In addition, a qualified person must accompany unqualified persons. Persons crossing into the flash protection boundary are required to wear the appropriate PPE. In some instances, calculations may decrease the boundary distance. NFPA 70E establishes the default flash protection boundary at 4 feet for low voltage ( < 600V ) systems where the total fault exposure is less than 5000 amperes-seconds (fault current in amperes multiplied by the upstream device clearing time in seconds). The FPB is a safe approach distance from energized equipment or parts. Therefore, personnel must obtain a risk assessment before the prohibited boundary is crossed.Īll of these limited approach boundaries are determined in tables outlined in NFPA 70E and CSA Z462, and all are based upon the voltage of the equipment. Only qualified personnel wearing appropriate PPE, having specified training to work on energized conductors or components, and a documented plan justifying the need to perform the work may cross the boundary entering the Prohibited Space. This boundary may be crossed by only qualified persons (at a distance from a live part) which, when crossed by a body part or object, requires the same protection as if direct contact is made with a live part. Also, he/she must have a written approved plan for the work to be performed and plan the work to keep all parts of the body out of the Prohibited Space. To cross the Restricted Approach Boundary into the Restricted Space, the qualified person (who has completed required training) must wear appropriate PPE. This consists of the shock protection boundary, and may only be crossed by qualified persons (at a distance from a live part).ĭue to its proximity to a shock hazard, the use of shock protection techniques and equipment are required. A qualified person must use the appropriate PPE and be trained to perform the required work to cross the limited approach boundary and enter the limited space. No untrained personnel may approach any closer to the energized item than this boundary. The limited approach boundary is the minimum distance from the energized item where unqualified personnel may safely stand. NFPA 70 defines the limited approach boundary as a shock protection boundary to be crossed by only qualified persons (at a distance from a live part), which is not to be crossed by unqualified persons unless escorted by a qualified person. The flash protection boundary is based on voltage, the available fault current and the time it takes for the upstream protective device to operate and clear the fault. The flash hazard analysis should determine the flash protection boundary (FPB) and level of personal protective equipment (PPE) that the worker must wear. (It is important to note that conductors and equipment are considered live when checking for voltage while putting equipment in a safe work condition as well). Until equipment is placed in a safe work condition, it is considered live. The limited approach boundary, restricted approach boundary and prohibited approach boundary classifications are based on the voltage of the energized equipment.īut before a worker can approach exposed electric conductors or circuit parts that have not been placed in a safe work condition, a flash hazard assessment must be performed. There are three shock approach boundaries: Click here to see the video.NFPA 70E and CSA Z462 have developed requirements to reduce the risk of injury due to shock and arc flash hazards. Also, I suggested all employees be shown a short 15 – 30 second video of a real-world electric arc, such as this video of an electric arc while racking a circuit breaker. I recommended the company train all employees on the prohibition from entering into these restricted areas. One client I worked with was flustered with his inability to enforce company policies to keep production supervisors out of the arc flash boundary. This poses a serious risk to the unqualified worker – electrocution from shock as well as ignition of their clothing in the event of an electric arc. Production supervisors other employees and in academia, students, are notorious for entering the established boundaries to talk to qualified employees while they are performing work on energized electrical conductors. During my NFPA 70E seminars and while working with clients, a constant concern I hear is unqualified workers entering both the arc flash and approach (shock) boundaries.
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