Armoured cable has become a key component in modern electrical installations, offering greater protection and durability. Designed to withstand physical threats and environmental conditions, armoured cable ensures the safe and reliable transmission of electrical power and signals.
In this guide, we’ll be explaining all you need to know about armoured cables, from choosing the right type for the job to correctly installing it.
What is Armoured Cable?
Armoured cable is a type of electrical cable reinforced with a metal sheath that protects it from physical damage. Its robust construction makes it ideal for use in environments where the risk of mechanical damage is high.
The key feature of armoured cable is its protective armour, typically made of steel or aluminium, which shields the inner conductors against mechanical damage and external pressures.
Thanks to its durable design, armoured cable boasts a longer lifespan, especially in harsh or outdoor environments where exposure to moisture, chemicals, and extreme temperatures is common.
Types of Armoured Cable and Their Applications
Steel Wire Armoured (SWA)
Steel wire armoured (SWA) cable is most commonly used in underground systems, power networks, and outdoor lighting installations. Its steel wire armour provides robust protection, making it suitable for direct burial.
Aluminum Wire Armoured (AWA)
AWA is similar to SWA but uses aluminium armour instead of steel, making it lighter. It's often used where lower weight is beneficial, such as in power transmission over long distances.
Steel Tape Armoured (STA)
STA cable is designed with steel tape armouring, offering a thinner protective layer. It's typically used in indoor and buried applications where space is limited but protection is still needed.
Each type of armoured cable serves a specific purpose, with its suitability dependent on the environmental conditions, the type of installation, and the electrical requirements of the project.
When Should You Use Armoured Cable?
Armoured cable is designed for use in situations where electrical wiring faces a higher risk of mechanical damage, interference, or exposure to harsh environmental conditions. It's a popular choice for ensuring safety and longevity in both commercial and residential settings.
Armoured Cable Applications
Outdoor Installations
Due to its robust protection against weather elements, armoured cable is ideal for outdoor electrical wiring, including garden lighting, power supplies to outbuildings, and other exterior applications.
Underground Routes
When electrical cables need to be run underground, armoured cable is essential. Its protective armouring shields the internal wires from moisture, soil corrosion, and physical damage caused by digging or other ground activities.
Areas Prone to Mechanical Damage
In industrial environments or areas where cables might be exposed to potential mechanical damage (e.g. warehouses, factories, and construction sites), armoured cable offers the necessary protection to maintain circuit integrity.
Public or High Traffic Areas
For safety and durability, armoured cable is recommended in places where there's a high likelihood of interference or physical impact, such as in public buildings, schools, and hospitals.
Armoured Cable Sizes
The size of armoured cable you choose is important for the safety, efficiency, and reliability of your electrical installation. Armoured cables come in a variety of sizes, which are determined by the cross-sectional area of the internal conductors measured in square millimetres (mm²).
Common Armoured Cable Sizes and Their Typical Uses
1.5 mm² & 2.5 mm²: Ideal for lighting circuits and small power tools in both residential and commercial settings.
4 mm² to 6 mm²: Suitable for larger lighting installations, power outlets in homes, and outdoor lighting that requires higher current.
10 mm² to 16 mm²: Often used for connections to heavy-duty electrical appliances, small industrial machinery, and large heating units.
25 mm² and Above: Reserved for high-load applications, including main power supply lines, industrial setups, and large electrical machinery.
How to Choose the Right Size Armoured Cable for Your Project
Selecting the appropriate cable size involves considering the total load of the devices the cable will power, the length of the cable run, and any potential voltage drop over distance. Using a cable size calculator or consulting with an electrical engineer can help ensure you choose a size that provides adequate capacity and safety for your specific needs.
What Thickness Armoured Cable Do I Need?
The thickness of your armoured cable is important in making sure it can handle the intended electrical load without overheating or experiencing excessive voltage drop. Here’s how to select the right armoured cable thickness for the job:
Calculate the Total Load: Sum the power ratings (in watts) of all devices that will be connected to the cable. Convert this to amperes to understand the current requirement.
Consider the Length: For longer runs, opt for a thicker cable to mitigate voltage drop and ensure efficient power delivery.
Check Regulations: Always refer to national electrical codes or standards, as they may dictate minimum thickness for specific applications or environments.
Selecting the appropriate thickness for your armoured cable is not just about meeting immediate needs but also about ensuring safety, compliance, and the adaptability of your electrical installation for future demands.
