ARCFLASHSAFETY BY JIM PHILLIPS
This is a pretty common response when
addressing the requirements of NFPA 70E
130. 5( 2), which necessitate that the arc-
flash risk assessment shall, “be updated
when a major modification or renovation
takes place. It shall be reviewed periodi-
cally, at intervals not to exceed 5 years, to
account for changes in the electrical distri-
bution system that could affect the results
of the arc-flash risk assessment.”
What if, during the review process,
you discover that some of the results
changed? Do the labels need changing,
too? This could become expensive.
NFPA 70E provides specific minimum
requirements for labeling, which include
listing the nominal system voltage and
arc-flash boundary. For listing arc-rated
clothing and personal protective equipment (PPE) requirements, the 2015
edition of NFPA 70E states that at least
one of the following must be used:
• Available incident energy and working
distance or the arc-flash PPE category
• Minimum arc rating of clothing
• Site-specific level of PPE
Arc rating only
Here are a few ideas that may help
avoid relabeling when a study is updated.
Most companies use a specific arc rating
(or two) for their arc-flash protection
requirements. Often this is 8 or 12 calories per square centimeter (cal/cm2) for
daily wear and 40 cal/cm2 for higher hazard areas. A simplified labeling method
for defining the PPE requirements is to
only list the arc rating. Do not include the
calculated incident energy on the label.
This is contrary to current common
practices, but it follows a similar logic
that is used for short-circuit studies. In a
traditional short-circuit study, the interrupting rating is listed on the equipment.
The calculated short-circuit current
is typically not listed unless required
by National Electrical Code 110. 24(A).
The short-circuit study documents the
analysis results and confirms the equip-
ment’s interrupting/withstand ratings
are adequate and where deficiencies may
exist. This concept can easily be used for
reviewing arc-flash risk assessments. List
the arc rating on the label, and use the
study to verify that the recommended arc
rating is still adequate or where a higher
arc rating is needed.
Although not required by NFPA 70E,
it is a good idea to also include the working distance when listing the arc rating
on the label. The arc rating is usually
based on a calculated incident energy,
which is a function of distance from the
prospective arc. Without the working
distance, the worker will not know if the
arc rating is sufficient at 18 inches, 24
inches or some other distance.
Standardized arc-flash boundary
The arc-flash boundary varies at each
location depending on the short circuit
current, arc duration and many other
important variables. Since the arc-flash
boundary only affects the person that is
not protected and not the person performing the work, you shouldn’t get caught up
in the details of whether it is calculated
as 2½ feet, 41/10 feet or another number.
Just keep unprotected (and unqualified)
people out of the way by using a large standardized minimum boundary. If possible,
8 feet, or perhaps 10, can be used, which
makes the electrical safety practices much
simpler and keeps unprotected people out
of harm’s way.
The standardized boundary should
be voltage-specific, i.e., one standard-
ized boundary for low voltage and maybe
a different one for medium voltage. This
is because arc-flash boundaries tend to be
larger at medium voltage.
The arc-flash risk assessment can be
used to confirm where the large boundary is adequate and may point out where
an even larger boundary may be necessary.
There may be some practical exceptions to this idea, such as an arc-flash
boundary that really is small, which means
using a large boundary would prohibit
pedestrian traffic in the area.
Since the definition of the arc-flash
boundary is the distance where the
incident energy is 1. 2 cal/cm2, it may be
desirable to use a different term if the large
standardized boundary method is used.
No new labels?
Using the simplified method of labeling
can make updating or reviewing the arc-flash risk assessment much simpler. The
study results can be used to confirm that
the arc ratings and standardized boundaries are still adequate at each location. As
long as the results of the new study don’t
exceed the arc rating or larger standardized arc-flash boundaries on the existing
label, there is no need to change the label.
But how would someone know if the
labels are still adequate after there has
been a new study? One method is to adhere
a small sticker on the label confirming the
arc-flash study was reviewed and the information on the label is still valid.
Although a date is not required on arc-flash labels, according to NFPA 70E,
including a date on the original label
and subsequent stickers can assist in
determining when the five-year review
Determine if relabeling is necessary
“WHAT DO YOU MEAN we need to relabel the electrical equipment? Didn’t we just
do this a few years ago?”
PHILLIPS, P.E., founder of www.brainfiller.com and www.ArcFlashForum.com, conducts training
programs around the world and is author of “Complete Guide to Arc Flash Hazard Calculation
Studies.” He is secretary of the IEEE 1584 Arc Flash Working Group and a member of many other
national and international standards organizations. Reach him at email@example.com. EG