Lesson Notes By Weeks and Term v3 - Senior Secondary 2
Trunking and Ducting
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Trunking and Ducting
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Subject: Basic Electricity
Class: Senior Secondary 2
Term: 1st Term
Week: 7
Theme: Electrical Wiring
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This topic introduces students to essential methods of cable containment and protection in electrical installations: trunking and ducting. Understanding these systems is fundamental for ensuring safety, durability, and neatness in both domestic and industrial wiring practices prevalent across Nigeria. These systems are crucial in preventing mechanical damage to cables, facilitating future maintenance or upgrades, and maintaining aesthetic standards in various built environments, from residential buildings in Lagos to commercial centres in Kano and industrial complexes in Port Harcourt. Specific Performance Objectives for Learners:
This section provides a detailed explanation of trunking and ducting, differentiating between them, and outlining their respective fittings.
Teacher Activities: Introduction (10 minutes): Begin by asking students to recall methods of protecting electrical cables (e.g., conduit). Introduce trunking and ducting as advanced forms of cable protection and management, vital for safety and neatness in various Nigerian settings.
Display visual aids: pictures/diagrams of different types of trunking and ducting, including their fittings. If possible, bring actual samples of PVC trunking and a piece of heavy-duty ducting/conduit.
Explanation of Trunking (15 minutes): Define trunking, explaining its purpose and typical installation (surface-mounted). Discuss common materials (PVC, metal) and their applications in local contexts (e.g., offices, homes, shops). Present and explain various trunking fittings (couplers, bends, tees, end caps, etc.), demonstrating their use with diagrams or actual samples. Ask students to identify places in their community where they might see trunking.
Explanation of Ducting (15 minutes): Define ducting, emphasising its robust nature and typical installation (underground, embedded). Discuss common materials (heavy-duty PVC, concrete) and their applications in Nigerian contexts (e.g., street lighting, main power feeds, industrial areas). Present and explain various ducting fittings (couplers, swept bends, inspection chambers, bellmouths), highlighting their differences from trunking fittings. Discuss the importance of ducting for long-term protection and critical infrastructure. Differentiation and Comparison (15 minutes): Facilitate a class discussion to draw out the key differences between trunking and ducting based on installation, purpose, materials, accessibility, and applications. Use a comparison chart on the board or projector to summarise the distinctions. Present the worked example (Computer Lab vs. Factory Power) and guide students through its solution, reinforcing the criteria for differentiation.
Activity Wrap-up and Q&A (5 minutes): Review key concepts. Address any student misconceptions or questions.
Student Activities: Observation and Recall: Students will recall previous knowledge on cable protection and observe the visual aids presented by the teacher.
Active Listening and Note-taking: Students will listen to explanations, take notes on definitions, characteristics, and applications.
Identification: Students will identify different trunking and ducting fittings from diagrams or physical samples.
Discussion and Participation: Students will actively participate in class discussions, contributing examples of where they have seen these systems in use locally.
Comparative Analysis: Students will engage in comparing and contrasting trunking and ducting based on the teacher's guidance and the worked example.
Sketching (Optional): Students may be asked to sketch a simple application of trunking in a classroom or a simple diagram of a ducting run under a road. The teacher should present these questions to the students, allowing time for individual or group work, then guide them through the solutions, explaining each step.
Question 1: A new block of hostel rooms is being constructed at a university in Abuja. The electrical wiring for individual rooms needs to be run neatly on the surface of the walls to allow for easy future modifications. For the main power supply from the generator house to the hostel block, the cables must cross an open ground area and pass beneath a pedestrian walkway. a) Which cable containment system is most suitable for the internal wiring of the hostel rooms? b) Which cable containment system is most suitable for the main power supply from the generator house to the hostel block? c) Briefly justify your choice for both (a) and (b).
Solution 1: a) Trunking (specifically, PVC trunking for aesthetics and ease of modification). b) Ducting (specifically, heavy-duty PVC or concrete ducting for underground protection). c)
Justification: For internal hostel wiring (a), trunking is suitable because it is designed for surface mounting, provides neatness, and allows for easy access for future modifications or maintenance. For the main power supply (b), ducting is necessary because the cables are underground and pass beneath a pedestrian walkway, requiring robust protection against mechanical damage, environmental factors, and for long-term durability.
