Basic Terminology: Wire vs Cable

A wire is a material (or conductor) that conducts electricity. It can be a stranded wire or solid metal conductor. It is often insulated using a nonconductive plastic coating.

A cable is a combination (or assembly) of two or more wires, assembled using a single jacket. Nonmetallic-sheathed cable (Type NM) is a cable assembly with an outer sheathing made of non-metallic outer covering.

Simply put? A wire is one electrical conductor, and a cable is multiple conductors encased in sheathing.

Colors

The color of the insulation covering a wire will tell you the purpose of the wiring. These are fairly standard across the industry but be sure to always read the manufacturer’s recommended usage.

White insulation — usually considered grounded or neutral conductors. Under specific situations, they can sometimes be used as ungrounded or hot wiring, and are often marked with black or red to indicate when it is now an ungrounded hot (live) wire conductor

Green insulation and bare copper — equipment grounding conductors or bonding wire conductors

Blue or Yellow insulation — Not limited to but could include ungrounded conductors hot wire pulled through a conduit

Black insulation — Not limited to but could include ungrounded conductors hot wire for switches and outlets

Red insulation — Not limited to but could include ungrounded conductors hot wire for switch legs and hardwired smoke detectors

Marking (NEC 310.8)

Everything that you need to know about a cable is usually stamped on the surface of the cable.

Ownership — The name of the manufacturer, a trademark, or other distinctive marking to let you identify the organization responsible for the cable. Additional manufacturing information may also be listed (such as the date it was made).

Type — The proper tyle letter or letters that indicate the type of cable being used. For example, is it a NM-B or a UF?

AWG Size or Circular Mil Area — In other words, the number of wires in the cable. For example, a cable that indicates 14-2 indicates that there are two insulated conductors (14 gauge).

Voltage rating — the maximum voltage that the cable can safely carry.

Presence of an Equipment Grounding Conductor  — If the word “GROUND” or the letter “G” indicates the presence of a ground wire.

UL Mark — every product that UL certifies has what’s called an E number followed by a series of digits that identify the manufacturer and the product. These may be listed on cables and conductors. The UL Mark will be indicated on the wire.