Ducting helps protect cables from the effects of exposure to the elements and other external factors. For this reason, you may be curious to determine whether or not armoured cables need ducting. We researched the topic to bring you an answer.
Generally, it is not necessary to duct an armoured cable since it has a steel cable to safeguard it against impact. However, it would be prudent to add an extra layer of protection through ducting if you install the cables in an area susceptible to impact.
Cables help to connect your home to the electric, telephone, or internet grid, among other roles. So, knowing how best to run them enables you to make informed decisions that increase the chances of safe connectivity. Dive in to learn more about armoured cables and other cable ducting topics.
Armoured Cables & Ducting
Armoured cables are primarily used for underground electrical transmission. Because these cables have mechanical protection, they are not easily damaged. Furthermore, their heavy weight makes it extremely difficult to bend them.
The Steel Wire Armoured (SWA) cable's design eliminates the necessity to duct them. The steel armor minimizes the possibility of the cables becoming damaged.
You can bury the SWA cables without adding an extra layer of protection, provided that you bury them at a sufficient depth to keep them safe. However, it is advisable to sandwich the cables between a sand or sifted coil layer to keep sharp stones from penetrating the cable's outer sheathing.
Armoured cables are not one-size-fits-all. So, choose the type that best suits your needs and the environment where you intend to use these cables.
Please note that some armoured cables have aluminum wire armor while others have steel wire armor. The steel armor is only used in multicore cables because the magnetic field that a single-core cable creates can induce an electric current in the steel wire, resulting in overheating.
Here are some types of armoured cables—
Two-Core Armoured Cable
The two-core armoured cable only has live and neutral cores. It is suitable for ferrying mains power to applications that do not need an earth connection, such as Class II or double-insulated appliances.
Earthing provides an alternate path for a faulty current to flow to the earth. Without it, the stray current can use you as a conduit as it moves from the live part to the earth, thus causing electric shock.
Class II appliances protect users from electric shock via double insulation—double insulation keeps the external casing from becoming live.
The first insulation layer cushions the electric cable from the appliance's internal components while the second layer separates the internal metal component (that can become live) from the external casing.
Besides using these cables for underground installation, you can also use cable cleats to mount the cables on buildings or other structures.
Three-Core Armoured Cable
The three-core armoured cable has live, neutral, and earth cores. This cable is suitable for supplying mains power to class I or single-insulated appliances since it has an earth core.
It's a heavy-duty cable often used for industrial applications or farming installations that require transporting mains power over a long distance.
Four-Core Armoured Cable
Four-core armoured cables are used to transport low-voltage and low-current signals. The low-voltage power supply is typical in factories that use automation. It also supplies power for low-voltage lighting and ground or roof-mounted solar panels.
This low-voltage power supply improves energy efficiency since they generate less heat. As a result, the cooling costs reduce.
You can use five-core armoured cables for low-voltage transmissions in three-phase lines with one zero-line for power supply.
It is best to consult an electrical expert to help determine an ideal wiring solution for your home. This helps ensure that you stay safe without compromising the performance of your electrical appliances.
What Is The Role Of Cable Ducting?
Cable ducting facilitates the safe distribution of cables by providing a clear, protected passage. For this reason, you can protect your cables from moisture, mechanical or chemical damage, or interference from humans and animals via cable ducting.
Underground cable ducting enhances aesthetics by reducing the number of unruly wires in our environment. Furthermore, when you bury power lines, you eliminate the chances of accidental fires and other safety risks, such as electrocution, from occurring due to downed lines.
Also, it minimizes weather-related blackouts, thus reducing maintenance costs while enhancing service delivery. But it is also important to note that line modifications become more expensive since the cables are not as accessible as they would be if they were installed above ground.
Guidelines For Underground Utility Ducting
These are some factors to consider to ensure safe underground utility connectivity. We discuss them below.
Adhere To Cable Color Codes
There are specific colors for different cable ducts. Each color represents the service or utility running through the ducting. The American Public Works Association (APWA) provides this guide on what the cable ducting colors represent:
- Red—electrical equipment like power lines, lighting cables, and other conduits
- Yellow—flammable substances such as natural gas, oil, steam, or petroleum products
- Orange—telecommunication lines such as fiber, alarm, and other signals
- Blue—drinking water
- Purple—water that is not safe for drinking, like slurry, irrigation, or reclaimed water
- Green—sewers or other drain lines
There are also pink and white colors representing temporary survey markings and proposed excavation borders, respectively.
Pink is the reserve of land surveyors who mark the legal boundaries associated with a project. On the other hand, white indicates where to dig underground infrastructures such as trenches or basements.
It is prudent to comply with the color codes since they inform everyone handling the cables what they are dealing with.
Any mix-up with the color coding can result in catastrophic accidents such as electrocution if one assumes that they are dealing with communication lines instead of power lines or costly repairs if sewer or water lines are mishandled.
Choose A Suitable Location For The Utility Lines
Running underground utility lines beneath a road or similar pathway that is easy to locate is ideal. You want to avoid incurring expensive repair costs that you would otherwise incur by digging areas that you should not dig.
Furthermore, if you can locate underground ducting easily, you can choose the ideal excavation tools for your project, minimizing the risk of damaging these lines.
Also, the location chosen should facilitate straight connectivity as much as possible. That way, it becomes easier to trace the utility's path from the point it enters your property to the point it enters your home at the meter.
Comply With The Stipulated Depth Requirements
Some guidelines state the minimum burial depth of each utility. Please note that the depth requirements vary depending on location.
If you install underground utilities below a roadway, ensure that you dig at least 48 inches deep. Dig at least 48 inches below ground level for electrical cables and 36 inches for other underground utilities installed in other areas.
You can dig at least 30 or 36 inches to install communication lines. Communication lines with longitudinal occupancy under the free-way right of way require at least 36 inches in depth.
There can be slight variations for any installations in a rocky area that is difficult to dig. But even under these circumstances, the utility lines should be at least 24 inches deep. Alternatively, the state's transportation department can inspect the site and approve other protective measures.
Choose The Right Material
The material choice will depend on whether you are running the ducts for a long or short distance. You may need to use ducting material with flexible coils for longer distances rather than short ones.
Also, you may need to choose a duct material with more strength for installations that need to withstand heavy loads.
If you are ducting electrical wires, ensure that you comply with the different ducting class types. So, use class 1 ducting for high-voltage lines, class 2 for low-voltage wires, and class 3 for everyday use.
Get Permits
Any digging task requires obtaining the relevant permits before beginning the exercise. The applicable permits will depend on the task at hand.
In addition, underground utilities should be inspected regularly. Chemical leaches can accelerate the corrosion of ducting and cables, thus damaging them. Also, storms and flooding can cause the lines to move or distort the connections.
The inspection exercise should involve assessing for physical damage, such as cracks, thinning of the material, or even disrupted connection. It is best to do this without touching the lines to stay safe.
Corrective measures should be taken as soon as possible to keep the problem from ballooning, thus leading to costly repair and maintenance expenses.
In Closing
We hope this post has shed more light on the handling and use of armoured cables and the guidelines that affect cable ducting. If you are considering wiring your property but are in doubt about how to proceed, please consult an electric technician to help you chart a suitable way forward.
Before you go, check out some of our other posts:
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