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Topic Title: Earth Clamp On Mains Incomer
Topic Summary: How to connect
Created On: 05 January 2007 02:27 AM
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 05 January 2007 02:27 AM
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deleted_styromaker

Posts: 35
Joined: 27 November 2006

Hi Guys.

Builder (interested in electrics) - have now got 2381 and workling on 2391.

Incoming 60a supply (2 seperate cables for live & nuetral). A Clamp has been sweated onto and between lead sheaths of both cables.

In centre of clamp is a nut/bolt (although it may be just a thread with nut can't quite remember).

In fear of being shot down I think it is TN-S.

Tails are 16mm which I think is OK for 60a, so 10mm main earth would do - but run is only short to consumer unit so 16mm seems reasonable (currently 4mm).

No equipotential bonding so 10mm for that (forget the adiabatic equation I have used table)

Is it OK to isolate (fuse does not have seal) and put/tighten cable around thread/nut. It would seem a crimp on the 16mm earth with an eyelet would seem to be a better connection.

Appreciate any comments on my thought process above.

-------------------------

Dean
To know the road ahead, ask those coming back.
 05 January 2007 03:26 AM
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deleted_nonsparky

Posts: 1962
Joined: 02 January 2004

Yo - crimp an eyelet onto it.

Before changing it though, you ought to do EFLI tests. I know that you are making it better than it was, but if Ze is too high because the sheath is sh*gged then you should be aware before you start, because you'll have to do the tests after the change....

-------------------------

I don't suffer from stress - I'm a carrier...

 05 January 2007 07:15 AM
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normcall

Posts: 8132
Joined: 15 January 2005

I'm trying to get my head round:
"Incoming 60a supply (2 seperate cables for live & nuetral). A Clamp has been sweated onto and between lead sheaths of both cables."

You learn somthing every day.

-------------------------
Norman
 05 January 2007 08:19 AM
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deleted_styromaker

Posts: 35
Joined: 27 November 2006

Hi,

I'll do a ELFI today. Norm I'll take a photo!

Thanks

Dean

-------------------------

Dean
To know the road ahead, ask those coming back.
 05 January 2007 08:35 AM
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deleted_vangelderp

Posts: 123
Joined: 28 September 2006

Are you sure there are 2 seperate cables for live and neutral ?

I had a similar set up round my mums house. This is the best picture I have of how it was

http://img403.imageshack.us/img403/338/origlw6.jpg

It looked like 2 incoming lead cables and initially I assumed a seperate live and neutral. However looking under the floorboards only the right hand is the incoming. The left hand cable feeds next door. So it seems they fed two houses with one cable and my mums house then links to next door.

It seemed to be an old DC type setup and even had fuses in both the live and neutral. I got that all changed but it still feeds next door, it may be worth looking under the floorboards to confirm.

Also if it is a similar setup to what my mum had then you only need earth clamp onto your feed cable as the DNO did when then updated the cutout.

http://img403.imageshack.us/img403/3185/newte7.jpg
 05 January 2007 12:32 PM
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windypick

Posts: 278
Joined: 14 December 2006

aftnoon,

can you post a photo?

just because its a mid terraced house downtown doesn't mean its not a TT supply of old.

eg. compound filled cast iron service tee joint on lead main creates high earth impedance. very common to have a looped supply ie. two cables second cable could feed more than one house in street.

contact DNO for upgrade of sub standard equipment if it looks anything like vangelderp's first photo.

windy
 05 January 2007 06:46 PM
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deleted_styromaker

Posts: 35
Joined: 27 November 2006

Hi,
Hadn't really thought if it could be feed in and out, first glance says it looks L&N but thinking that doesn't make sense, fuse seal is cut but I haven't opened it yet but I don't think I could see the links between cables. Sorry not to photgraph top of incomer but only L (left) & N (right) conductors appearing.

Incomer

Another One


Didn't get around to ELFI Check as found more cans of worms, like a polarity failure on the landing light (why because the live was connected into a joint box from the 20a radial circuit.

So far in my limited experience eyes

No equipotential bonding on gas or water
Inadequate main earth
No cpc on lighting,
no RCD on sockets - for potential use outside, which means everything at least downstairs anyway
Non identified circuits
no earth sleeving
no labels for anything
loose wires in jbs.

