Understanding NEC Article 625: Electric Vehicle Power Transfer System
NEC Article 625 establishes the safety standards for electric vehicle (EV) power transfer systems, including conductive, inductive, and wireless charging methods. It addresses installations in residential, commercial, and public settings, covering equipment construction, installation, and operational requirements.
Scope of Article 625
This article applies to:
- Electrical conductors and equipment connecting EVs to the premises wiring for charging or power export.
- Both bidirectional and unidirectional power transfer systems.
Key Notes:
- Includes conductive, inductive, and wireless power transfer.
- Applies to residential garages, public parking, commercial facilities, and other locations.
Referenced Standards:
- UL 2594: For conductive EV supply equipment.
- UL 2202: For charging systems.
- UL 2750: For wireless power transfer equipment.
Key Requirements for EV Power Transfer Systems
- Voltage and Current Ratings
- Systems must operate at nominal voltages of up to 1000 volts AC or DC.
- Branch circuits supplying EVSE (Electric Vehicle Supply Equipment) must have overcurrent protection rated for continuous loads at 125% of the equipment’s maximum load.
- Cords and Cables
- Must be listed and suitable for damp or wet locations.
- Maximum cord length is 25 feet, with provisions for cable management systems.
- Ground-Fault Protection
- All EVSE receptacles must include GFCI protection to prevent electrical shocks.
- Disconnecting Means
- Equipment rated over 60 amperes or 150 volts must include a disconnecting device accessible and lockable in the open position.
- Ventilation
- Ventilation may be required for certain charging systems to prevent the accumulation of hydrogen gas.
- Outdoor systems or naturally ventilated areas do not require additional mechanical ventilation.
Wireless Power Transfer Equipment (WPTE)
Wireless charging systems must meet specific installation and operational requirements:
- Control boxes must be mounted at least 18 inches indoors and 24 inches outdoors above the floor or grade.
- Primary pads must be flush with the surface or embedded to avoid obstruction in areas subject to vehicular traffic.
Bidirectional Systems and Energy Management
- Bidirectional systems allow EVs to serve as backup power sources or feed power back to the grid.
- Energy management systems can help avoid overloading existing electrical systems by dynamically managing EVSE loads.
Applications
NEC Article 625 supports safe and efficient EV charging in:
- Residential Garages: Home charging stations.
- Public Parking: Charging infrastructure for commercial and retail spaces.
- Fleet Operations: High-capacity chargers for commercial fleets.
Conclusion
NEC Article 625 ensures the safe and reliable operation of electric vehicle power transfer systems. By addressing equipment standards, grounding, ventilation, and bidirectional capabilities, it supports the growth of sustainable transportation solutions.
