Proper cable management is one of the most important aspects of any commercial or industrial electrical installation. Whether you’re wiring an office building, manufacturing facility, hospital, warehouse, or data centre, keeping cables organised and protected helps improve safety, simplify maintenance, and support future system expansions.
One of the most common questions electrical contractors, consultants, and facility managers ask is: “What size cable trunking should I use?” The answer depends on several factors, including the number of cables, cable diameter, future expansion requirements, and the installation environment.
Choosing cable trunking that is too small can lead to overcrowding, poor heat dissipation, and difficult maintenance. On the other hand, selecting an oversized trunking system may increase installation costs and occupy unnecessary space.
In this guide, we’ll explain standard cable trunking sizes, when each size should be used, and how to choose the right option for your project. We’ll also include a practical cable trunking sizes chart to help you make informed decisions.
What Is Cable Trunking?
Cable trunking is an enclosed cable management system designed to route, organise, and protect electrical wiring. Unlike conduits, which typically carry a small number of cables, trunking provides larger enclosed pathways capable of accommodating multiple power, control, and communication cables.
Cable trunking is widely used in:
- Commercial buildings
- Industrial facilities
- Manufacturing plants
- Hospitals
- Educational institutions
- Warehouses
- Data centres
- Infrastructure projects
High-quality GI Cable Trunking also protects cables from dust, accidental impact, and mechanical damage while providing easy access for future cable additions or maintenance. Raiden’s GI cable trunking is available in standard 2.44 m and 3 m lengths and is manufactured from pre-galvanized or hot-dip galvanized steel to BS 4678 Part 1 standards.
Why Choosing the Right Cable Trunking Size Matters
The size of your cable trunking directly affects the performance, safety, and maintainability of an electrical installation.
A correctly sized trunking system helps:
- Prevent cable congestion
- Improve airflow and heat dissipation
- Protect cable insulation
- Simplify future cable additions
- Reduce maintenance time
- Maintain a neat and professional installation
Many designers also leave spare capacity within trunking to accommodate future expansion without replacing the existing system. Industry guidance commonly recommends avoiding overfilling trunking to maintain cable performance and ease of maintenance.
Standard Cable Trunking Sizes Chart
Below are some of the most commonly used GI cable trunking sizes for commercial and industrial projects.
Trunking Size (mm) | Typical Applications |
50 × 50 mm | Small commercial cable runs, lighting circuits, office wiring |
75 × 50 mm | Medium-sized distribution systems, retail spaces |
75 × 75 mm | Multiple power and data cable installations |
100 × 50 mm | Commercial electrical distribution |
100 × 75 mm | Industrial control panels and manufacturing plants |
100 × 100 mm | Large commercial installations |
150 × 50 mm | High-density cable routing |
150 × 75 mm | Industrial facilities and process plants |
150 × 100 mm | Heavy-duty electrical services |
200 × 100 mm | Main power distribution systems |
225 × 100 mm | Infrastructure projects |
300 × 100 mm & Above | Large industrial and utility installations |
Raiden Industries also offers single-compartment as well as 2, 3, and 4-compartment GI cable trunking, allowing power, data, and communication cables to be segregated within the same trunking system.
Factors to Consider When Choosing Cable Trunking Size
Selecting the right cable trunking involves more than simply choosing the largest available option.
Number of Cables
The first consideration is the total number of cables that will pass through the trunking. As the number of cables increases, so does the required trunking size.
Always allow additional capacity for future installations instead of designing around current requirements alone.
Cable Diameter
Larger power cables occupy significantly more space than control or communication cables.
For example:
- Control cables
- Instrumentation cables
- Fire alarm cables
- Power cables
- Data cables
Each requires different levels of space inside the trunking.
Future Expansion
One of the biggest advantages of cable trunking is the ability to add new circuits later.
Choosing slightly larger trunking today can eliminate the need for costly modifications in the future.
Heat Dissipation
Electrical cables generate heat during operation.
Overcrowded trunking restricts airflow, potentially affecting cable performance and reducing insulation life.
Maintaining adequate spacing inside the trunking improves ventilation and contributes to safer electrical installations.
Installation Environment
Indoor commercial offices have different requirements than manufacturing facilities or outdoor industrial plants.
