Electrical Wiring in North America - Terminology

Terminology

Although much of the electrician's field terminology matches that of the electrical codes, usages can vary.

• A neutral wire is the return conductor of a circuit; in building wiring systems the neutral wire is connected to earth ground at least at one point. North American standards state that the neutral is neither switched nor fused. The neutral is connected to the center tap of the power company transformer of a split-phase system, or the center of the wye connection of a polyphase power system. American electrical codes require that the neutral be connected to earth at the “service panel” only and at no other point within the building wiring system. Formally the neutral is called the “grounded conductor”; as of the 2008 NEC, the terms “neutral conductor” and “neutral point” have been defined in the Code to record what had been common usage.
• Hot is any conductor (wire or otherwise) connected with an electrical system that has electric potential relative to electrical ground or neutral.
• Grounded is a conductor with continuity to earth.
• Leg as in “hot leg” refers to one of multiple hot conductors in an electrical system. The most common residential and small commercial service in the U.S., single split-phase, 240 V, features a neutral and two hot legs, 240 V to each other, and 120 V each to the neutral. The most common three-phase system will have three “hot” legs, 208 V to each other and 120 V each to the neutral. An older but still widely used high-leg delta system uses three phases with 240 volts phase-to-phase for motor loads, and 120 volts for lighting loads by use of a center-tapped transformer; two of the phases are 120 volts to neutral. The third phase, the “high leg” of the system, has 208 V to neutral and is not used for single-phase connections, so is distinctively colored. For larger commercial installations 277/480 V three phase is common.
• An outlet is called a receptacle in the NEC. In the NEC, an outlet is “a point in the wiring system at which current is taken to utilization equipment.”