If you are new to lighting circuits, this is a good place to start. Here we will explain how the most common lighting circuit works then we’ll move on to some variations that you may see in your home that may appear to differ from this.
N.B. The diagrams below shows the new (harmonised) cable colours. If the cables in your circuits are Red and Black please see Multi-point radial lighting circuit – old cable colours.
Fig 1 shows what is referred to as a radial circuit (sometimes called a ‘loop-in’ or ‘multi-point radial lighting circuit’).
The light wiring diagram shows how the live feed from the Consumer unit (fuse board, shown in blue in Fig 1) feeds into the first ceiling rose (ceiling rose A, Fig 1). This would be cable A in the diagram below (Fig 2) which shows how the ceiling rose is terminated. This live feed now loops back out of the rose (cable B, Fig 2) and feeds power to the next ceiling light in the radial circuit (Ceiling rose B, Fig 1). This repeats for each light in the circuit until we reach the last light.
Once we reach the last light, you can see that there is only The feed from ceiling rose B (Fig 1), This is Cable A in the diagram below (Fig 3), which show how the last ceiling rose in the circuit is terminated.
Notice that each of the three ceiling roses in Fig 1 has, in addition to the power feeds, an additional cable that feeds down to the light switches (the switch wire). This the Cable C in fig 2 & Fig 3.