Who's right EDF or me??

[plug444]

I will apologise in advance for a rather long first post but this has really (NO SWEARING) me off today.

Been doing a 400 year old barn conversion. Had to have EDF do a new mains install comprising of a 3 phase 100A PME supply. This involved major underground ducting work due to the overhead power poles needed to be removed from the 4 acre garden etc. This all went very smoothly and they installed my new service head into my external enclosure

My distribution board is mounted some 15mts away so I have run a 25mm 4 core swa, in the correct ducting under the foundations,to a 4 pole isolator. This isolator is mounted in a IP65 enclosure fixed to the side of my surface meter box, 25mm tails from this into the meter box

Now the problem!! Today was the big day for the meter to be installed. I had dead tested and certificated all my wiring to BS7671, made sure everything was clearly marked up with warning labels etc, all bonding etc done, great or so I thought.

Meter man turned up and walked round the barn like a big proud cockerell looking for problems of which he could find nothing. Opened my enclosure and said 'thats no good' refering to my isolator. Apparently he say's that I must fit a TPN switch fuse, not a isolator, to protect their fuses and the sub main cable. Now I am pretty sure that the regs state that I must provide a means of isolation for my cable, which I have done, nothing about fusing it twice

He waffled on about the possability of a major fault occuring and blowing their supply fuses. Now every circuit on my distribution board is protected via a RCBO on a PME supply. By my calculations it would take a fault of over 33kA to blow the head fuses and my protected circuits would shut down way before that so whats his problem!!

Opinions greatly received.

 

[Spudnik]

Sorry but he is right.

They will only protect the first 3 or 4M of tails, any further than that then YOU must provide a suitable switch fuse.

Its the same with all the DNO's domestic or commercial.

 

[slocm3105]

As Jason said mate he is correct. Bit of a pain I know but i'm sure it wouldn't take ya long to install a FCU in there .

 

[plug444]

As Jason said mate he is correct. Bit of a pain I know but i'm sure it wouldn't take ya long to install a FCU in there .

Its not so much the time as cost. £300 plus for a MEM switch fuse and a new enclosure too suit!

Whats to stop me installing a 100A type 'C' mcb into my enclosure. Far greater protection than a BS88 or 1361?

 

[slocm3105]

Its not so much the time as cost. £300 plus for a MEM switch fuse and a new enclosure too suit!

Whats to stop me installing a 100A type 'C' mcb into my enclosure. Far greater protection than a BS88 or 1361?

To be fair, you should have known about this. So protect it suitably and get it done .

 

[plug444]

To be fair, you should have known about this. So protect it suitably and get it done .

We can't all be perfect

 

[Spudnik]

Not at all mate,

Everyday is a school day in this game.

 

[sparks1234]

To be fair, you should have known about this. So protect it suitably and get it done .

Disagree here.

I have had various electric boards give different versions of what they require in this situation.

I work around the country and the story for various stuff is different everywhere.

I cannot remember the last time I actually had an electric board person check the installation, once you have signed that bit of paper it takes the responsibility away from them.

I have had sub-mains connected without a switch-fuse after the main fuses,

Think the lesson here is to make the call first

HTH

 

[plug444]

Disagree here.

I have had various electric boards give different versions of what they require in this situation.

I work around the country and the story for various stuff is different everywhere.

I cannot remember the last time I actually had an electric board person check the installation, once you have signed that bit of paper it takes the responsibility away from them.

I have had sub-mains connected without a switch-fuse after the main fuses,

Think the lesson here is to make the call first

HTH

Exactly that, every area seems to be different. I am also doing a installation in South London with new mains and they have asked for isolators to be fitted not switch fuses.

I have signed a piece of paper which makes this installation my responsability not theirs.

As far as I am concerned what goes on after the meter has nothing to do with EDF which is why I spent hundreds of pounds a year to have my work checked by assessors to make sure everything I do is safe.

Would also like to add that I came on this forum for genuine advice and not to be patronised by some, and I will be the first to admit that I learn something new every day even after 28 years and am proud of what I do!!

 

[Steve1412]

The supply regs do say there should be a fusible switching device as close a practicable to the incoming supply. You should have made them take the supply to your dist board. I have never had a supply guy check the install...the most they ever do is say'"Ow big are these tails mate???"

 

[Spudnik]

Exactly that, every area seems to be different. I am also doing a installation in South London with new mains and they have asked for isolators to be fitted not switch fuses.

