) There are no continuous metallic paths bonded to the grounding
system in each building or structure involved.
(3) Ground-fault protection of equipment has not been installed on
the supply side of the feeder(s).
If the grounded conductor is used for grounding in accordance with
the provision of this exception, the size of the grounded conductor shall
not be smaller than the larger of either of the following:
(1) That required by 220.61
(2) That required by 250.122
Exception No. 2: If system bonding jumpers are installed in accordance
with 250.30(A)(1), Exception No. 2, the feeder grounded circuit
conductor at the building or structure served shall be connected to the
equipment grounding conductors, grounding electrode conductor, and
the enclosure for the first disconnecting means.
(2) Supplied by Separately Derived System.
(a) With Overcurrent Protection. If overcurrent protection
is provided where the conductors originate, the installation
shall comply with 250.32(B)(1).
(b) Without Overcurrent Protection. If overcurrent protection
is not provided where the conductors originate, the installation
shall comply with 250.30(A). If installed, the supply-side
bonding jumper shall be connected to the building or structure
disconnecting means and to the grounding electrode(s).
(C) Ungrounded Systems.
(1) Supplied by a Feeder or Branch Circuit. An equipment
grounding conductor, as described in 250.118, shall be installed
with the supply conductors and be connected to the building
or structure disconnecting means and to the grounding
electrode(s). The grounding electrode(s) shall also be connected
to the building or structure disconnecting means.
(2) Supplied by a Separately Derived System.
(a) With Overcurrent Protection. If overcurrent protection
is provided where the conductors originate, the installation
shall comply with (C)(1).
(b) Without Overcurrent Protection. If overcurrent protection
is not provided where the conductors originate, the installation
shall comply with 250.30(B). If installed, the supply-side
bonding jumper shall be connected to the building or structure
disconnecting means and to the grounding electrode(s).
(D) Disconnecting Means Located in Separate Building or
Structure on the Same Premises. Where one or more disconnecting
means supply one or more additional buildings or
structures under single management, and where these disconnecting
means are located remote from those buildings or
structures in accordance with the provisions of 225.32, Exception
No. 1 and No. 2, 700.12(B)(6), 701.12(B)(5), or 702.12,
all of the following conditions shall be met:
(1) The connection of the grounded conductor to the
grounding electrode, to normally non–current-carrying
metal parts of equipment, or to the equipment grounding
conductor at a separate building or structure shall not
be made.
(2) An equipment grounding conductor for grounding and
bonding any normally non–current-carrying metal parts
of equipment, interior metal piping systems, and building
or structural metal frames is run with the circuit conductors
to a separate building or structure and connected to
existing grounding electrode(s) required in Part III of
this article, or, where there are no existing electrodes, the
grounding electrode(s) required in Part III of this article
shall be installed where a separate building or structure is
supplied by more than one branch circuit.
(3)The connection between the equipment grounding
conductor and the grounding electrode at a separate
building or structure shall be made in a junction box,
panelboard, or similar enclosure located immediately
inside or outside the separate building or structure.
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