Circuit protection is the foundation of electrical safety. Consumer units distribute power throughout a property while housing protective devices that automatically disconnect circuits during faults—preventing electric shock, fire, and equipment damage.

Under BS 7671, all new consumer units in dwellings must have a metal enclosure to contain any fire resulting from an internal fault. External domestic installations can have a consumer unit with a non-metallic enclosure. Protective devices include CBs (Circuit-Breakers, or alternatively MCBs Miniature Circuit Breakers) for overcurrent protection, RCDs (Residual Current Devices) for earth fault protection, RCBOs (Residual Current Breaker with Overcurrent protection) which combine both functions in a single unit and SPDs (Surge Protection Devices) a device that protects electrical installations from voltage spikes caused by lightning or power surges. Amendment 4 reinforces the importance of correct device selection, particularly for circuits supplying new technologies like EV chargers and battery storage systems.  

Correct cable selection and installation are critical to a safe and compliant electrical system. BS 7671 specifies cable types, current-carrying capacities and installation methods based on the external influences and circuit requirements. 

Flat, twin and earth cable remains the standard for fixed domestic wiring, while SWA (Steel Wire Armoured) cable) is required for underground and external installations where mechanical protection is needed. Amendment 4's new Section 716 introduces specific requirements for Power over Ethernet (PoE) cables, addressing thermal load management when data cables carry power to smart home devices, IP cameras, and LED lighting systems. Proper cable management - using trunking, conduit, and clips -protects cables from damage and ensures installations meet regulatory standards.   

Earthing provides an essential protective pathway that allows fault currents to flow safely to Earth and enables protective devices to disconnect the fault quickly. Without correct earthing, RCDs cannot operate and fault currents may flow through unintended paths - including people. 

There are two main types of bonding. BS 7671 requires main protective bonding to connect incoming gas, water and oil services to the main earthing terminal.  Supplementary equipotential bonding may be required in locations of increased risk, such as bathrooms or swimming pool installations. Amendment 4 includes updated guidance on functional earthing for ICT systems (Section 545), distinguishing between earthing for safety and functional earthing for equipment performance in data-rich environments. The amendment also introduces new test result schedules for recording supplementary protective equipotential bonding conductor resistance. 

The growth of renewable energy and electric vehicles has transformed electrical installation work. Amendment 4 directly addresses these technologies with Chapter 57 - the first dedicated BS 7671 chapter for stationary secondary batteries used in home energy storage systems. 

Electric Vehicle Charging 

EV charger installations must comply with BS 7671 requirements for circuit protection, cable sizing and isolation. Dedicated circuits with appropriate overcurrent and RCD protection are essential. 

Home Battery Storage 

Chapter 57 introduces formal requirements for battery storage systems covering thermal runaway mitigation, safe isolation during maintenance, ventilation, and location restrictions - batteries are now prohibited in high-risk areas such as lofts and escape routes. 

Solar PV 

Solar installations require careful consideration of DC isolation, string protection, and integration with battery storage systems. Amendment 4 brings battery requirements into the formal regulatory framework rather than relying solely on manufacturer guidance. 

Regular inspection and testing ensure electrical installations remain safe throughout their lifespan. BS 7671 requires initial verification of all new work and periodic inspection at intervals appropriate to the installation type—typically every 5 years for domestic properties and more frequently for commercial and rental premises. 

The Electrotechnical Assessment Specifications has set new individual competence requirements for those carrying out inspection and testing, formalising the skills and knowledge expected of qualified inspectors. Testing equipment—including multifunction testers, insulation resistance testers, and RCD testers—must be calibrated and appropriate for the tests being conducted. Detection equipment such as voltage indicators, socket testers, and non-contact voltage detectors are essential for safe working and fault diagnosis.