EV charging systems: is your installation compliant with the Wiring Regulations?

Electric vehicle charging is now a routine part of new developments, refurbishments, and infrastructure upgrades. However, designing an EV charging installation is not just a case of adding another circuit. UK regulations place specific and often misunderstood requirements on EV charging equipment — particularly around earthing, protection, and supply capacity.

For clients, developers, and installers alike, getting this wrong can mean non-compliance, delays, or costly rework. This is where good electrical design makes a real difference.

EV charging systems can pose a large load burden on existing electrical supplies and infrastructure

The Regulatory Framework in plain English

All EV charging installations in the UK must comply with:

• BS 7671 (IET Wiring Regulations)

• Section 722 of BS 7671, which introduces additional requirements specifically for EV charging

• The IET Code of Practice for Electric Vehicle Charging Equipment Installation, which provides practical guidance on how to comply

  
  

Section 722 is mandatory. The Code of Practice explains how to apply it safely and correctly in real-world installations.

BS 7671 (Requirements for Electrical Installations) Section 722 defines the specific requirements for EV charger installations in the UK

Why EV charging is treated differently

EV charging is classed as a long-duration, high-current load, often installed outdoors and frequently connected to PME (TN-C-S) supplies. This combination introduces risks that do not exist in most traditional electrical installations.

As a result, Section 722 places particular emphasis on:

• Dedicated circuits

• Enhanced RCD protection

• Earthing arrangements (especially PME)

• Safe isolation and disconnection

• Protection against DC fault currents

  
  

These are design issues — not just installation details.

Dedicated circuits and load management

BS 7671 requires each EV charge point to be supplied by a dedicated final circuit. Designers must also consider:

• Continuous current demand (and rated diversity factors)

• Voltage drop over long cable runs

• Available supply capacity

• Future expansion

  
  

In many projects, especially residential blocks and commercial car parks, load management or smart charging is essential to avoid costly supply upgrades. Early-stage design input can significantly reduce project costs.

Earthing: the most common compliance issue

One of the most critical aspects of Section 722 is its treatment of PME (TN-C-S) earthing systems.

Direct connection of EV charging equipment to a PME earth is not permitted without additional protective measures, due to the risk of an open PEN conductor. Compliant solutions include:

• Charge points with built-in open PEN detection and automatic disconnection

• Use of a TT earthing arrangement for the charger

• Approved devices that disconnect all live conductors under fault conditions

  
  

Selecting the wrong approach at design stage can result in equipment rejection or redesign during installation.

A TN-C-S (PME) earthing arrangement (courtesy of The IET https://electrical.theiet.org/media/2606/figure-3-tn-c-s-system-with-pme.jpg)

RCD and DC fault protection for EV charging systems

Section 722 also introduces enhanced requirements for protection against electric shock:

• Each charge point must have 30 mA RCD protection and must disconnect all live conductors (including the neutral)

• Due to the presence of DC, this can effectively blind a Type A RCD and cause it to not operate. This is where an RDC-DD (Residual Direct Current Detecting Device) is required. This is often part of the car charging system and would be suitable for use with a Type A (or F) RCD if the RDC-DD can detect and disconnect DC faults above 6 mA.

• Where an RDC-DD is not provided, a Type B RCD will be required on the supply to the car charger. Type B RCDs can detect and disconnect the DC in the circuit.

• Therefore additional protection against 6 mA DC fault currents must be provided, either:

  • Within the charge point, or

  • By using a Type B RCD

  
  

This is essential to prevent DC currents from disabling upstream protection devices — a risk unique to EV charging.

The complications do not end here with the use of RCDs! A standard Type AC RCD should not be fitted upstream - for protection of the circuit under BS 7671 - of a Type A or B RCD as the characteristics of these devices could affect the correct operation of the Type AC device. The correct use of RCDs should always be based on the individual scenario and take into account both the specifics of the car charger itself and also the requirements of the circuit protection as defined in the Wiring Regulations.

Isolation, switching, and safety in use

EV charging equipment must be provided with:

• A local means of isolation for maintenance and emergency use

• Isolation that disconnects all live conductors

• Clearly labelled controls and protective devices

  
  

In public and commercial environments, emergency switching and safe cable management are especially important considerations at design stage.

Why good design saves time and money

Many EV charging projects run into problems because compliance is only considered after equipment selection or installation has begun. Typical issues include:

• Inadequate earthing arrangements

• Incorrect RCD selection

• Insufficient supply capacity

• Non-compliant layouts in car parks or external areas

Engaging an electrical design consultant early helps to:

• Ensure compliance with BS 7671 Section 722

• Reduce redesign and rework

• Support installers with clear, buildable information

• Provide confidence to clients, building control, and DNOs

There are different types of EV chargers on the market, categorised into Modes 1, 2, 3 and 4 - which EV charger type do you need? Each mode has specific requirements.

How we can help

As a small, independent electrical design consultancy, we support:

• Developers and property owners

• Architects and project managers

• Electrical contractors

• Facilities and estates teams

Our services include:

• EV charging feasibility studies

• Load assessments and capacity checks

• Compliant earthing and protection strategies

• Electrical design to BS 7671 and the IET Code of Practice

• Clear design and drawing information for installation and certification

Whether you’re planning a single domestic charger or a multi-bay commercial installation, getting the design right from the outset is key.

Thinking about an EV charging project?

If you’d like support with compliant, cost-effective EV charging design, feel free to get in touch. An early conversation can often save time, money, and headaches later in the project.