Which arrangement describes standard 120/240 V residential service in the US?

Which arrangement describes standard 120/240 V residential service in the US?

• A. 277/480 V three-phase service.
• B. 208 V three-phase service.
• C. 120/240 V split-phase service.
• D. 600 V delta service.

Answer: (C)

The core idea is that US homes typically get a split‑phase setup from a center‑tapped transformer. This gives two hot conductors that are 180 degrees apart. Each hot to neutral provides 120 V, which is what most lighting and outlets use, and the two hot conductors together provide 240 V for large appliances like ranges and dryers. The neutral carries the return current for the 120 V circuits, while grounding provides safety. Other voltages you might see are for different systems: 277/480 V three‑phase is used mainly for commercial/industrial lighting and equipment; 208 V three‑phase (often from a 120/208 V wye) is common in some commercial buildings, with 120 V line‑to‑neutral but 208 V line‑to‑line; and 600 V delta is an industrial service. None of these are standard for residential homes.

The core idea is that US homes typically get a split‑phase setup from a center‑tapped transformer. This gives two hot conductors that are 180 degrees apart. Each hot to neutral provides 120 V, which is what most lighting and outlets use, and the two hot conductors together provide 240 V for large appliances like ranges and dryers. The neutral carries the return current for the 120 V circuits, while grounding provides safety.

Other voltages you might see are for different systems: 277/480 V three‑phase is used mainly for commercial/industrial lighting and equipment; 208 V three‑phase (often from a 120/208 V wye) is common in some commercial buildings, with 120 V line‑to‑neutral but 208 V line‑to‑line; and 600 V delta is an industrial service. None of these are standard for residential homes.