The 2011 version of the National Electrical Code (NEC) expanded the labeling requirements for all types of PV systems. These requirements, in addition to those already in the Code, help to ensure quality workmanship; prevent confusion between AC and DC conductors; facilitate PV system service and maintenance; and help protect emergency responders. Additionally, the 2012 International Fire Code (IFC) has labeling requirements that mirror or, in some cases, expand on those of the NEC.
The various requirements are noted throughout the NEC, appearing in Articles 690 and 705, as well as in articles that are not specific to PV systems. For example, Section 110.22, “Identification of Disconnecting Means,” requires that a disconnect be “legibly marked to indicate its purpose unless arranged so that the purpose is evident.” This will be augmented by PV-specific requirements for marking. However, Articles 690 and 705 do not allow unmarked equipment even if its purpose is obvious.
Labels and markings must be suitable for the location in which they will be installed. Section 110.21 states that “markings that indicate voltage, current, wattage, or other ratings shall be provided as specified elsewhere in this Code. The marking shall be of sufficient durability to withstand the environment involved.” While requirements for materials may be based on the requirements of the authority having jurisdiction (AHJ), in general there are three choices: preprinted or customized stickers, engraved plastic, and engraved metal.
Depending on the location and the AHJ, a particular job may require more than one type. For instance, stickers may not be adequate for locations that receive direct sun, but their lower cost may make them preferable for interior applications (such as conduit inside an attic). Additionally, engraved signage and labels can still be read even if they are painted over; however, they do have longer lead times for their fabrication and higher cost, and care must be taken when choosing an adhesive for attaching them.
As with other changes made to protect firefighters working on buildings with PV systems, Section 690.4(F) requires marking the location of PV source and output circuits that are embedded in built-up, laminate, or membrane roofing in areas not covered by PV modules or system equipment. There are several products on the market to help accomplish this, the goal of which is to minimize or eliminate the chance of a firefighter accidentally cutting through energized PV circuits.
A new addition in 2011 that explicitly allows multiple inverters on a single building or structure, Section 690.4(H) also requires a directory to be installed—as per Section 705.10—when the inverters are not adjacent to each other. While not defined, a directory is a map and description of the equipment’s location. Together, these sections require that the locations of all service disconnecting means, interconnected power production sources (PV systems), and accompanying AC and DC disconnects be identified via a directory at each of the noted locations. This can result in a lot of directories when equipment is spread out. An exception states that directories are not required when the equipment is all grouped at the main service disconnect. This directory requirement is also stated in Section 690.56(B).