Electric Wire Color Code
With all the professionals, technicians, and other technical staff, along with the DIYers directly involved in working on electrical devices, it is crucial as a DIYer that you would know at least the very basic rules about electrical wiring color coding systems and be able to read the coding accurately.
The color of the wires you’re looking at is actually telling you crucial information about the function it serves within a circuit, what it carries, and how lethal or not lethal it might be.
It is generally not very complex to learn, but if you don’t pay attention and hook up circuitry with whatever wiring you already have on hand, it could prove very dangerous for you or anyone else that might service this very circuit later on. So knowledge is of the essence.
There are certain specific standards that have been established and can vary depending on your location, the kind of current, the voltage, and other factors that you must follow for each of your specific projects—the rules will vary, for example, when you’re working at installing a ceiling fan from doing electrical repairs in your vehicle.
The same for the DIYer in South Africa who will work with some different color coding than what you will use in the US or in Canada. The rules throughout North America, however, are very similar.
The Household and Commercial 240 VAC Feed
The power line feeding your home or any commercial buildings comes into your electrical panel at 240 volts with a center tap from the main transformer at the street, dividing it into two lines of 120 volts AC each (Figure 1a- left).
Except for the Neutral wire which needs to be color-coded white, electric wiring larger than # 6 AWG is typically manufactured with black insulation. The two black lines from the utility company carry 240 volts AC and are both considered “Hot,” while the third wire with white insulation and tapping right in the center of the transformer coil is considered Neutral with 0 volts with reference to the Ground and therefore provides you with the 120 volts AC to each one of the hot black wires.
Consequently, of the two wires coming from the breaker panel connected to a 120 volts circuit breaker and wired through a 12/2 or 14/2 cable, you have a black wire hooked directly to the circuit breaker’s only terminal, which in turn is connected to one of the two Hot wires feeding the electric panel while the white is hooked up to the Neutral bus bar.
So following the protocol, you should only use cables containing one white, one black, and one green or copper wire when adding to a regular 120 volts junction or terminal box.
Single-Phase 240 VAC
The 240 volts circuit breakers in your electric panel have two terminal screws or two separate circuits—each one of them connected to one of the two black Hot wires. In a single-phase 240 volts circuit, the AC voltage is produced from a sine wave going from a positive peak of +120 volts, then dropping to 0 volts at the midpoint to keep dropping to a negative peak of -120 volts (Figure 1b - right).
You can see from this that even though both lines are at 240 volts, they’re both different in the fact that while one is at a maximum +120 volts, the other one is at its minimum of -120 volts. From the circuit breaker on, when you tap two wires coming from the same cable in order to get 240 volts, each of the two wires must be coded by 2 different colors (but never white).
1) Single-Phase 208 VAC
In commercial buildings throughout North America, a single-phase 208 VAC is commonly used to power single-phase lighting and larger heating, ventilating, and air conditioning loads. Although you occasionally hear about it, you probably will not or shouldn’t ever have to work with it as a DIYer as it is not encountered in private homes. It does, however, follow the same rules as other single-phase color coding.
1.1) - USA Wiring Color Code for Single-Phase Power
a) Protective Ground (PG or G) - Is identified with green, green-yellow, or bare wire.
b) Neutral (N) - Is identified with white or sometimes gray insulation.
c) Single-phase Line (L) - In principle, any color besides the ones listed above may be used for the power conductors. The colors usually used as the local practice are black, and red for a second hot, but blue, orange, or any other different color may also be used.
1.2) - Single-Phase Canadian Color Coding
a) Protective Ground (PG, G, or GND) - The ground is always identified by green, yellow-green insulation or bare wire.
b) Neutral (N) - The neutral always has white insulation.
c) Single-phase Line (L) - The hot or live wires are black and also red for a second active line, although blue, orange, or any other different color may also be used.
Note - Blue, yellow, orange, or other wire colors are often used as travelers on 3-way and 4-way switches or as switch legs when wiring ceiling fans, lights, and switched outlets.
2) Commercial and Industrial 3-Phase Power Feeds
Single-phase voltage, as described previously, is the voltage produced from 1 phase or secondary winding of its generating transformer, while the 3-phase configurations of a transformer’s secondaries produce voltages across every one of those three phases. The 3-phase power feeds can be produced using two different configurations:
a) The Delta system (figure 2) has three hot lines at full voltage plus one ground wire with the hot lines connected across each of 3 transformer secondary windings
b) The Wye system (Figure 3) has a total of 5 wires—3 hot wires, one neutral wire, and a ground wire. Each of the three hot lines is connected to one of three secondary transformer windings at one end, with the other end of every winding connected together at a single neutral point.
A three-phase voltage supply is commonly used to power large motors and other heavy loads to avoid power fluctuations. It is therefore used in most commercial and industrial situations and sometimes in large homes drawing large currents of electricity to power up larger appliances.
2.1) USA 3-Phase Color Coding
a) Protective GND and Neutral As noted previously, white remains the universal color of choice in all the different systems’ coding, with the exception sometimes given to gray in the US. Also following the rules of single-phase, the GND will keep being identified with green, green-yellow, or bare wire.
The USA has its own wiring colors for electrical circuits, black, red, and blue are used for 208 VAC three-phase; brown, orange, and yellow are used for 480 VAC.
b) Line L1 on the 3-phase L1 - Black is the common color of choice, with brown as an alternative.
c) Line L2 on the 3-phase L2 - Red insulated wires are commonly used with orange as an alternative.
d) Line L3 on the 3-phase L3 - Blue wires or yellow as an alternative are used for the L3 phase.
2.2) Canadian 3-Phase Color Coding
a) Protective GND and Neutral The color coding for the GND (G) and the neutral (N) follows the same rules as for the Canadian single-phase wiring.
b) Line L1 on the 3-phase L1 - Phase 1 is identified with the red color.
c) Line L2 on the 3-phase L2 - Phase 2 is identified with black.
d) Line L3 on the 3-phase L3 - Phase 3 is identified with blue.
It should be mentioned at this time, however, that even though you may now know a little more about 3-phase wiring, it should never be tampered with by anyone not certified to do so (namely DIYers), as it presents many more hot lines to deal with thus considerably increasing the chances of getting injured in the process.