Came across a very strange circuit set up today and was wondering if anybody had seen anything like it before. I will state now that this is not a UK installation so BS 7671 might not be applicable. OK we have six lighting circuits with 4 fittings per circuit each controlled by a 1 gang 1 way switch (very simple so far). Each circuit is fed via a 15A 3871 MCB but is fed from 2 seperate DB's. For example lighting circuit No. 1 is fed from DB 1 circuit 1L1 and also DB 2 circuit 1L1 and lighting circuit 2 is fed from DB 1 circuit 1L2 and DB 2 circuit 1L2. The neutral for the circuit only comes from DB 1. The circuits are all wired in pvc insulated cable within galvanised conduit and trunking. I have attached a schematic drawing for 1 circuit to try and give a clearer picture of the set up. I hope someone can explain this as it took me about 4 hours today to isolate the damned things as the 2 DB's are not even close to each other and i hadn't got a clue that they were fed from different sources. :mad2: