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Arc Flash & Circuit Breaker
Coordination Studies
Arc Flash Analysis and Labelling
Commercial, industrial and institutional facilities are now required to
comply with regulations governing arc flash energy in their electrical
distribution systems. All distribution equipment must be clearly labelled
with the calculated arc flash energy available and required personal
protective equipment (PPE) for energized work, as well as clear
descriptions of the allowable approach distances. GEi has the expertise
to perform these studies and develop all required documentation &
labelling. In addition GEi will review overcurrent protective device
characteristics and settings to determine if modifications would improve
personnel safety without materially affecting system reliability.
Selective Coordination
The National Electrical Code requires all legally required standby
systems to be selectively coordinated. This process involves a
painstaking analysis of the electrical distribution system and trip
characteristics of all protective devices to develop settings that will
ensure the circuit breaker or fuse closest to an electrical fault will act
first, before larger devices upstream trip and cause a more widespread
loss of power.
While selective coordination is only required by Code in select situations,
any distribution system with multiple protective devices in series should
be properly coordinated for maximum safety and reliability. GEi can
provide complete coordination studies and trip setting
recommendations for existing installations and new construction. For an
existing system we will utilize existing documentation in conjunction
with a detailed survey of the system to gather the required data. For new
construction we will review the construction documents to ensure that
the system as designed can be properly coordinated, and recommend
settings on all adjustable circuit breakers.
Accident Costs and Penalties for Noncompliance:
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OSHA has levied 6-figure fines in connection with
insufficient labelling of electrical hazards. Furthermore,
noncompliance carries the risk of far higher monetary
damages as well as the burden of knowing an employee
or contractor was badly injured or killed due to a
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preventable incident. The average cost of medical
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treatment for EACH survivor of an arc flash incident is
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$1.5 million. The total costs have been estimated to be
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$12 - $15 million, which includes the following:
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1. Medical Expenses
2. Lost productivity of worker
3. Equipment / Facility down time
What is an arc flash?
4. Equipment replacement
An Arc Flash is an electrical explosion due to a fault
5. Insurance complications
condition or short circuit when a phase (live) conductor
6. Fines and Fees
momentarily contacts ground or a different phase
7. Litigation
conductor. In some cases when the conductors are
separated, there is enough energy present to make Advantages of Selective Coordination:
current flow through the air, creating an arc. Arc flashes Proper coordination of overcurrent devices in a complex
can be likened to explosions in which arc-plasma fireballs electrical distribution system is key to the system’s
are formed within electrical equipment. Temperatures reliability as well as maintainability and personnel safety.
may exceed 35,000° F (the surface of the sun is 9000° F), When an electrical system is installed without benefit of
causing an arc blast with rapid heating of surrounding air a coordination study, common practice is to simply set
and extreme pressures. The arc flash/blast will often all adjustable trips to their highest setting to minimize
vaporize copper conductors, which will expand up to nuisance tripping. Unfortunately this has two
67,000 times their original volume when vaporized, as undesirable side effects:
well as producing flying shrapnel. Arc flashes happen
● It can cause miscoordination in which an
without warning and are lightning quick. The results of
upstream breaker trips before a downstream
this violent event can include destruction of the
device, thereby affecting loads that were
equipment involved, fire, and severe injury or death to
operating normally.
any nearby people.
● Clearing time for all breakers is increased,
Arc Flash Compliance & Regulations:
OSHA 29CFR, Part 1910, Subpart S mandates that
employers identify electrical hazards, warn employees
about the hazards and provide them proper protection
and training regarding the hazards. Compliance with
OSHA is mandatory for all US companies. OSHA
regulations do not tell you HOW to comply; guidance on
how to properly implement the OSHA regulations may be
found in NFPA 70 & 70E and IEEE 1584.
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especially in a 208V system with low available
fault current. This significantly increases the total
available arc flash energy, often to the point
where it is more dangerous to work on an
uncoordinated 208V system than on a properly
coordinated 480V system!
GIUFFRIDA ENGINEERING inc.
564 Pine Street
Middletown, CT
06457
(860) 346-3094
info@giuffrida.com
www.giuffrida.com