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[PhilHolmes]

I am replacing an electric socket at home which wasn't working.
Having removed the old socket I find there are two cables coming in. One cable has L, N and E. The 2nd cable has a L and N and a further wire with both black and red covering. This wire was not connected to any terminal in the socket . Should I connect this to Earth ?

[ericmark]

Black and Red are not colours used for earth so I would not connect without further investigation. Likely something wrong. Although there could be an explanation in the main sockets will have two cables if part of a ring. Three cables if part of a ring and origin for a spur. And one cable if the completion of a spur.

Although there are systems using thicker cable or fused connection units or other means to reduce the max current to below the normal 30/32A used on a ring they are not to common.

So alarm bells are ringing. If I came across something like that the first thing would be to test and find if part of a ring or not. Relativity easy even with a simple multi-meter. Power off main isolator off nothing plugged in all FCU's off with a ring the two line and two neutral wires will be connected and the same should apply to earth cables (Which is why isolator off or earth and neutral will be connected).

Clearly we can't test it for you. I am sure you realise something does not seem to be right. Since we don't know your skills can't say if you can DIY or if time to call someone in.