When designing a workspace, you must maintain unobstructed pathways to and from electrical equipment per the NEC.
When designing and installing electrical equipment, you must provide for adequate illumination and easy access in and out of the workspace. To ensure a safe exit in case of a short-circuit or ground-fault, you must provide one way (and in some cases two) to enter or leave the workspace. If you don't, workers could get trapped at one end of the workspace with fire between them and the exit. The NEC has required a reliable entry and safe exit route for workers since 1978, and enforced the appropriate illumination rule since 1965.
So how do you design a workspace to meet the requirements of the NEC? A quality design and installation will address these requirements.
Access and entrance to working space [Secs. 110-26(a), (b), and (c), Exception 1]. For workers to take voltage measurements, check continuity of circuits, adjust or replace defective overcurrent protection devices, and tighten loose connections, electrical equipment must be accessible and located in an area with adequate working space. The space in front of electrical equipment must be free from stored materials that might block access to overcurrent protection devices — which must be accessible in case of emergencies — or the disconnecting means of equipment for routine maintenance.
Conditions allowing one entrance [Sec. 110-26(c)(1), Exception 1]. Where there is a continuous and unobstructed way of entrance and exit travel, the Code only requires one means of access to the working space. For example, if a support column blocks the route of travel, then you must provide another means of travel space.
Conditions requiring two entrances [Sec. 110-26(c)]. This requirement is crucial for people who work in the space discussed above. Remember, there must be at least one entrance large enough to give adequate working space to the electrical equipment inside. The NEC requires 6-ft or wider switchboards and control panels with a rating of 1,200A or more to have one entrance at each end that is at least 24 in. wide and 6½ ft tall. Thus, in some cases, at least two entrances must be available for safe and dependable entry and exit routes for workers.
Workspace doubled [Sec. 110-26(c) Exception 2]. The NEC requires one means of access and entrance to the working space where the workspace is doubled per Table 110-26(a), based on conditions 1, 2, or 3. With the workspace doubled in front of the equipment, a worker can move back out of the endangered workspace and exit along the length of the equipment. The deeper workspace in front of the equipment provides a safer route to exit without the expense of providing two entrances.
Illumination [Sec. 110-26(d)]. For the safety of the workers servicing the equipment, installations housing service equipment, switchboards, panelboards, and motor control centers must provide adequate lighting where live parts are accessible. Lighting fixtures may be incandescent, fluorescent, or any other type that provides the proper footcandles necessary to clearly illuminate the equipment and parts in service.
Lighting fixtures must have a headroom clearance of at least 6½ ft so people have sufficient room to stand in front of the equipment without their head or headgear contacting metal.
Appropriate clearances and proper workspace dimensions are mandatory. Therefore, it is imperative that the engineer determine the clearances necessary for providing a safe workspace in the design phase. This is especially true where the equipment is likely to require routine examination, adjustment, and maintenance — and where electricians will be exposed to energized parts. Electricians and inspectors must also ensure the equipment they install and inspect has an adequately sized workspace. It takes the combined efforts of engineers, electricians, and inspectors to comply with NEC and OSHA clearance and workspace rules.