ELECTRICAL SPACES FOR ARCHITECTS

For non-sparky types, identifying electrical space requirements for systems rated 600 Volts or Less, can be a little confusing. A couple years ago I was working with an Architect on a project  reviewing the space requirements when she jokingly suggested one might need an algorithm constructed to solve all the If/Then statements. In reality, the NEC isn’t that complicated, but there are a few details that require special attention and are easily overlooked in the design process.

The following is a short overview covering some of the more common questions I have  encountered on design projects. Refer to NFPA 70 for a comprehensive description of space requirements. 

1. Entrance and Egress – in general, at least one means of Entrance and Egress, measuring no less than 24 inches Wide by 78 inches tall is required, except where equipment rated 1200 Amps or more, and measuring 6 feet or more in width is installed. In these instances, an entrance/egress is required at each end of the space. 
2. Doors – By code, personnel doors used as entrance and egress for spaces housing equipment rated 1200 Amps or more, must swing in the direction of egress, and be equipped with panic hardware. 
3. Exceptions to the Two Exit Requirement – code provides two exceptions allowing the use of a single entrance/exit; 1) where double the required working space is provided, or 2), where there is a continuous and unobstructed egress path 
4. Electrical Room Dimensions – the size and orientation of electrical rooms is driven predominantly by the equipment being located in the space, and the code required depth, width, and height of working clearances for the associated equipment. Ultimately the horizontal dimensions of the space end up being a function of the overall required widths of working clearances combined, with consideration for equipment layout and room orientation. Room height requirements are largely driven by the equipment dimensions. 
5. Width of Working Space – defined by the NEC as the width of the equipment or 30 inches, whichever is greater. Additionally, the work space must permit at least a 90 degree opening of equipment doors or hinged parts. 
6. Depth of Working Space - except in cases where exposed live parts are located on both sides of the working space, the minimum required clearance is 3 feet from exposed live parts, or from the enclosure or opening if live parts are enclosed. In cases where live parts are located on both sides of the working space, the minimum clearance is 4 feet. 
7. Height of Working Space – extends from the grade, floor, or platform to a height of 6.5 feet, or the height of the equipment, whichever is greater. 

 
Additionally, the following are a few  common misconceptions I've encountered:

1. Dedicated Space – This requirement is often misunderstood to imply that equipment must be located in a separate closet or confined space dedicated solely to electrical equipment. In reality, the NEC provides a great deal of flexibility in where electrical equipment can be located. It is not uncommon to see electrical panels recessed in walls in corridors, or other back of house spaces. The NEC specifies that for indoor applications, "Dedicated Electrical Space" is the “space equal to the width and depth of the equipment and extending from the floor to a height 6 feet above the equipment or to the structural ceiling, whichever is lower."  Routing of piping, ducts, leak protection apparatus, or other equipment foreign to the electrical installation within this space is prohibited. However, the area above the "dedicated space" is permitted to contain foreign systems such as piping, ducts, etc. provided measures are in place to protect the electrical equipment from condensation, leaks, or breaks. Additionally, sprinkler protection is permitted. Lastly, suspended ceilings are not considered structural ceilings. 
2. Exterior Doors – contrary to popular belief, exterior doors are not required for main electrical rooms. However, in some cases there are operational benefits to providing an exterior door to main electrical rooms. Generally, this is an owner preference design requirement. 
3. Electrical Room Door Width – although not specifically a code requirement, providing adequate door width to allow ease of access for replacing equipment falls into the “best practices” category. Typically, Electrical Engineers will request at least one four-foot door be provided for electrical spaces where switchgear, large transformers, and other large equipment is installed. 

As I mentioned above, this is by no means a comprehensive list of requirements and should not be interpreted as a formal interpretation of the requirements outlined in the NEC.