WORKSHOP: Designing Commercial-Scale PV: Three-Phase, the NEC, and Interconnection – Presented by SEI

Moving from residential to commercial PV means larger services, new voltage configurations, and more demanding code requirements. This course is for mid-level PV designers, installers, and inspectors who have residential experience and are moving into commercial-scale projects. Participants should already be comfortable with basic PV system components, single-phase residential design, and core NEC Article 690 requirements.
 
Participants start with the grid itself. They learn the role of transformers, common service voltages in the U.S. and abroad, and how to read and evaluate single-, split-, and three-phase services. That includes 208Y/120, 480Y/277, and 400Y/230 wye systems as well as ungrounded and high-leg delta configurations. The course also covers available fault current and the SCCR and AIC ratings it requires.
 
Next, the course applies NEC 690.7 and 690.8 to calculate maximum voltage and current for PV source and output circuits and inverter circuits. It then presents a six-step method for sizing conductors and OCPDs for larger arrays, covering conditions-of-use corrections, terminal temperature limits, and voltage drop.
 
Finally, participants work through Article 705 interconnection:
• Load-side connections and the six busbar options, including the 120% rule
• Feeder and tap connections
• Supply-side and additional service connections
• Balancing single-phase inverters on three-phase systems
• Power Control Systems