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S

SKY

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Started a job today running in cables, after the customer cleared out the coats and shoes from the meter cupboard I find this DIY bad boy.

A clamp on the outer containment of the incoming main - I did a quick loop test on the socket with reading of 0.40ohms.
Will do a full ZS and ZE when I go there in a few day.

I guess this must have been a TT system in the past but there is no sign of the rod.

Do I need to inform DNO to sort this out?

IMG00292-20120814-1640.jpg
 
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S

Spazz

  • Thread Starter Thread Starter
  • #2
As you did the Zs on the socket it will be higher, you need to do the Ze on the incoming main to get a good reading, you will prob find it is under 0.35ohms
 
S

SKY

  • Thread Starter Thread Starter
  • #3
As you did the Zs on the socket it will be higher, you need to do the Ze on the incoming main to get a good reading, you will prob find it is under 0.35ohms
Cheers understand that - just did a quick test at sockets to ensure that there was earth just to make me sleep at night.
just worry that a earth connection like this will loosen over time.
 
1

1shortcircuit

  • Thread Starter Thread Starter
  • #5
Looks like TNS to me, incorrectly done with the earth clamp i may add
Yes, looks like it to me too.

Can't see the earth connecting to the Neutral which will make it a DIY TNCS???
 
S

SKY

  • Thread Starter Thread Starter
  • #6
Sorry chaps meant TNS.

The DNO own the cable so what do I do??

Should they come out and solder onto the lead.

My NICEIC guidance book says: under no circumstances should an earthing clamp (complying with BS 951 or any other) be attached to the lead sheath of any any cable. in the case of a supply cable this practice is wrong for two reasons;

The supply cable is the property of the electricity distributor and
The securing to the lead sheath is likely to damage the conductor insulation of the supply cable and is likely to loosen over time
 
Just one thing to say first Sky , it's a DIY TNS.
It has been common practice, amongst the less informed, to put an earth clamp on either a lead sheath or on armourings of incomers where they find a TT. This is done for a number of reasons, either they think they are making it safer because they get a nice low Ze or they do not understand why a rod system is there and how a TT works.
If it's the first well to a point it's true BUT a standard earth clamp is not the right thingto install. it should either be sweated on or should have a constant force spring, as far as I know The DNO should carry out both of these operations although I stand to be corrected there. This type of clamp should never be installed onto the lead sheath of a cable, proper earth rods intended for purpose should be used.
There's acres of discussion and debate on here re TTs and how to get a good effective one
 

rodney12

-
Arms
Be interesting to know what the neighbours arrangements are, ie tt or tns, but really you could just inform the dno what you have found and would have thought that they would have to come and sort it or even ask you to rod it if it's meant to be a tt

- - - Updated - - -

:smile5:
 
S

SKY

  • Thread Starter Thread Starter
  • #10
Will let DNO know - who is it for Basildon, Essex? (UK Power Network)??
I can TT but I don't think customer will pay, will have to mention it on my EIC as a departure to 7671 if they don't.
I hate things like this.
 
DNO will tell you to rod it mate and, I believe, could disconnect if it doesn't happen although once again I stand to be corrected on that one
 
1

1shortcircuit

  • Thread Starter Thread Starter
  • #12
Will let DNO know - who is it for Basildon, Essex? (UK Power Network)??
I can TT but I don't think customer will pay, will have to mention it on my EIC as a departure to 7671.
I always look around the property beforehand to see if there are any visual faults that sound alarms. Once this is done I then start testing to see if there are any underlying issues with the installation that couldn't be seen. When testing is complete I commence my work and at the end of that... I test all over again to make sure everything is still good.

Obviously there are some people out there that are so good that they don't need to do any of the above and they're even capable of calculating results in their head for the schedule of test results.

I would have spotted this and informed the DNO. It's their equipment so they can deal with it :D
 
Just about every TNS system I have seen around my way totaling about ten have all had these clamps on them.

I have yet to find one TNS round here with the correct clamp on the outer sheath of the cable.
 

Cbigfoot

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Arms
looks to me like there is a 2.5/4mm (or most probably a bit of 7/0.29) cable attached to the service, bare tinned copper sweeping around behind the G/Y cables possibly into the end terminal. In which case it is a TNS service.

This wire beloings to the DNO and is the mian earthing point into the MET. The question is should you upgrade it, assume it is not the correct size and suppleemnt it with earth rods, or ask the DNO to upgrade it which they are not required to do as they are not required to provide an earth?
 
S

Snapester

  • Thread Starter Thread Starter
  • #15
The DNO used to use clamps such as these not so long ago ive seen them on loads of installs and from mates at the DNO. Infact i did it on an install last week whoops........ oh well at least they have an earth with a decent reading, i would leave as you have a decent reading and the DNO well they wouldn't care as they leave properties without an earth alot of the time........
One rule for one and one for another.......... Its safe
 
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