- According to IEC and GB Standard
- XLPE & PVC Cable
- Approved by ISO,CE, SGS
- Large stock armored cable with different sizes
Armoured cable protective layer can be added to any structure of the cable to increase the mechanical strength of the cable and improve the erosion resistance. In addition, the purpose of adding armour layer to the cable is to enhance the tensile strength, compressive strength, etc., which can protect the cable and prolong its service life.
Armoured Cable: Proper Selection and Usage is Critical
When carrying out any electrical project requiring the use of armoured cable, it’s important to choose the right cable for the right job. Once you’ve made your choice, how you use the armored cable during installation also matters. Below, we address some important questions around the selection and use of these cables, including armored cable outdoor usage.
1.What is armoured cable?
When speaking in terms of distributing electricity, or other power distribution applications, armoured cable typically refers to a special type of cable that’s also known as swa cable or steel wire armoured (SWA) cable. These are specially-built, hardy power cables that deliver power from transmission sources to mains power points.
Armored cables typically comprise of 5-parts:
- Conductor: This is usually made from copper and may be solid or stranded
- Insulation: They are often Cross-linked polyethylene (XLPE)
- Bedding: To protect the inner layer of the cable from the outer, bedding made from Polyvinyl chloride (PVC) is used
- Armour: Steel armoured cable offers mechanical protection to the cable. This means the cable can bear extra stress and pressure during installation, or can withstand pressure once installed in underground or external environments
- Sheath: Usually this is of PVC material, and is used to hold together all other components inside the cable. The usual standard is to use black PVC to designate power cables and blue for communication cables
While SWA is common for multi-core cables, such as 3-core or 4-core, single-core cables typically use aluminum wire armour (AWA) instead of steel. Why use aluminum instead of steel for the armour? Well, current passing in a single core generates a magnetic field, and that field can result in cables overheating. Since aluminum is non-magnetic, it prevents overheating risk.
There are several types of armored cables, including 11 KV and 33 KV cables. These are often found in cable ducts, are used for power networks, and also buried in underground power transmission situations.
2.What size armoured cable?
The size of armoured cable you choose to use depends primarily on the application you intend to wire. Additionally, the types of armored cable chosen must also factor the voltage drop to make the application safe and effective. For example, if you are running a cable that’s originating from a consumer unit that’s located approximately 42 meters away, using a 16 A power supply, you’ll need a 2.5mm armoured cable at minimum.
As a rule of thumb, the further the distance, the higher the cable size. Increase the armoured electric cable one size up for every 100 feet of additional distance. Another rule of thumb to determine armoured electrical cable size is the amount of voltage involved. Low voltage applications require special emphasis on voltage drop when determining cable size. For how voltage applications, when determining armored cable sizes, take into consideration the current-carrying capacity of the cable.
3.How deep should armoured cable be buried?
When laying armored cable in an outdoor environment, it is important to protect the cable from potential external shock or damage. For instance, any cable laid out on a roadway or across a field, even though it might be steel armoured cable, runs the risk of damage due to traffic, field ploughs or tractors running over it.
There is no regulated depth at which armored cables must be buried in the UK. However, one could use the NJUJ guidelines and recommendations to determine the depth to bury them. These guidelines would suggest burying at depths of between 350 to 400mm (15” to 18” minimum) in a footway (sidewalk), and at least 600mm in carriageways. It is important to remember that these stipulations apply to public roadways and pathways.
Alternately, although no specific regulations exist to govern how deep armoured cables can be buried on private property, BS7671 does offer some hints on what to do. These regulations require that cables be buried deep enough so as not to be disturbed by any reasonably foreseeable activity – such as digging with a spade or a lawnmower and that a yellow warning tape be used to alert of the presence of buried cable.
To be safe therefore, you may look at burying armored cable at a depth of at least 400mm so that reasonably expected activity on the property does not unearth the cables.
4.How to cut armoured cable?
It is extremely important that when you install armored cable, there should be no damage to the body or interior core of the cable. A damaged 100m armoured cable will only compromise the entire electrical project in which it is used. However, one place where damage is most likely is when cutting the cable. So, the question is: How do you cut an armoured electrical cable without damaging it?
The best way to cut armored cable to desired lengths is by using the right tool for the job. And that tool is an armoured power cable rotary cutter. The best way to use it is with a small cutting blade (wheel). Measure the length of cable that you wish to cut, and then mark it clearly with a luminous indelible marker. If it’s thicker cable, for example a 3 phase armoured cable, you could also wrap a piece of electrical tape around to delineate the position to cut.
Next, position the blade of the armored cable cutting tool above the marked position, and crank the tool with it’s manual (hand) cranking lever. If done correctly, this process will result in the undamaged cutting of any armored cables, whether it’s a flexible armoured cable or a rigid 10mm armoured cable. The trick, however, is to exert firm pressure on the crank handle without excessive squeezing. An overly excess squeezing motion might damage the face of the armored cable where it is cut. It could also destroy the tool.
5.How to connect armoured cable?
Let’s say you had a requirement to connect electrical equipment or appliances, using power between two buildings that are several meters apart. Ideally, you would use steel wire armored cable for this application. The type of armoured cable used would depend on the individual application. If this is an industrial application, running heavy machinery, it might require the use of a 5 core armoured cable. Less intense electrical applications might work with only a 2 core armoured cable.
To connect the armored cable you’ll need to dig a trench between the two locations. The cable must be laid in a trench of suitable depth. The armored cable underground depth must be at least 18-inches (or 400mm to be safe). You could drill two holes, put a junction box and connect the cables. You may also need a SWA gland to make the connection.
There is another way to connect the armoured cable exiting from one location and entering another. The alternate way is to use a galvanized conduit box with entry and exit holes. This is a great way to also connect (or join) underground armoured cable together. For example, let’s say you had a 200-meter 10mm armoured cable coming out of one building and entering another, and you wanted to connect another 200-meters of cable with a similar armoured cable rating at the other end, a galvanized conduit box would be the best way to connect those two lengths of SWA cable.
6.How to run armoured cable to shed
To run power from the main house to an exterior building, like a greenhouse or a shed, you’ll need to run armoured cable outdoor. The best way to do that is to connect the two buildings directly with a cable. And the safest method to run electricity to the shed is by using an armoured electrical cable from the main home right to the shed (or any other external location) outside of the main house.
Best practice suggests that the armoured electric cable you use must be buried underground. To do that, you’ll need to dig a trench and run the underground armoured cable from your main panel (inside the main house) to the shed.
So, the question is: What type of armoured cable would you use to run power to your shed? Will a 2.5mm armoured cable suffice, or do you need to consider something larger – like a 25mm armoured cable?
Well, it really depends on what your intended use of that space is. Assume you don’t want to operate a full-blown manufacturing plant in your shed or build a recreational center or kitchen there, then 4mm armoured cable might be a good choice. This should be enough for a few sockets and a few lights – typical use of sheds. However, if your budget allows for slightly more money, you may wish to consider a 6mm armoured cable. This will allow more sockets and connections.
7.Armoured cable vs unarmoured cable
Armored cable has a steel layer of coating around it – like an armour plating – to protect it from the elements. That’s why this type of cable is also known as steel wire armoured cable, or SWA. The extra steel layer in the SWA cable also shields the inner cores from electromagnetic interference (or EMI). Unarmoured cable on the other hand does not include this additional layer of steel coating.