From what year were four-wire 240V circuits commonly required in electrical installations?

The requirement for four-wire 240V circuits in electrical installations became common in 1996 as outlined by the National Electrical Code (NEC). This change was implemented to improve safety and functionality, particularly with regard to grounding and neutral connections. The addition of a separate ground and neutral conductor in a four-wire system allows for more efficient operation of certain appliances and reduces the risk of electrical shock and fire hazards.

Additionally, this configuration supports modern electrical appliances that require a dedicated ground to function correctly and safely. The transition to requiring four-wire systems reflects an evolution in electrical safety standards intended to minimize risks associated with older wiring practices that did not incorporate a separate grounding conductor.