Earth Clamp on supply

[danrich123]

Hi,
I've been to two properties in the last two days that have an ordinary earth clamp on the outer sheath of the incomer. Is it ok for this to be like this, as I've been told a previous electrician put the earth clamp on one of the properties incomer?
I suspect a spark isn't allowed to do that, but if the clamps already there and you get a good reading is this ok?

On another point, another supply i've seen, was originally TNS but has also got an earth rod on it as well as earth to sheath, I presume that supply should be classed as a TT now?

ta

 

[Spark123]

You shouldn't attach clamps to the suppliers cable, however if one is already there and giving good readings then I wouldn't be too bothered about it.

A TT system doesn't connect to the sheath - if this has been done to correct the supply cable not being connected to earth then it is dangerous. In the event of a fault on the supply cable and everything connected to the same earthing system can become live.
What reading did you get for the Ze on the sheath?

 

[PrinceofDarkness]

There's a great deal of myth and old wive's tales regarding the fitting of a standard clamp to a lead service - and some of it comes from so-called respected institutions and organisations.

The plain fact is that most of those clamps have been fitted by the supplier - and they continue to do so even now, when a replacement clamp is needed on an elderly supply.

I spent twenty years with the LEB, and the common old earth clamp was used routinely on the lead sheath. Those inner-lead-sheated cables are a lot tougher that some imagine them to be. I used to (and still do, occassionally) fit the clamp damn tight, make the other connections and then return to the clamp to give it another 'tweak'. I've seldom come across a loose and unreliable clamp on a sheath.

Yet, I constantly hear fabulous remarks about how the sheath is made of blancmange and it's 'highly dangerous to fit a clamp'.

However, it's certainly true that suppliers, in general, take a dim view of an 'ordinary' sparky replacing or interfering with their clamp - or any other of their apparatus for that matter.....


Lucia.