Domestic Electrical Installations 21
Lid
Label
Concrete pit Earthing conductor protected from corrosion and mechanical damage Earth electrode
FIGURE 2.7
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Earth electrode installation.
Ring final circuits are almost unique to the United Kingdom. The ring final circuit is always used to feed 13 A socket outlets to BS 1363. The circuit starts at the consumer unit, loops in and out of each socket and, finally, returns to the consumer unit to terminate in the same terminals as it started.
Let us now look at the various circuits in a little more detail.
Lighting circuits The ‘loop-in’ system This is the most common of all lighting circuitry and, as the name suggests, circuit cables simply ‘loop’ in and out of each lighting point (Figure 2.8). It should be noted that the cpc’s have been omitted from Figure 2.8 for clarity. They must, however, always be present. In the case