What do the colors of the wires mean?
Release time:
2018-06-11
Black, white, green, red, blue, orange, brown and gray, the color of the insulating sheath on the outside of the wire usually has its own meaning. So, when fiddling with your new light fixture, in addition to turning off the circuit breaker, determine what each colored wire you're going to touch next means.
Black, white, green, red, blue, orange, brown and gray, the color of the insulating sheath on the outside of the wire usually has its own meaning. So, when fiddling with your new light fixture, in addition to turning off the circuit breaker, determine what each colored wire you're going to touch next means.
Residential electricity usage in the U.S. began without systematic color coding, or even a set of standards for proper use. In 1879, shortly after Edison first introduced the electric light bulb, the insurance industry began issuing some safety guidelines. The first formal set of guidelines appeared in 1881 and covered addressing capacity, insulation and installation. But there is no classification of wire colors.
In 1882, the National Board of Fire Underwriters (NBFU) also adopted earlier safety regulations. In 1893, the National Insurance Electric Association began an attempt to unify state-by-state codes and specifications for electrical installations, proposing a national coding standard for light and power installations wired to buildings.
The first National Electrical Code (NEC) was proposed by the NBFU in 1897, which also ignored the normalization of wire color issues. Later, in 1928, the NEC was updated and revised, one of which was to establish a specification for the color of the ground wire, which was later white or natural gray, and also prohibited these colors from being applied to live and neutral wires.
Further color coding is a new version introduced by NEC in 1937, which uses color-coded wires with "multi-branch circuits", and stipulates that the wires of three-branch circuits should be black, red and white. More branches can be added with other colors, such as yellow and blue.
In 1953, NEC changed the color of the ground wire to green or bare wire. Green is also prohibited for circuit wires (such as live and neutral).
The 1971 version of the NEC encoded the colored multi-legs to run, although the white, natural gray, green, and chartreuse stripes remained, and those colors were also banned from ground wire. This time the specification drops the stereotypical color-coding requirements for via wires, because there aren't enough colors to differentiate systems, voltages, and circuits.
In the US now, the ground wire is green, yellow-green striped, or bare, the neutral wire should be white or grey, and the circuit wire may be black, red, blue, yellow, orange, or yellow, depending on the voltage.
These color standards are for the US, other country codes are different (Canada's is very similar to the US). For example, Australia and New Zealand and the United States have the same ground wire color, and their neutral wire is blue or black. Also, live wires can be used in any color other than ground and neutral. Red and brown are the recommended colors for single-phase wires, and red, white and blue are the recommended colors for multi-phase live wires.
The UK last (2004) changed the system to comply with the International Electrotechnical Commission (EC). Their ground wire color (yellow-green stripe) remained the same, and the neutral wire color changed from black to blue. Likewise, single-phase wires that used to be red are now brown. In addition to this, the marking and colouring of polyphase lines in the UK has also changed: L1 from red to brown, L2 from yellow to black, and L3 from blue to grey.
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