FOR MORE INFORMATION CONTACT
CARSON MOSER | CARSON.MOSER@HEI-ENG.COM
ED GRIGGS | ED.GRIGGS@HEI-ENG.COM
913.742.5000
noteS on Arc Flash
| Energy Release electrical explosion
INTRODUCTION
An arc flash is a very rapid and massive release of energy that occurs during an arcing fault. During an arc flash, the massive release of energy vaporizes wiring and bus bars causing an expansion of up to 67,000 times the original volume. This
can cause massive damage to the surrounding equipment or personnel in the path of the energy release. Damage can also
result in catastrophic injuries including hearing and vision damage, shrapnel from equipment, flash burns, and blunt force
trauma, as well as prolonged outages of power to repair damaged equipment and wiring.
ARC FLASH CAUSES
An arc flash can be caused by failing wiring insulation, faulty bus bars, debris in equipment, rodent infestation, condensation build up in equipment and human error.
Typical procedures prone to arc flash incidents include:
• Working inside live equipment such as motor control centers transfer switches, switchboards or panel boards
• Racking-in circuit breakers or switches in switchboards
• Closing disconnect switches or transfer switches
• Unbolting and removing protective panels from equipment
STRATEGIES TO MITIGATE ARC FLASH INCIDENTS
• To avoid human error as the cause of an arc flash will require that no maintenance or construction be undertaken
on live electrical equipment. This is not always possible in a healthcare environment
• Provide means to mitigate the level of arc flash by adjusting circuit breakers or provide fusing that limits the incident energy available during an arc flash
• Provide proper training and planning to personnel involving work on live electrical equipment
• Provide the proper protective equipment for personnel to work on live electrical equipment
• Maintain and test all electrical equipment to ensure that it is functioning correctly
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FOR MORE INFORMATION CONTACT
CARSON MOSER | CARSON.MOSER@HEI-ENG.COM
ED GRIGGS | ED.GRIGGS@HEI-ENG.COM
913.742.5000
noteS on Arc Flash
| Energy Release electrical explosion
OWNER & FACILITY RESPONSIBILITIES
OSHA requires an employer to provide a safe working environment, establish safety procedures and policies and provide
the proper safety training necessary for the work their employees are undertaking. This extends to contractors working on
equipment within the Owner’s facility as well.
Additionally, Joint Commission as well as city and state inspectors are frequently requiring facilities to prove that they are
meeting the OSHA requirements.
EMPLOYEE OR CONTRACTOR RESPONSIBILITY
It is the responsibility of the employee or contractor to implement all safety procedures and utilize the proper equipment
for the work to be undertaken. If the employee or contractor does not follow the safety procedures or utilize the proper
equipment they are assuming the liability associated with a potential incident.
REASONS TO UNDERTAKE AN ARC FLASH STUDY
• To provide a safe work environment and meet all of the OSHA requirements, the owner must provide all of the
information to its employees to ensure work is done in a safe manner. If this information is unknown the employee must assume the worst case conditions and must utilize the most protective safety equipment for the work.
This is also the most restrictive and could cause undo difficulties to perform the required work. The time to do the
work may also be increased causing more expense to the owner.
• To ensure that the owner’s equipment is properly sized and designed for the potential arc flash hazard incident
energy.
• To provide the proper labelling of equipment per the NEC (2011 Requirement) including the arc flash hazard
category and the proper personal protective equipment required for work on the equipment.
www.hei-eng.com
FOR MORE INFORMATION CONTACT
CARSON MOSER | CARSON.MOSER@HEI-ENG.COM
ED GRIGGS | ED.GRIGGS@HEI-ENG.COM
913.742.5000
noteS on Arc Flash
| Energy Release electrical explosion
WHAT IS INCLUDED IN AN ARC FLASH STUDY
• Verification of all electrical equipment including service entrance switchboard, distribution panel boards, branch
circuit panel boards, motor control centers, transfer switches or other major pieces of electrical equipment that
may require service while energized (chillers, starters, UPS’s), etc.
• Development of a one-line diagram indicating all of the above mentioned equipment including how it is fed,
what it is fed by (fuses, circuit breakers, etc.), the settings or sizes of the fuses or circuit breakers.
• Verification of equipment conditions and recommendations for replacement, service or equipment testing.
• Perform all calculations on the above mentioned equipment to determine the available arc flash hazard.
• Make recommendations to limit the available arc flash hazard including adjustments to breakers or replacement of
fuses to limit the arc flash hazard energy.
• Create the NEC required labels indicating the available arc flash hazard energy and required personal protective
equipment.
• A coordination study can also be provided to ensure that power interruptions are limited as much as possible in
the event of a circuit breaker tripping or fuse opening.
CODE REFERENCES
NFPA 70E is the guideline that has been written and revised in conjunction with OSHA (Occupational Safety and Health
Administration) and the National Electric Code.
OSHA Article 1910 will enforce NFPA 70E
NFPA 70 (National Electrical Code) now requires all equipment to have the available fault current labeled on all Service
Equipment.
CONCLUSION
As a facility owner, it is your responsibility to provide a safe working environment for your employees, sub-contractors,
vendors, property managers, etc., along with protecting your sensitive and valuable electrical equipment. It is also imperative to maintain a continuity of electric service for the safety of your patients. An Arc Flash and Coordination study will
provide you with the required information and labeling to do all of the above.
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