Part 1 - Scope, Object and Fundamental Principles

Overview

Part 1 of BS 7671 establishes the foundation upon which all other parts of the Wiring Regulations are built. It defines the scope of the standard, sets out the object of the regulations, and lays down the fundamental principles that every electrical installation must satisfy. Although it carries a relatively modest exam weighting, the concepts introduced here underpin every design decision, inspection procedure, and testing methodology covered in later parts.

Understanding Part 1 is essential because it frames the purpose of every regulation that follows. It makes clear that the overriding objective of BS 7671 is the safety of persons, livestock, and property against dangers and damage that may arise from the use of electrical installations. Every regulation in the standard traces back to the principles established in this opening part.

Key Sections

Regulation 110 - Scope

Regulation 110 defines what BS 7671 covers and, equally importantly, what it does not.

Installations covered by BS 7671 include:

• Design, erection, and verification of electrical installations in buildings
• Temporary installations
• Installations in caravans and caravan parks
• Agricultural and horticultural premises
• Construction site installations
• Marinas and similar locations

Installations excluded from BS 7671:

• Systems for the distribution of electricity to the public
• Lightning protection systems (covered by BS EN 62305)
• Certain specialist installations such as mines and quarries (which have their own dedicated standards)
• Electrical equipment of machines (covered by BS EN 60204)
• Radio interference suppression equipment

Regulations 120-132 - Fundamental Principles

This group of regulations sets out the core safety objectives:

• Regulation 120 — Requires that good workmanship and the use of proper materials are essential for compliance
• Regulation 131.1 — Persons and livestock shall be protected against electric shock
• Regulation 131.2 — Protection must be provided against thermal effects, including burns, fires, and ignition of flammable materials
• Regulation 131.3 — Conductors must be protected against overcurrent
• Regulation 131.4 — Protection must be provided against fault currents
• Regulation 132.1 — Every installation must include appropriate means of isolation and switching

These principles require that every installation is designed and erected so that it provides adequate protection throughout its intended life, assuming reasonable maintenance.

Regulations 133-135 - Assessment, Design and Erection

These three regulations establish the logical workflow for any electrical installation project:

1. Regulation 133 — Assess the general characteristics of the installation before design work begins
2. Regulation 134 — Design the installation based on the assessment, including selection of protective measures and devices
3. Regulation 135 — Erect and install with proper workmanship in accordance with the design

This assess → design → install sequence is fundamental and frequently tested. No design work should commence until the characteristics of the supply, the environment, and the intended use have been fully assessed.

Important Regulation Numbers

• Regulation 110.1 - Defines the scope of BS 7671 and the types of installations covered
• Regulation 120.3 - Requires that good workmanship and proper materials are used
• Regulation 131.1 - States that persons and livestock shall be protected against electric shock
• Regulation 131.2 - Requires protection against thermal effects including burns, fires, and ignition
• Regulation 131.3 - Addresses protection against overcurrent
• Regulation 132.1 - Establishes the requirement for means of isolation and switching
• Regulation 133.1 - Requires assessment of general characteristics before design begins
• Regulation 134.1 - Sets out design principles including selection of protective devices

Common Exam Topics

• Identifying which types of installation are covered by BS 7671 and which are excluded
• The fundamental requirement for protection against electric shock
• The logical sequence: assessment → design → erection
• The overriding object of the standard (safety of persons, livestock, and property)
• What constitutes good workmanship and proper materials
• The distinction between protection against electric shock and protection against thermal effects

Study Tips

• Read Part 1 carefully even though it is short. The principles here are referenced throughout the exam.
• Make a list of installations that are excluded from the scope of BS 7671. These exclusions are frequently tested.
• Remember the logical sequence: assess general characteristics first, then design, then erect. This order matters.
• Pay attention to the distinction between protection against electric shock and protection against thermal effects, as the exam treats these as separate topics.
• Use Part 1 as a framework for understanding why later regulations exist. Each detailed requirement in Parts 4, 5, and 6 can be traced back to a fundamental principle stated here.

Related Topics

• Part 2 - Definitions
• Part 3 - Assessment of General Characteristics
• Part 4 - Protection for Safety