Question 2: You are working on an electrical installation project for a new bank branch in Port Harcourt. One requirement is to run data and power cables across the floor of the main banking hall, beneath a raised floor system, for connectivity to ATM machines. Another requirement is to neatly route power cables along the walls from the distribution board to various sockets and light switches within the offices. a) Identify the primary difference in the installation method for the cable containment systems used for the ATM cables and the office wall cables. b) What are two key benefits of using the system chosen for the office wall cables?
Solution 2: a) The primary difference in installation method is that the system for the ATM cables (likely a form of ducting or cable tray beneath a raised floor) is concealed/embedded within the floor structure, whereas the system for the office wall cables (trunking) is surface-mounted and visible on the walls. b) Two key benefits of using trunking for office wall cables are: Aesthetics/Neatness: It provides a clean and organised appearance, concealing wires that would otherwise look messy. Accessibility for Maintenance/Modification: The removable covers allow easy access to cables for troubleshooting, adding new cables, or rerouting existing ones without significant disruption.
Question 3: An electrician is planning to install a new lighting circuit in a small shop in Onitsha market. The existing wiring is surface-mounted. He also needs to connect the shop's main distribution board to a new power meter located outside the shop, requiring a short underground run. a) Name two fittings that would likely be used for the internal lighting circuit's cable containment. b) Name two fittings that would be essential for the underground power meter connection's cable containment.
Solution 3: a) For the internal lighting circuit (which would use trunking): Flat Bend (90-degree): To change direction along walls.
End Cap: To neatly finish off the trunking run. (Other acceptable answers include Coupler, Tee Piece, Internal/External Angle) b) For the underground power meter connection (which would use ducting): Coupler/Socket: To join lengths of ducting underground.
Swept Bend: To create a gentle curve for the ducting run, facilitating cable pulling. (Other acceptable answers include Inspection Chamber, Bellmouth Entry, End Cap/Sealing Plug)
Differentiation Strategies: For Struggling Learners (Remediation): Visual Aids Reinforcement: Provide simplified diagrams of trunking and ducting installations, clearly labelling parts and showing their application. Use physical samples extensively, allowing learners to touch and examine the materials and fittings.
Paired Work/Peer Tutoring: Pair struggling learners with more capable peers to review definitions and identify fittings. Encourage them to explain concepts to each other.
Focus on Core Concepts: Prioritise understanding the fundamental difference in installation location (surface vs. embedded/underground) and protection level. Break down the list of fittings, perhaps focusing on just two common ones for each system initially.
Hands-on Matching Activity: Prepare cards with names of fittings and corresponding pictures. Learners match the names to the images, then sort them into "Trunking Fittings" and "Ducting Fittings." For High-Achieving Learners (Extension): Research and Presentation: Task them with researching other types of cable containment systems (e.g., cable trays, conduits, busbar trunking) and comparing their advantages and disadvantages relative to trunking and ducting, perhaps focusing on a specific industrial application in Nigeria.
Design Challenge: Provide a simple floor plan of a small office or residential room and challenge them to sketch a wiring layout incorporating trunking, indicating where different fittings would be used. They could also consider the sizing of trunking based on a hypothetical number of cables.
Cost-Benefit Analysis: Ask them to consider a scenario where both trunking and ducting could theoretically be used (e.g., routing cables along a wall vs. embedding them). Challenge them to discuss the factors (cost, accessibility, aesthetic, future flexibility, level of protection required) that would influence the choice in a Nigerian context, considering local material availability and labour costs.
Community Development Projects: In many Nigerian communities, electrification projects involve running power lines. Trunking is often used for internal wiring in newly constructed community centres, schools, or health clinics, providing a safe and organised visible installation. Ducting is crucial for the main power feeds from community transformers to these buildings, especially when crossing roads or open areas, ensuring robust protection of the supply cables.
Urban and Commercial Development: Modern commercial buildings, shopping plazas, and office complexes in Nigerian cities heavily rely on both systems. Trunking is extensively used for internal power distribution, data networking, and telecommunication cabling within the visible spaces of offices and retail units, often incorporating multi-compartment trunking to separate different services. Ducting is indispensable for the primary power infrastructure, underground fibre optic networks, and utilities that supply these large establishments, protecting critical services from environmental and mechanical damage.
Industrial Sector: Nigeria's burgeoning industrial estates (e.g., those in Lagos, Kano, or Aba) utilise heavy-duty ducting for distributing high-voltage and high-current power cables across the complex, often underground or embedded in concrete floors, to withstand the harsh industrial environment. Within the factory buildings themselves, large metal trunking systems are used to route power to machinery, providing a robust and accessible pathway for heavy cables. This ensures safety for workers and operational continuity.