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I am connecting an outdoor electrical cable to a switch. The existing cable that goes out into the garden has 4 wires - red (live I assume), green&yellow (earth I assume), black and blue. How do I connect these to a switch with 3 connectors for live, neutral and earth ?

Hi mpears123,
don't like to sound unhelpful, but outdoor wiring now comes under Part P of building regs and must comply to them, some it is a job for a part p electrician. It could make your house insurances invalid if accident occurs and is against the law.
And question a bit vague what are trying to connect a switch, what's the current/fuse rating and Cable Size?
Sorry Mate
KB

One can't assume anything. You need someone with knowledge to do a site visit. As soon as I saw green/yellow alarm bells started to ring it is unusual to find steel wire armor cable with an earth coloured core. And if one does the rest of the cores are normally white. It is common to double up on cores when using three phase cable on single phase so even if you live in Bonny Scotland where there is no Part P I would recommend you get it done by an electrician bad enough in the house but outdoors you can't afford mistakes.

Thanks guys. As I live in Scotland there is no part P but the outdoor cable was installed by an electrician. I am just trying to move it across to a new switch which is the same as the old one but unfortunately did not take enough notice of how it was wired when I dismantled the old one. From the second message posted, do I connect both the black and blue cables to the negative pole of the switch ?

Is this cable going to connect to a mains socket, mains switch or a light switch? Is it a 2-way lighting circuit, one switch indoors and one outdoors for outside lighting? Need to know the function of the switch first of all.

Hi Chappers, thanks for your interest. It is just a mains socket switch, no two way lighting circuits involved. I expected the wires coming into the garden would be the usual 3 wires but there are four as previously indicated.

Is it a
1 switch
2 13 amp socket
3 13 amp socket with a switch on it to turn the socket off.
What connections are marked on it ie. L N E
Can you check the other end of the cable to see what he done there , he may have just used the wrong cable and simply just not used one wire.

Sounds like cable is
red
Yellow
blue
black
Usually used as 3 ph and n
He proberly got it cheap
It is ok to use though
used to use red as live
yellow as earth (sleeved with gr/yellow)

However black MAY BE neutral
but when colours started to change during the transition period we started
to use blue as neutral.
Sleeving the red as brown

THEREFORE THE ONLY WAY IS TO LOOK AT THE OTHER END AS
NEUTRAL POSSIBLY BLACK OR BLUE.

You need to do something with the spare core like seal it off.
He may have even used it as well, although not reccomended to double up the neutral

Is the cable still stripped from where you took the socket off as the copper will be exposed .

Thanks for your help guys - I've sorted it. When I followed advice and checked at the connection into the Consumer Unit I discovered that the black cable was neutral and the blue cable wasn't connected to anything at all. So its a normal configuration of RED (L) BLACK (N) and GREEN/YELL (E). Thanks again.