The NEC can be a confusing source of information for those individuals who don't truly grasp the terms used within it. That's why it's valuable to take a few minutes to become familiar with the definitions in Art. 100.

  • Accessible. This means anyone can get to it. The NEC has three flavors:
    1. As applied to equipment. Typically, the NEC limits what you can do if the equipment is accessible. The concern is the safety of unauthorized personnel.
    2. As applied to wiring methods. Typically, the NEC limits what you can do if the wiring method is not accessible. The concern is ease of maintenance and repair.
    3. Readily accessible. With "readily," the idea is you can walk right up to it for access. No climbing over stuff or up ladders is required.
  • Ampacity. The NEC provides ampacity requirements (and tables) based on how small a conductor can be, not on how big it should be. This is a crucial distinction. Meeting the ampacity requirements won't necessarily provide you with an efficient design. Not meeting them will necessarily provide you with an unsafe design.
  • Approved. This doesn't mean approved by a manager in your company — it means approved by the authority having jurisdiction (AHJ). The AHJ is determined by your state's electrical board (EB). The EB members are appointed by your governor (or, in some locales, the EB and AHJ are determined at the city, not state, level).