Greetings Mr. Design Engineer,
Thank you for submitting your question with regards to the proper application of section 110.26(C)(2)(a) as it pertains to establishing a compliant and safe single entrance to and egress from large electrical equipment rated 1200 amps or more and over 6 feet wide that contain overcurrent devices, or control devices, or switching devices.
The general rule in section 110.26(C)(2) is that with respect to the aforementioned electrical equipment, one properly sized (24” or wider by 6.5’ or higher) entrance to and egress from opening at each end of the large electrical equipment. When this is not possible then the installer/designer has two options to the general rule. We will focus on option 110.26(C)(2)(a) in this part of the series.
110.26(C)(2)(a) - Unobstructed egress. For example, switchgear located in a room that offers proper working space clearances per section 110.26(A)(1) and provides no additional ability to maneuver around the working clearance space in the event of an electrical accident or hazardous occurrence where no adequate opening at each end of the equipment per the general rule is provided. The designer has created a serious unsafe condition to the future electrical worker.
Assuming you have the proper working space clearance in front of the electrical equipment and then another few feet to freely maneuver around the potential hazard without having to egress through the actual working space clearance then one unobstructed entrance to and egress from the working space may be acceptable. However, it is vital to understand that when using this option you can’t use the working space clearance as the egress path because it has the potential to be an obstruction in a potentially hazardous event, such as an electrical fire that could effectively block an electrical worker, inspector, engineer or visitor to one side of the electrical equipment.
The reason the general rule requires properly sized entrances to and egress from both sides of the working space and electrical equipment as described earlier is to provide the electrical worker or other unfortunate individual two direct paths out of the potentially hazardous event area. The allowance for one entrance to and egress from the working space is when you can clearly step back out of the working space and then proceed unobstructed to the properly sized opening, while removing the unnecessary and potentially dangerous movement through the working space.
Need more evidence? Notice the second option 110.26(C)(2)(b), known as the double working clearance option, you double the working space clearance as expressed in 110.26(A)(1), you maintain no less than the prescribed working space clearance as defined in section 110.26(A)(1) from the nearest edge of the electrical equipment to the entrance. This double the working clearance and minimum clearance to the entrance from the electrical equipment provides the ability to step back into the “double” working space zone provided and effectively egress out the opening without having to traverse through the working space clearances as defined in section 110.26(A)(1).
In closing, It is my opinion that those who accept an installation that could place workers in danger and who knowingly permit improper application of the NEC rules may be found negligent in the event someone is trapped and ultimately harmed or killed in an electrical accident.
Paul W. Abernathy, CMI, CMECP®
Electrical Code Academy, Inc.