Is earthing sockets to their casing dodgy?

[umbauk]

Hi all,

I've just moved into a new place, quite an old flat that was apparently rewired in the 1970's.

I've just found that the cable supplying the majority of the sockets only contains live and neutral wires which are surrounded by some kind of powdery substance and then incased in copper.

I thought this very odd so I opened up one of the sockets to see if they were earthed at all and there is an earth cable but it is simply attached to the metal casing of the socket.

Is this ok/legal/madly dangerous?

I'm worried they may have got some dodgy electrician to do the rewiring and we're going to have to get the whole place rewired ourselves...

Thanks in advance for any help!

Darren.

 

[JohnD]

It may or may not be.

there is a rather expensive wiring system that uses the Mineral-Insulated Copper Clad cables. In this system the earth conductor is the copper sheathing. It is a fireproof system. and not often installed in domestic properties. Is yours a house or flat or was it ever offices or workshops?

However, when properly installed, the copper sheaths should be fimly connected to the metal back-boxes of the sockets with a brass gland; and the mineral insulation material should be sealed so that it can't get out (or be seen) as it is a compressed incombustible powder.

If you can see the powder that suggests that the ends aren't properly sealed.

Can you see the brass glands sealing the copper sheathing to the metal back-boxes? It has to be present at every box to give a reliable continuous earth connection, and every box must be metal.

If you are able to lay your hands on a digital camera and put up a few pics of the sockets and the connection at the consumer unit (fuseboard) we will be able to see if it has the appearance of a well-installed system or not.

I have a feeling that your system is going to need professional inspection at the least, and probably some rectification work. If the cable ends are left unsealed moisture can get into the compressed powder and make it swell and break up. It is also very difficult for an amateur without the right tools and a certain amount of skill to work on, and the brass glands are not very cheap.

 

[Pensdown]

As Johnd as said, if you can see white powder there is a problem and this could be quite a major problem. The ends of the cable should have a brass “pot” on the end with a black top where the wires exit. The brass pot may just be clamped in the socket or it may have another brass gland around it if it’s a metal clad socket

If you can see white powder my concern is there maybe no pot at all.

 

[umbauk]

Thanks for the quick responses!

It's a flat that has always been residential.

The reason I can see the insides is because when the builders were knocking down the kitchen wall they exposed this wire and knocked it out of the consumer unit. The cable had a brass gland on it like you mentioned but this came off after being trampled on etc by them exposing the insides.

This cable ran from the consumer unit through the kitchen and bathroom walls to the main bedroom where it went into a socket. Given the sockets still work, removing the cable from the consumer unit must have turned it from a ring circuit to a radial circuit.

I gather this isn't ideal but is it still safe?

You can not see the inisides of any of the cables elsewhere, they are all as you mention with the brass glands.

Thanks again.

 

[JohnD]

...when the builders were knocking down the kitchen wall they exposed this wire and knocked it out of the consumer unit. The cable had a brass gland on it like you mentioned but this came off after being trampled on etc by them exposing the insides.

Buffoons!

If only there was some way of getting people who'd damaged your property to pay for repairing it

You need to get a qualified electrician in to repair it. once opened to the air it will deteriorate and may be unsafe already.

when you phone round, ask if they're members of a self-certification scheme (the correct answer is "yes") and tell him you have a [MICS sorry - this is wrong - see below ] installation that has been damaged and needs inspection and rectification.

Consider the possibility of making a claim against the "builders"

 

[Lectrician]

An open end to the ring floating on the floor......umm......NOT GOOD AND VERY DANGEROUS.

I hope you missed the part where you meant to say "I have disconnected this cable from the socket end as well"?

Get a sparky in, and don't say I have a MICS system - tell them you have an MI / MICC system

 

[JohnD]

That's funny, I first typed MICC and then thought it didn't look right. Was trying to remember if it was "Clad" or "Sheathed".

What's the correct name for the all copper one, and what do you call it when it' got a plastic cover?

 

[Adam_151]

There are two issues here, just to clarify in one post:

1) The classic broken ring, you now have an overloaded radial (oh and thats besides having a loose leg floating around!)

2) The white powder is (well unless you have had kate moss over for a house party... ) magnesium oxide, its hygroscopic (absorbs moisure from the air) which means when exposed, the insulation resistance starts to drop off, now if the circuit in question is RCD protected, it should eventually trip out with the current tracking to earth), but if not, then long before it becomes a dead short and clears fuses, there will be a stage where the IR is such that it becomes a pretty good heating element and heats whatever it is fastened to... in some cases causing it to burn (the cable itself doen't burn unless its pvc coated)

Yeah say MI/MICC *as lec says, or Pyro

*Mineral Insulated Copper Cable. ( http://en.wikipedia.org/wiki/Mineral_Insulated_Copper_Clad_cable )

 

[Pensdown]

That's funny, I first typed MICC and then thought it didn't look right. Was trying to remember if it was "Clad" or "Sheathed".

What's the correct name for the all copper one, and what do you call it when it' got a plastic cover?

MICC
MICV

But please don't ask why its called MICV because I can't remember

 

[Lectrician]

I always call in Mineral Insulated (MI).

MICC stands for Mineral Insualted Copper Covered. Many people (and this isn't wrong) call it Mineral Insulated Copper Coated, Mineral Insulated Copper Cable or Mineral Insulated Copper Clad.

Also known as MIMS - Mineral Insualted Metal Sheathed.

If you want a PVC sheath - you ask for MICC with a sheath

MI was originally made by a company called BICC (gets confusing) - British Insulated Calendar Cables (i recall). There brand name was Pyrotenax (hence why this cable is often refered to as pyro).






At the end of the day - do you own a hoover or a vacume

 

[umbauk]

Indeed I did miss the part where I disconnected the trailing end from the socket when I realised what it was!

Thanks everyone for your help. you've dismissed my confusion and a lot of my worries!

Out of interest, would it be possible to remove the trailing end of MI/MICC/MICV/MIMS/Pyro and complete the ring in normal 3 core or would using two different types of cable in the ring cause issues?

 

[Lectrician]

LOL

 

[JohnD]

LOL

I guess I must have seen it somewhere

 

[plugwash]

Out of interest, would it be possible to remove the trailing end of MI/MICC/MICV/MIMS/Pyro and complete the ring in normal 3 core or would using two different types of cable in the ring cause issues?

no it won't cause any issues. just make sure the cable is appropriately routed (MICC can be run anywhere because of its integrated metal sheath, T&E can't)

 

[SparkyMarky]

MI was originally made by a company called BICC (gets confusing) - British Insulated Calendar Cables (i recall). There brand name was Pyrotenax (hence why this cable is often refered to as pyro).

I live and learn. I'd always thought that BICC stood for British Insulated Cable Company! I don't know where I got that from!

Where I work it's always called pyro. We only use it to wire fire alarm and emergency lighting systems which need to have some level of fire resistance, so the nickname 'pyro' is quite fitting.