RELATED: What is load balancing for EV charging?
Supply and Capacity
A single 7kW charger typically draws 32 amps from a single phase supply. Your building needs enough spare electrical capacity to support the number of chargers you plan to install. If spare capacity is limited, load balancing shares available power across all chargers without requiring a supply upgrade.
Three phase supply is needed for 22kW chargers or larger installations where single phase cannot support the demand. Most office buildings already have three phase power. Smaller premises on single phase may need an upgrade, which involves an application to the distribution network operator. We handle this application and coordinate the lead time as part of your project.
We calculate maximum demand for your site using BS 7671 Regulation 311. This accounts for diversity, meaning not every charger will draw full power at the same time. Diversity assumptions depend on whether smart load control is in place. With load management active, the calculation works in your favour and can reduce the need for supply upgrades.
RELATED: How many EV chargers does a business need in the UK?
Circuit Protection and Wiring
Chargers can be wired individually or networked on a shared circuit, where multiple units link from one to the next. This is common for larger installations with five or more chargers. BS 7671 requires every charging point to have individual 30 mA RCD protection and to disconnect all live conductors, regardless of the circuit arrangement.
The type of RCD depends on the charging equipment. Type A, Type F, or Type B RCDs can all be used, provided DC residual current protection is in place. Some chargers include this protection within the unit itself. Where the equipment does not provide DC protection, an RDC-DD device or Type B RCD is used instead. We specify the correct arrangement for each installation so you do not need to navigate this yourself.
Outdoor chargers must provide at least IPX4 protection against water and IP4X protection against solid foreign bodies. Standard commercial chargers already meet these ratings.
Earthing arrangements must comply with BS 7671 Section 722. Where a PME (TN-C-S) supply is used for outdoor EV charging, additional protective measures may be needed under Regulation 722.411.4.1. This typically involves PEN fault protection or an alternative earthing arrangement. We assess this during the site survey and design the system accordingly.
If your existing distribution board does not have enough spare ways, we install a dedicated EV consumer unit or sub board. This is common for installations of five or more chargers.
Smart Charging Compliance
In Great Britain, new private workplace charge points sold for installation must meet the Electric Vehicles (Smart Charge Points) Regulations 2021. The regulations apply to most new private workplace chargers, with some exclusions including charge points intended for public use, rapid chargers, and sales in Northern Ireland.
Compliant chargers must be capable of sending and receiving data, responding to demand signals, defaulting to off peak charging, and operating with built in cybersecurity protections.
We handle compliance as part of the specification and commissioning process. Every charger we install meets these requirements.
