Wire and cable labeling is an essential characteristic of cables that allows you to choose the best product for your electrical project. Reading manufacturer labels is a crucial aspect of wire and cable literacy. 

As a rule, all cable labels are printed on the cable jacket. This guide focuses on all cable manufacturer labels, including gauge, voltage, and insulation.

Size of conductor wire label

The size of the conductor label indicates the size of the cable measured in AWG (American wire gauge). For cables also sold in Europe, manufacturers may use square mm2 or mm to identify the cable size.

Sometimes, the marking of the cable size may also contain the number of wires found in the electrical cable and whether the ground wire is present (f.e. 10-3 w/G - means 10 AWG, three wires with the ground).

Possible markings identifying cable size: 14 AWG, 12 AWG, 10 AWG, 10-3w/g, 8-2G.

UL file marking

This type of marking is a long code that describes the name of the certified manufacturing company to produce the specific cable type. This label does not contain any information about the cable beyond the fact that it is produced by a UL-certified company.

Possible markings: E802357

Type of cable label (insulation and application)

This section contains the actual name of the cable, which also describes the characteristics of the said cable.

For example:

• THHN: thermoplastic high-heat-resistant, nylon-coated 
• RHHW: rubber insulated 90 C moisture-resistant
• SE: service entrance cable
• NM-B: non-metallic sheathed 90 C 
• UF-B: underground feeder branch circuit cable

Sometimes, the cable can be identified by its insulation instead of the full abbreviation of the cable type:

• XLPE: cross-linked polyethylene insulation
• PVC: polyvinyl chloride insulation
• FEP: fluorinated ethylene propylene

Meaning of common letters in cable labels:

These are the basic letters that are often found on different types of cables. Some types of wiring, such as portable power cables, will have different letters.

Insulation maximum rated voltage label

The voltage rating of the cable is indicated by numbers and the letter V or just by a number.

Examples: 600v, 300v, 12,5kV, 300, 600.

Type of conductor label

The metal the cable conductors are made of is indicated as cu for copper or al for aluminum.

Manufacturer label

Some manufacturers might have their entire name on the cable, such as Belden.

Specification label

Certifications of the cable may often be found on the cable markings.

• UL: Underwriter Laboratories-certified
• TUV: Certification for solar panels
• ISO: Certified by International Organization for Standardization
• VW-1: Passes vertical flame test administered by UL
• FT-2: Type of fire testing

There are other specifications that might end up on the jacket of the cable. NEC articles are never mentioned for cable labeling, as NEC is not a certification.

Temperature Ranking

If the cable is standardized by CSA, it can have its maximum operating temperature written on the cable.

Examples: 75°C, 90°C.

Other types of labels

•  "SUNLIGHT RESISTANT," "SUN. RES." or "SR" - indicates resistance to UV lights.
• “OIL RESISTANT I”, “OIL RES I”, “OIL RESISTANT II”, “OIL RES II” - indicate various types of oil resistance.
• “FOR DIRECT BURIAL,” “DIRECT BURIAL,” “DIR BUR” or “DIR BURIAL” - the cable is suitable for direct burial

UL-certified cables with appropriate labels are sold by NNC, one of the fastest-growing wire and cable distributors in North America.