Who's right EDF or me??

[ajelec10]

Hi plug, Your right the armouring is large enough, have you provided brass bolts banjo's and 16mm fly leads at both ends, if you have they really are being jobs worths. Have had a problem with EDF before, went to look at a job about 40miles away from were I live did an assement and found no bonding in place and the ZE was about 6 ohms on a TN-S, said to client would be back in a few days to install new board and bonding. called edf to sort out the earth first, then went on my way, got a call later from client saying the edf guy has turned up seen no bonding pulled out the main fuse and walked out. this was a mother with two kids in at the time. I had to return to property install bonding just so they would come back convert it to a TN-C-S and turn power back on!!!

 

[Lou7]

Sorry chaps but I'm sure I've seen somewhere that armouring should not be used if supply is PME, I think it was in the NICEIC technical guide.

 

[zupos40]

I am not going to let this one go. Have got them coming to site again on Friday and I will be armed with my regs books, tables etc and will not rest until they connect. Watch this space!!!

I would not bother with regulation use GN 1 (sorry do not have copy with me at present, but I know one of the appendices cover amoured cable).

when I get return home I look in ESQCR, even if you prove your correct, from personal experience you still may have to do what they want.

Best of luck for friday

 

[Lou7]

Found it,

Where PME conditions apply
3.1 Cable conductor overheating
Where PME conditions apply* , the use of the armouring of a cable as a main bonding conductor may result in overheating of the live conductors where they are to be operated at a significant proportion of their current-carrying capacity for sustained periods or at higher ambient temperatures. ‘Overheating’ of a live conductor, in this context, is where the conductor operating temperature exceeds the rated value appropriate to the insulation material (such as 70 °C for thermoplastic (general purpose pvc)), which can lead to premature ageing and deterioration the insulation.
Such overheating is related to the diverted neutral (or network circulating) currents which the main bonding conductors of a PME supplied installation may have to carry for sustained periods under certain conditions. Part of the I2R heating produced in armouring, when it carries diverted neutral current, is transmitted to the live conductors of the cable, which can result in their overheating.
The probability of the live conductors of a cable overheating due to diverted neutral current in the armouring, such that consequent premature ageing of the insulation is likely, is reduced in the following two cases.
• Where the cable is lightly loaded (bearing in mind that the heat produced in a conductor is proportional to the current squared) and the ambient temperature is in the normal range expected for occupied areas.• Where it is expected that the armouring will not carry a significant magnitude of diverted neutral current. (That is, where none of the extraneous-conductive-parts which the armouring connects to the main earthing terminal are in contact with the general mass of Earth or may reasonably be expected to come into such contact).

 

[plug444]

Hi Dave
Re meter tails and sub main feeder.

For your information;
From the on site guide BS7671: 2008

Page 17 - 2.2.3 Meter Tails
Where the meter tails are protected against fault current by the distributor’s cut-out
The method of installation, maximum length and minimum cross sectional area must comply with the requirements of the distributor.

From BS7671: 2008 434.3 discusses omission of devices for protection against fault current
A device for protection against fault current need not be provided for:
The origin of an installation where the distributor installs one or more devices providing protection against fault current and agrees that such a device affords protection to the part of the installation between the origin and the main distribution point of the installation where further protection against fault current is provided.
PROVIDED THAT BOTH THE FOLLOWING CONDITIONS ARE SIMULTANEOUSLY FULFILLED:
The wiring is carried out in such a way as to reduce the risk of fault to a minimum
And
The wiring is installed in such a manner as to reduce to a minimum the risk of fire or danger to persons.
Note: 433.3 also discusses omission of devices but in this case for protection against overload

537.1.4 discusses isolation at the origin of every installation
537.1.4 a main linked switch or linked circuit breaker shall be provided as near as practicable to the origin of every installation as a means of switching the supply on load and as a means of isolation.

Having mentioned the above
And although this is not referenced directly in the wiring regulations
It is good practice where meter tails are to exceed 3m for a fused isolator or similar to be installed on short tails from the meter. The fused isolator then offers a protected sub main feeder run from the fused isolator to the consumer unit.
Additionally giving isolation at the origin of the installation.

Having considered the given details of the installation I would consider this installation to be compliant with section 543 of BS7671 in particular 543.1 that considers the CSA of protective conductors.
From table 54.7 BS7671: 2008 page 130 the minimum CSA of the protective conductor for a 25mm line conductor is 16mm.
The attached table shows:
A 4 x 25mm PVC SWA to have an actual steel CSA of 76mm and an equivalent CU CSA of 33.7mm
A 4 x 25mm XLPE SWA to have an actual steel CSA of 70mm and an equivalent CU CSA of 22.5mm as you state in your e-mail.

You can also if you wish as the designer calculate the CSA of protective conductors using the adiabatic equation, this by experience will generally calculate to a smaller CSA than given in table 54.7.

It could also be argued that although EDF have the right not to connect, if you have offered isolation and discrimination at the origin of the supply that is compliant, from that point and for the rest of the installation as the designer you are the person responsible for considering and quantifying any departures from BS7671 which you must then detail on the electrical installation certificate.
I would be interested to discuss any constructive comment made by EDF as reasons not to connect.


Regards
ECA Technical Officer
For the Elecsa technical helpline.

 

[Lou7]

U R D Man!!

 

[plug444]

U R D Man!!

Obviously not, still refusing to connect even after proving that the armouring was more than twice the required size and I passed him over on the phone to the ECA's chief technical officer who also tried to tell him he was wrong

He just kept on about 'my boss says no and thats final'

Insistant on overlaying a 16mm copper cpc.

I hope people take note of this for any future 3 phase domestic jobs as it has proved to be very costly to myself!!
Another lesson learn't the hard way

 

[Spudnik]

Trouble is though mate its their 'equipment' so its their rules.

BS 7671 doesnt strictly come into it.

 

[plug444]

Trouble is though mate its their 'equipment' so its their rules.

BS 7671 doesnt strictly come into it.

I beg to differ. Its their equipment up to my switch fuse, after that its my responsability as my testing starts from that point.

Just my opinion