Romex (NM Cable)
The standard cable inside modern American homes: two or three insulated conductors plus a bare ground, wrapped in a plastic sheath. Romex is a brand name; the generic term is NM (non-metallic) cable.
Walk through any home built after the 1960s and virtually every wall hides NM cable: white sheath for 14-gauge (15-amp circuits), yellow for 12-gauge (20-amp), orange for 10-gauge (30-amp) in modern color coding. Inside the sheath: a black hot, a white neutral, and a bare copper ground.
NM cable is rated for dry, protected locations, which defines where it cannot go: outdoors, underground, or exposed to damage, where UF cable or conduit takes over. When an electrician opens your walls during a remodel, the era and condition of the NM cable (early versions used rubber or cloth insulation that crumbles) often decides whether the project includes rewiring.
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- Junction Box : An enclosed box where wires are spliced together.
- Knob and Tube Wiring : The original residential wiring method (roughly 1880 – 1940s): individual conductors on ceramic knobs and tubes, with no ground wire and air-cooled design that modern insulation defeats.
- Aluminum Branch Wiring : Branch-circuit wiring installed in millions of homes from about 1965 – 1973 that develops loose, overheating connections at outlets and switches.
- Pigtail : A short jumper wire connecting a device to the circuit wires in a box, so the device hangs off the circuit instead of carrying it through.