120240V

120/240 V in residential North American systems refers to a split-phase electrical service that provides two hot conductors each at about 120 volts relative to a neutral conductor, while the voltage between the two hot conductors is about 240 V. The two hot legs are 180 degrees out of phase and derive from a center-tapped transformer. This arrangement allows standard 120 V circuits for outlets and lighting, alongside 240 V circuits for higher-power appliances.

A typical setup uses three or four conductors: two hot wires (often black and red), a neutral (white), and an equipment grounding conductor (green or bare). Time, energy, and safety depend on the neutral carrying only unbalanced current between the hot legs. The service panel includes a main disconnect and a bank of breakers, with common residential service ratings ranging from roughly 100 to 200 amperes.

Safety and codes govern grounding and bonding. The neutral is bonded to the grounding system only at the main service equipment. Ground-fault and arc-fault protection are required in many locations. Wiring and receptacles follow standardized color coding and Ampacity ratings to prevent overloads and shock hazards.

Applications and variants: In homes, 120 V circuits power most outlets and lighting, while 240 V circuits feed large appliances such as electric ranges, electric dryers, and some air-conditioning units. In other regions, different standards apply; three-phase systems like 120/208 V (line-to-line 208 V) or 277/480 V are common in larger buildings, and many countries use 230 V single-phase or 400 V three-phase distributions.

The term 120/240 V is commonly written as a split-phase or center-tapped system and remains a standard foundation of North American domestic electrical infrastructure.