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NM Cable (Romex®)

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NM is a type of cable that contains insulated conductors enclosed within an overall nonmetallic jacket. It is commonly known as “Romex®”, which is the brand that is most widely used. NM cable contains two or more insulated wires and a bare ground wire. NM is normally used in one- and two-family dwellings, and certain multifamily dwellings. NM-B is what you will see when shopping for NM cable, which is rated for 90 degrees C (194 degrees F).

There are many different ways to wire a dwelling during initial construction using NM cable. The most common type of NM used are 2-wire and 3-wire.

A 2-wire NM contains one black wire (usually hot) and one white wire (usually neutral) and a bare ground wire. When used in switch wiring, the white wire is sometimes used as a hot wire.

A 3-wire NM contains a black, red, white, and a bare ground wire. The black and red wires can be used for 120 volts A and B phases, or as travelers in 3- or 4-way switch wiring.

14 AWG NM rated for 15 amps

14 AWG NM rated for 15 amps

12 AWG NM rated for 20 amps

12 AWG NM rated for 20 amps

10 AWG NM rated for 30 amps

10 AWG NM rated for 30 amps

A 12-2 NM cable (2-wire) contains 2 insulated 12 AWG current carrying conductors (black and white) and a bare ground wire.

A 14-3 NM cable (3-wire) contains 3 insulated 14 AWG current carrying conductors (black, red, white) and a bare ground wire. The 2 hot wires are different phases (A and B) and share the neutral wire for return current.

Wire AWG

12-2

Number of current carrying conductors