Which statement correctly describes the service configuration for the 50-unit apartment complex with 4 kW dryers?

Which statement correctly describes the service configuration for the 50-unit apartment complex with 4 kW dryers?

• A. 120/208V 3-phase 4-wire
• B. 120/240V 3-phase 4-wire
• C. 277/480V
• D. 120/208V 3-phase 3-wire

Answer: (A)

In a multi‑unit dwelling like a 50‑unit complex, you need both 120V circuits for lights and outlets and a suitable voltage for large appliances. A 120/208V, three-phase four‑wire system fits this need. It uses three hot legs with a neutral (the fourth conductor). Each hot leg to neutral provides 120V for general-purpose circuits, while any pair of hot legs gives about 208V for larger loads. The neutral allows 120V loads on any phase and helps keep the system balanced. This configuration is standard for larger buildings served by a three‑phase feeder, providing the necessary neutral for 120V loads and 208V for equipment, along with good capacity and balancing options. The other options either lack a neutral, present a nonstandard or unsuitable high voltage for typical apartment dryers, or don’t provide the 120V/208V combination needed.

In a multi‑unit dwelling like a 50‑unit complex, you need both 120V circuits for lights and outlets and a suitable voltage for large appliances. A 120/208V, three-phase four‑wire system fits this need. It uses three hot legs with a neutral (the fourth conductor). Each hot leg to neutral provides 120V for general-purpose circuits, while any pair of hot legs gives about 208V for larger loads. The neutral allows 120V loads on any phase and helps keep the system balanced.

This configuration is standard for larger buildings served by a three‑phase feeder, providing the necessary neutral for 120V loads and 208V for equipment, along with good capacity and balancing options. The other options either lack a neutral, present a nonstandard or unsuitable high voltage for typical apartment dryers, or don’t provide the 120V/208V combination needed.