Understanding NEC Articles 690 and 705

The National Electrical Code (NEC) is the benchmark for safe electrical design, installation, and inspection to protect people and property from electrical hazards. Within the NEC, Articles 690 and 705 play critical roles in the regulatory framework governing solar photovoltaic (PV) systems. Article 690 focuses on solar photovoltaic systems, while Article 705 covers interconnected electric power production sources. Understanding the differences between these two articles is crucial for professionals involved in the design, installation, and maintenance of solar power systems.

Article 690: Solar Photovoltaic (PV) Systems

Article 690 is specifically dedicated to solar photovoltaic systems. It provides guidelines and requirements for the wiring and installation of these systems to ensure safety and efficiency. The article covers a wide range of topics, including circuit sizing, overcurrent protection, grounding, and marking.

Key Provisions of Article 690:

1. Circuit Sizing and Protection: Article 690 outlines the requirements for calculating the size of PV source and output circuits. It emphasizes the necessity of overcurrent protection devices to safeguard these circuits from overloads.

2. Grounding and Bonding: Proper grounding is critical to ensure safety and prevent electrical shock. Article 690 specifies the methods for grounding PV arrays, including the use of equipment grounding conductors and grounding electrode conductors.

3. Disconnecting Means: The article mandates the use of disconnecting means for PV systems, allowing easy disconnection from power sources during maintenance or emergencies.

4. Marking and Labeling: Clear labeling of PV system components is required to provide information on system ratings, voltage, and current levels, ensuring safe operation and maintenance.

Article 705: Interconnected Electric Power Production Sources

Article 705 deals with systems where multiple power sources are interconnected, such as solar PV systems connected to the utility grid. This article addresses the interconnection of electric power production sources to ensure they work harmoniously with the grid while maintaining safety and reliability.

Key Provisions of Article 705:

1. Interconnection Requirements: Article 705 establishes the criteria for safely interconnecting distributed generation sources, like solar PV systems, with the utility grid. This includes requirements for the inverter, which converts direct current (DC) from PV panels to alternating current (AC) compatible with the grid.

2. Backfeed Protection: The article outlines measures to prevent backfeeding, which can pose hazards to utility workers and damage equipment. It ensures that excess power generated by the PV system does not flow back into the utility grid in an uncontrolled manner.

3. Overcurrent Protection: Similar to Article 690, Article 705 emphasizes the importance of overcurrent protection for interconnected systems. It ensures that all interconnected sources have adequate protection to prevent overloads.

4. Coordination with Utility: Article 705 requires coordination between the PV system and the utility. This includes obtaining the necessary approvals and complying with utility standards for interconnection.

Comparing Articles 690 and 705

While both articles are integral to the safe deployment of solar PV systems, they serve different purposes. Article 690 is more focused on the internal aspects of PV system installation, ensuring that the system itself is safe and compliant with electrical standards. In contrast, Article 705 deals with the external aspects, specifically the interaction between the PV system and the utility grid.

The primary difference lies in their scope of application. Article 690 applies to standalone PV systems, while Article 705 applies to systems that are interconnected with other power sources or the utility grid. Understanding these distinctions is crucial for professionals to ensure compliant and safe solar power installations.

Conclusion

Navigating the complexities of NEC Articles 690 and 705 is essential for those involved in the solar industry. Each article addresses different aspects of solar PV systems and their integration with the utility grid. By adhering to the specific requirements outlined in these articles, professionals can ensure that solar installations are safe, efficient, and compliant with national electrical standards. Whether dealing with standalone PV systems or interconnected power sources, understanding the nuances of these articles is key to successful solar projects.