Knightsbridge SN8420 20A Junction Box 4-Terminals White

Product Information

A junction box is a type of electrical enclosure that allows you to safely and easily join 2 or more pieces of cable together and ensure that any connections and terminals are well hidden and protected from causing injury or fire.

Junction boxes are rated in amps (typically 5, 20 or 30 amp). The size used should equate to the current rating of the circuit being connected into - you can always use a higher rated box than the circuit but never a lower rated box.Step 1 – Isolate Power: Before doing anything at all, the very first job is to isolate the power to the circuit you are going to be working 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. 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. Junction boxes can also be used to add lights and switches. For more information please see our lights and switches project.

Step 1 – Isolate Power: Before you do anything at all, first isolate the power to the circuit you are working on!

How to Wire a Junction Box

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? 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