Knightsbridge SN8420 20A Junction Box 4-Terminals White

Product Information

Please note that all electrical wiring and installation details given on diydata.com is for information purposes only.

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. Stripping the inner cores of the cable should be such that minimal conductor is exposed once the connection has been made.Once the junction box has been fixed to a secure surface, and the wiring has been connected to the terminals and tested you can close the junction box, they must never be left open and exposed. The cover is screwed closed using the provided securing screw (or possibly screws) through the cover and fixing it to the base. It is often necessary to adjust the wiring inside the junction box to allow the cover to close. Avoid simply forcing the cover closed with the screw as this can risk causing damage to cables. 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. This section explains how to wire a traditional or standard style junction box. It doesn’t matter about the rating or number of terminals, the process is the same in each case. Joining Two Sections of Wire Together 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.

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. One thing to watch out for with the number of terminals, is the type of terminal used. Two basic types are available: 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 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. 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. Electrical junction boxes come in a range of different types. There are two key differences that you will need to look out for when purchasing your junction box:

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! 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! 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

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.