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Topic Title: Overcurrent protection of underground cable
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Created On: 02 December 2013 01:31 PM
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 02 December 2013 01:31 PM
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superstardeejay

Posts: 3
Joined: 02 December 2013

We've just had a new steel outbuilding put up approx 60m from the main building which has a 200A supply from our pole transformer. The new tenant in the building has organised their own supply to be sourced from our own with a seperate meter which we shall use for billing him.

The question is that the electrician they used has come out of our main meter on henley splitter blocks, into a new meter and then and connected the meter to the 16mm 4 core SWA that feeds the new building.

My concerns are that

a) the 16mm is only protected by our 200A cutout.

b) there's no way of isolating the new building

c) a fault on the cable may blackout our entire site

The electrician must have opened our cutout box and then 'resealed' it which I know is common but may reflect badly on us from the supplier point of view.

Am I right to be worried and should I get another electrician to look over it?
 02 December 2013 02:10 PM
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OMS

Posts: 19851
Joined: 23 March 2004

Am I right to be worried and should I get another electrician to look over it?


Your concerns are valid, and if not another electrician, at least an opinion from someone competent

I'd have expected a "main switch fuse" to protect the 60m sub main and provide a point of isolation

Regards

OMS

-------------------------
Failure is always an option
 02 December 2013 02:26 PM
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AJJewsbury

Posts: 11696
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c) a fault on the cable may blackout our entire site

I'd add as another possibility (depending on the exact numbers involved):
d) a fault on the cable might not blow any fuse, but leave the earthing system at a raised voltage for an extended period of time, posing a shock risk not just for their building but yours as well.

- Andy.
 02 December 2013 05:00 PM
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John Peckham

Posts: 7577
Joined: 23 April 2005

Welcome to the forum.

Sounds like a crap job to me. Is the electrician registered with one of the regulating bodies? If so you can complain to them. Did he/she issue an electrical installation certificate? If so on the Schedule Of Inspection Form did he/she tick the box for "Choice and setting of protective and monitoring devices (for fault and/or overcurrent protection)?

-------------------------
John Peckham

http://www.astutetechnicalservices.co.uk/
 02 December 2013 05:19 PM
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UKPN

Posts: 541
Joined: 17 January 2012

"The DNO should be notified immediately and they will disconnect the illegal wiring. There is too much of this nonsense going on these days.
Its no good getting other people round, the seals have been broken, on poss both the cut-outs and meter, it could be overloaded, incorrect earthing/bonding and goodness what else. the longer this fiasco is left the bigger the danger, the "installer" will disappear or blame someone else. (probably us).

Regards.
 02 December 2013 05:34 PM
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superstardeejay

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Yes I'd forgotton about compromising earth protection; my field is power electronics...I'm a circuit board and transistor man. The 'contractor' I've found is a medium-sized firm who has quite a snazzy headquarters in the city centre, no guarantee of NICEIC or IET membership of course. However, our electrician of choice most certainly is and I'm going to get him here asap.
I've just spoken to the member of the company who let them in at the weekend and he said the guy was muttering about 'no spare ways' in our main dist. board and 'derating the cable'. I'm not sure how he's derated anything.
Sorry about the 'acting thick' post but when I was at college 15th edition had just been published and things have moved on!
 02 December 2013 06:37 PM
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OMS

Posts: 19851
Joined: 23 March 2004

Sorry about the 'acting thick' post but when I was at college 15th edition had just been published and things have moved on!


Not much - 200A fuses protecting 16mm2 cable is a tad reckless

4 Core SWA may also be a problem depending on your earthing arrangements - that steel frame building is going to be a pretty good electrode, so you don't want too much diverted neutral current going down that 16mm2 cable. If you currently have PME earthing, then you could well be in a "rip it out and start again" scenario.

Presumably anything the tenant does needs landlord consent, so I'd consider turning them off subject to you getting a report on the problems on your desk.

However, our electrician of choice most certainly is and I'm going to get him here asap.


OK - get him to check what means of earthing you have and just remind him about Guidance note 8 and the use of SWA as a bonding conductor

Regards

OMS

-------------------------
Failure is always an option
 02 December 2013 07:25 PM
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UKPN

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"NICEIC/IET membership does not allow disconnection of DNO mains/disconnect meters.

Regards
 04 December 2013 10:16 AM
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AJJewsbury

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"NICEIC/IET membership does not allow disconnection of DNO mains/disconnect meters.

Some DNOs seem to accept it - e.g. http://www.ssepd.co.uk/uploade...mentOfCutOutSeals.pdf

Although in this case we seem to be assuming that the seals have been cut - equally someone might have worked live and left the original seals intact. (Not recommended of course, but a possibility)

- Andy.
 04 December 2013 10:35 AM
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UKPN

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We are not assuming the cut-out seals were cut, the poster says they were. But the bottom line here is this work must be put right. I cannot believe that experienced posters encourage owners of property to employ private companys (whether "scheme" providers or otherwise, to interfere with services which are provided under the ESQCR.

Regards
 04 December 2013 10:57 AM
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alancapon

Posts: 5811
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Originally posted by: AJJewsbury
. . . Some DNOs seem to accept it - e.g. http://www.ssepd.co.uk/uploade...CutOutSeals.pdf
. . .

There is an interesting quote in the middle of that document:

. . . Trade Associations shall ensure that there members are competent to remove and replace live cutout fuses ensuring safety is maintained at all times. Note: SSEPD staff are required to use a visor and insulated electrical gloves when undertaking live fuse removal and replacement. . .

It would be interesting to know what training, requirements and checks the various organisations make for this as they appear to have the liability (although that could only be truly tested in a court of law). I suspect that I can already guess the answer . . .

Regards,

Alan.
 04 December 2013 11:00 AM
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Jaymack

Posts: 4754
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Originally posted by: UKPN
I cannot believe that experienced posters encourage owners of property to employ private companys (whether "scheme" providers or otherwise, to interfere with services which are provided under the ESQCR.

Er, that would be owners', properties and companies Scottish Hydro supply paper seals to registered contractors; 5 at a time, with a traceable list at Oliver Twist time. It was 10 at a time but for reasons unknown to moi, the numbers have been reduced. SSE also gave them out when I was in the High Wycombe area.

Regards
 04 December 2013 02:36 PM
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superstardeejay

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Joined: 02 December 2013

We certainly haven't employed any company at all to interfere with anything. Our tenants, who are involved in national cable-laying contracts, said they would arrange their own contractor to carry out the connection, and at their cost. I know enough to know the work isn't correct, and decided to learn about the correct way, from the horse's mouth, so to speak.
If WPN need to be called to this our NICEIC contractor will have a contact there already.
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