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Section 2 Installation
Copyright Goodheart-Willcox Co., Inc.
Ground
240 V
120 V
120 V
Ungrounded
(hot)
Grounded
(neutral)
Ungrounded
(hot)
Figure 10-34. Single-phase, three-wire system. By connecting an ungrounded wire and a grounded wire to a load,
120 V service is obtained. Connecting both ungrounded wires to a load will deliver 240 V.
Utility supply and
ground at pole
System ground
120 V
120 V
120 V
208 V
208 V
208 V
Figure 10-35. A more versatile alternative to single-phase wiring is three-phase wiring. The wye-connected, three-
phase, four-wire arrangement provides 120 V/208 V circuits.