2020 AFPM Summit: 2020 NEC® revision reduced risk for electrical workers
2020 NEC® revision reduced risk for electrical workers
EDDIE GUIDRY and RICHARD P. ANDERSON JR., Fluor Enterprises Inc.
The 2020 NEC® revisions include a change to Section 110.26(C)(2) that will profoundly affect electrical rooms and substation buildings. According to the revision, some open equipment doors must be regarded as obstructions blocking entrance paths into and egress paths leading from the working space. The revision aims to allow personnel to escape quickly and unimpeded when necessary and to afford rescuers access to injured workers. This change only applies to large electrical equipment, 1000 V nominal or less, 1200 A or more, and wider than 6 ft. This change applies in each jurisdiction that has adopted the 2020 NEC®, so new projects using the 2020 NEC® will require larger, more expensive substations.
Example diagrams. NEC® Table 110.26(A)(1) provides the depth of working space about electrical equipment for various voltages and installation conditions. Although easy to use for years, use of the table has become more complicated owing to the mentioned revision; in response, diagrams have been prepared to illustrate the new requirement. To simplify the diagrams, the equipment has been standardized into large, 480 V equipment that is 36-in. wide, has 36-in. doors that open only 90°, and has non-removable doors. All equipment lengths in the diagrams exceed 6 ft.
What was legal. Illustrating what was legal in the 2017 NEC®, FIG. 1 shows the plan view of a piece of large electrical equipment in a substation building. In the figure, the front of the 480 V LV SWGR represents exposed live parts, with a wall surface (grounded) opposite the front of the equipment, as corresponds with NEC® Table 110.26(A)(1), Condition No. 2. Thus, if the doors to the equipment are open, the entrance path to and egress path leading from the working space will be blocked. If an electrical fault or fire occurs, the escape path for electrical workers could be blocked by an open door.
FIG. 1. Open doors may block entrance and egress paths.
New requirement. FIG. 2 shows the same equipment as FIG. 1, albeit with increased spacing between components. Because the 2020 NEC® requires a 24-in. minimum entrance or egress path when the doors to the equipment are open, the substation building must be larger, and installation costs will be higher. In the example, costs increased by $23,000 based on $750/ft2.
FIG. 2. Open doors do not block entrance and egress paths.
What may be added. As of today, the 2020 NEC® does not contain the same new provision for the 24-in. path with doors open for equipment with voltages exceeding 1,000 V. However, if determined that the rule should have been applied to medium-voltage (MV) installations as well, then a Tentative Interim Amendment could be written and accepted by the NFPA Standards Council before the 2023 NEC® is issued.
What might need to change. The 2020 NEC® does not contain provisions for any exceptions, including when two pieces of equipment face each other, one is not being serviced and its doors are closed. In such cases, a waiver or special permission from the authority having jurisdiction (AHJ) (90.4) could be used. If the facility observes procedures to prevent the front of both pieces of equipment from remaining open and being maintained at the same time, then the AHJ may determine that the facility’s procedure provides equivalent safety to electrical workers and that less space is acceptable. The 2020 NEC® also does not contain any exceptions to allow new equipment to be installed in existing facilities but not comply with the minimum 24-in. clearance into and out of the workspace. Such issues must be addressed on a case-by-case basis.
Takeaway. Intended to promote safety, the revision to the 2020 NEC® ensures that the entrance path to and egress path leading from the working space will be a minimum of 24 in. Although large MV equipment is not now required to comply with the “doors open” rule stipulated by the 2020 NEC®, AHJs may interpret that such compliance is necessary, and different building integrators and AHJs may decide to apply the new rule to MV installations, as well. Those entities may not interpret or implement the revision consistently, and the rule more than likely will appear in the Code of Federal Regulations (i.e., OSHA). Public input on revisions to the 2023 NEC® has been submitted, and may be accepted. Finally, everyone should be involved in the standard-making organizations for their area of specialization—to work well, the codes and standards systems depend upon input from all of us.
NFPA, NFPA 70, National Fire Protection Association, National Electrical Code, and NEC are registered trademarks of the National Fire Protection Association.
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ABOUT THE AUTHORS
EDDIE GUIDRY is a Senior Fellow—Electrical Engineering with Fluor Enterprises Inc.
RICHARD P. ANDERSON JR., P.E., is a Director of Electrical Engineering/Fellow with Fluor Enterprises Inc.
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