Earth clamp on lead sheathed cable

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Hi All and thanks for any info,

Is the clamp in these pictures a method commonly used by a DNO to provide an earth? I thought they tended to be soldered on to the sheath. Was asked as a favour to replace a faulty light switch. Fair enough, quick test revealed Zs of 11 Ohms. Only earth was through the main bonding to the incoming water main. No main earth connection, but Ze measured to the clamp was 0.29 Ohm. Allegedly the consumer unit was replaced by the same guy that changed the meter and cutout about 8 years ago :rolleyes: Have fitted a main earthing conductor to the clamp, would you recommend verifying with the DNO that it was fitted for that purpose?

 
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Hello,

I have seen this type of clamp fitted, not 100% sure but I think they need to be BS951 type.

Ed
 
I think that that type of service fuse holder has an earth terminal to the far right of the neutral block - it is often a sign of a PME system?

Have a close look at the right hand side - is there a hole at the right edge marked EARTH etc?
 
Is the clamp in these pictures a method commonly used by a DNO to provide an earth?

No, but it is a common method used by people who like tampering with DNO equipment.

The correct method is soldered or a spring clamp.

would you recommend verifying with the DNO that it was fitted for that purpose?
Probably not, as they most likely won't know what is fitted in your property without sending someone to look. They may well charge for this, unless the earth is defective (Ze of 0.29 would suggest it is not).
 
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No, but it is a common method used by people who like tampering with DNO equipment.

Yeah, that is what I suspected. It just seemed a lot of trouble for someone to tamper with it and then not bother connecting it to anything! I would have thought if the earth had been disconnected by the guy that changed the meter and cut out because he thought it an inappropriate method, then he should have removed the clamp and done something about the earth connection. I am at least happy that Ze is good now. Problem is you don't really know who did what and peoples version of events is not necessarily correct.
 
I think that that type of service fuse holder has an earth terminal to the far right of the neutral block - it is often a sign of a PME system?

Hmm, I will take another look next time I am in the area. There was certainly nothing obvious. If it were PME then should the distributor have provided an MET linked from the connection or is it possible to access the terminal for connection without dismantling the cutout?


Thanks again for all replies.
 
If it were PME then should the distributor have provided an MET linked from the connection

Yes. If no connection there, then nothing you can do. Even if there is, this does not mean PME/TNCS. Plenty of TNS supplies installed that way.

As for the wrong clamp, unless it has been recently installed or recently tightened up (which could crush the cable), probably nothing wrong with leaving it. 1000s like it all over the country.
 
Cheers Flameport,

Clamp looks like it has been there for some time and I didn't touch the tensioning screw. Ze good so I will be content with leaving it.


Thanks again.
 

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