The reason why the wiring of a lighting circuit is more complex than a power circuit is that each outlet or light fitting needs to be controlled by a separate switch. Here we have a 5 amp 4 terminal junction box that is ideal for use in lighting circuits.
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Lighting circuit junction box wiring. Any standard outlet switch box or light fixture box can serve as an approved enclosure but where a wiring splice needs to occur in other locations along the circuit the approved enclosure is usually a junction boxa junction box is simply a standard electrical box that is. One way of providing for this is to install a four terminal junction box in which the cable from a light and the cable from its switch can be connected to the circuit cable. Fig 2 the feed cable comes from a previous junction box or from the consumer unit the red black and earth wires are connected to separate. Radial or junction box wiring. Fig 1 the junction box should be wired as shown below. Fig 2 explanation of above picture.
The junction box should be wired as shown below. Line diagram of a one way lighting circuit using junction boxes fig 1. Wiring diagram of a one way lighting circuit using junction boxes fig 1. You will often see these used in old looped radial circuits instead of a ceiling rose in older houses. Junction boxes have 3 4 5 or 6 terminals and the number required depends upon the application. Picture 2 below shows a typical radial or junction box lighting system a two core and earth cable runs from the consumer unit to a series of junction boxes one for each lighting point ceiling rose.
They are useful for breaking in to an existing radial power loop to add additional wall lights in a room for example. It is possible to use a higher amp rated junction box on a lower rated circuit but never the other way around to summarise. Ring mains and radial circuits 30 amp. For a lighting circuit use a 20amp junction box and for a ring main or radial circuit use a 30 amp junction box. Explanation of above picture. Junction box wiring for looped radial lighting circuit notice that each of the three junction boxes in fig 1 has in addition to the power feeds an additional cable that feeds down to the light switches the switch wire.
Lighting circuits using junction boxes. Junction boxes come with either 3 4 5 or 6 terminals so work our which you will need to complete your project. Junction box terminals and wiring. Lighting circuits 20 amp. Two basic types are available. The junction box effectively replaces the ceiling rose.
From each junction box a separate cable runs to the light and another runs to the switch. An alternative method this uses the same wiring principles as the looped ceiling roses but here the connections are made in junction boxes rather than the ceiling rose. Fig 2 the feed cable comes from a previous junction box or from the consumer unit the red black and earth wires are connected to separate terminals. The national electrical code nec dictates that no wiring splices are allowed outside of an approved enclosure. One thing to watch out for with the number of terminals is the type of terminal used.
Gallery of Lighting Circuit Junction Box Wiring
