UNIT REVISION

City & Guilds 2366-03 Unit 304: Electrical Design Practices and Procedures — Complete Revision Guide

A structured revision walkthrough of every topic in City & Guilds 2366-03 Unit 304 (Electrical Design Practices and Procedures). Use it as a personal study checklist — work through each topic, tick off the points you can confidently explain or calculate, and use the linked Elec-Mate tools to practice the calculation-led parts. Designed for Level 3 apprentices.

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18 min readUpdated 2026-05-18Andrew Moore, Founder of Elec-Mate

Written and reviewed by Andrew Moore, founder of Elec-Mate, against BS 7671:2018+A4:2026, IET Guidance Note 3 and the IET On-Site Guide.

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Key Takeaways

  • 1City & Guilds 2366-03 Unit 304 — Electrical Design Practices and Procedures — is a core component of the Level 3 Diploma in Electrotechnical Technology.
  • 2This unit is typically delivered to Level 3 apprentices and covers 8 main topic areas.
  • 3Across the 8 topics there are 44 specific points you should be able to explain, demonstrate or calculate before the end-of-unit assessment.
  • 4Common assessment formats include online multiple-choice exams, written short-answer papers, and practical workshop tasks observed by your tutor.
  • 5Use the structured topic list below as a personal checklist — work through each point and confirm you can explain it without referring to your notes.
  • 6The Elec-Mate apprentice tier includes mock exams, flashcards, and revision notes mapped to this unit. Use the tools to test yourself between college blocks and on-site days.
01 · Unit Revision

Topic 1: How to prepare for the installation of wiring systems

In this section you should be confident with the following points. Each one is a specific topic you should be able to explain, demonstrate, or calculate.

  • The sources of statutory and non-statutory information that may be used when undertaking electrical design.
  • The requirements to ensure that electrical work sites are correctly prepared in accordance with Health & Safety legislation.
  • The potential pre-existing damage and dangerous findings to customer/client property prior to commencement of work activity.
  • The processes of checking and reporting any pre-existing damage to customer/client property.
  • The suitability of different methods for protecting the fabric and structure of the property before and during electrical work.
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02 · Unit Revision

Topic 2: The applications of wiring systems

In this section you should be confident with the following points. Each one is a specific topic you should be able to explain, demonstrate, or calculate.

  • The constructional features of electrical cables.
  • The characteristics of containment, support and wiring systems used in electrical installations.
  • Determination of the size of conduit and trunking as appropriate to the size and number of cables.
  • The factors which affect the selection of wiring systems, associated equipment and enclosures.
  • Suitable wiring systems and equipment appropriate to the installation.
03 · Unit Revision

Topic 3: The practices and procedures for carrying out electrical work

In this section you should be confident with the following points. Each one is a specific topic you should be able to explain, demonstrate, or calculate.

  • The procedures for selecting appropriate tools and materials for safe use.
  • The equipment for measuring and marking out wiring systems, equipment and enclosures.
  • The criteria for selecting tools and equipment for fixing and installing wiring systems, associated equipment and enclosures.
  • The suitability of fixing devices for different environments, building materials and applications.
  • The installation methods and considerations to ensure domestic, commercial and industrial specifications are met in accordance with statutory and non-statutory regulations.
  • The methods and considerations for restoring the building fabric upon completion of work.
04 · Unit Revision

Topic 4: The characteristics and applications of electrical supply systems and consumers equipment

In this section you should be confident with the following points. Each one is a specific topic you should be able to explain, demonstrate, or calculate.

  • The characteristics and applications of earthing arrangements.
  • The characteristics and compatibility of electrical supply systems.
  • The considerations for electrical installations and systems with regard to provision for isolation, switching and protection of circuits.
05 · Unit Revision

Topic 5: Earthing and protection

In this section you should be confident with the following points. Each one is a specific topic you should be able to explain, demonstrate, or calculate.

  • The purpose of earthing conductors and bonding conductors.
  • The difference between extraneous and exposed conductive parts.
  • The measures for protection against electric shock required by BS 7671.
  • The maximum disconnection times for different types of earthing systems and circuits.
  • The component parts of earth fault loop impedance paths of each earthing arrangement.
  • Applications of functional earthing.
  • The selection of suitably sized protective conductors in accordance with BS 7671.

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06 · Unit Revision

Topic 6: Protection against overcurrent

In this section you should be confident with the following points. Each one is a specific topic you should be able to explain, demonstrate, or calculate.

  • Types of overcurrent and possible causes.
  • The limitations of protective devices.
  • The fault current capacities of devices.
  • The need for selectivity between protective devices.
07 · Unit Revision

Topic 7: Electrical systems and circuits

In this section you should be confident with the following points. Each one is a specific topic you should be able to explain, demonstrate, or calculate.

  • The types of standard electrical circuits.
  • The applications of electrical systems and circuits.
08 · Unit Revision

Topic 8: How to apply a cable design

In this section you should be confident with the following points. Each one is a specific topic you should be able to explain, demonstrate, or calculate.

  • The purpose and methods of applying diversity factors when carrying out maximum demand calculations.
  • Verify if the disconnection times have been achieved.
  • Evaluate thermal constraints.
  • Interpret the requirements of sources of technical information in the design of an installation.
  • Select suitable equipment, considering energy efficiency and sustainability, to relevant codes of practice and manufacturer instructions.
  • Calculate the maximum demand of an installation after the application of diversity.
  • Calculate design current.
  • Select a suitably rated protective device type for a given circuit.
  • Select the installation reference method.
  • Calculate appropriate cable rating factors.
  • Determine the minimum cross-sectional area of live conductors taking into consideration current-carrying capacity and voltage drop.
  • Identify if the voltage drop is acceptable.
09 · Unit Revision

Study This Unit with Elec-Mate

Elec-Mate’s apprentice tier turns this unit checklist into an active study plan. You get mock exam questions, flashcards, and revision notes mapped to this unit, plus working calculators for every calculation-led topic. Most apprentices use the app between college blocks and on the train to site — short bursts of revision compound across the year.

For apprentices

The Elec-Mate apprentice tier includes mock exams, flashcards, and revision notes for City & Guilds 2366-03 Unit 304 plus every other unit in your qualification. 7-day free trial — see your progress on the tutor dashboard.

A Five-Step Revision Plan for This Unit

A repeatable approach that works for City & Guilds 2366-03 Unit 304 and every other unit in your qualification.

1

Read through every topic point once

Start at Topic 1 and read every bullet point. Don’t try to memorise — just get familiar with the scope. Note any topic that feels unfamiliar so you can come back to it.

2

Map each topic to its calculator or guide

For calculation-led topics, open the relevant Elec-Mate calculator and try one worked example. For theory-led topics, find the matching section in BS 7671 or the IET On-Site Guide.

3

Work through Elec-Mate mock exam questions

The Elec-Mate apprentice tier includes mock questions mapped to this unit. Aim for 80%+ on a clean run before the real exam.

4

Get hands-on time on the bench

For practical units (inspection and testing, installation), ask your tutor for additional workshop access. The bench is where the points click.

5

Self-explain each topic to a peer

If you can explain a topic in your own words to another apprentice and they understand it, you know it. This is the single highest-leverage revision tactic.

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