Free notes
Socket circuits: rings and radialsWhat's the difference between a ring and a radial?
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| Circuit | Protective device | Min. copper CSA (T&E) | Max. floor area |
|---|---|---|---|
| Ring final | 30 or 32 A | 2.5 mm² | 100 m² |
| Radial | 20 A | 2.5 mm² | 50 m² |
| Radial | 30 or 32 A | 4.0 mm² | 75 m² |
- This table is for normal socket-outlet circuits. Lighting (usually 6 A), cookers, showers and immersion heaters go through the full design process instead.
- Floor area means the room area served, not metres of cable. On a 20 A radial, 50.02 m² is already too much.
- Many kitchens now use a 32 A radial in 4 mm² instead of a ring. Rings go on a 32 A device. If you need smaller breakers, use two 20 A radials instead.
Electrician's Guide to the Building Regs · 4.2 Final circuits using 13 A socket-outlets · Table 4.2.1 · p.77 On-Site Guide · Appendix H · Table H2.1: final circuits using socket-outlets · p.218 Worth highlighting
On-Site Guide · Appendix A: maximum demand · p.149
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