Section 110.26(A)(3) requires that the workspace in front of equipment be clear of obstructions, and that it extend from the “grade, floor, or platform” to a height equivalent to that of the equipment or 6.5 feet, whichever is greater. Another key requirement is that equipment does not extend more than 6 inches out from the front of other equipment that is mounted above or below it, to prevent personnel from having to lean over or duck under equipment. A common violation of this requirement occurs when a battery box is located directly underneath a wall-mounted inverter and extends more than 6 inches past the front of the inverter. In fact, the majority of equipment used in PV systems is surface-mounted, while a lot of other electrical equipment—especially that used in residential applications—is flush-mounted; this situation can lead to unintended violations of this requirement.
Section 110.26(D) requires illumination for workspaces. At the very least there must be some plan for lighting, whether it is battery-operated, runs off a generator, or is standard AC lighting. Just keep in mind when you are going to need the light, which is most likely when something isn’t working. In particular, installing a DC light in an otherwise unlit battery or inverter room makes a lot of sense for battery-based PV systems, to prevent troubleshooting an inverter problem in the dark.
Section 110.13(B) requires that equipment be mounted in a manner that does not block vents and allows adequate cooling; be sure to follow manufacturers’ installation instructions. In fact, you should always read the instructions that are included with listed equipment—Section 110.3(B) requires manufacturer instructions be followed. To maintain adequate airflow and provide cooling, many inverters have specific spacing requirements, whether they are being mounted side by side, close to a corner, or in a closet.
Three separate definitions in Article 100 cover accessible as it pertains to equipment, wiring methods, and the concept of readily accessible. Equipment accessibility means that the equipment can be easily approached—locked doors or the height of the equipment can render it inaccessible. However, note that Section 110.26(F) states that equipment in locked rooms can be considered accessible to qualified personnel, provided they have access to the key or combination.
Wiring accessibility means that it is not permanently contained within the building structure in a manner that would require removing material and would result in damaging the building. For example, wiring is not accessible (meaning it is “concealed,” per the definition in Article 100) within a framed wall cavity behind plasterboard. It is accessible if it is above a dropped ceiling with lift-out panels, or in a junction box or service panel with a removable cover. Section 690.34 specifically allows junction or pass-through boxes (meaning they do not contain overcurrent protection, switches, or disconnects) to be installed behind PV modules, as long as they are accessible by removing the module (or modules). This is easily accomplished with typical top-down mounting clips and the use of flexible USE-2 or PV wire module interconnects and home runs.
The NEC definition of Accessible, Readily is: “capable of being reached quickly for operation, renewal, or inspections without requiring those to whom ready access is requisite to climb over or remove obstacles or to resort to portable ladders, and so forth.” Again, locked rooms, limiting access to only those who need it, is an acceptable and common practice. However, if a portable ladder is required to access a rooftop it is not considered “readily accessible;” nor is the wiring on the back of a pole mount if a ladder is required to reach it. A commercial rooftop, with controlled access hatches, is considered readily accessible, as is an attic with pull-down stairs, unless the equipment being accessed requires climbing through rafters and over open ceiling framing.