Do panelboards require a grounded conductor ?

[bigal1]

Thought I heard or read somewhere that all panelboards were required to have a grounded "neutral" conductor if available on the supply side. Anyone know if this is true?

 

[iwire]

You are close.

Apply it to just service enclosures and you are on the money.



2011 NEC

250.24 Grounding Service-Supplied Alternating-Current
Systems.

(C) Grounded Conductor Brought to Service Equipment.
Where an ac system operating at less than 1000 volts
is grounded at any point, the grounded conductor(s) shall
be routed with the ungrounded conductors to each service
disconnecting means and shall be connected to each disconnecting
means grounded conductor(s) terminal or bus. A
main bonding jumper shall connect the grounded conductor(
s) to each service disconnecting means enclosure. The
grounded conductor(s) shall be installed in accordance with
250.24(C)(1) through (C)(4).

 

[bigal1]

Thanks. That,s what I was looking for.

 

[jtinge]

Thought I heard or read somewhere that all panelboards were required to have a grounded "neutral" conductor if available on the supply side. Anyone know if this is true?

Just to be clear, the requirment is for service supplied equipment. If it is a panelboard fed by a separately derived system, the requirement that a grounded conductor be routed with ungrounded conductors is not there as in 250.24(C). There are similar requirements for separately derived systems "if" a grounded conductor is installed.

250.30 Grounding Separately Derived
Alternating-Current Systems

(A) Grounded Systems.
(3) Grounded Conductor. If a grounded conductor is installed
and the system bonding jumper connection is not located at the
source, 250.30(A)(3)(a) through (A)(3)(d) shall apply.
(a) Sizing for a Single Raceway. The grounded condu ctor
shall not be smaller than specified in Table 250.102(C)(1).
(b) Parallel Conductors in Two or More Raceways. If the
ungrounded conductors are installed in parallel in two or more
raceways, the grounded conductor shall also be installed in
parallel. The size of the grounded conductor in each raceway
shall be based on the total circular mil area of the parallel
derived ungrounded conductors in the raceway as indicated in
250.30(A)(3)(a), but not smaller than 1/0 AWG.
Informational Note: See 310.10(H) for grounded conductors
connected in parallel.
(c) Delta-Connected System. The grounded conductor of
a 3-phase, 3-wire delta system shall have an ampacity not less
than that of the ungrounded conductors.
(d) Impedance Grounded System. The grounded conductor
of an impedance grounded neutral system shall be installed in
accordance with 250.36 or 250.187, as applicable.

The requirements of 250.30(A)(3)(a) and (b) are similar to those in
250.24(C)(1) and (C)(2) for the grounded service conductor. In
addition, grounded and neutral conductors that carry current as
part of normal circuit operation are required to be sized in accordance
with 220.61.