Electricity: Wires and Connectors

How to Read Cable

It’s critical to understand the information imprinted along the length of wires or cables. Manufacturers abbreviate the descriptive code names for all of the different types of wires and cables. In this example:

The wording AWG 14 CU 3 CDR with AWG 14 GROUND indicates three insulated No. 14 American Wire Gauge (AWG) wires and a bare or green-insulated grounding wire. NM indicates nonmetallic- sheathed cable. CU indicates the wire is copper. AL indicates aluminum. B indicates the insulation on the wires in the cable is rated for 90°C.

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Brand Name Manufacturers
3/0 Gauge:  200 Amps (Service entrance), 1/0 Gauge: 150 Amps (Service entrance and feeder wire), 3 Gauge: 100 Amps (Service entrance and feeder wire)
6 Gauge: 55 Amps (Feeder and large appliance wire), 8 Gauge: 40 Amps (Feeder and large appliance wire)
10 Gauge: 30 Amps (Dryers, appliances, and air conditioning), 12 Gauge: 20 Amps (Appliance, laundry and bathroom circuits), 14 Gauge: 15 Amps (General lighting and receptacle circuits)

Wire Gauges, Ampacity, and Use

Note: The amperages listed above are based on equipment terminations rated at 75°C. For dwelling-service installations, smaller conductors may be permitted by code.

Types of Cable

Type NM-B (nonmetallic sheathed) cable contains two or more insulated wires and a grounding wire with a nonmetallic outer sheath that's flame retardant and moisture resist ant. NM-B cable is only permitted in dry locations and can be installed in both exposed and concealed work in one- and two-family dwellings. (2-wire with ground; 3-wire with ground)

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Types of Cable (cont.)

Type SE (service-entrance) cable is often used indoors for feeding sub-panels or large appliances. Type USE (underground service entrance) cable is approved for direct burial to detached garages and other structures.

Type UF-B (underground feeder and branch-circuit) cable is approved for direct burial and is used to run power to garages, outdoor lights and well pumps.

Type AC (armored cable) contains a metal strip to qualify the sheath for grounding purposes. Plastic inserts inside connectors prevent wire abrasion. Use in dry indoor locations only.

Wire Connectors

Always use the right connector for the job. Read the package instructions to determine the size, type (solid or stranded) and number of wires that can be used with each connector, how much installation to strip from each wire and whether the wires first need to be twisted together.

Screw-on connectors. Strip insulation, hold wires parallel to each other with ends lined up and twist connector in clockwise direction. No bare wire should show below connector skirt.
Grounding connectors. Special connectors for splicing only grounding wires allow one longer wire to protrude as a pigtail to connect to receptacles and switches.
Direct-bury connectors. Connectors approved for direct burial are filled with silicone sealant and often used for lampposts, lawn sprinklers or other high-moisture applications. AL/CU connectors. For homes with aluminum wiring, special AL/CU connectors allow aluminum and copper wires to be spliced together. Copper pigtails then connect to standard receptacles and switches.
Direct-bury splice kit. Underground splice kits allow simple repair of damaged cables. Direct-bury splice kit. Underground splice kits allow simple repair of damaged cables.

Last modified: Saturday, 2007-11-03 1:12 PST