Electrical wiring in general refers to conductors used to carry electricity and their accessories. General aspects of electrical wiring as used to provide power in or to buildings and structures, commonly referred to as building wiring, are described in Electrical wiring. It has been suggested that Conductor (power engineering) be merged into this article or section. ... Lightning strikes during a night-time thunderstorm. ... Electrical wiring in general refers to conductors used to carry electricity and their accessories. ...

This article provides information specific to electrical systems in common use in the U.S.. ...

Design and installation conventions

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 which they cannot distribute for copyright reasons and then distribute documents describing how local codes vary from the published codes. 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 arizing from the use of electricity.

In addition to new construction, additions or major modifications must follow the legal code, 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 each 5yr) 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 which 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 more expensive).
• minimum 14AWG wire, copper or 12 awg aluminum for 15 amp circuits (some local codes require a minimum of 12 gauge 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 receptacles 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, recepticals in the crawl space, basements, bathrooms and a receptacle for the laundry, 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. Such breakers are still used.)

Since the GFCI senses the unbalance of current between the phase | hot wire, and the grounded neutral wire, this type receptacle must be used to upgrade 2 wire circuits having no grounding conductor in the cable. Such are to be labeled "no grounding". ... Neutral means balanced between two or more opposites. ... In electrical engineering, residual current circuit breakers (RCCB) or residual current devices (RCD) are circuit breakers that operate to disconnect their circuit whenever they detect that current leaking out of the circuit (such as current leaking to earth through a ground fault) exceeds safety limits. ...

Most GFCI receptacles allow the connection and have GFCI protection for down- stream connected receptacles. These so protected receptacles should be labeled "GFCI protected".

• all bedroom circuits with receptacles must have arc-fault circuit interrupter protection, because arcs produce high temperatures.
• most circuits have the metallic components interconnected with a grounding wire connected to the third, round prong of a plug.
• recommended to put light fixtures on separate circuits than outlets
• minimum of two 20 amp countertop circuits for kitchen use
• furnaces, water heaters, heat pumps, central air conditioning units, stoves on dedicated circuits
• recommended to put ALL major appliances on dedicated circuits (including refrigerator and dishwasher)
• use of exterior components for exterior lighting and outlets
• electrical boxes must be properly sized to prevent heat build- up, especially from joints, and just having so many items in too small a space. (Incorrect box size is a very common mistake.)

An arc-fault circuit interrupter (AFCI) is a device designed to prevent fires by detecting electrical arcs and disconnecting power before the arc starts a fire. ... A kitchen is a room used for food preparation. ... A furnace is a device for heating air or any other fluid. ... A water heater or hot water system is an appliance for heating water above its ambient temperature. ... A heat pump is a machine which moves heat from a low temperature reservoir to a higher temperature reservoir under supply of work. ... Note: in the broadest sense, air conditioning can refer to any form of heating, ventilation, and air-conditioning. ... A stove is a heat-producing device. ... The inside of a fridge A refrigerator (often shortened to fridge) or freezer is an electrical appliance that uses refrigeration to help preserve food. ... A dishwashing machine The term dishwasher can represent either a person who washes (cleans) dishes (a term commonly used in the food service industry) or a machine that performs a similar function. ...

See also

• National Electrical Code (US)
• Electrical wiring

The National Electrical Code is Part 70 of a set of codes and standards set forth by the National Fire Protection Association (NFPA). ... Electrical wiring in general refers to conductors used to carry electricity and their accessories. ...

External links

• The NEC at NFPA.org
• Summary of NEC Color Code