34 ELECTRICALCONTRACTOR | SEP. 17 | WWW.ECMAG.COM
circuit breaker is less than the available
arcing current and ( 2) an instantaneous
override that is less than the available
Compliance with Section 240.87
can never be achieved by simply stating that the manufacturer ships devices
with instantaneous trip set at the minimum. The actual settings for each circuit
breaker must individually be reviewed
to comply with one of the seven methods
provided to achieve arc-energy reduction.
Why does the NEC permit electrical
equipment to have ventilation openings
that would easily permit a metal fish
tape to pass through the enclosure and
into live parts? I was recently working in
a large gear room where we mounted a
temporary panelboard. I forgot to blank
off a 7⁄8-inch hole on the bottom of the
equipment, and the general contractors
safety consultant wrote us up because
that is an OSHA violation. Directly
opposite the temporary panelboard
was service equipment and a large
transformer. All along the bottom of
the transformer, there are ventilation
openings that would easily permit a
metal fish tape to enter the enclosure
and come into contact with both line and
load. Why does the inspector permit this?
There are many types of electrical
equipment, including transformers that
require ventilation to dispose of the heat
created under normal operation. Section 90. 7 provides general requirements
for examination of equipment for safety.
Where equipment—such as the trans-
former you have described—is listed by
a qualified electrical testing laboratory in
accordance with an applicable product
standard, ventilation openings are both
necessary and permitted. These ventila-
tion openings must be in place to ensure
the heat can be readily disposed of to
allow the transformer to function prop-
erly. The 7/8-inch hole in the panelboard
is an “unused opening,” and Section
110. 12(A) requires it to be closed to afford
protection “substantially equivalent to
the wall of the equipment.”
Where any work is performed in the
vicinity of energized equipment, a job-
safety analysis should be performed.
Justified energized work requires a shock
and arc flash risk assessment. Using a
metal fish tape where there are venti-
lation openings in energized electrical
equipment, such as transformers, is a rec-
ognized hazard. Section 130.7(D) in NFPA
70E addresses requirements for insulated
tools and equipment, which includes
readily available fiberglass fish tapes.
Are the accessibility requirements in
Annex J enforceable? When we need to
comply with accessibility requirements,
does Annex J contain everything we need
Annexes in the NEC are informational
only; they are not an enforceable part of
the Code—see Section 90. 5 (D). Annex J
provides information based on standards
for accessible design. The information in sections J. 1 through J. 7 is just a
part of the 2010 Americans With Dis-abilities Act, Standards for Accessible
Design. The referenced requirements
include but are not limited to protruding
objects such as a panelboard in walkways and unobstructed forward and side
Add up the amp ratings?
I am reviewing a set of electrical plans for
a new 1,200A service at 480/277 volts (V).
The service conductors enter the building
in a wireway, and there are three 400A
service disconnects. It is well understood
that three disconnects are permitted.
What I am struggling with is the
requirements for ground-fault protection
of equipment (GFPE), doors that open
in the direction of egress and large
equipment requirements for two doors.
This is essentially a 1,200A service with
three 400A disconnects. Are these ratings
cumulative, and can I add them up to get
the 1,200A to invoke other requirements?
No, you cannot add the service disconnect ratings to get to 1,200A to invoke
additional requirements. We need to look
at each one of these rules in the NEC.
Section 230.95 for GFPE applies only
to service disconnects rated at 1,000A or
more. Section 110. 26(C)( 3) for personnel doors that open in the direction of
egress with panic hardware is limited to
equipment rated at 800A or more. Section 110. 26(C)( 2), which requires large
equipment to have a door at each end
of the working space of the equipment,
is limited to equipment rated 1,200A or
more and at least 6 feet wide.
The NEC requirements are clear, and
prescriptive values are provided in each
of these sections. The GFPE requirements
are intended to protect the equipment.
The requirements for doors that open in
the direction of egress with panic hardware and for doors at each end of the
working space (large equipment) are
safety driven and affect everyone that
will install and maintain this equipment.
I encourage you to get involved and submit public inputs to revise the 2020 NEC.
For more on GFPE, see Code Comments
on page 128.
DOLLA RD is the safety coordinator for IBEW Local No. 98 in Philadelphia and works closely
with contractors to ensure job-site safety and compliance with all installation codes and
standards. He is a member of the NEC Correlating Committee, NEC CMP- 10, NEC CMP- 13, NFPA
70E, NFPA 90A/B and the UL Electrical Council. He can be reached at email@example.com.
Annexes in the NEC are informational only;
they are not an enforceable part of the Code.
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