Earth-less Sockets!!!

[eveares]

So the front room of my house had all the plaster ripped off a few months back due to damp problems and is due to be re-plastered next year.

Well today I went to remove the wire terminating at a junction box from the only socket in the room and discovered the CPC of the cable was not connected to the socket , and thus also not connected to the cable going to the junction box what used to feed the other sockets before the room was stripped!

So In the nearly 4 years I have been living at my house, I have had un-earthed sockets in the front room. And no, I have never checked the sockets in there as I have not touched the wiring of the sockets in that room before and thus assumed everything was ok!

Also as is typical with old wiring, the single gang metal back box was unearthed, there was no rubber grommet round the cable entry. Further more the aluminium Line & Neutral wires were twisted and shoved into the terminals of a double socket, what the pattres box for the double socket was scrwed into the single gang back box making the tension on the cables excessively tight!

On a side note, as the single gang box has 4 screw lugs and has no built in provision for a earth connection, is it acceptable to earth the back box by using a eye crimp screwed into one of the unused screw lugs or do I need to replace the back box?

In essence, never assume something is all good.

 

[ericmark]

When I got my new earth loop impedance tester I went through my house getting use to using it. I have two fuse boxes each fed from a RCD and left hand RCD would never hold in for ELI test, right hand with oddly more on it and same batch number on RCD all sockets passed. Not really worried about left fuse box if RCD trips then not really worried about what the reading is.

However had I not got a ELI tester I would not have tested house. I am sure there are many houses without an effective earth my dad's house had the earth stake fitted by BT when party line fitted as it's only earth connection. Was around 3mm².

My son wired a house before the DNO gave them a supply and was verbally told by the DNO it would be TN-C-S and to leave a 10mm² or bigger earth wire with the line and neutral tails for them to connect which he did. He called back some weeks latter just to see if all OK as of course no live testing had been done only to find earth wire not connected. This was before 2008 so no RCD either. Emergency job to fit earth rod and 100 mA RCD.

I am sure there are many other stories about no earth including where SWA has corroded through. Years ago the DNO would inspect a house before connection today it seems they use third party installers paid one assumes by the house and are not really interested past the head and meter.

Scotland is talking about enforced EICR on rented property, not sure if in yet? But in the main only when some one is injured is anyone interested. Until 2004 and Part P laws many electricians never had access to a loop impedance tester after 2004 likely any house would be tested but there must be loads wired before that date with many earth faults.

 

[PBC_1966]

Further more the aluminium Line & Neutral wires were twisted and shoved into the terminals of a double socket

Are you sure it's aluminum and not tinned copper, which was the norm with Imperial-sized cables? What sort of age is the wiring?

 

[PrenticeBoyofDerry]

On a side note, as the single gang box has 4 screw lugs and has no built in provision for a earth connection, is it acceptable to earth the back box by using a eye crimp screwed into one of the unused screw lugs or do I need to replace the back box?

There is no requirement to earth the backbox if you have rigid lugs, but doing so with not compromise the safety aspect, and can only improve it.

In essence, never assume something is all good.

Indeed!

 

[eveares]

Are you sure it's aluminum and not tinned copper, which was the norm with Imperial-sized cables? What sort of age is the wiring?

The wiring is 1960's, and the cores have the colour of a dull greyish-silver. I just assumed it would be aluminium.

 

[stillp]

If you scrape the wires you'll probably find copper underneath.

 

[eveares]

So where and when was aluminium wires used?

 

[Taylortwocities]

IIRC. In the early 70's there was a copper shortage and for a while PVC aluminium T/E cable was available and used. Some of this was copper covered ally....some was just plain aluminium. It is single strand and the conductors are slightly larger than the copper equivalent. Installations with all ally cables suffer as the aluminium is soft and easily compressed, leading to poor connections over time.

There's a reg, somewhere that does not allow aluminium conductors of less than 16mm² in today's installations/

 

[JohnW2]

There is no requirement to earth the backbox if you have rigid lugs, but ...

All of us (including myself) always say that, but I wonder whether there actually are (or ever have been) any metal backboxes in which at least one of the lugs is not 'rigid'? I certainly don't think that I have ever see one - has anyone?

The above does not, of course, not apply in the case of plastic light switches, which rarely, if ever, have provision for earthing a backbox via faceplate screws.

Kind Regards, John

 

[Taylortwocities]

The back boxes for the old style MK sockets (the ones with two screws top and bottom, not at 9 and 3 o'clock) had a total of six lugs in the box. None of them were fixed..

 

[JohnW2]

The back boxes for the old style MK sockets (the ones with two screws top and bottom, not at 9 and 3 o'clock) had a total of six lugs in the box. None of them were fixed..

Ah - interesting - it's a long time since I last even saw one of those, and I hadn't realised that none of the lugs were fixed.

Kind Regards, John

 

[eveares]

Are you sure it's aluminum and not tinned copper

Just fixed the socket. Yep, just checked and the cores are tinned copper. I suppose one single gang socket in the room is better than none at all.

My steel back box in question has 4 fixed lugs; top middle, bottom middle, left middle, and right middle. Also tried to get fit a 20mm open grommet where the cables enter the back box as it was missing, but the knock out where the cables enter was some size less than 20mm and the cables feeding it after all are buried in a solid stone wall so are unlikely to move.

 

[stillp]

Cut the grommet and cut out a couple of millimetres to make it a smaller diameter. You could superglue the ends back together, but there's not much point, it's not going to go anywhere.

 

[PBC_1966]

Just fixed the socket. Yep, just checked and the cores are tinned copper.

Most likely the old 7/.029 (with 3/.036 earth).

 

[eveares]

Cut the grommet and cut out a couple of millimetres to make it a smaller diameter. You could superglue the ends back together, but there's not much point, it's not going to go anywhere.

Will try next time I open the socket up. Cable's not going to move anyway, their in their tight.

Most likely the old 7/.029 (with 3/.036 earth).

Probably, cable was multi stranded cable with the CPC made up of 3 strands.