Home DIY

There are a couple of things you can try if you have the tools. Obviously check the wires in the back of the socket and the cable at the CU are not live before you do anything. Then you can connect line and neutral together at one end and check the continuity at the other end, then repeat for line and earth. If continuity is confirmed you now know for sure they are connected but you still don't know if they are connected by a single piece of wire or in the back of another socket etc.

If you don't have a spare breaker of the correct rating inside the CU then you need to establish the type of circuit you have and what the appropriate breaker rating should be. At this point it would be illegal for you to carry on anyway. In any case you would be skirting breaking the rules if you had an appropriate breaker installed as you are still adding a circuit.

The reason for the rules is the rating of breaker and testing it's operation are fundamental to the safety of the wiring and risk of fire and safe disconnection should an earth fault happen. If the hallway is close to an external door you also have to consider RCD provision although a new CU will probably have that.

You can just add it to another circuit if you know the rating of the breaker is suitable and you can test the disconnection times and calculate the Zs.

The more I think about it, the more it seems like you need to get someone in and the last guy should probably be doing it at least at a reduced rate for having missed it the first time.

If you were connecting it as a spur from a ring of sockets it would be a lot easier. If you can find your downstairs ring and chop a 13amp fused spur into it near the CU then you could run that socket from the fused spur. You just need the power off to the ring to do that. I still wouldn't want to recommend that unless you have at least a proper voltage tester or switch off the entire system while you are working on it.