Flipping the Switch on Electric School Buses: Charging Infrastructure: Module 2 (Text Version)
This is a text version of the video for Flipping the Switch on Electric School Buses: Charging Infrastructure: Module 2.
Welcome to Part 4 of the Flipping the Switch on Electric School Buses series, where we will discuss electric school bus charging infrastructure. If you've been following along to Part 4 of the Flipping the Switch series, "Electric School Bus Charging Infrastructure," you'll already know that it consists of two modules. Module 1 provided information on how to determine charging needs and how to select a charger. Module 2, which we're covering today, will discuss charging infrastructure installation considerations. Now let's get started with Module 2 of the "Electric School Bus Charging Infrastructure, Installation Considerations." As previously mentioned, when selecting a vehicle charger, also referred to as electric vehicle supply equipment, or EVSE, there are a few key types to consider when planning for an electric fleet. Many light-duty vehicles can benefit from a simple portable level one EVSE unit that plugs into a standard 120-volt outlet. However, most bus applications will require something more powerful, such as a level two EVSE that can provide up to 10 times the power of a level one. These units require higher voltage, such as 208 or 240 volts, and are typically a hard-wire installation with either a wall-mounted or pedestal unit. In addition to the AC level one and level two charging, there are also DC fast charging options that are typically supported through the combined charging standard, or CCS. These EVSE units provide more power than a level two but are also more expensive to install and operate. They typically require a 480 volt, three-phase service and are generally not necessary for most electric school bus applications with a conventional overnight dwell period exceeding eight hours. However, some applications requiring rapid mid-day charging for longer routes or to support after-school activities may require this higher-power charging option.
In order to install and support the deployment of EVSE, it is important to understand the national codes regarding their operation. The National Electric Code, or NEC, Section 625 details the installation requirements for EVSE. This includes the requirement for each EVSE to be installed on a dedicated circuit, meaning there will have to be a dedicated circuit breaker for each EVSE port that is installed. This circuit breaker should also be sized to protect 125% of the maximum EVSE load in amps. Therefore, a typical 16 amp level one EVSE, designed to provide 1.9 kilowatts, will require the installation of a 20 amp breaker, while an 80 amp level two EVSE, designed to provide up to 19.2 kilowatts, will require a 100 amp breaker. There are also guidelines and requirements for conductor gauge and length that should be discussed in more detail with your electrician, as well as specific requirements that an EVSE must not back-feed into the grid during a grid outage, unless islanded as a microgrid system.
In addition to the breaker rating requirements outlined in the NEC, level one and level two will require different types of circuit breakers based on the voltage they require. All level one EVSE will require a single-pole breaker to supply the EVSE with 120 volts. However, the level two units require a double-pole breaker to provide the EVSE with 208 or 240 volts, depending on the service voltage. When looking at a service panel, it is important to consider the number of spare breaker positions, as indicated in red on the image to the right. The single breaker position on the left column in the image could support a single-pole breaker for level one EVSE, while the two vertically adjacent positions on the right column would be needed for a level two unit. Also, although the voltage provided to level one units is always 120 volts, level two units will receive 240 volts from a single-phase service, which is most common in residential households and small buildings, while three-phase services may only provide 208 volts to the EVSE.
In addition to the service panel upgrades, all installations will also require site layouts to outline the conduit and wiring needed to supply this power to the EVSE. The key considerations in determining a site layout are the locations of the service panel, distribution transformer, and parking spots. It is best to place the EVSE at parking locations that minimize the wiring and conduit run length to minimize equipment and trenching costs, which are much higher when digging through concrete as opposed to dirt. When expanding on a building's existing service panel, this will be the distance from the nearest service panel to the parking locations. However, in locations where there's insufficient building capacity, a new service panel may be installed and should be located close to the existing transformer and parking locations. During this time, it is also important to consider planning for the future by installing additional capacity in the service panel and provide the wiring and conduit necessary for future EVSE through stub outs, as shown in the image on the right.
After determining an optimal site layout and partnering with an installer, it's important to touch base with your local utility rep to consider any potential upgrades that may be required as a result of these new loads. The installation of new branch circuits and upgraded service panels could require a larger service from the utility, and if this is the case, the utility may be required to install a new service line or upgrade a distribution transformer to accommodate the larger load.
However, because this process can be somewhat challenging for many fleets, utilities are offering new and innovative service options to simplify this process. In addition to the standard service model, where utility owns and maintains the transformer, service line, and electric meter, newer EVSE make-ready or full-service options expand the utility's ownership. In some EVSE make-ready service models, the utility will install the panel, conduit, and wiring necessary for new EVSE, leaving the EVSE itself as the only responsibility for the fleets, while in the full-service option, the utility owns and operates all equipment up to and including the unit. Some utilities also offer incentives or rebates on EVSE to reduce the capital cost for fleets interested in electrifying. This is why it is important to reach out to the utility rep early in the electrification process to consider all of the available options.
In conclusion, most electric school bus applications will require a 19 kilowatt, level two charger which, according to the NEC, should be protected using a 100 amp breaker, which requires two vertically adjacent breaker positions in a service panel. The site layout for these devices should be designed to minimize conduit run and trenching length, and possibly plan for future growth. Throughout this process, be sure to maintain close contact with the local utility representative to learn about service options and incentive programs, as well as communicate installation plans and consider possible equipment upgrades that might be needed.
Thank you for listening. That concludes Module 2 of Part 4 of Flipping the Switch series, "Charging Infrastructure Installation Considerations." That concludes all modules of Part 4 for this series. Now that you've completed Part 4 of the Flipping the Switch series, "Charging Infrastructure," you'll want to see what's coming next. In the following parts, we'll discuss infrastructure planning and solutions; vehicle in-use performance; training for both drivers and technicians; and finally, cost factors. As a reminder, you can find all the content for the Flipping the Switch on Electric School Buses series, including each part of the series and associated modules, as well as handouts with a summary of information and links to all the resources mentioned today, on the Alternative Fuels Data Center's Electric School Bus page.