NFPA 70E and NETA
What PPE Do I Need When Working
on a MCC?
F
Ron Widup or the 70E article in this issue we decided to look at a common series
of tasks, hazards, and questions related to working on 480-volt motor
control center equipment.
Location: An American industrial facility
Task: Change motor T-leads on bottom of starter to correct reverse
rotation problem
Equipment: Energized 480-volt motor control center
Exposure:
Category 2 risk exposure; 7.2 cal/cm2 of incident energy
Ok, so you are about to work on a [line-side energized] motor control center
to correct a rotation problem on the executive washroom ID fan – what personal
protective equipment (PPE) should you wear? How many times have you asked,
or been asked, a similar question? If only we had a quarter for each time we were
asked this question! (Notice we said quarter and not nickel because of inflation.)
Being involved with the 70E, one thing we find as a common occurrence is that
when you are so closely involved with a consensus-based standard, the language
used becomes understood and the approach to everyday issues does not seem to
be too burdensome. While it is true that because of the way in which standards
must be written, the language and approach to a particular situation will at times
be communicated to the reader in a different manner and approach than how a
typical electrical worker thinks and communicates in the workplace.
This situation is one that we answer questions about on a regular basis, and we
were just discussing it a few days ago – how do you tie the intent and requirements of the 70E, which has to be written in a specific style and approach to be
enforceable, to the specific instructions for electrical worker who is working in
the field and just wants to know what is the right thing to do? One key to understanding the 70E is to become qualified in your field and to understand what all
the terms and hazards associated with electrical work are. Here is a challenge and
a key to success – read Article 100 (Definitions) of the 70E and have a thorough
www.netaworld.org Jim White
Shermco Industries
understanding of all the definitions.
This will go miles in understanding
the tasks you must perform every day
in your job, such as….
Let’s state the task – performing
work inside a motor control center
bucket installed in a 480-volt MCC.
For the purposes of this discussion
the task itself is not as important
as the exposure to the hazards. The
technician might be correcting motor
rotation by interchanging the T-leads,
troubleshooting a control problem or
testing fuses. It is the exposure that is
the key. As an example, the MCC is a
480-volt section and has various size
starters in it.
First step – push the stop/off button to de-energize the load through
the contactor and then open the main
power source to the bucket by operating the switch or breaker with the door
closed. This leaves us with a fairly low
hazard (the short-circuit current to
the line-side of the bucket), and the
risk is also fairly small (could have a
fault during opening, but not likely).
If it did blow up when you operated it,
and you operated the breaker or switch
from the hinged side of the starter, you
should be okay; beat up, maybe, but not
french-fried! Another safety item to be
mentioned at this point is that if you
Summer 2009 NETA WORLD
69