1. 120/240V Single Phase
- Use: This is the standard for most residential homes. It powers lighting, appliances, and small machinery.
- Setup: It typically involves two 120V hot wires and a neutral wire. The voltage between the hot wires is 240V (used for high-power appliances like ovens and dryers), and between either the hot wire and the neutral, it's 120V (for standard outlets).
2. 120/208V Three Phase
- Use: Common in larger residential buildings like condominiums and also in commercial properties. It's preferred for systems that need a more balanced power load, like HVAC systems and commercial refrigeration.
- Setup: This system uses three hot wires and a neutral. The voltage between any two hot wires is 208V, and between any hot wire and neutral, it's 120V. This setup provides a more consistent power flow and is more efficient for running three-phase motors.
3. 120/240V Three-Phase Delta
- Use: Often seen in older commercial and industrial installations. It's unique due to its 'high leg' or 'wild leg' feature.
- Setup: This configuration has three hot wires, with one of them (the 'high leg') being at a higher voltage to ground (typically around 208V). The voltage between the other two hot wires and the neutral is 120V, and between any two hot wires is 240V. This setup allows for both 240V and 120V loads to be served, but special attention is needed due to the high leg.
4. 277/480V Three-Phase
- Use: Common in large commercial and industrial facilities. This higher voltage is efficient for powering large equipment, lighting systems, and HVAC systems in big buildings.
- Setup: Similar to the 120/208V setup, it has three hot wires and a neutral. The voltage between any two hot wires is 480V (used for heavy machinery), and between any hot wire and the neutral, it's 277V (commonly used for lighting fixtures in commercial buildings).
Additional Considerations:
- Safety and Efficiency: Each voltage type has its safety considerations and efficiency benefits. The choice depends on the power needs of the building and the equipment used.
- Transformer Configurations: These voltage types are achieved through different transformer configurations at the utility level or within the building's own electrical system.
- Regulations and Codes: Always comply with the National Electrical Code (NEC) and local regulations when dealing with these systems.