Review of electrical panels
Introduction
Electrical installation in the United States of America follows the regulations and standards for the installation of wiring in buildings. Electrical wiring in the United States is generally in accordance with the standards of the National Electrical Code (NEC), a standard sponsored by the National Fire Protection Association that has been periodically revised since 1897. Local modifications or additions to this model code are common in American cities or states. For electrical wiring in Canada, the Canadian Electrical Code is a very similar standard published by the Canadian Standards Association since 1927.
Terminology
Although much of the terminology in the field of electricity coincides with that used in electrical codes, uses may vary.
• - The neutral is the return path of a circuit; In building wiring systems, the neutral wire is grounded at least at one point. North American standards establish that the neutral must not be connected to a switch or a fuse. The neutral is connected to the center tap of the transformer of a power company's split-phase system, or to the center of the star connection of a multi-phase power system. American electrical codes require that the neutral be grounded only at the distribution panel (service panel). 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 has been in common use.[1].
• - Live (Phase or Active) is called any conductor connected to a system that has an electrical potential with respect to a ground or neutral connection.
• - Grounded (sometimes called grounded) is a conductor with continuity to ground.[1].
• - Take refers to each of the live or active lines in an electrical system. The most common residential and small business service in the US, it has a neutral and two active outlets of 240 V to each other, and 120 V each outlet to the neutral. The most common three-phase system has three active outlets. An older but still widely used system is the single-phase three-conductor system that uses three phases of 240 volts phase-to-phase for motor loads, and 120 volts for lighting loads through the use of a delta-connected, center-tapped transformer; Two of the phases have a voltage of 120 volts with respect to the neutral. The third phase has a potential of 208 V with respect to the neutral and is not used for single-phase connections, so it has conductors with distinctively colored insulation. For large commercial installations 277/480 V three phase is common.