En un código eléctrico típico, es obligatorio codificar los cables por colores. Existen numerosas normas y excepciones locales según el país, estado o región.[1]​ Las instalaciones más antiguas varían en sus códigos de color, y los colores pueden desteñirse con la exposición del aislamiento al calor, la luz y el envejecimiento.

Starting in 1970, European countries began a process of harmonizing the colors of their wiring, since several countries had chosen the same color to designate different cables. The new harmonized colors were chosen mainly because no country had used them. Colors such as pink, orange and turquoise were not available as they were considered too similar to other colors. Still, inevitable conflicts occurred. Blue was a phase driver in the United Kingdom and Ireland, which delayed the adoption of the new colors for several decades. However, the flexible cable was changed almost immediately after pressure from appliance manufacturers.[2][3]​.

Post-harmonized European colors

Since March 2011, the European Committee for Electrotechnical Standardization (CENELEC) requires the use of cables with green/yellow stripes as protective conductors, blue as neutral conductors and brown as single-phase conductors.[10]​.

The use of the striped green/yellow color for ground conductors was adopted for its distinctive appearance to reduce the likelihood of dangerous confusion of safety ground wires with other electrical functions, especially by people with red-green color blindness.

In Sweden there is a notable exception for blue: although this color is normally used for the neutral, it can be used as a connecting cable between switches and between the switch and the luminaire, as well as as a phase cable in a two-phase circuit, provided that a neutral cable is not used in the circuit in question.[11]​[12]​.

In the UK, it is quite common to use three-phase, colour-insulated, three-pole cable for some of the wiring in two-way lighting switches. To avoid confusion, it is acceptable to add brown or blue sleeves to the ends, as appropriate, to indicate how the cables are used.[13]​.

USA

The United States National Electrical Code requires a bare copper protective conductor, with green or green/yellow insulation, a white or gray neutral, and any other color for single phase. The NEC also requires that the high-branch conductor of a high-branch delta system have orange insulation or be identified by other appropriate means, such as labeling. Prior to the adoption of orange as the suggested high-branch color in the 1971 NEC, it was common practice in some areas to use red for this purpose.[14]

The introduction to the NEC clearly states that it is not intended to be a design manual, and therefore creating a color code for ungrounded or "live" conductors is outside its scope and purpose. However, it is a common misconception that the Code requires color coding of "live" conductors.

In the United States, color coding of conductors in three-phase systems follows a de facto standard: black, red, and blue are used for 120/208-volt three-phase systems, and brown, orange or purple, and yellow are used for 277/480-volt systems. (Purple avoids conflicts with the NEC's high voltage delta rule.) In buildings with multiple voltage systems, the grounded (neutral) conductors of both systems must be identified separately and distinguished to avoid connections between systems. Most commonly, 120/208 volt systems use white insulation, while 277/480 volt systems use gray insulation, although this particular color coding is not currently an explicit requirement of the NEC.[15]​ However, some local jurisdictions do specify the required color coding in their local building codes.

En un código eléctrico típico, es obligatorio codificar los cables por colores. Existen numerosas normas y excepciones locales según el país, estado o región.[1]​ Las instalaciones más antiguas varían en sus códigos de color, y los colores pueden desteñirse con la exposición del aislamiento al calor, la luz y el envejecimiento.

Starting in 1970, European countries began a process of harmonizing the colors of their wiring, since several countries had chosen the same color to designate different cables. The new harmonized colors were chosen mainly because no country had used them. Colors such as pink, orange and turquoise were not available as they were considered too similar to other colors. Still, inevitable conflicts occurred. Blue was a phase driver in the United Kingdom and Ireland, which delayed the adoption of the new colors for several decades. However, the flexible cable was changed almost immediately after pressure from appliance manufacturers.[2][3]​.

Post-harmonized European colors

Since March 2011, the European Committee for Electrotechnical Standardization (CENELEC) requires the use of cables with green/yellow stripes as protective conductors, blue as neutral conductors and brown as single-phase conductors.[10]​.

The use of the striped green/yellow color for ground conductors was adopted for its distinctive appearance to reduce the likelihood of dangerous confusion of safety ground wires with other electrical functions, especially by people with red-green color blindness.

In Sweden there is a notable exception for blue: although this color is normally used for the neutral, it can be used as a connecting cable between switches and between the switch and the luminaire, as well as as a phase cable in a two-phase circuit, provided that a neutral cable is not used in the circuit in question.[11]​[12]​.

In the UK, it is quite common to use three-phase, colour-insulated, three-pole cable for some of the wiring in two-way lighting switches. To avoid confusion, it is acceptable to add brown or blue sleeves to the ends, as appropriate, to indicate how the cables are used.[13]​.

USA

The United States National Electrical Code requires a bare copper protective conductor, with green or green/yellow insulation, a white or gray neutral, and any other color for single phase. The NEC also requires that the high-branch conductor of a high-branch delta system have orange insulation or be identified by other appropriate means, such as labeling. Prior to the adoption of orange as the suggested high-branch color in the 1971 NEC, it was common practice in some areas to use red for this purpose.[14]

The introduction to the NEC clearly states that it is not intended to be a design manual, and therefore creating a color code for ungrounded or "live" conductors is outside its scope and purpose. However, it is a common misconception that the Code requires color coding of "live" conductors.

In the United States, color coding of conductors in three-phase systems follows a de facto standard: black, red, and blue are used for 120/208-volt three-phase systems, and brown, orange or purple, and yellow are used for 277/480-volt systems. (Purple avoids conflicts with the NEC's high voltage delta rule.) In buildings with multiple voltage systems, the grounded (neutral) conductors of both systems must be identified separately and distinguished to avoid connections between systems. Most commonly, 120/208 volt systems use white insulation, while 277/480 volt systems use gray insulation, although this particular color coding is not currently an explicit requirement of the NEC.[15]​ However, some local jurisdictions do specify the required color coding in their local building codes.