Design & planning / REFERENCE GUIDE

EV charging circuit design,
with the context included.

An EV charger adds a sustained and potentially managed load with installation-specific protection requirements.

What a proper assessment needs

Before this topic can be assessed for a real installation, the person responsible for the design or verification needs to establish the relevant facts:

  • Charger instructions and charging modes
  • Available supply capacity and phase arrangement
  • Load-management function and failure behaviour
  • Earthing and protection arrangement
  • Cable route and network-operator process

Factors to consider

Charger kilowatts alone do not identify the suitable protection, earthing measures or network process. A load-management setting also needs to be assessed as part of the whole installation.

Keep the evidence with the decision

Record the equipment, installation conditions and the source of the data used. Where a manufacturer supplies product-specific instructions or coordination data, the exact product matters. A generic example should not silently replace that information.

For UK installation work, use the applicable edition of BS 7671 together with relevant guidance and manufacturer instructions. The IET’s publication hub is the starting point for current editions and supporting material. This brief does not reproduce the standard or establish compliance with it.

IET · BS 7671 and supporting guidance

Related calculations

Our arithmetic tools show their scope, inputs and formulas explicitly. They can help you understand a relationship between quantities. They cannot replace the installation assessment described above.