NEC in the Facility

Commonly misunderstood/misapplied terms, part 6.

• Overload. When you're working with circuit protection devices, keep clear in your mind what this term means. Don't confuse an overload with a fault. They aren't the same thing, and protection against one isn't necessarily protection against the other. Overload means operating equipment in excess of its normal, full-load rating (or pulling more current through a conductor than its ampacity permits), when sustaining this long enough would result in damage or dangerous overheating.
• Plenum. If you don't understand the layout of the air distribution system in a structure, you could inadvertently run non-plenum-rated cable in a plenum. A plenum doesn't have to be enclosed in sheet metal. The inside space of a wall might be a plenum. An example is the "in the wall" cold air return commonly used in residential dwellings. If an air duct connects to a chamber (or compartment), then that chamber is a plenum.
• Qualified person. Being given a task and being qualified to do it aren't the same thing. Nobody wants a botched job or an industrial accident, so speak up if you don't have the skills, knowledge, and safety training a particular task requires. Some tasks may require equipment-specific knowledge. Evaluate each assignment to ensure you’re qualified to do it.