Check out the photo link for some of the quality of the wiring

Top Quality

-------------------------

Dean
To know the road ahead, ask those coming back.
 05 January 2007 06:50 PM
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alancapon

Posts: 5770
Joined: 27 December 2005

Styromaker,

Please ignore nonsparky's suggestion. His proposal is extremely dangerous and illegal. You must contact the DNO to confirm the earthing arrangement - they should make an earth connection if they supply an earth. It would seem from your post that this is a "looped service", which was quite common at one point. One of the cabes will be the supply from the street, the other will be a supply to next door's installation. If the supply is TT, which it could conceivably be, the DNO will not provide an earth. If you make the connection, it is quite conceivable that a fault will create a safety hazard in the adjacent property. Connecting earth cables onto a lead cable should only be carried out by the DNO, or their contractors - if the cable is damaged during the work, and this can include squashing the cores through the lead, you will have a sizeable fireball in front of you, which may burn for some time.

Removing the service fuse is dangerous and illegal, as I have posted many times on this forum before. It should only be removed by the DNO, and it should be sealed. In your scenario, this fuse will not isolate either of the cables entering the cutout anyway. The supply authority I work for can and do take action against persons tampering with our supply equipment.


Regards,

Alan.
 05 January 2007 06:58 PM
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deleted_styromaker

Posts: 35
Joined: 27 November 2006

Hi Alan,
Appreciate your comments re main fuse. I underdstand you are coming from. Could you take a look at the first photo on the link as 'an earth' is already connected to the soldered connector between the 2 cables. The 2 cables are
1) to the main earth in the consumer

2 The 2nd goes to a 951 earth clamp connected to a cold water feed (in the attic) for the boiler upstairs.

Again appreciate any comments.

Thaknks

-------------------------

Dean
To know the road ahead, ask those coming back.
 05 January 2007 07:01 PM
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deleted_Blackpoolsparks

Posts: 56
Joined: 11 January 2005

Originally posted by: alancapon

Styromaker,



Please ignore nonsparky's suggestion. His proposal is extremely dangerous and illegal. You must contact the DNO to confirm the earthing arrangement - they should make an earth connection if they supply an earth. It would seem from your post that this is a "looped service", which was quite common at one point. One of the cabes will be the supply from the street, the other will be a supply to next door's installation. If the supply is TT, which it could conceivably be, the DNO will not provide an earth. If you make the connection, it is quite conceivable that a fault will create a safety hazard in the adjacent property. Connecting earth cables onto a lead cable should only be carried out by the DNO, or their contractors - if the cable is damaged during the work, and this can include squashing the cores through the lead, you will have a sizeable fireball in front of you, which may burn for some time.



Removing the service fuse is dangerous and illegal, as I have posted many times on this forum before. It should only be removed by the DNO, and it should be sealed. In your scenario, this fuse will not isolate either of the cables entering the cutout anyway. The supply authority I work for can and do take action against persons tampering with our supply equipment.





Regards,



Alan.


 05 January 2007 07:05 PM
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deleted_Blackpoolsparks

Posts: 56
Joined: 11 January 2005

Hi Alancapon
Could you please tell me the correct procedure (in as far as the supply authority is concerned) on how to go about connecting/ disconnecting supply when performing work to a domestic property.
Thanks
 05 January 2007 07:08 PM
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alancapon

Posts: 5770
Joined: 27 December 2005

Styromaker,

Having seen your photos, the lower half of the cutout will be filled with pitch, and you would probably not see anything useful. The last cutout of this type I removed the fuse from, I discovered the fuse fixings had failed. I ended up with the fuse in my hand, still connected to both the supply and the installation, and obviously still live. Now considering that the next fuse back could be up to 400A, how would you get out of that scenario?


Regards,

Alan.
 05 January 2007 07:11 PM
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normcall

Posts: 8132
Joined: 15 January 2005

I must confess it looks like a standard loop cable service head to me with service cable in and out to next door or wherever. Used to see a lot in post war council housing.

-------------------------
Norman
 05 January 2007 07:15 PM
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deleted_styromaker

Posts: 35
Joined: 27 November 2006

Hi,

I will not be touching the main earth,in our area conversion to a TT now sounds easier and quicker than waiting 6 weeks for the DNO to come (if they can decide who they are and who is responsible for the hardware).

