Mains Wiring Questions

Aug 26, 2015 8 Replies

I need to extend the wiring to a relocated double wall socket. I intend to use a junction box and 2.5mm T&E cable. Is it OK to take a spur from the junction box to supply an additional socket, or is some other arrangement required?



Also, I happened by some double sockets in Aldi's reduced section. There's nothing on the web, packaging, the unit or the documentation to indicate single or double pole. How can I tell?


It depends if the original dws is on a ring main or a radial ciruit. it is not good practice to use junction boxes in concealed situations unless they are accessible for future maintenance (i.e checking the tightness of the terminal screws)

UK style DSSO's are normally single pole. You should be able to check if it is double pole using a continuity test meter by attaching one lead to the nuetral pin outlet on the faceplate and the other to the nuetral connection terminal at the rear and operating the 'dolly' switch. If it is DP, the meter will show a break in nuetral continuity when you 'switch off'.

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If it's on a ring, and you want to keep it on the ring, use two separate junction boxes, and 2 x cables

Not best practice to take 2 x spurs from the same point on a ring - which is what you are doing if you only extend the existign socket with 1 cable.

If it's a radial then no restrictions apply, but you must use the same size cable as the existing, which will be 2.5mm on a 20A radial or 4mm on a 32A radial.

Owain

You can have one (single or double) socket as an unfused spur, so what you propose is fine.

With a multimeter.

Indeed. Best practice.

That is not entirely true. You can use a 2.5mm cable for an unfused spur from a 4mm 32A radial - just like you can use a single 2.5mm unfused spur from a 32A ring circuit. The same rules apply about what the unfused spur can feed ie one single or one double socket or one FCU and definitely no unfused spurs of unfused spurs:-)

Tested with the beeper continuity setting.

Another socket marked 'double pole' behaves as follows:

Neutral switches off - no signal Neutral switches on - signal

Same result when connected to live

The Aldi one behaves differently:

Neutral - signal, with switches on or off Live - signal, only with both switches on

Single pole then?

IIUC it's only taking one spur from the ring. The junction box serves 2 purposes - to extend the 2 ring cables to the relocated socket, and serve as a feed for the spur.

It makes more sense to me that way as it saves wire, and avoids stuffing an extra cable into the relocated backbox/socket. Although if this extra stuffing is -

I should rethink?

That is what i would expect from a double pole switched outlet.

Yes that is what i would expect from the single pole switced outlet.

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