By Diane Oneil on February 27 2018 16:54:05
In North American practice, an overhead cable from a transformer on a power pole to a residential electrical service usually consists of three twisted (triplexed) conductors, with one being a bare neutral conductor, with the other two being the insulated conductors for both of the two 180 degree out of phase 120 V line voltages normally supplied. The neutral conductor is often a supporting "messenger" steel wire, which is used to support the insulated Line conductors.
Special versions of non-metallic sheathed cables, such as US Type UF, are designed for direct underground burial (often with separate mechanical protection) or exterior use where exposure to ultraviolet radiation (UV) is a possibility. These cables differ in having a moisture-resistant construction, lacking paper or other absorbent fillers, and being formulated for UV resistance.
The first electrical codes in the United States originated in New York in 1881 to regulate installations of electric lighting. Since 1897 the US National Fire Protection Association, a private non-profit association formed by insurance companies, has published the National Electrical Code (NEC). States, counties or cities often include the NEC in their local building codes by reference along with local differences. The NEC is modified every three years. It is a consensus code considering suggestions from interested parties. The proposals are studied by committees of engineers, tradesmen, manufacturer representatives, fire fighters and other invitees.
Since 1927, the Canadian Standards Association (CSA) has produced the Canadian Safety Standard for Electrical Installations, which is the basis for provincial electrical codes. The CSA also produces the Canadian Electrical Code, the 2006 edition of which references IEC 60364 (Electrical Installations for Buildings) and states that the code addresses the fundamental principles of electrical protection in Section 131. The Canadian code reprints Chapter 13 of IEC 60364, but there are no numerical criteria listed in that chapter to assess the adequacy of any electrical installation.
Although the US and Canadian national standards deal with the same physical phenomena and broadly similar objectives, they differ occasionally in technical detail. As part of the North American Free Trade Agreement (NAFTA) program, US and Canadian standards are slowly converging toward each other, in a process known as harmonisation.
Some components and symbols of wiring diagram are: Capacitor, used to store electric charge. Toggle Switch, stops the flow of current when open. Push Button Switch, momentarily allows current flow when button is pushed in, breaks current when released. Battery, stores electric charge and generates a constant voltage .Resistor, restricts current flow. Ground wire, used for protection. Circuit breaker, used to protect a circuit from an overload of current. Inductor, a coil that generates a magnetic field. Antenna, transmits and receives radio waves. Surge protector, used to protect a circuit from a spike in voltage. Lamp, generates light when current flows through. Diode, allows current to flow in one direction indicated by an arrowhead or triangle on the wire. Microphone, converts sound into electrical signal. Electrical motor. Transformer, changes AC voltage from high to low or vice versa. Headphone. Thermostat. Electrical outlet. Junction box.
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