This article provides information specific to electrical systems in common use in the U.S. .
Although much of the Electrician 's field terminology matches that of the National Electrical Code (US) , usages can and do vary.
- Neutral refers to a conductor with continuity to the electrical system's neutral Bus in the main service panel. Code requires that this bus also be well Grounded .
- is any conductor (wire or otherwise) connected with an electrical system, that has Electric Potential to Electrical Ground or Neutral (ground and neutral should be Equipotential in a correctly-configured system). Because a person is more likely to provide a path from a conductor in the electrical system to an inadvertent ground/neutral (the floor, a pipe, equipment housings, etc...), rather than the opposite, such a person is likely to experience 'hot' wires as hot, and neutral or ground wires as not-so-hot.
- is a conductor with continuity to earth.
- as in 'Hot leg' refers to one of multiple '''Hot''' conductors in an electrical system. One such leg will have a higher potential to another hot leg than to ground or neutral, typically 208V or 240V, depending on the Electrical Service for the system. The most common service in the U.S., single-phase, 240V, features a neutral and two hot legs, 240V to each other, and 120V each to the neutral.
- is a wiring configuration in which the full-potential circuit is available at the fixture location, while one half of the circuit (hot in new installations, but often neutral in older Knob-and-tube systems) is routed from the fixture location, through a switch, and back and into the fixture itself.
The National Electrical Code (NEC) specifies acceptable wiring methods and materials in the United States. Local jurisdictions usually adopt the NEC or another published code and then distribute documents describing how local codes vary from the published codes. They cannot distribute the NEC itself due to copyright reasons. A new NEC is published every three years by the National Fire Protection Association (NFPA) after public input. The stated purpose of the NEC is to protect persons and property from hazards arising from the use of electricity.
New construction, additions or major modifications must follow the legal code, which is not necessarly the latest code. However, no court has ever punished anyone for using the latest code. Generally, unless major work is being done, the existing wiring does not have to be changed to meet new codes; however, it is recommended that older wiring be inspected periodically (about every 5 years) for safety.
Note: What is commonly called an outlet is called a receptacle in the NEC. In the NEC an outlet is a device for easily connecting a utilization device by inserting a mating plug.
For residential wiring, some basic rules based on the 2002 NEC are:
(This is just a brief overview and should not be used as a replacement for the actual code.)
- '' Phase '' wire in a circuit may be black, red, orange (high leg delta) insulated wire, sometimes other colors, but never green, gray, or white whether of these as solid colors nor of stripes.
- '' Neutral '' wire is connected to the center tap of the final step- down transformer; identified by gray or white insulated wire, perhaps with stripes; most commonly bonded to earth for a fixed known path to stabilize the voltages only at the main service panel; many times called the grounded wire. Note that all metallic systems in a building are to be bonded to the panel; eg: water, gas, HVAC piping, etc.
- ''Grounding'' wire of circuit may be bare or identified insulated wire of green or having green stripes.
- Larger wires are furnished only in black, these may be properly identified with suitable paint or tape. The phase wire for a switch "leg" is the white wire of a two insulated wire cable, the black wire is connected to the light.
- Minimum 12AWG copper wire for 20 amp circuits (stranded may also be used, but is slightly more expensive).
- Minimum 14AWG copper wire or 12 AWG aluminum for 15 amp circuits. Some local codes require a minimum of 12 gauge copper for 15 amp circuits, except for switch legs -- that is, circuit portions that are strictly between a light switch and the light that it serves.
- All wiring in a circuit except for the leads that are part of a device or fixture must be the same gauge. Note that different size wires may be used in the same raceway so long as they are all insulated for the maximum voltage of any of these circuits.
- A maximum of 8 Duplex Receptacle s on a normal wiring circuit; a better recommendation is a maximum of 4. Refer to the code for specific formulas.
- Ground-fault Circuit Interruptor (GFCI) protection is required on receptacles in wet locations. This includes all small appliance circuits in the kitchen, receptacles in the crawl space, basements, bathrooms and a receptacle for the laundry room, as well as outdoor circuits within easy reach of the ground. However, they are not required for refrigerators because unattended disconnection could cause spoilage of food, nor for garbage disposals. (The first GFCI protection was by breakers, but the cheap, lossy circuit cables caused so many nuisance trips, that this protection is applied at the receptacle. GFCI breakers may still be used.)
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