Consider factors such as:
- Moisture
- Dust
- Chemical exposure
- Mechanical impact
- Corrosion
For demanding environments, hot-dip galvanized GI cable trunking offers enhanced durability and corrosion resistance.
Single vs Multi-Compartment Cable Trunking
Choosing the right compartment configuration is just as important as selecting the correct size.
Single Compartment Trunking
Single-compartment trunking is commonly used where all cables belong to the same electrical system.
Typical applications include:
- Power distribution
- Lighting circuits
- Industrial equipment
Multi-Compartment Trunking
Modern commercial buildings often require separate routing for different services.
Multi-compartment trunking allows installers to segregate:
- Power cables
- Data cables
- Communication cables
- Fire alarm wiring
- Security system cables
This improves cable organisation while reducing electromagnetic interference between different systems. Raiden manufactures multiple-compartment trunking options with compatible accessories.
Common Applications of GI Cable Trunking
GI cable trunking is widely used across numerous industries due to its strength and durability.
Common applications include:
Commercial Buildings
Office complexes, shopping centres, hotels, and educational institutions require organised cable routing for power, lighting, and communication systems.
Manufacturing Facilities
Factories often contain extensive electrical installations serving production equipment, control panels, and automation systems.
Data Centres
Cable trunking supports structured cable management while allowing future expansion.
Hospitals
Healthcare facilities depend on well-organised electrical infrastructure for medical equipment, emergency systems, and communication networks.
Infrastructure Projects
Airports, railway stations, public utilities, and industrial developments require heavy-duty cable management systems capable of supporting large cable installations.
Common Mistakes When Selecting Cable Trunking
Even experienced installers can make sizing mistakes.
Avoid these common issues:
- Selecting trunking based only on current cable requirements
- Ignoring future expansion
- Overfilling cable trunking
- Choosing unsuitable compartment configurations
- Ignoring environmental conditions
- Selecting poor-quality accessories
Proper planning at the design stage helps reduce maintenance costs throughout the life of the installation.
Accessories That Complete a Cable Trunking System
A cable trunking installation is more than just the trunking itself. To achieve a safe, durable, and professional finish, it’s important to use compatible accessories that ensure proper alignment, protection, and support throughout the cable route.
Depending on the project, these may include:
- Flat bends
- Internal and external bends
- Tee sections
- Reducers
- Couplers
- End plates
- Suspension hangers
- Cable retainers
- Covers and fixing systems
Using matching accessories helps maintain the integrity of the cable management system while making future maintenance and modifications much easier. Raiden supplies a complete range of compatible trunking accessories for its GI cable trunking systems.
Choosing the Right Cable Trunking for Long-Term Performance
Selecting the correct cable trunking size isn’t simply about fitting cables into an enclosure—it’s about creating a cable management system that remains safe, organised, and easy to maintain throughout the life of the building. Considering factors such as cable volume, future expansion, environmental conditions, and compartment requirements during the planning stage can help prevent costly modifications later.
For commercial and industrial projects, high-quality GI cable trunking manufactured to recognised standards offers dependable protection and long-term durability. Whether you’re designing a new electrical installation or upgrading an existing facility, choosing the right trunking system helps improve safety, simplify maintenance, and support future growth.
Explore Raiden Electric’s range of GI Cable Trunking, compatible accessories, and technical resources to find the right cable management solution for your next project.
Frequently Asked Questions
What is the standard size of cable trunking?
Cable trunking is available in a wide range of sizes, with common commercial dimensions including 50×50 mm, 75×50 mm, 100×50 mm, 150×75 mm, and 200×100 mm. The appropriate size depends on the number and type of cables being installed.
How do I choose the right cable trunking size?
Consider the number of cables, cable diameters, future expansion requirements, installation environment, and whether separate compartments are needed for power and data cables.
Why is GI cable trunking used?
GI (Galvanized Iron) cable trunking provides excellent mechanical protection, corrosion resistance, and durability, making it suitable for commercial, industrial, and infrastructure applications.
Can power and data cables be installed in the same trunking?
Yes, but they should be separated using multi-compartment trunking to minimise electromagnetic interference and improve cable organisation.
Does cable trunking allow future cable additions?
Yes. One of the key advantages of cable trunking is that it provides easy access for maintenance and allows additional cables to be installed without major modifications, provided adequate spare capacity has been planned.
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