As I noted in last month’s blog,
there are three components to ensuring personnel are safe from workplace
hazards associated with equipment:
- Proper Installation of Equipment (normal operation)
- Proper Maintenance of Equipment (maintenance)
- Proper Safety Procedures when working on or near Energized Circuits (abnormal operation)
The National Electrical Code (NFPA 70) describes the minimum
requirements for the installation of equipment. Components (e.g. circuit breakers, fuses,
conductors, etc.), equipment (e.g. switchboards, industrial machines, control
panels, surge protective devices, etc.), and systems (e.g. emergency power,
etc.). All components, equipment, and systems have general and specific minimum requirements to ensure safe
installation and operation. While there
are a number of general requirements, the three general requirements that I
think are the most important to ensure that the equipment is safe for operation
are Article 110.3, Article 110.10, and Article 110.16.
The first important requirements (NFPA 70, Article 110.3) is that equipment be suitable for the environment, of sufficient mechanical
strength, and be installed and used in accordance with any manufacturer’s
instructions, listing, or labeling requirements. This broad requirement is intended to make
sure that the equipment is used in accordance with its intended
application. For example, if an
industrial machine is intended to be intended to be connected to a power source
with a rated voltage of 208Y/120, 3-phase Delta, 4W+G, then connecting to a
power source of another voltage can cause the machine to be inoperable or
create a hazardous condition.
The second important requirement (NFPA 70, Article 110.10) is that the short circuit current rating (SCCR) of the equipment be equal to
or greater than the short circuit (fault) current at the point of
application. If the analysis of the
power system finds that the short circuit at a specific point in the power
system is 33,500 A, then any equipment installed at that point must have a
short circuit current must have a SCCR that exceeds 33,500 A. Common values of SCCR range from 5,000 A to 200,000A. The next closest SCCR value to 33,500 A is 42,000 A.
The third important requirement (NFPA 70, Article 110.16) is
that specific equipment for use other than dwelling units shall be field marked
to warn qualified persons of potential arcing hazards. This includes switchboards, switchgear,
panelboards, industrial control panels, motor control centers, and meter socket
adapters. Equipment labels should meet
the requirements noted NFPA 70E, Standard
for Electrical Safety in the Workplace, and ANSI Z535.4, Product Safety Signs and Labels. The dangers associated with arc hazards are
well documented. There are many changes that have been introduced and I will
discuss those in more detail in the coming months.
Where I still see gaps related to
electrical safety is ensuring that equipment is installed in accordance with
the manufacturer’s requirements, and ensuring that the equipment has a SCCR
that is equal to or greater than the short circuit (fault) current at the point of installation.
If equipment is not installed properly and within
its rating, then the foundation of electrical safety is on shaky ground. Like any program, starting with a solid
foundation provides the opportunity to be successful. Ensuring that equipment is installed in
accordance with the requirements detailed in the National Electric Code (NFPA 70) provides the solid foundation to
ensure that your electrical safety program is successful.
If you have questions equipment design or installation, or issues related to electrical safety, send me an e-mail at cole3250@gmail.com.
