Is a ring mains circuit parallel?

Answer 1

All electrical circuits used in domestic installations are 'parallel' circuits. In most countries, 'power' (as opposed to 'lighting') circuits are called radial circuits. In the UK, however, a unique system, called a final ring (or, more commonly, 'ring main') is used.

You can think of a ring main as being two radial circuit, connected together at their remote ends, but both supplied through just one fuse or miniature circuit breaker. This allows the load to draw current in both clockwise and counterclockwise directions around the 'ring' from the supply, allowing the cross-sectional area of each cable conductor to be significantly reduced (although not halved) compared to a radial circuit.

This leads to a significant saving in the amount of copper required in any given installation (the main reason for its introduction, post war, when copper was in sort supply). Individual plugs are then fused according to the loads to which they are connected -for example, a 3-kW kettle will have a 13-A fuse fitted to its plug, whereas a bedside lamp would be fused at just 3 A.

Ring mains are not common outside the UK because they are much more time consuming to test following their installation.