One of the key to proper electrical wiring installation is the use of correct letters and colors of electrical wires. These specifications of electrical wires need to be followed accurately in order for the electrical appliance, unit or system to function safely and efficiently.
The different colors of electrical cables will tell the purpose of the wires. Those in black are at all times utilized as hot wires. They are frequently used for switch legs and may be fed to an outlet or switch. These wiring must never be used in ground or neutral connections.
Red wires are used like black ones. They are utilized as hot wires or switch legs such as that in ceiling fans. Electrical installations of circuits that run on 220 volt power, reds serve as second hot-wires. Wires in red color are also applied as the wire that interconnects hardwired detectors for smoke.
Other colors utilized as hot wires are yellow and blue colored. They are frequently heaved in conduits. Switches with 3 or 4 way applications which are commonly installed for travelers are used with blue wires. Fans and light switches also have switch legs in blue wiring. Generally, yellow colored wirings are used as switch legs for controlling units such as fans, light and other outlets that require switches.
Bare or exposed copper cables as well as green wires are basically utilized for grounding installations. Such will be connected to grounding units and devices or linked to a junction box and appliances intended for safety reasons.
In some instances, wiring colors are also applied in electrical wiring installation that does not adhere to the general rules of wiring. A white for example, that is inside a cable with 2 conductors is utilized as succeeding hot wire in an outlet or appliance running on 240 volts. Whites may also be used as switch leg in a 3-way switch or lighting fixture. It is important to properly mark it to indicate that it is used for such application other than being a neutral wire. The end of the wire may be simply attached with red or black electrical tape.
Aside from the colors, they also have letter specifications that will indicate the wire's traits and purposes. A wire labeled THWN is fire and heat resistant. The insulation can very well be utilized in either damp or dry settings but not in wet areas. THHN are frequently used in installations of conduits found in residential and commercial areas. They have a nylon insulation that makes the wires smaller and more flexible than wires with rigid plastic insulation. THW labeled wiring are also heat and fire resistant as well as moisture retardant. These wires can be used in wet, damp or dry applications. Underground feeds which are likely exposed to moisture are ideally used with this type of wires. XHHN wires are for service entrance applications.
The letter T means that that cable has thermoplastic insulation. H denotes that it can resist heat. HH is an indication that it can resist heat and may endure higher temperature ratings of up to 194 F. W denotes that it may be used in wet or damp locations but may also be suitable in dry applications. X means the wire is made with fire-proof synthetic polymer and N means nylon insulation covers the wire.