BS 7671 Amendment 4: Commercial EV Charging

Commercial EV charging installations present challenges that scale beyond domestic installations — multi-charger load management, three-phase high-power charging, and the integration of EV infrastructure with existing building electrical systems. Amendment 4 addresses these specifically, moving beyond the domestic focus of earlier guidance.

Multi-charger load management is now explicitly addressed in BS 7671. For commercial premises with multiple EVSEs, Amendment 4 requires that the total connected load does not exceed the available supply capacity under any operating scenario. This means either static load limitation (fixed maximum power per EVSE based on the number of chargers) or dynamic load management (real-time adjustment based on actual demand). Amendment 4 states that the load management system must be documented as part of the electrical installation design, including the communication protocol between EVSEs and the management controller.

Three-phase EV charging (11 kW and 22 kW AC, and DC rapid chargers up to 150 kW) requires careful attention to load balance. Amendment 4 specifies that three-phase EVSE installations must not cause neutral current to exceed 50% of the phase current under any loading combination. This effectively requires a load management system that distributes charging across phases to maintain balance, or individual protection on the neutral conductor.

Sub-distribution design for dedicated EV charging hubs receives specific guidance. Amendment 4 recommends a dedicated EV sub-distribution board with its own incoming supply (metered separately for energy management), individual circuit protection per EVSE, and a dedicated earth bus. The sub-distribution board should include provision for future expansion — Amendment 4 recommends 25% spare capacity in the enclosure and incoming switch rating.

Fire risk in EV charging areas is cross-referenced with fire safety legislation. Amendment 4 requires that cables serving EV charging in enclosed car parks maintain circuit integrity for a minimum period aligned with the building's fire strategy. This typically means fire-resistant cables (to BS 8519 or equivalent) for EV circuits in multi-storey or underground car parks.

Accessibility requirements for disabled parking spaces with EV charging are mentioned for the first time. The EVSE and its associated isolation devices must be accessible to wheelchair users, with controls between 750 mm and 1200 mm above finished floor level.

ECalPro's EV Charging Calculator handles commercial multi-charger designs per Amendment 4, including load management calculations, phase balance verification, and sub-distribution sizing.