Replacing socket, old wiring query

[tigergirl]

Hi

you can see our plug socket here:
http://homepage.ntlworld.com/username59/extrapics/elec.jpg

it is a single plug socket flush in the wall. Then it appears someone has mounted a box proud of the wall to convert to a double socket. We want to replace this with a double socket flush to the wall. However there seems some oddities. As there are two of each, live & neutral i see its part of a ring, not spur. The mains cabling appears old, it is red and black, which is insulated, around this insulation is a metal solid spiral then this again has insulation around it. Each mains cable has a red and black. What is puzzling me though is a single earth enters the box in the wall (see link with photo. This earth cable connects to box. Then at top left of box a very short earth cable connects the box to the earth terminal in the sockets ( (2) in link picture). What i dont understand is why there is not then an earth cable running back out of the earth terminal as surely a ring circuit requires this.
Also the metal solid spiral is stretched out and connected to the bottom of the box, effectively earthing the metal spiral.

Advice please... should the metal be connected to the box? Should there be a second earth cable and where is it?

 

[fireman22]

cant really see well enough in the pic but are you saying that there are no earths incorperated in the grey cables, only red and black?

 

[tigergirl]

there was a single earth cable, and two red, two black entering the box. The earth cable appeared seperate to the pairs of black/red

I will wait till tmoro (daylight). Switch off all the elec, mains & fuses and have another look and post again.

 

[JohnD]

In the picture I see the earth marked "connects to box." I have a feeling that if you were to take this off and slide back the g/y sheathing, you would find it has an earth connection from both the ring-in and the ring-out cables.

When you mention a spiral this might be steel-wire-armoured cable, though it is not common to find it indoors on a domestic installation. most domestic work is done in twin-and-earth which is a flattish cable with a red, a black and a bare copper in it - the bare copper has green and yellow sheathing slid onto it when the grey or white cover is cut back. Alternatively, sometimes people twist the two bare coppers together before sliding on the g/y sheathing - might your spiral be two twisted copper wires?

More modern T&E made in the last year or so has brown, blue and bare copper in it.

 

[fireman22]

tigergirl, as john says pull up the green sleeving and you will probably see two earth cables incorperated in the grey pvc cable if it is older cable these earths will be a number of twisted wires together, but these are your earths.

 

[tigergirl]

thanks. Yes on further reflection i think maybe there are two earth cables which have been sheathed with the green insulation. This would seem logical as i see from pictures of old wiring on websites that generally there is a red, black and bare copper earth running between, so i guess the presence of green sheathing indicates this maybe the case. Heres hoping as that means the earth enters and leaves the box thus maintaining the integrity of the ring.
Also i think it is as mentioned by john a steel armour around the cable.. why though has this been connected to the box also?

I will check there are two earths intertwined entering the box tmoro and post again.. meanwhile many thanks

 

[Steve]

Also i think it is as mentioned by john a steel armour around the cable.. why though has this been connected to the box also?

i very much doubt it is SWA. SWA has 3 insulated cores - and it is not coloured in single phase colours, that you have there.

Unless someone has used a 2-core and taken a couple of strands from each wire to connect to that crimp ring.

But how is the "spiral" "connected" to the bottom of the box??? i see no glands. If you could sweep out all that debris and take another picture from the right - that would be good.