BS 7671 Onsite Guide: An Essential Resource for Installation Electricians

BS 7671:2018+A2:2022 Requirements for Electrical Installations 18th Edition, widely known as the IET Wiring Regulations, is the definitive standard for electrical installation in the United Kingdom.

An essential part of this suite of documents is the BS7671 Onsite Guide.

This guide is an indispensable tool for installation electricians, offering a condensed, user-friendly version of the regulations.

In this article, we will explore the Onsite Guide’s significance, its guidance on circuit design, compliance with building regulations, circuit disconnection times, and best practices.

What is the BS 7671 Onsite Guide?

The BS 7671 Onsite Guide is a companion document to the full IET Wiring Regulations.

It provides a simplified overview of the most critical aspects of the regulations, tailored specifically for the practical needs of electricians working on site.

The guide helps electricians quickly reference key information and ensures that installations comply with the latest version of the Wiring Regulations.

Importance of the Onsite Guide for Installation Electricians

For installation electricians, the BS 7671 Onsite Guide is vital for several reasons:

  1. Quick Reference: It offers quick and easy access to essential information, saving time on the job.
  2. Practical Application: The guide translates complex regulations into practical guidance, making it easier to apply the rules in real-world scenarios.
  3. Compliance and Safety: It helps ensure that electrical installations are safe and compliant with current regulations, which is crucial for the safety of occupants and the legality of the work.

Requirements for Circuit Design

The Onsite Guide provides concise instructions on circuit design, which is fundamental in ensuring the safety and efficiency of electrical installations.

Key aspects covered include:

  1. Cable Sizing and Selection: Guidance on choosing the right size and type of cable for different types of installations.
  2. Protection Against Overloads: Instructions on how to design circuits that are protected against overcurrent.
  3. Earthing and Bonding Requirements: Essential details on earthing systems and bonding arrangements for safety.

Compliance with Building Regulations

Adhering to building regulations is a legal requirement in the UK. The Onsite Guide includes information on how electrical installations can comply with various parts of the Building Regulations, such as:

  1. Part P: Requirements for domestic electrical installations.
  2. Part L: Energy efficiency requirements.
  3. Part B: Fire safety considerations in electrical installations.

Circuit Disconnection Times

One of the critical aspects covered in the Onsite Guide is the circuit disconnection times. These are the maximum times allowed for a circuit to disconnect in the event of a fault.

The guide provides:

  1. Disconnection Times for Different Types of Earth Fault Protection: Including RCDs, circuit breakers, and fuses.
  2. Guidance on Selecting Protective Devices: Based on the type of installation and the disconnection time requirements.

Best Practices Contained in the Onsite Guide

The Onsite Guide goes beyond just explaining the regulations. It includes best practices that are essential for high-quality electrical work. These include:

  1. Inspection and Testing Procedures: Detailed steps for properly inspecting and testing electrical installations before they are put into service.
  2. Safe Isolation Practices: Methods to ensure that electrical systems are safely isolated before work begins.
  3. Dealing with Special Locations: Specific guidance for installations in locations such as bathrooms and kitchens, where the risk of electric shock is higher.
  4. Considerations for Renewable Energy Sources: With the increasing use of renewable energy sources, the guide includes information on integrating these systems safely with standard electrical installations.

Keeping Up-to-Date with Changes

The Onsite Guide is updated regularly to reflect changes in the Wiring Regulations.

Electricians must ensure they are referencing the latest version to remain compliant with current standards.


The BS 7671 Onsite Guide is an essential resource for installation electricians. It simplifies and distils the comprehensive information found in the full Wiring Regulations, making it more accessible and practical for day-to-day use.

By adhering to the guidance on circuit design, building regulations compliance, circuit disconnection times, and best practices, electricians can ensure their work is safe, efficient, and compliant.

As the field of electrical installation continues to evolve with new technologies and regulations, the Onsite Guide remains an invaluable tool for keeping electricians at the forefront of safe and effective practice.