EV Equipment, based on the 2020 NEC

Figure 01

Note: This article is based on the 2020 NEC.

The electrical conductors and equipment for connecting an electric vehicle to premises wiring must meet specific requirements.

Electric vehicles (EVs)have been around for a long time. Factories and warehouses often use electric lift trucks, and of course there’s the familiar golf cart. These and other off-road vehicles have charging requirements that are easily accommodated by small charging systems.

Now a new challenge is increasingly common: the electrically powered passenger car, truck, bus, or motorcycle. Such vehicles, especially an electric car or bus, can weigh considerably more than a golf cart so just moving one takes a proportionately larger drive motor. Some have multiple drive motors.

Those motors are powered by batteries. Adding to the battery sizing requirement are other demands. For example, these vehicles:

• Must be able to travel at highway speeds over distances comparable to those traveled by their internal combustion engine counterparts.
• Have powered accessories that you typically don’t find on a golf cart, such as air conditioning, electric windows, stereo systems, windshield wipers, security systems, and window defrosters.
• Are expected to start in summer heat and in brutal winter cold.
  

The battery system for an electrically powered passenger vehicle is therefore considerably larger than that for a golf cart or other typical off-road EV.

An electrically powered passenger vehicle needs a dedicated charging circuit. Article 625 provides the requirements for installing the conductors and equipment for electric vehicle charging, power export, or bidirectional current flow. Figure 01

This article consists of three parts:

1. Part I. General. This includes the scope, voltages, and listing/labeling requirements.
2. Part II. Equipment Construction. Most of this applies to the manufacturer, but you need to know some of the requirements.
3. Part III. Installation. This covers overcurrent protection and the disconnect, plus the requirements for indoor and outdoor locations.
   

Definitions
Prior to the 2023 revision, the definitions important for applying Article 625 were in 625.2. Now all definitions are in Article 100. You should understand these three:

• EV Power Export Equipment (EVPE). The equipment, including the outlet on the vehicle, used to provide electrical power (at voltages greater than 30V ac or 60V dc) to loads external to the vehicle (as the source of supply).
• EV Supply Equipment (EVSE). Conductors, EV connectors, attachment plugs, personnel protection system, devices, and power outlets installed for the purpose of transferring energy between the premises wiring and the EV. Note: EVPE and EVSE are sometimes contained in one piece of equipment, which is a “bidirectional EVSE.”
• Wireless Power Transfer Equipment (WPTE). Equipment consisting of a charger power converter and a primary pad. The two devices are either separate units or they are contained within a single enclosure.
  

Voltages
Unless otherwise specified, equipment covered by this article must be supplied by the following voltages:

• 120, 120/240, 208Y/120, 240, 480Y/277, 480, 600Y/347, 600, or 1000 volts AC
• DC system voltages up to 1000V.
  

Output voltages to the EV are not specified [625.4].

Listing
All EV power transfer equipment for the purposes of charging, power export, or bidirectional current flow must be listed [625.6].

Equipment construction
The power supply cord must comply with 625.17(A)(1), (2), and (3). For example, if it’s 8 AWG or larger its ampacity must comply with the 60°C columns of Table 400.5(A)(2).

The power output cable must be either integral to the supply equipment or be one of the types listed in 625.17(B)(1).

Requirements for overall cord and cable length are in 625.17(C). These vary, depending upon whether the equipment is portable or the cabling is interconnecting.

Installation
Each outlet for EV supply equipment greater than 16A or 120V must be supplied by a dedicated branch circuit that serves no other outlets [625.40].

Overcurrent protection for circuits supplying EVSE, including bidirectional EVSE and WPTE, must be sized at least 125 percent of the maximum load of the EV supply equipment [625.41].

Consequently, the conductors must be sized to be protected by the circuit overcurrent protective device per 240.4, including 110.14(C)(1) considerations, plus 310.16.

The power transfer equipment must have sufficient rating to supply the load served. The NEC considers EV charging loads to be continuous loads. Services and feeders must be sized per the product ratings [625.42]. Where an automatic load management system is used, the maximum equipment load on a service and feeder is the maximum load permitted by the automatic load management system [625.42(A)].

