What is an Electric Vehicle Power Transfer System?

By: Robert Key | Dec 06, 2021

Electric vehicles are likely here to stay, but they are a rapidly evolving technology. Lighter lithium-ion type batteries have made electric cars, bicycles, motorcycles, and more, a reality. The code-making panels have significantly revised Article 625 for the 2020 National Electrical Code (NEC) to regulate the safety of electric vehicle charging. Even the title of the Article has changed, from “Electric Vehicle Charging” to “Electric Vehicle Power Transfer System.” 

Acronym School 

There are a lot of abbreviations in Article 625. Perhaps a brief acronym primer would be helpful.  

• EVSE (Electric Vehicle Service Equipment)  
• EVPE (Electric Vehicle Power Export Equipment) 
• WPT (Wireless Power Transfer) 
• WPTE (Wireless Power Transfer Equipment) 

What’s New for 2020?  

What’s new for 2020? Quite frankly, a lot. There is an abundance of gray highlighted text which indicates a revision, as well as many (N)’s in the margin, which show where a new definition or subsection is found.  

One of the newer developments for electric vehicles is wireless power transfer. This technology is not actually new. Cell phones have had that capability to be charged wirelessly for some time now. This method uses coil induction, similar to a transformer, to charge a vehicle wirelessly. It is reported to be up to 91% efficient over a 10-inch air gap. The concept of wireless power transfer is far from new, however, having been pioneered by Nikola Tesla who patented the idea in 1897! 

Another recent development requiring adaptation of the NEC is EV Power Export and Bidirectional Current Flow. What this means is that in addition to being recharged by premises wiring, an electric vehicle can act as an alternate power source for premises wiring or other outlets when the primary current source is not available. The Informational Note provided for the definition of EVPE reminds us that these are sometimes referred to as bidirectional EVSE (electric vehicle service equipment). 

2020 NEC New Code Requirements 

Probably the most important new code requirement is found in Section 625.54, Ground-Fault Circuit-Interrupter Protection for Personnel. In past editions of the Code, an electric vehicle charging receptacle may or may not have required GFCI protection, depending on the location. If it was installed in one of the locations found at Section 210.8, Ground-Fault Circuit-Interrupter Protection for Personnel, then it was required, but if not, then no protection was stipulated. With the adoption of the 2020 NEC, all electric vehicle charging receptacles shall have ground-fault circuit-interrupter protection for personnel. 

 Other new Code requirements include: 

• Section 625.56, Receptacle Enclosures, stipulates that outlet boxes for electric vehicle charging installed in wet locations be in an enclosure that is weatherproof with the attachment plug cap inserted or removed, also known as an in-use cover. The outlet box itself must be listed and identified as extra-duty. 
• The power transfer equipment and overcurrent protective device must be rated at 125% of the maximum load of the equipment, since it is a continuous load, often lasting more than three hours.  

• Ventilation for indoor charging is not new, but these important requirements have been altered. They can be found at Section 625.52, Ventilation.  
• The requirements for cords and cables used for EV charging found at Section 625.17, Cords and Cables, have seen significant changes for 2020. 
• As discussed, the outlets in the vehicle itself are even regulated by the NEC now. Per Section 625.54, they must have overcurrent protection and GFCI protection for personnel. The enforcement of this would of course be the responsibility of the manufacturer, not the installer or AHJ.  

These are just some of the special requirements for the installer of an Electric Vehicle Power Transfer System. It is always wise to read through Article 625 prior to starting the installation, especially if you don’t do this often. The EV user is relying on the electrician and inspector to keep them safe.