Efficient Plant June 2020 - 16

feature | electrical safety

Service
panelboards
without a
main and
six or fewer
disconnects
will no
longer be
permitted.

16

EP2006featon.indd 16

lent. This new short-circuit current rating requirement
parallels changes that affected power-distribution
blocks (PDBs) from the 2017 cycle, but now addresses
other types of termination devices. The update has
far-reaching implications for manufacturers.
Rationale: The 2017 label change only accounted
for one type of solution used in that application. The
2020 update now requires marking all termination
types, including PDBs, pressure connectors, and
devices for splices and taps used in these locations, as
suitable for use on the line side of service equipment
to assure connectors are tested for given locations in
the circuit. Manufacturers currently don't build devices for use on the line side of service equipment, so
manufacturers and standards developers must quickly
bring solutions to market. The requirement's effective
date offers manufacturers leeway to bring products up
to speed.

SAFETY DISCONNECT
Language now exists in Section 230.85 for emergency
disconnects (formerly the firefighter disconnect) on
the exterior of one- and two-family dwelling units so
that first responders may quickly disconnect power to
a structure. Language in Section 445.18 also addresses
emergency generator shutdown.
Rationale: In addition to fire, gas leaks, and other
dangers, first responders often must account for electrical hazards during emergencies. These situations can
be chaotic, requiring responders to ventilate buildings
on rooftops, break through windows, and open walls in
seconds. With that, there's a real danger of coming in
contact with energized conductors and equipment.
Typically, first responders look to turn the power off before entering a blaze, but many residential
panelboards are in basements. Terminating power at
the transformer, which could be atop a pole, is not
something any untrained person should attempt. This
change mandates placing emergency disconnects near
the service- entrance equipment outside of a structure.
Concerns were raised during requirement debates
that safety disconnects allow anyone to terminate the
power to a home. The NEC's response was to allow
installation of disconnect locks to thwart unauthorized power access. While the locks will not impede
firefighters or other first responders and may provide a

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level of comfort to the owner, contractors will still have
to explain the expense of safety disconnects, especially
in locations where it's not common practice to add
outdoor service panelboards.

LINE-SIDE BARRIERS
AND SIX DISCONNECT RULE
What many refer to as "the six disconnect rule" was
modified per Section 230.71 such that service panelboards without a main and six or fewer disconnects
will no longer be permitted. Hazards associated with
six disconnects without a main in a service panelboard
have always been a concern. Changes in 2017 to NEC
Sections 110.16, 240.87, 240.67, and 408.3 furthered
that awareness and inspired more change during the
NEC 2020 development process.
The changes in the latest cycle provide options on
leveraging as many as six disconnects instead of a single main overcurrent protective device (OCPD), with a
how-to section outlining four options:
 separate enclosures with a main service disconnect
 panelboards with a main service disconnect
 switchboards with only one service disconnect and
barriers separating each vertical section
 service disconnects in switchgear/metering centers
with disconnects located in separate compartments.
In addition, line-side barrier requirements are
expanded to service equipment beyond panelboards
and switchboards.
There are two reasons for the change:
Exposing hazards. The NEC changed Section
408.3 in 2017 to require barriers on service-entrance
panelboards, recognizing that adding line-side barriers
on panelboard service disconnects may not be possible
with six disconnects used in the same panelboard.
This decreased the likelihood of workers coming in
contact with energized terminations on the line side
of the main service OCPD or switch. However, one
panelboard with six means of disconnect with no main
circuit breaker results in electrical workers lacking the
ability to apply barriers to the line side of each overcurrent device because the line side is a bus. The 2017
NEC update included an exception for these types of
applications.
The 2017 Code focused on panelboards, switchboards, and low-voltage assembly solutions, but war-

JUNE 2020

5/27/20 4:50 PM


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Efficient Plant June 2020

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