Copper pipe used as earth contact

[frediaz]

I live in a property where there is still the old method of taking the earth connection, with the mains cable from the electricity meter, using a copper pipe instead of a wire. This copper pipe is then connected to the fuse box in the flat by fastening it to the metal body of the box. The body, in turn, contains the earth blocks to which the mains cables going to the wiring in the flat are connected.

My question is, is this still allowed by the regulations? and if I want to replace the old fuse box with a consumer unit (having a plastic box), how can I connect the earth block in the unit to the earth pipe in a way that is allowed? is this possible?

Running an earth wire to replace the copper pipe involves a fair amount of building work.

Thanks

 

[breezer]

any chance of a pic?

it sounds like the "copper pipe" is infact a "pyro"

a pyro is a "special" cable that is solid copper that is insulated (internaly)with magnesium oxide, it was origonaly used for very hot places, and fire alarms since if in a fire it will not melt. its outer sheath is the earth connection

 

[plugwash]

if it is pyro *DO NOT* desturb the seal on the pot

and get someone in who knows how to check reterminate it properly

a metal CU is almost certainly going to be the way to go here (even though it will cost slightly more)

 

[ban-all-sheds]

Pyro for meter tails? There's a novelty. Didn't know that meters were ever designed to terminate the stuff...

Wouldn't it just make more sense to replace them with normal tails?

 

[breezer]

we wont know untill we get picture

 

[frediaz]

Sorry about the delay to post the pictures as it took me some time to work out how to do it on this site -not easy-. It looks like the pipe is a proper conduit. It is threaded where it is fastened to the fuse box and the live and neutral wires are inside the pipe. Here are the pictures of the offending pipe.

And the wires coming out of the pipe inside the fuse box, also showing the earth bar fastened to the metal box to make the earth connection to the pipe through the box.

Any more feed-back will be appreciated

 

[plugwash]

what about the other end where it joins to the meter

frankly it looks undersized anyway though

 

[breezer]

8) , its a pyro, for a pyro i would say its not undersized

As mentioned previously the easiest solution would be to get another metalclad cu. much less hassle, also a plastic one may get bent (shouldn't, but you dont want to chance it.)

alternatively you could put an adaptable box up, fit banjo get earth from banjo, find out wires are too short, because they are in metal box.

Also you WILL need to undo the bush (sort of nut) that holds the socket (coupler) to the cu.

may be time to get "mr electrician"

 

[plugwash]

and i would still like to see a picture of the other end

btw an alternative to replaceing the CU is to put an rcd for each ring cuircuit after the CU in a seperate box

 

[frediaz]

I cannot see the other end of the pipe as it disappears under the floor. It does not reach the meter so there must be a connection between the wires from the meter and the pipe inside the floor. I guess the thing to do is to measure the impedance (the Ze reading) of the pipe to make sure it is properly connected to earth, then it can stay there, am I right? if so how is the impedance measured and what is the correct impedance value?

I also guess an electrician should know how to connect the pipe to the earth bar in the CU but any more ideas will be welcome. I know that the coupler between the pipe and the existing fuse box can be removed exposing the thread on the pipe to fasten something else like this banjo nut.

Now that I think about it, I seem to remember that the wires inside the pipe were potted. I hope that a plastic CU box can be used as it has been bought already

I do not know what you mean by undersized, do you mean the diameter?

 

[breezer]

please stop calling it a pipe, it really is called a pyro.

the earth block inside you CU is fixed to the cu itself which is also metal (sorry to state the obvious) the bush that you can see inside the coupler actually electricaly connects the metal cu to the coupler, which is in turn connected to the pyro, the outer sheath of the pyro is the earth.

thing is as has been mentioned it we do need to see the other end, the plastic cu could be used, but will need a banjo (guess what it looks like) or an earth clamp.

I would still recomend geting an electrician in to have a look, but it may be worth asking first will they work with pyro, as its a "nuisance" some may say no, also its very rare in a domestic situation

 

[frediaz]

Hello breezer,

Thanks for the feed-back. OK maybe we can call it a piro. The main thing was to find out that I do not need to do substantial building and decorating to replace the pyro. Then I can call the electrician.

 

[plugwash]

its impossible to tell if it need replaceing without more info

especially as you say it doesn't reach the meter

the thing with meters is that its pretty hard to make a regs compliant connection to them with anything but double insulated tails

 

[ban-all-sheds]

What's the deal with all those unsheathed earth conductors?

 

[frediaz]

What's the deal with all those unsheathed earth conductors?

I do not really understand the question but I will still appreciate it if somebody can tell me how to check the earthing effectiveness as per the so called Ze reading and what the value should be.

Cheers