Tracing Wiring


Finding Junction Boxes

Before you can fix lighting problems, you must understand how your lighting is wired. Downstairs wiring is located in the void between the downstairs ceiling and upstairs floor. So the first task is to lift some floorboards. You must keep lifting floorboards until you have found every junction box.

Carpet, underlay, hardboard , floorboards

All landing junction boxes found

Underneath my landing carpet I found a layer of hardboard, which was an added nuisance, however the good news was that many of the floorboards had been lifted before, which meant they were cut into easy to handle lengths.

On the landing I found junction boxes huddled together in three places. Once I located them all I unscrewed the covers and inspected the wiring. The junction boxes are pictured below:-

Three groups of junction boxes

Tracing Wiring

Once you have found the junction boxes you must trace the wiring. This can usually be done visually by seeing where the wire goes. It took me two hours to interpret the wiring into the diagram below:-

After completing the diagram I realised that the porch and hall lights were missing. I found these boxes under the floorboards in the third bedroom. The final piece of the wiring jigsaw is shown below:-

Now that I understand the wiring I can start to fix problems.

In a lighting circuits the current flows out from the consumer unit along the live cable, and back along the neutral cable. In between the circuit is interrupted by a switch which breaks the flow and allows you to turn the light off an on.

Lighting circuits are radial, the cable supplies each light in turn ending with the one furthest from the consumer unit.

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