A quick method to find a fault, without removing the sockets.

Let's have a look at the ring final circuit and finding a break in continuity without having to remove any of the sockets. In BS7671, you'll find appendix 15 and this tells you how a ring final circuit is constructed and any permitted additions. But basically a ring final circuit starts and finishes at the distribution

board and is connected to a 30 amp or a 32 amp overcurren protected device. It's generally a 32 amp RCBO nowadays, but you will find many installations with a 32 amp MCB or even a 3036 rewable fuse. Plenty of those still about. It's generally wired in 2.5 millimeter squared twin and earth and that's got

live conductors live and neutral 2.5 millime squared and a CPC of 1.5 mm squared. There are additions you can add to the ring circuit as you can see in the diagram. It generally involves fusing down the additions. We won't go that deep into the construction of a ring final circuit and the reasons for

it in this video. This is primarily a fault finding video. So let's get on to that. So as we know a ring final circuit starts and finishes at the distribution board. So therefore we have a ring we'll have three conductors R1 which is a line R2 which is a CPC and RN which is a

neutral. The line in neutral R1 and RN have a cross-sectional area of 2.5 mm squared. And the CPC has a cross-sectional area of 1.5 mm squared. The difference between the two 2.5 / 1.5 is 1.67. So the CPC had a smaller cross-sectional area. So it's going to have a high resistance. So with the

installation isolated, we would disconnect the conductors from the MCB. the neutral bar or the earth bar and measure the resistance of each leg. We take a resistance reading between the two lives, between the two neutrals and between the two CPCs. We're measuring that loop, that ring, because the line and the neutral are the same