BS 7671:2018 Amendment 2 — The 7 Changes That Affect Every Design

Overview

BS 7671:2018+A2:2022 came into effect on 27 March 2022. While it's formally an amendment rather than a new edition, it introduced substantial changes. Here are the seven that affect everyday design work.

1. Section 722: EV Charging Installations (Major Rewrite)

The biggest change. Section 722 was comprehensively rewritten to address the explosion of EV charging installations:

Load management is now explicitly addressed. Regulation 722.311.1 permits dynamic load management systems that adjust charging current based on available supply capacity
PME earthing: Regulation 722.411.4.1 confirms that where a PME (TN-C-S) earthing system is used, additional earth electrode(s) are required for the EV charging circuit
Cable sizing: Must account for continuous load (EVs charge for hours). Regulation 722.533.1 requires the circuit to be rated for continuous duty

2. Section 714: Prosumer Installations (New)

Entirely new section covering installations that both consume and produce electrical energy — solar PV with battery storage being the primary use case:

Defines requirements for switching and isolation of generation sources
Addresses anti-islanding protection
Requires clear labelling at the origin of the installation and at the meter position
Covers battery energy storage system (BESS) installations

3. Section 8: Energy Efficiency (New)

A first for BS 7671 — an entire section dedicated to energy efficiency in electrical installations:

Encourages (but does not mandate) cable sizing beyond minimum thermal requirements to reduce I²R losses
Introduces the concept of "economic cable sizing" where the cost of larger cables is offset by reduced energy losses over the installation's life
Addresses power factor correction at the installation level
Requires consideration of harmonics and their effect on system losses

4. Arc Fault Detection Devices (AFDDs)

Regulation 421.1.7 recommends AFDDs for:

Higher-risk locations (HMOs, sheltered accommodation, premises with sleeping accommodation)
Locations with combustible construction materials
Locations with combustible stored materials

AFDDs remain a recommendation, not a requirement, in the UK. But the recommendation is strengthening with each amendment, and some building insurers now request them.

5. Surge Protection Devices (SPDs) — Tightened

Amendment 1 made SPDs mandatory in many situations. Amendment 2 clarified and tightened the requirements:

SPD selection must now consider the prospective fault current at the point of installation
Coordination between SPDs at different levels (Type 1, Type 2, Type 3) is explicitly addressed
Backup protection for SPDs must be coordinated with the installation's overcurrent protective devices

6. RCD Requirements Updated

Key RCD changes:

Type B RCDs explicitly required where smooth DC fault currents may occur (EV chargers, VFDs, PV inverters)
RCD selection tables updated to clarify Type A vs Type F vs Type B requirements based on load characteristics
Socket outlet circuits up to 32A: 30mA RCD protection now has fewer exceptions

7. Documentation Requirements Enhanced

Regulation 132.13 and Chapter 63 now require more comprehensive documentation:

Electrical Installation Certificate must include energy efficiency considerations
Maximum demand calculations must be documented with methodology
EV charging installation details must be specifically recorded

Practical Impact

For most domestic and commercial installations, the key actions are:

Always include EV charging provisions in new residential designs (even if not installed immediately)
Specify Type B RCDs for EV and VFD circuits
Document energy efficiency considerations in the design certificate
Consider SPD requirements from the outset rather than as an afterthought

Apply these requirements: Use ECalPro's calculators for Cable Sizing, EV Charging, and Solar PV design to BS 7671 Amendment 2.

Frequently Asked Questions

What standards govern cable sizing calculations?

The primary standards are AS/NZS 3008.1.1:2017 (Australia/NZ), BS 7671:2018 (UK), IEC 60364-5-52 (International), and NEC Article 310 (USA). Each has different assumptions for ambient temperature, installation methods, and derating factors.

Why do different standards give different cable ratings?

Standards differ in reference ambient temperature (AS/NZS uses 40°C, BS 7671 uses 30°C), test conditions, grouping factor calculations, and installation method classifications. A 50mm² XLPE cable can vary by 15% between standards.

Cable Sizing Calculator - Interactive calculator with standards compliance
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