The NEC and more recently the NFPA 70E state that any of the following types of electrical equipment located in manufacturing and commercial establishments (other than dwelling occupancies) must be field marked with a warning label if subject to examination, adjustment, service or maintenance while energized:
• Switchboards
• Panelboards
• Industrial Control Panels
• Meter Socket Enclosures
• Motor Control Centers
The labeling requirement is the responsibility of the employer, not the manufacturer or installer of the equipment.
In accordance with the 2012 edition of the NFPA 70E, labels applied to the required electrical equipment prior to September 30, 2011 are acceptable if they contain the available incident energy or required level of PPE. However, labeling does need to be applied if the equipment is ever modified or upgraded in any way. For example, at least one OSHA representative has stated that he considers changing a fuse or a breaker to be a modification that would require labeling.
Many employers are also labeling bus ducts and other electrical equipment not specifically called out in article 130.5 (C). Again, the logic is the same. If live electrical work may be performed on these systems, the risk of accident and injury exists. Clearly it is better to properly warn workers of the hazard.
The NFPA and NEC requirement states that the marking must be located so that it’s clearly visible to qualified persons before they begin work. Typically, the label is placed outside the panel or enclosure door.
In some cases, however, companies choose to put the label inside the door (e.g., to protect it from harsh environments), but this should only be done if the door must first be opened (allowing the label to be seen) before the panel face or enclosure can be removed. The key point is that the label be easily noticeable by workers before they may be exposed to any potentially dangerous live parts.