No Earth cable in orginal ring circuit flex

[jgreer]

Inspecting sockets in my flat, I notice that the original flex is only two cables (red and black). No earth.

I'm adding some spurs and my new 25mm flex has three cables (red, black, green-yellow).

Should I be concerned?

 

[ban-all-sheds]

Yes.

1) It appears that the circuit has no earth.

2) It appears that it is wired with flex, not cable.

3) You appear to be wiring new sockets with 25mm flex, not 2.5mm cable.

4) You don't know what you are doing.

 

[jgreer]

It appears I've made some errors in terminology. Apologies. Here's what's going on.

2) It appears that it is wired with flex, not cable..

No. It's cable. I only just now learned the diff between flex and cable.

3) You appear to be wiring new sockets with 25mm flex, not 2.5mm cable.

Per my answer above, I have actually purchased Pirelli 2.5mm(squared) solid twin & earth cable.

4) You don't know what you are doing

That's why I'm here.

Now, should I be concerned? Has anyone else seen this?

 

[breezer]

Now, should I be concerned? Has anyone else seen this?

yes, its fairly common.

its can also be dangerous, probaly very old, and time for a rewire.

and before you ask, no there is no way round it other than complete rewire, but let me guess something.

the existing twin and no earth, can you see the colour of the cores? are they silver and stranded?

 

[jgreer]

the existing twin and no earth, can you see the colour of the cores? are they silver and stranded?

I can't see the colour of the cores on this socket, but on other sockets it is copper and a solid cable. There is a ground cable in every socket. But it only connects between the face plate and the socket box. It's not part of the ring.

This ground cable, though, I can see. It's copper and solid.

 

[breezer]

as has been said earlier, your "terms" are not right, the cable you see has been added on at a later date. I just wondered as i bet its aprox 25 years old, deffinently needs a complete rewire. sorry

 

[theshogun]

Are the cables in your socket boxes inside metal conduit, can you see a brass nut that the cables pass through?
The metal conduit is used a an earth on some systems.

 

[mapj1]

Before you panic and rush off to rewire, if the wire is plastic coated, not cotton covered, it would not have been legal without an earth at the time it was wired. (un-earthed power circuits stopped being approved in new work circa 1927, although odd 2 pin sockets circuits were still being extended for a further 20 odd years )
It is possible, but unlikely. that there really is no earth. It is far more likely the earth is a bare wire outside of the original cable, or as Shogun suggested, the conduit pipework forms the earth. If so be careful that all joints to the pipework are tight, they may one day be needed to save your life. If you have a meter, on the 'ohms' range, you can check this,

1) check that with probes touching you get a low reading, and not otherwise, (this checks you have a working meter -a prudent but oft forgotten step..)

2) read the resistance between the earth pins of any pair of sockets, and/or each socket earth and the main earth bar at the consumer unit.
If the resistance is similarly low, then you do have an earth really, and when you extend the system, you need to pick up the existing earth, and continue it. Oh, and cover the bare earths in green=yellow sleeving, to make the identity clearer.

If you get a no connection reading, then I agree with the earlier posters - time to call in the pros, as you have no earth.

regards
M.

 

[jgreer]

2) read the resistance between the earth pins of any pair of sockets, and/or each socket earth and the main earth bar at the consumer unit.
If the resistance is similarly low, then you do have an earth really, and when you extend the system, you need to pick up the existing earth, and continue it.

Okay, you lost me here. Ohms measure resistance. I know that. I do have a meter and have used it to measure resistance before. Just not clear on what you mean by "earth pins", "socket earths" and the "main earth bar".

I do have metal conduits for the ring. I'm not sure how tight the joints are though.

The building was constructed in 1979. I'm sure the wires haven't been re-done since then.

 

[theshogun]

Earth on a socket is the middle top .

With the socket released from the wall/back box ,the earth terminal on the back is the one that has the cable linking it to the back box,this cable could be bare copper or green ,green/yellow .
If bare copper it needs to be covered with green/yellow sleeving.

Cu earth bar/terminal is the one with the afore mentioned cables connected to it .
It is not the one with all the black cables connected to it , this is the neutral.
Hope this helps

 

[breezer]

conduit, so obvious i over looked that but it means you are going to have to get a twin and earth cable clamp, lock ring. (i also nowassume the conduit is surface)

you will need these to exit the back box you intend to connect to. any electrical wholesalers will supply them

 

[mapj1]

by main earth I meant the place all the green wires converge near or in the fuse board - basically I'm saying check for low resistance between somthng known to be 'earth' at the supply end, and the furthest socket - this checks your conduit is intact. You can take your new earth from the earth terminal on the back of the socket you are spurring from, if, and only if, you can show this already has a low resistance path back to the main, so you are connecting to something you know is already earthed (it is no good connecting it all together if there is no metallic path back to the supply earth point.)
come back if still confoodled.
regards M.

 

[ban-all-sheds]

jgreer - don't take this the wrong way, but if your need for those new sockets is not pressing, I suggest you postpone doing them until you've learnt more about wiring...

Also - Q to all - isn't the integrity of a conduit system supposed to be tested by applying a significant voltage to it, not just checking its resistance?

 

[mapj1]

Yes, ideally the earthing should be tested with an ELFI meter, but only after a low current resitance check. If he has no RCD, that could also be verified with a socket tester of the sort that applies a load between L and E.
However, as we are not sure he even has an earth, an ohm meter test is a very good start!
regards M.

 

[jgreer]

My fuse board has a sticker on it that says "this installation is connected to a PME system".

Googling this I found:

PME Protective Multiple Earthing - commonly used in this area for new buildings. Only the Live and Neutral (or to be precise the PEN conductor) conductors enter the building, and the Neutral and Earth are joined just after they enter the building. Inside the building they are separate. This gives faster blowing of fuses etc. in event of a fault - but is not entirely without its drawbacks.
PEN means a conductor combining the functions of both earth and neutral.

Is this why the cables I have don't contain three wires?

I'm still going to check the resistance tomorrow, though.