Understanding NEC Article 692: Fuel Cell Systems

NEC Article 692 provides guidelines for the installation and operation of fuel cell systems, which generate electricity through electrochemical reactions rather than combustion. These systems serve as standalone power sources, grid-interactive units, or supplementary sources integrated with energy storage.

Scope of Article 692

This article applies to:

• Fuel cell systems with alternating current (AC) and/or direct current (DC) outputs.
• Systems supplying buildings or structures, either standalone or in conjunction with other power sources.

Examples:

• Hydrogen-based fuel cells.
• Natural gas or liquefied petroleum gas (LP-Gas) systems​.

Key Requirements for Fuel Cell Systems

1. System Installation (692.4)
   • Installations must be carried out by qualified persons to ensure safety and compliance.
   • Systems supplying power alongside other sources must be marked with a directory for power source identification​.
2. Listing and Approval (692.6)
   • Systems must be listed for the application or evaluated and labeled in the field to meet safety requirements​.

Circuit Requirements

1. Conductor Sizing (692.8)
   • Conductors must handle the greater of the system’s nameplate-rated current or the protective device rating.
   • Neutral conductors must accommodate unbalanced loads and the fuel cell output to prevent overheating​.
2. Overcurrent Protection (692.9)
   • Circuit overcurrent protection is required unless the system provides sufficient internal protection.
   • Devices must be easily accessible for maintenance and emergency purposes​.

Disconnecting Means

1. Complete Isolation (692.13)
   • Disconnecting means must isolate all current-carrying conductors of the fuel cell system.
   • A warning sign must be displayed when disconnect terminals remain energized​.
2. Switch Requirements (692.17)
   • Switches or breakers must be manually operable, readily accessible, and meet NEC labeling standards​.

Marking and Safety

1. System Markings (692.50)
   • Markings must indicate output voltage, power rating, and current at the disconnecting means.
2. Fuel Shut-Off and Stored Energy (692.51–692.52)
   • Locations of manual fuel shut-off valves must be clearly marked.
   • Warning signs for stored energy systems must alert personnel to potential hazards​.

Connection to Other Systems

1. Transfer Switch (692.61)
   • Required for non-grid-interactive systems with utility grid backup to maintain isolation between networks.
   • Must comply with Article 230, Part V when connected to utility service conductors​.

Applications

NEC Article 692 supports safe installation and operation in:

• Residential Backup Systems: Fuel cells supplying emergency power during outages.
• Commercial Buildings: Integration with existing electrical infrastructure for primary or supplementary power.
• Industrial Facilities: High-capacity installations for critical operations.

Conclusion

NEC Article 692 provides essential guidelines for the safe use of fuel cell systems, addressing installation, circuit design, disconnecting means, and interconnections. These standards enable the safe adoption of this clean and reliable energy source.