A split-phase or single-phase three-wire system is a type of single-phase electric power distribution. It is the alternating current (AC) equivalent of the original Edison Machine Works three-wire direct-current system. Its primary advantage is that, for a given capacity of a distribution system, it saves conductor material over a single-ended single-phase system, while only requiring a single phase on the supply side of the distribution transformer. This system is common in North America for residential and light commercial applications. Two 120 V AC lines are supplied to the premises that are out of phase by 180 degrees with each other (when both measured with respect to the neutral), along with a common neutral. The neutral conductor is connected to ground at the transformer center tap. Circuits for lighting and small appliance power outlets (i.e., NEMA 1 and NEMA 5) use 120 V circuits—these are connected between one of the lines and neutral using a single-pole circuit breaker. High-demand applications, such as ovens, are often powered using 240 V AC circuits—these are connected between the two 120 V AC lines. These 240 V loads are either hard-wired or use NEMA 10 or NEMA 14 outlets which are deliberately incompatible with the 120 V outlets. Other applications of a split-phase power system are used to reduce the electric shock hazard or to reduce electromagnetic noise. Connections A transformer supplying a three-wire distribution system has a single-phase input (primary) winding. The output (secondary) winding is center-tapped and the center tap connected to a grounded neutral. As shown in Fig. 1, either end to center has half the voltage of end-to-end. Fig. 2 illustrates the phasor diagram of the output voltages for a split-phase transformer. Since the two phasors do not define a unique direction of rotation for a revolving magnetic field, a split single-phase is not a two-phase system. In the United States and Canada, the practice originated with the DC distribution system developed by Thomas Edison. By connecting pairs of lamps or groups of lamps on the same circuit in series, and doubling the supply voltage, the size of conductors was reduced substantially. The line to neutral voltage is half the line-to-line voltage. Lighting and small appliances requiring less than 1800 watts may be connected between a line wire and the neutral. Higher wattage appliances, such as cooking equipment, space heating, water heaters, clothes dryers, air conditioners and electric vehicle charging equipment,