Blackpoolsparks, I assume resending Alan's post was your way of ending my questions i.e go no further. As I suggested in my post I trying to learn this trade (by the way I have a number of electrical/electronic qualifications far higher than my 2381 or the 2391 I am studying) but I am wise enough to know that domestic/industrial wiring is a completely different beast to my life in the manufacturing/maintenance/breakdown world.

For a newcomer like me it's a big step to post for fear of looking dumb/silly/stupid or all of the above!

I am prepared to do this so I dip into the large pool of knowledge on this forum and ultimately to learn. (although I do think some regular users it incorrectly and as a tool to see how condescending to others they can be).

the last paragraph not related to you blackpoolsparks

I am trying to understand what I have seen regarding this job and what the options are (i would ask the same of the DNO when if ever I can found out who they are!)

Cheers

-------------------------

Dean
To know the road ahead, ask those coming back.
 05 January 2007 07:15 PM
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alancapon

Posts: 5770
Joined: 27 December 2005

Blackpool Sparks, I understand that with the "competition" in the UK supply market it can be difficult finding out whether it is the DNO or Meter Operator who should withdraw the fuse. We have the advantage that we are still owned by our government, so there is not a problem over who to call.

In terms of how we would replace a cutout, our rules require two people on site (in case of a mishap), then using the appropriate PPE (insulated gloves, face shields & insulated tools), we would work it live, applying temporary insulation as and when required.


Regards,

Alan.
 05 January 2007 07:17 PM
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deleted_styromaker

Posts: 35
Joined: 27 November 2006

By the way,

another positive about posting is that slowly I may learn to control my fingers on the keyboard and actually make some sense.

-------------------------

Dean
To know the road ahead, ask those coming back.
 05 January 2007 07:24 PM
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alancapon

Posts: 5770
Joined: 27 December 2005

Styromaker, never be afraid of asking questions, no matter how daft you think they might be. If asking a question makes you think more about what you are doing, or helps you understand, then crack on. As I work with voltages between 24v and 132kV, safety is always a priority. My goal is that myself and my colleagues go home at night in exactly the same state they arrived at work that morning - injury free.


Regards,

Alan.
 05 January 2007 07:27 PM
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evang

Posts: 55
Joined: 12 August 2004

If your DNO cut out looks like vangelderp's nasty photo. contact DNO for upgrade of sub standard equipment as it looks like a pre 1937 set up with a fused neutral. Very Dangerous.

See ESCQR REGS 2002 2. Application of Regulations 2(3) to 2(7):- (iii) Pre-1937 cut-outs with fuses in earth or neutral conductors must be removed from service by 2013.

Those clamps around the lead cable are the pre tensioned (constant pressure)wrap around strip type that you get in scotch cast thru joint kit for jointing swa's underground. For earthing the earth strap between the to swa's being jointed together. Shown in photo 2

Cheers
 05 January 2007 07:31 PM
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deleted_styromaker

Posts: 35
Joined: 27 November 2006

Thanks Alan,
Beleive it or not 10 years ago after a 3 day course with SEE I became 11kv switching authorised (we had a big 3.3kv motor on site which the wolf drill continually failed and we had to charge by hand and re-energise.). Every time the buytton on the SCADA touch screen didn't switch it on, my pants considered turning a different shade every time!

I am a 24v DC PLC man and anything ending in kv is not my scene. although I am aware of a number industrial sparks where 100a fused faults has caused serious injury.

Could you also elaborate on your comment re introducing fault next door if the earth was touched?

Cheers for constructive support.

Does the TT scenario seem reasonable I would be interested how others would approach (even if they may upset Alan!!).

-------------------------

Dean
To know the road ahead, ask those coming back.
 05 January 2007 07:37 PM
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EEBADS

Posts: 18
Joined: 04 January 2007

"I will not be touching the main earth,in our area conversion to a TT now sounds easier and quicker than waiting 6 weeks for the DNO to come (if they can decide who they are and who is responsible for the hardware)."


styromaker

This may not be as quick as you think, if converting to TT you will need an RCD installing (checked your photo's not installed) so you will probably have to call the DNO anyway to fit an isolation switch unless your going to do it live!! (not an easy option)
IET » Wiring and the regulations » Earth Clamp On Mains Incomer

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