3wire

3wire is a term most often encountered in electrical engineering and residential wiring. It typically denotes a cable or conductor assembly consisting of three separate conductors: two hot wires and a neutral. It is not a universal or standardized product on its own.

In North American split-phase systems used for homes, the two hot legs are equal magnitude but opposite phase; the voltage between the two hots is 240 V, while each hot to neutral is 120 V. A three-conductor cable was used to provide both 120-V circuits and 240-V service via a single run. In some older appliances, the neutral also served as a ground path; a strap inside the appliance connected the frame to neutral. Modern installations typically use four conductors (two hots, a neutral, and a separate equipment-grounding conductor).

Code and safety: Many jurisdictions allow existing three-wire services in older residences but require updates for new work. The 4-wire standard improves safety by providing a dedicated grounding path and separating neutral from equipment grounding. Work should adhere to local electrical codes and be performed by qualified professionals.

Beyond wiring, "3wire" may appear as a brand name or product designation in various technical fields, but the term itself primarily refers to the three-conductor wiring arrangement.