Wiring – OLD UK Lighting Live wire in neutral, how is this working? is it safe


I'm in the process of upgrading our ceiling lights in our rather old home. The wiring of the lights in the house pre-dates 1977 and therefore the colours are slightly different which I'll list below.

Pre 1977

  • Live = Red
  • Black = Neutral
  • Earth = Green

Post 2004

  • Live = Brown
  • Blue = Neutral
  • Earth = Green/Yellow

Below is a picture of the wiring in question.

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The diagram below for easier viewing, notice that the neutral wire of the bulb is paired with the switch (Live) and that the bulb live is paired with the neutral in and out.

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It is my understanding, the little I have is that it should look something like this:

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My question is…

Is this safe? is this even possible?

Best Answer

It'll still work - a light bulb doesn't care which terminal is live and which is neutral - it's just a dumb resistor. Generally speaking however, the socket in which you put the light bulb should be designed such that the live terminal is harder to reach / harder to accidentally touch, than the neutral terminal. Since you have the ceiling rose open already, you might as well swap them to the correct configuration (your second picture).