Class: Senior Secondary School 1 (SS1 / SSS 1)
Term: 3rd Term
Week: 6
Age: 15 years
Duration: 45 minutes
Subject: Electrical Installation and Maintenance Work
Curriculum Theme: Technology
Previous Lesson: Practical Class on the Installation of Fuse.
Topic: INSTALLATION OF CURRENT OPERATED CIRCUIT BREAKER
Subject Matter: sketching circuit breaker installation diagram, IEE regulation on circuit breakers, connecting 2 points of light to a single phase circuit breaker, connecting to a 3 phase circuit breaker, safety and testing after installation

Specific Objectives

By the end of the lesson, pupils should be able to:

Cognitive Domain:

State at least three IEE regulations related to circuit breaker installation.
Describe the steps for connecting light points to a single-phase circuit breaker.
Explain the importance of safety and testing after circuit breaker installation.

Affective Domain:

Appreciate the importance of safety measures during electrical installations.
Value adherence to electrical regulations for proper and safe wiring.

Psychomotor Domain:

Sketch a basic circuit breaker installation diagram.
Connect two points of light to a single-phase circuit breaker under supervision.
Connect two points of light to a three-phase circuit breaker under supervision.

Collaborate effectively with peers during practical connection activities.
Communicate clearly about safety procedures in the workshop.

Reference Materials

The following resources were used in planning this lesson:

9 Years Basic Education Curriculum for Electrical Installation and Maintenance Work.
State Unified Scheme of Work for Senior Secondary Schools.
Electrical Installation and Maintenance Work for Senior Secondary Schools, Book 1.
https://www.ieerules.org
https://www.electricaltechnology.org

Instructional Materials

The teacher will teach this lesson with the aid of:

Single-phase circuit breaker
Three-phase circuit breaker
Wiring board
Assorted electrical cables
Light bulbs and holders
Multimeter for testing
Chalkboard/whiteboard and markers
Diagrams of circuit breaker installations

Rationale for the Lesson

This lesson helps pupils understand how to correctly install current-operated circuit breakers, which are essential for electrical safety. Proper installation prevents electrical hazards and ensures the protection of electrical circuits and appliances in homes and workplaces.

Prerequisite/Previous Knowledge

Pupils have basic knowledge of electricity, simple circuits, and the function of different electrical components like switches and wires.

Lesson Content/Board Summary

INSTALLATION OF CURRENT OPERATED CIRCUIT BREAKER

Circuit Breaker Installation Diagram

A circuit breaker installation diagram shows the connection of the circuit breaker within the electrical system, indicating input and output terminals, and how it protects a circuit.

IEE Regulations on Circuit Breakers

The Institution of Electrical Engineers (IEE) Wiring Regulations (BS 7671) provide standards for safe electrical installations. Key regulations concerning circuit breakers include:

All circuit breakers must be correctly rated for the circuit they protect, considering current and fault level.
Circuit breakers must be easily accessible for operation and maintenance.
Proper earthing and bonding must be ensured for all installations.
Clear labeling of circuit breakers is required to identify the circuits they control.
Residual Current Devices (RCDs) or Residual Current Circuit Breakers (RCCBs) are required for specific circuits to provide additional protection against electric shock.

Connecting Light Points to a Single-Phase Circuit Breaker

To connect two points of light to a single-phase circuit breaker:

Ensure the main power supply is off.
Connect the live wire from the main supply to the input terminal of the single-phase circuit breaker.
Connect the live wire from the output terminal of the circuit breaker to the switch for the first light point.
Connect the switched live wire from the first switch to the live terminal of the first light holder.
Loop the live wire from the first light holder to the second light holder, or run a separate switched live wire from the switch to the second light holder.
Connect the neutral wire from the main supply to the neutral terminals of both light holders.
Connect the earth wire from the main supply to the earth terminals of the light holders, if applicable.

Connecting Light Points to a Three-Phase Circuit Breaker

A three-phase circuit breaker is used for circuits requiring higher power or balanced loads across three phases. Connecting two points of light to a three-phase breaker:

Ensure the main power supply is isolated.
Connect one phase (e.g., L1) from the main supply to one input terminal of the three-phase circuit breaker.
Connect the output of this phase from the breaker to the switch controlling the light points.
Connect the switched live wire from the switch to the live terminals of the light holders.
Connect the neutral wire from the main supply to the neutral terminals of the light holders.
Ensure proper earthing is established for the entire circuit.

Safety Precautions and Testing After Installation

Safety is paramount during and after electrical installations. Important safety precautions include:

Always switch off and isolate the main power supply before working on any circuit.
Use appropriate Personal Protective Equipment (PPE) such as insulated gloves and safety glasses.
Ensure all connections are tight and secure to prevent loose contacts and overheating.
Never work on live circuits unless absolutely necessary and with extreme caution.
Keep the work area clean and free from obstructions.

Testing after installation is critical to verify correct wiring and safety. Common tests include:

Continuity Test: To ensure continuous paths for conductors and check for breaks.
Insulation Resistance Test: To check the integrity of insulation between conductors and between conductors and earth.
Earth Fault Loop Impedance Test: To ensure the earth fault protection operates quickly enough.
RCD Test: To verify that Residual Current Devices trip within specified times.
Polarity Test: To ensure live, neutral, and earth conductors are connected to the correct terminals.

