Circuit design
How many sockets on a ring main?
Check whether a ring final or radial circuit suits a floor area, and how many spurs it can serve. The number of socket-outlets on a ring final is not limited. The floor area and the spurs are.
Per the IET On-Site Guide: a 32 A ring final serves up to 100 m², a 20 A radial up to 50 m², a 32 A 4 mm² radial up to 75 m².
Ring finals, radials and spurs
There is no limit in BS 7671 on the number of socket-outlets on a 32 A ring final circuit. What the standard and the On-Site Guide limit is the floor area the circuit serves and the way you add spurs.
Floor area is the real limit
- 32 A ring final (2.5 mm²): up to about 100 m².
- 20 A radial (2.5 mm²): up to about 50 m².
- 32 A radial (4 mm²): up to about 75 m².
These areas assume normal domestic loading. A kitchen full of heavy appliances may need its own circuit well before the area limit, which is a judgement call rather than a rule.
Spurs done properly
A non-fused spur may feed one single or one double socket, or one fixed appliance. The number of non-fused spurs must not exceed the number of socket-outlets and points wired directly into the ring. To run more from one point, use a fused connection unit, which protects everything beyond it at 13 A. When a ring is at its area limit, a second circuit is better than stretching it, and that feeds into your maximum demand assessment.
FAQs
How many sockets can you have on a ring main?
There is no limit on the number of socket-outlets on a 32 A ring final circuit, as long as the floor area served is within about 100 m2 and the spurs follow the rules.
How many spurs can a ring final have?
The number of non-fused spurs must not exceed the number of socket-outlets and fixed appliances wired directly into the ring. Each non-fused spur feeds one single or one double socket, or one fixed appliance.
When should I use a radial instead of a ring?
A 20 A radial in 2.5 mm2 suits areas up to about 50 m2 and a 32 A radial in 4 mm2 up to about 75 m2. Radials are simpler to fault-find and common for kitchens or small dwellings. Rings remain popular for general socket circuits in larger UK homes.