PV systems—with expected lives of 25 years or more—will require some degree of preventive maintenance and/or reactive service over their lifetimes. Ensuring that service and maintenance can be performed safely and efficiently must be considered during the design process. A key topic in Chapter 1 of the National Electrical Code is required workspace clearance and accessibility—two critical factors in effective system design. These NEC requirements are minimums—meeting them does not necessarily mean an installation is “efficient, convenient, or adequate for good service” [Section 90.1(B)]; exceeding them can result in a system that is easier and safer to service and maintain.
The reasons for the workspace clearances defined in NEC Section 110.26 are a more user-friendly working environment and safer conditions. Envision an area the size of a telephone booth in front of electrical equipment—approximately this amount of space is required so that workers do not have to stand sideways, reach over the top of a device, or crouch underneath an overhang to access equipment. These requirements apply to systems that are 600 volts (AC or DC) or less, and which are likely to require service or maintenance while energized. This will certainly be the case with most PV systems. Section 110.30, while not covered in this Code Corner, addresses systems greater than 600 volts, which are becoming more common in commercial, industrial, and utility-scale applications.
All of the described workspaces are to be kept clear and not used for storage [110.26(B)], and they must be dedicated to the electrical equipment [110.26(E)]. In addition to commonly stored items, other equipment, such as plumbing, ducts, and other systems’ components, must be kept out of the dedicated space.
The depth of the workspace required by Section 110.26(A)(1) varies based on the system’s voltage. For systems from 0 to 150 volts to ground (for ungrounded DC systems, this is the voltage between positive and negative), a minimum of three feet of depth is required on the sides of the equipment where access is required. (This is typically the front of the equipment, though larger equipment or battery banks may require access to their sides as well). This applies to 120/240 and 120/208 VAC systems, which are common residential and commercial service voltages. When the voltage to ground is between 151 to 600 V—typical on the DC side of grid-connected PV systems with string inverters as well as higher-voltage AC services—the minimum depth required depends on which one of three conditions is encountered:
Section 110.26(A)(2) requires 30 inches of width—or the width of the equipment, whichever is greater—in front of the equipment. This required space must also allow all doors or hinged panels to open to at least 90º, which can also affect the required depth: If the door is wider than 3 feet, then a space of more than 3 feet is required to allow it to open. Equipment does not have to be centered in the minimum 30 inches of required width. For example, an AC service panel can be mounted against a corner and, when multiple pieces of equipment are mounted next to each other, their required workspace widths can overlap—again provided that any doors or covers can open to at least 90° and do not interfere with each other.