Arc Flash Labels Explained

By R.W. Hurst, The Electricity Forum

Arc Flash Labels
Arc Flash Labels Required By NFPA 70e

Arc Flash Labels

Arc Flash Labels are required by NFPA 70e in the United States and CSA Z462 in Canada. The latest edition of NFPA 70e identifies the minimum arc flash warning label requirements that must be field installed at time of installation. It states:

Article 110.16: Flash Protection. Switchboards, panelboards, industrial control panels, meter socket enclosures, and motor control centers in other than dwelling occupancies, which are likely to require examination, adjustment, servicing, or maintenance while energized, shall be field marked to warn qualified persons of potential electric arc flash hazards. The marking shall be located so as to be clearly visible to qualified persons before examination, adjustment, servicing, or maintenance of the equipment.

OSHA requirements requires employers to be responsible for workplace safety signs and other methods to make sure their workers are safe. It also mandates that to improve electric shock and arc flash safety and worker compliance, additional information can be included on labels, including the flash hazard boundary, working distance and required PPE. When additional arc flash labeling is included, it must be assured that the information is understood by everyone required to work on the equipment. Too much information that is unclear to the workers will be ignored and can be as bad, if not worse, than no information at all. It is extremely important the arc flash label is as clear and accurate as possible. While it is obvious that insufficient PPE is dangerous, over-clothing workers can also increase the risk of an arcing fault due to limited mobility and visibility.

Large equipment such as switchgear can often have different levels of incident energy due to feeder and protective device configuration. Multiple arc flash labels can also be placed on a single piece of equipment depending on the access point and proximity to the arc source for a given activity. However, it is good practice to provide a single arc flash label for the largest incident energy available. Workers should not enter the flash protection boundary to work on live parts unless they are wearing the proper PPE for the level of hazard that could occur. The specific flash protection boundary, working distance, and incident energy values should be readily accessible to all workers, either identified by an equipment mounted label, or otherwise documented and available for reference or review.

Boundaries

The limited, restricted and prohibited approach boundaries stated on an electrical safety warning arc flash label.

Flash Protection Boundary

This boundary number on the arc flash lable dictates the nearest anyone may approach without the use of PPE. In order to determine the flash protection boundary, you need to know the available short circuit current, predicted fault duration and the voltage.

Limited Shock Approach Boundary
The shock approach boundary number on an electrical safety label may only be crossed by an "unqualified" person when they are accompanied by a "qualified" person.

PPE Required
Arc rated Personal Protective Equipment (PPE) level protect employees is dependent on the incident energy at every point for employees working on energized electrical equipment. Occupational safety and health regulations in this matter must be followed. An electrical engineer or other qualified person should first perform the calculations that determine incident energy. Appropriate PPE should cover all parts of the body of the worker that may be exposed to an explosion. This could include shoes, gloves, flame resistant clothing, safety glasses, etc.

 

Arc Flash Label Questions and Answers

Question: Who is responsible for producing and maintaining the Arc Flash Assessment Labels?

Answer: Per NFPA 70E, Section 130.5.D, The owner of the electrical equipment shall be responsible for the documentation, installation, and maintenance of the field marked label.

Question: Now that you have the labels, where should the labels be placed on the equipment?

Answer: The labels need to be placed on the outside front cover of the equipment. However, when it comes to panelboards, it is acceptable to place the labels on the inside of the door They need to be clearly visible to any person who will be working on the piece of equipment while it is energized. Also, there are some instances where you will have line side and load labels for one piece of equipment. 

Question: What does all of the information on the labels mean?

Answer: Refer to Figure 1. This is a sample of an arc flash label. The notations explain what each line of information means.


 

 

Sample Arc Flash Label Description

#1: If you are within 12 Ft 5 in front of the source of the arc flash, you are within the flash hazard boundary* (1.2 Cal/cm2). This is where you could receive a second degree (blister) burn and have possible ignition of non-arc rated clothing. However, if you are more than 12 Ft 5 in away from the source of the arc flash, then you are considered safe and not at risk from the arc flash.

#2: If you are 1 Ft 6 in away from the source of the arc flash, you will physically receive 38.3 Cal/cm2 of energy. This is also referred to as “the working distance”, which is the distance measured from the arcflash source to the upper torso.

#3: This equipment voltage is 208 volts. If you remove the cover of the equipment while it is energized, you must protect yourself from shock by wearing insulated gloves or covering the energized parts with an insulated rubber blanket.

#4: This shows what minimum class of protective insulated gloves that need to be worn when working on this equipment while it is energized.

#5:  This is the limited approach boundary*. An unqualified person has to be at least the distance listed or farther away from the energized equipment.

For the example label above, an unqualified person has to be 12 Ft 5 in or farther away from the exposed energized conductor due to the arc flash.

If the Arc Flash Boundary is less than the limited approach boundary and there is no arc flash hazard**, then an unqualified person can be escorted by a qualified person up to the restricted boundary.

#6: This is the restricted approach boundary. Only a qualified person wearing the proper PPE can be within the distance listed of the energized equipment. According to Figure 1, a qualified person wearing the proper PPE can get no closer than 12 Inches from the panel while it is energized. (The qualified person must also have an Energized Electrical Work Permit EEWP)

#7: This is the date the label was printed, and which edition of IEEE and NFPA 70E the label was based on.

#8: The “Equipment ID (Name)” is the actual piece of equipment that the label is for and should be applied to. The “Protective Device” is the upstream device that is protecting this specific piece of equipment.

#9: For some protective devices such as switchgear and switchboard mains, a calculation is performed on the line side. If the “Line Side of” is not shown, then the label would be for the main bus of the equipment.

#10: This line shows which operating scenario the information on the label applies to. When arc flash hazard calculations are performed, they are  calculated under different possible operating scenarios of the electrical system. This is done in order to find the worst possible case of arc flash incident energy at each piece of equipment. For example, let’s say there is an electrical system that has many motors and can be fed from a utility source or generator source. There would be four operating scenarios in which the calculations would be performed; two would be when the system is being fed power from the utility source, one with all the motors running at full capacity and one with all the motors out of service. The other two operating scenarios would be when the system is fed power by the generator, with all motors running in one scenario and the other with all motors out of service. Performing the calculations this way tells us the different incident energies at each piece of equipment under various circumstances. The label provided for each piece of equipment is the worst possible case out of all the operating scenarios calculations.* Place temporary barrier tape or rope at the greatest distance of either Arc Flash Boundary or Limited Approach boundary.** To determine if there is an arc flash hazard, see NFPA 70E Table 130.7(C)(15)(A)(a) Arc Flash Hazard Identification for Alternating Current (ac) and Direct Current (dc) Systems.

 

 

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