Adjustable settings are allowed only on fixed-in-place equipment. If adjustments affect the rating label, those changes must be per manufacturer’s instructions, and the adjusted rating must appear on a label with sufficient durability to withstand the environment [625.42(B)].

EV supply equipment with restricted access to an ampere adjusting means can have an ampere rating(s) equal to the adjusted current setting. Sizing the service and feeder to match the adjusting means is allowed.

Restricted access must prevent the user from gaining access to the adjusting means. Restricted access must be accomplished by one of the following:
(1) A cover or door that requires the use of a tool to open.
(2) Locked doors accessible only to qualified personnel.
(3) Password protected commissioning software accessible only to qualified personnel.

EV equipment rated more than 60A or over 150V to ground must have a readily accessible disconnect that is capable of being locked in the open position with provisions for locking to remain in place whether the lock is installed or not [625.43, 110.25].

Equipment connection rules depend upon whether the EV equipment is:

• Portable. Use one of the four methods in 625.44(A). It’s going to be some type of non-locking, 2-pole receptacle.
• Fastened-in-place. Use one of the four methods in 625.44(B). It’s going to be some type of non-locking, 2-pole or 3-pole receptacle.
• Fixed-in-place. Permanently wire it in.
  

EVSE that incorporates a power export function and is part of an interactive, optional standby system or electric power production source or a bidirectional power feed must be listed and marked as suitable for that purpose [625.48]. When used as an optional standby system, the requirements of Article 702 apply; when used as an electric power production source, the requirements of Article 705 apply.

Locate EVSE to permit direct electrical coupling of the EV connector to the EV [625.50].

Unless specifically listed and marked otherwise, the coupling means of the EVSE must be at least 18 in. above the floor for indoor locations, and at least 24 in. above grade for outdoor locations.

Mechanical ventilation is not required where the EV supply equipment is listed for charging EVs indoors without ventilation [625.52(A)].

Mechanical ventilation is required where the EV supply equipment is listed for charging EVs with ventilation for indoor charging [625.52(B)]. The ventilation must include both supply and exhaust equipment permanently installed and located to intake and vent directly to the outdoors.

Ventilation requirements must be determined by one of these four methods:

1. Table values. Use the appropriate value from Table 625.52(B)(1)(1) (cubic meters per minute) or Table 625.52(B)(1)(2) (cubic feet per minute) [625.52(B)(1)].
2. Other values. If it’s not covered by the tables, calculate it using one of the general formulas in 625.52(B)(2).
   
3. Engineered systems. It’s permitted to integrate the EV supply ventilation with the building ventilation, if a qualified person performs the calculations for the design [625.52(B)(3)].
   
4. Supply circuit interlock. The supply circuit can be electrically interlocked to the mechanical ventilation equipment, if the arrangement meets the requirements of 625.52(B)(4).
   

EV charging receptacles in wet locations must have a weatherproof enclosure [625.56]. All receptacles installed for the connection of EV supply equipment must be GFCI protected [625.54].

GFCI breakers or receptacles typically used in dwelling units are not suitable for back feeding. That prohibits their use for a bidirectional EVSE. This GFCI requirement applies to all cord-and-plug-connected EVSE, making hard wired EVSE the only type suitable for bidirectional use.

Alternating-current receptacles installed in EVs and intended to allow for connection of off-board utilization equipment must be listed and rated a maximum of 50A, 250V, single-phase [625.60(A) and (B)]. The overcurrent protection for these must be integral to the power export system [625.60(C)]. All receptacles must be GFCI-protected. The GFCI reset and indication must be in a readily accessible location [625.60(D)].

Avoiding mistakes
Much of the push for EVs now comes from the notion that electricity is an energy source rather than an intermediary between an energy source and the utilization equipment. This flawed thinking leads to flaws in planning and communication. Before installing any EV-related equipment, ensure the user/owner completely understands whether it is charging only or bidirectional. Assess exactly what equipment is needed versus what’s been provided for you to install, and resolve any differences.

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