Armoured Cable Glands
Armoured cable glands play an important role in cable installations, acting as the interface between the armoured cable and the equipment or enclosure it connects to. These components not only secure the cable in place but also provide essential sealing and grounding functionalities.
Cable Glands and Their Role in Armoured Cable Installations
Cable glands are engineered to attach and secure the end of an armoured cable to the equipment. They offer several benefits:
Securing the Cable: Glands firmly hold the cable, preventing it from being pulled out of the system.
Maintaining Integrity: They help maintain the ingress protection rating of the enclosure, keeping out dust, moisture, and other environmental contaminants.
Grounding and Termination: For armoured cables, glands also ensure proper grounding of the armouring and create a safe electrical connection to the system.
Types of Glands and Selecting the Right One for Your Cable
Selecting the right cable gland is critical for the safety and effectiveness of the cable installation. The primary types include:
Brass glands
Nylon (Plastic) glands
Aluminium glands
Brass glands are durable and corrosion-resistant, suitable for both indoor and outdoor applications.
Nylon (Plastic) glands are lightweight and suitable for non-hazardous areas, particularly where corrosion or metallic components are a concern.
Aluminium glands are typically preferred in installations where aluminium armoured cable is used, due to their compatibility and corrosion resistance.
Choosing the right gland involves considering factors such as the type of armoured cable, the environment (hazardous or non-hazardous), and the requirements for grounding and sealing.
Installation Tips for Armoured Cable
Proper installation of armoured cable is key for the safety and longevity of your electrical system. Here are basic steps and the tools needed for a successful installation.
Measure and Cut: Accurately measure the length of cable required and use a suitable cutting tool to cut the cable, ensuring not to damage the inner wires.
Strip and Prepare: Carefully strip the outer sheath and armour to expose the inner conductors, without nicking them.
Fit the Gland: Select the appropriate gland size and type, and fit it to the end of the cable, securing the armour and ensuring a tight seal.
Connect the Conductors: Terminate the inner conductors to the equipment or enclosure, following wiring regulations and ensuring secure connections.
Secure the Gland and Cable: Ensure the gland is tightly secured to the equipment, providing a firm hold and proper grounding for the cable.
Remember, safety should always be your number one priority. Always turn off the power supply before starting the installation and wear appropriate safety gear.
Armoured Cable FAQs
What's the difference between SWA cables and AWA cables?
The primary difference between SWA (Steel Wire Armoured) and AWA (Aluminium Wire Armoured) cables is in their armouring material. SWA cables use steel wire armour, making them more suitable for applications requiring high mechanical protection.
AWA cables, on the other hand, use aluminium wire armour, making them lighter and a preferred choice for installations where weight is a concern, such as power distribution in industrial settings. Both offer protection against mechanical damage, but the choice between them depends on the specific requirements of the installation.
Is armoured cable necessary for all outdoor electrical installations?
No, armoured cable is not necessary for all outdoor installations, but it is highly recommended for most due to its durability and protection against environmental hazards. It's ideal for areas exposed to potential mechanical damage or where additional protection is required.
Can armoured cable be used underground?
Yes, armoured cable is specifically designed for underground installations. Its robust construction protects against moisture, soil corrosion, and physical damage, making it a safe choice for burying directly under the ground.
What are the legal requirements for installing armoured cable in the UK?
In the UK, the installation of armoured cable must comply with the Wiring Regulations (BS 7671), which cover the installation of fixed cabling. Installations must be carried out by a competent person, and specific attention should be given to the protection of the cable, the depth of burying underground, and the use of appropriate glands and accessories.
How do you cut armoured electrical cable?
While there are a few different tools you can use to cut armoured cable, such as side cutters or a hacksaw, the best option is to use dedicated cable cutters specifically designed for the task.
Before cutting the cable, you should accurately measure the cable length required and mark the outer sheath at the cutting point. Then, adjust the cutters’ blade depth correctly to allow it to cut through the armour. You should position the cable in the cutters’ wire guide and align it with the cutting point you marked. Secure it in place and then carefully make the cut.
Do I Need Armoured Cable for Outdoor Lights?
Using armoured cable for outdoor lights is highly recommended. Outdoor lighting installations are exposed to various environmental factors such as rain, snow, and extreme temperatures, which can compromise the safety and functionality of electrical wiring.
