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Topic Title: concentric cable
Topic Summary: concentric cable recombining from the meter to a second cut-out before the consumer unit
Created On: 04 February 2011 01:53 AM
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 04 February 2011 01:53 AM
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anton

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Joined: 09 September 2003

hi, i have an installation that uses a concentric cable to connect the meter to a second cut-out which is several meters away from the main cut-out. is this the distributors equipment and if not, is this installation usual? any guidance gratefully received.
 04 February 2011 06:37 AM
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Jobbo

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Have you contacted the distributor? That would be your first step. Perhaps you could upload a picture on this thread, so it would be easier to give a more accurate opinion.

Regards

Jobbo
 06 February 2011 02:57 PM
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anton

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hi jobbo, here is a link to the pic -

http://i1223.photobucket.com/a...202011/-110206124.jpg

I will also talk to the SA and find out what they think, thaks, anotn
 06 February 2011 03:15 PM
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Jobbo

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It's not the most common set-up, but it does look to be the property of the network supplier (I've seen some similar arrangements) . What is the earthing arrangement? Have you contacted the supplier?

Regards

Jobbo
 06 February 2011 03:26 PM
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slittle

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Is this by chance an intake to a flat ??. I've seen similar on them.

The earthing type (at the second cutout) can only be TNCS or TT can't it ?


Stu
 07 February 2011 02:13 AM
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anton

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hi, thanks for the replies. Its reassuring to know this has been seen before.
The earthing is tncs at the second cut-out and measures-up in terms of low ze (<0.32 ohms) at the board and everything works and is within limits.
It is a bungalow that has been bashed about a bit so this may have been a patch but I will check with the SA today and let you know.

thanks again, anotn
 07 February 2011 01:05 PM
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alancapon

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Originally posted by: anton
. . . The earthing is tncs at the second cut-out . . .

The earthing will be TT. It cannot be TNC-S, as the submain from the meter is "straight concentric" with only phase and neutral conductors. With TNC-S, the earth connection must be made by the supplier to the neutral conductor before the electricity meter. The ESQCR regulations prohibit a combined neutral & earth conductor within the consumer's installation.

Regards,

Alan.
 07 February 2011 04:27 PM
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Jobbo

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I was expecting you to say TT for sure. If it is TN-C-S then that's a big no no, like Alan has mentioned above
 07 February 2011 06:36 PM
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typiod

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I expect that the installation is in the old wessex area of sse, (used to be done a lot), and yes it is tncs, they were never that worried as long as the meter fitted had a solid nuetral link. you could try and ask them if they will move the meter inside. Is the second cut out an fsmi red link?
 08 February 2011 01:04 AM
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anton

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hi, thanks for the interest, yes typiod you hit the nail on the head. below is the pic of the other end of the cable.

Alan i will pass it by the SA (havent had a chance in daylight yet) and let you know. Do you know by any chance why the regs prohibit tncs after the meter?


thanks anton

http://i1223.photobucket.com/a...om%202011/IMG_0667.jpg
 08 February 2011 07:24 AM
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JonSteward

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That could be a DIY TN-CS. No seal visable and a dodgy looking bit of g/y fitted and RCD at start suggests could have been TT
 08 February 2011 09:46 AM
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anton

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hi, I have spoken to the SA and they confirm that the arrangement is a 'lateral service' used where tails would exceed 3m between the meter position and the consumer unit - so it is distributors equipment.

The tncs on the other hand must have been a bit of diy as you say because the main earth has to join into the concentric cable neutral directly and using the path through the meter is unreliable.

thanks for you help, anton
 08 February 2011 04:58 PM
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alancapon

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Originally posted by: anton
I have spoken to the SA . . . The tncs on the other hand must have been a bit of diy as you say because the main earth has to join into the concentric cable neutral directly and using the path through the meter is unreliable. . .

What did the DNO say about the eathing type? Did they confirm that it should have been a TT supply?

Regards,

Alan.
 08 February 2011 07:17 PM
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typiod

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Alan
I doubt that sepd (poole depot) would have said it should be a TT. Over the years up untill about 2 years ago this is how they have done a lot of supplys especially when they have replaced services, also a large number of flats in the area as well as serverel housing estates were also wired this way, and some even had the pme label at the fsmi, as I said in the post above they were never that concerned as long as the meter fitted had a fixed nuetral. For all new sub mains installed in flats splint concentric is now used.
 08 February 2011 07:42 PM
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alancapon

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My personal belief is that the arrangement shown in the photos provided is not a satisfactory method of providing a PME supply. There is possibly a "non standard" method of achieving it, but this solution is not it.

Regards,

Alan.
 08 February 2011 11:07 PM
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anton

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I will post the reply from the SA requesting a tncs at the main cut out - the conversation i had with them suggested it would be but the area engineer will probably need sight of the job before confirming.

anotn
 17 February 2011 12:35 AM
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anton

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It may be useful to add that the red cut-out fuse carrier is a solid link where the main cut-out next to the meter has the cartridge fuse
 17 February 2011 09:53 AM
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perspicacious

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"Do you know by any chance why the regs prohibit tncs after the meter?"

It used to require permission from the Secretary of State but from a practical point, how do you intend getting a RCD to work on such a system?

Regards

BOD
 17 February 2011 10:52 AM
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anton

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hi bod,
I have contacted the SA to establish if they did the install and are satisfied with the arrangement or to tncs at the main cut-out if their tranmsformer is tied to grnd (work in progress)
or I will advise the client to add an earth rod.
 18 February 2011 07:16 PM
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AJJewsbury

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"Do you know by any chance why the regs prohibit tncs after the meter?"

Isn't it more an issue with TN-C within "the consumer's installation" - as the meter isn't necessarily the boundary. Indeed many "installations" don't have meters (e.g. lighting for advertising hoardings, bus shelters etc). In this case it sounds like it could be the supplier's system up to and including the red cut-out.
- Andy.
IET » Wiring and the regulations » concentric cable

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