In terms of accessibility, this means that a builder or electrician can easily remove part of the floor or ceiling etc. and access the junction box when required. Junction boxes may not be buried in plaster or other similar materials. For a lighting circuit use a 20amp junction box and for a ring main or radial circuit use a 30 amp junction box. Terminals You can also read a brief synopsis on the electrical guidelines and what they mean by visiting our Approved Document P project here. Single screw terminal – The terminal has one screw which is screwed closed on to the cable cores being joined together to secure them all in one single connection point. These are typically found in the Standard junction box, and allow the connection of a larger number or sizes of cable cores that the other terminal types

If you have ever needed to join 2 sections of cable or wire together or create an additional spur for a new piece of cable then you should be well aware of the existence of the junction box and if not, this is the product you want if you are needing to do either of these jobs. There is no requirement for a junction box to be either round or square, and they are commonly both. As a rule of thumb the more common round junction boxes are typically used for lower current cables. Likewise, the cables running into and out of the junction box should also be secured to a suitable, stable surface. If not, then “mechanical strain” could take place and over time, wires may become loose causing loose connections. A problem when purchasing Junction Boxes is to know which type of terminal is fitted and, where Bus Bars are fitted, how many cable cores can be connected to each terminal. Using Junction Boxes Use green and yellow earth sheathing to cover the earth which will most likely be bare at present. As commented, this is a legal requirement stated in the Wiring Regulations. Which Colour Wires are Which?

Step 4 – Fix and Close Junction Box: Once you have ensured that each terminal screw is screwed down nice and tight, screw the junction box to a nearby joist or timber and then screw the cap down on Bus Bar screw terminals - with these types of terminals, each cable core has its own location hole and screw for securing to a terminal. The number of cores which can be joined is limited by the number of holes/screws in each terminal - these can vary from 2 to 6. The cover should always be fixed in place using the screw (or screws) provided - the position of the internal wiring may need to be adjusted to allow the cover to sit on the body of the junction box before securing - never use the cover screws to force the cover down onto the cables, this can cause damage. Examples of Junction Box use Junction boxes come with either 3, 4, 5 or 6 terminals so work our which you will need to complete your project. The terminals are where the connections will be made by inserting the wire core from either side or the wiring run and then screwing the terminal close to create a safe electrical junction and join. In short they are used for joining wires or running a spur from an electrical circuit safely. Whenever you need to join two or more electrical wires, then you should use a junction box. As a result they are commonly used and very useful for anyone involved in wiring and electrics.

Single screw point terminal - as the name implies, each terminal has just one large screw which is used to secure all the cable cores being joined together. Increasingly common are the “Maintenance Free” Junction boxes. These are designed to replace the standard round junction boxes commonly use in household wiring. The reason that they have become so popular is that they can save nearly 75% of the time required to wire a traditional junction box. Junction boxes are rated in amps to protect them, you and the circuit. Make sure you have the right box for the right job. A ring main ( more about ring mains can be found in our project here) and also a radial circuit ( more about radial circuits in our project here) will need a 30 amp junction box, whereas a lighting circuit (although you can buy 5amp junction boxes) will need a 20amp junction box. Junction Box with spur wiring diagram – Adding a Spur using a Junction box Fixing cables into the Junction Box We will explain the differences between these types of junction box and their various benefits shortly, however it is important that you have the right rating whichever type that you choose. Junction Box Amp Rating

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Step 2 – Cut and Strip Cables: The next task is to cut any cables where you will be installing the junction box (if this needs doing, you may just have 2 ends that just need joining). Once cut, strip the main outer protective sheath and then strip 12mm or so from the end of each core wire The cable cores will need to be stripped before being inserted into the terminals. Try to expose the minimum amount of the conductor as necessary. 10 – 12mm will be typically sufficient for this, unless you are doubling them over then around 15mm is required.

In this guide we take a look at junction boxes and how they are wired up and used, read on to find out more. Working With Electricity and Junction Boxes One thing to watch out for with the number of terminals, is the type of terminal used. Two basic types are available: The main reason for this change was to ensure that any cabling used from that point onwards would harmonise (be the same) as those used in Europe. When using junction boxes to extend ring mains or radial circuits, remember that the regulations limit the length of cable for both ring and radial circuits, and also how spurs are connected to ring mains. These regulations must be adhered to to avoid possible overloading the electrical wiring. Step 3 – Connect Wires: Once all stripped, connect the same core wire from each length of cable to the same terminal in the junction box e.g. brown live to live, blue neutral to neutral and earths to earth (remember to add some earth sheath to the earth wires – this is a legal requirement!). Make sure you screw each terminal screw down nice and tight

Step 3 – Connect to Terminals: Once all stripped, connect each core wire to an individual terminal ensuring that each type of core is connected to the same from the other cable, e.g. a 3 brown lives in one terminal, all 3 blue neutrals in another terminal and all 3 earths in another terminal. Also ensure that you add earth sheath to each bare earth wire – This has to be done by law!