Teaching Methods/Instructional Techniques

Discussion, Lecture, Demonstration, Question and Answer, Visual Aids, Practical Activity

Instructional Procedures

Step 1: Introduction

Time: 5 minutes
Teaching Skill: Set Induction
Teacher’s Activity: The teacher greets the pupils and asks them about the importance of circuit breakers in electrical installations. The teacher then introduces the topic: “Installation of Current Operated Circuit Breaker.”
Pupils’ Activity: Pupils respond to the teacher’s questions and listen attentively to the introduction of the topic.
Learning Point: Pupils recall the basic function of circuit breakers and prepare for the lesson.

Step 2: Presentation of Circuit Breaker Installation Diagram

Time: 8 minutes
Teaching Skill: Explanation/Illustration
Teacher’s Activity: The teacher sketches a simple circuit breaker installation diagram on the board, explaining the different parts and their connections within a circuit. The teacher clarifies the flow of current and the protection offered.
Pupils’ Activity: Pupils observe the diagram, ask questions for clarification, and copy the diagram into their notebooks.
Learning Point: Pupils understand the visual representation of a circuit breaker installation.

Step 3: Explanation of IEE Regulations

Time: 7 minutes
Teaching Skill: Explanation/Lecture
Teacher’s Activity: The teacher explains the key IEE regulations related to the installation and use of circuit breakers, emphasizing their importance for safety and compliance.
Pupils’ Activity: Pupils listen, take notes, and ask questions regarding the regulations.
Learning Point: Pupils learn about the mandatory standards for circuit breaker installations.

Step 4: Demonstration of Single-Phase Connection

Time: 7 minutes
Teaching Skill: Demonstration/Practical
Teacher’s Activity: Using the wiring board, single-phase circuit breaker, cables, and light points, the teacher demonstrates how to connect two points of light to a single-phase circuit breaker. The teacher explains each step clearly.
Pupils’ Activity: Pupils observe the demonstration carefully, paying attention to the connections and safety precautions.
Learning Point: Pupils visually grasp the practical steps for single-phase circuit breaker wiring.

Step 5: Demonstration of Three-Phase Connection

Time: 7 minutes
Teaching Skill: Demonstration/Practical
Teacher’s Activity: The teacher then demonstrates the connection of two light points to a three-phase circuit breaker, highlighting the differences and similarities compared to the single-phase connection.
Pupils’ Activity: Pupils observe the second demonstration, noting the specifics of three-phase wiring.
Learning Point: Pupils understand the procedures for connecting light points to a three-phase circuit breaker.

Step 6: Discussion on Safety and Testing

Time: 6 minutes
Teaching Skill: Discussion/Questioning
Teacher’s Activity: The teacher leads a discussion on essential safety precautions during installation and the importance of testing the installation after completion. The teacher lists various tests that should be performed.
Pupils’ Activity: Pupils contribute to the discussion, share their knowledge of safety, and list the different types of tests.
Learning Point: Pupils learn about critical safety measures and post-installation testing procedures.

Step 7: Evaluation/Review

Time: 5 minutes

Teaching Skill: Questioning/Assessment

Teacher’s Activity: The teacher evaluates the learning by asking the following questions:

Mention three IEE regulations related to circuit breaker installation.
Describe two steps involved in connecting light points to a single-phase circuit breaker.
State two important safety precautions to observe during electrical installation.
List two tests performed after installing a circuit breaker.

Pupils’ Activity: Pupils answer orally and in writing.

Learning Point: Pupils demonstrate understanding of the lesson.

Step 8: Conclusion

Time: 3 minutes
Teaching Skill: Summarization
Teacher’s Activity: The teacher summarizes the key points of the lesson, reiterating the importance of correct circuit breaker installation for safety. The teacher assigns homework: “Draw a detailed diagram showing the connection of a single-phase circuit breaker protecting a lighting circuit.”
Pupils’ Activity: Pupils listen to the summary and copy down the homework assignment.
Learning Point: Pupils consolidate their understanding and are given an opportunity for further practice.

Lesson Keywords

Circuit Breaker – An automatic electrical safety switch designed to protect an electrical circuit from damage caused by overcurrent or short circuit.
IEE Regulations – Standards set by the Institution of Electrical Engineers for safe electrical installations.
Single-Phase – An alternating current power system that uses one phase wire and one neutral wire.
Three-Phase – An alternating current power system that uses three phase wires and often a neutral wire, providing more consistent power.
Installation – The act of setting up or putting into place equipment for use.
Testing – Procedures performed to verify the safety and functionality of an electrical installation.
Safety Precautions – Measures taken to prevent accidents or injury during work.

Differentiation

For pupils who grasp concepts quickly, the teacher can challenge them to identify different types of circuit breakers and their specific applications. For pupils needing additional support, the teacher will provide one-on-one guidance during the practical demonstration and assign a simpler diagram to sketch for homework, or pair them with a more capable peer during practical activities.

Note for teachers using this lesson plan

Ensure all electrical components used for demonstration are in good working condition and that safety measures are strictly enforced during practical activities. Emphasize the dangers of working with electricity without proper knowledge and precautions. Supervise all practical connections closely. Encourage pupils to ask questions and participate actively.