I have signed a piece of paper which makes this installation my responsability not theirs.

As far as I am concerned what goes on after the meter has nothing to do with EDF which is why I spent hundreds of pounds a year to have my work checked by assessors to make sure everything I do is safe.

Would also like to add that I came on this forum for genuine advice and not to be patronised by some, and I will be the first to admit that I learn something new every day even after 28 years and am proud of what I do!!

Many DNO's are now fitting 'self connect' switches for the purpose that the electrician can connect the tails without removing seals etc. In fact many new builds have 'self connect' meters which serve the same purpose.

I agree about the installation being your responsibility, however, its their equipment that you want to connect to, so they do have some say in it and that is 3 or 4 meters max for length of tails and anything further must have a switch fuse.

 

[plug444]

I have managed to source an IP65 rated 100A TPN switch fuse which will be fitted on monday to keep them happy. Far cheaper than a MEM switch fuse plus the enclosure to fit it in was enormous. Job done!!!

 

[Spudnik]

Good job bud.

You know it makes sense

 

[plug444]

Good job bud.

You know it makes sense

Was never going to win, lesson learn't and won't get caught out again. Learn something new every day and a bargain @ £200

 

[slocm3105]

Was never going to win, lesson learn't and won't get caught out again. Learn something new every day and a bargain @ £200

Nice one mate. I didn't mean to sound like a bit of an a** in my previous post, just read it back so sorry about that. But good job on getting it sorted

 

[plug444]

Round 2 with EDF. Different meter man turns up today to connect my new supply. Has the usual walk round site checking my bonding etc all OK. Checks my new switch fuse, meter tails etc all OK. Askes what size my sub main cable is to which I reply, 25mm 4 core swa. Askes if I am using the armouring as my main cpc to which I reply yes. Looks at me and says well I cannot connect as the armouring is of insufficient size as I must have a minimum csa of 16mm. I then try to explain to him that the csa of the armouring was calculated and worked out to be more than sufficient for this new supply. He then phones his boss and comes back to me and says not allowed to connect. Asked him if he could give me 5 minutes to prove he was wrong and with that he handed me a failure notice, got in his van and drove off!!!
I have double checked this again using in section 543 using tables 54.4, 54.7 and 43.1 and basically the armour equates to a csa of 70mm in steel which is the equivalent csa of 22.5mm of a copper cpc. A completely wasted day, most of which was spent on the phone trying to get through to someone sensible at EDF.

 

[slocm3105]

Round 2 with EDF. Different meter man turns up today to connect my new supply. Has the usual walk round site checking my bonding etc all OK. Checks my new switch fuse, meter tails etc all OK. Askes what size my sub main cable is to which I reply, 25mm 4 core swa. Askes if I am using the armouring as my main cpc to which I reply yes. Looks at me and says well I cannot connect as the armouring is of insufficient size as I must have a minimum csa of 16mm. I then try to explain to him that the csa of the armouring was calculated and worked out to be more than sufficient for this new supply. He then phones his boss and comes back to me and says not allowed to connect. Asked him if he could give me 5 minutes to prove he was wrong and with that he handed me a failure notice, got in his van and drove off!!!
I have double checked this again using in section 543 using tables 54.4, 54.7 and 43.1 and basically the armour equates to a csa of 70mm in steel which is the equivalent csa of 22.5mm of a copper cpc. A completely wasted day, most of which was spent on the phone trying to get through to someone sensible at EDF.

You shoulda chopped his arms off, an used them to connect it up yourself mate . No talking to them about anything mate they won't understand lol.

 

[plug444]

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!!!

 

[ian.settle1]

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!!!

Regs book will be a waste of time as it only cover your installation and not the supply from the DNO who come under ESQCR regs which they work to, your in a no win situation.

I would just contact them to find out what they want before you get them to site again.

 

[plug444]

Regs book will be a waste of time as it only cover your installation and not the supply from the DNO who come under ESQCR regs which they work to, your in a no win situation.

I would just contact them to find out what they want before you get them to site again.

I know exactly what they want, my sub main cpc to have a csa of least 16mm. I can prove that my armouring way exceeds that so whats the problem with connecting. Easy to say just do what they want but tell the owner that he now has to dig up his newley landscaped garden because EDF say so and make up the rules as they go along.

 

[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