New CU and EDF + Part P

Hi,

The House renovation plans progress... I've been examining possibilities for siting the new CU I'll be installing (which will be BNA'd along with 6 million other notifiable small works). Been busy reading up on the 17th and testing procedures in readiness.

Part of this may involve asking EDF to install a supply isolator and move the tails.

I heard a rumour that EDF are in the habit of asking for an EIC *signed by a member of one of the approved bodies*.

Seeing as an EIC is required for alterations and changes which exceed minor works, and an EIC can only be signed by the relevant designer, installer and tester (ie noone else apart from me, with the possible exception of the tester) - doesn't this rather contradict Part P notifiable work via the Building Control route?

I don't have any problem providing an EIC as an unqualified person (in fact it is becoming a point of pride to make sure I do everything correctly to the 17th), but if EDF won't accept it and no-one else can do it, then I'm stuffed.

Anyone had any experience of EDF moving or reconnecting the supply under similar circumstances?

It sounds like nonsense in principle as what happens if there is a sound supply but no EIC (so more than half the properties in England I imagine)?

There are work-arounds...

1) I could work live on the existing henley block. It's not something that fills me with joy though having seen pictures of burns victims. But I wouldn't have to involve EDF. However, apart from it being inadvisable, the henley block is in a less than ideal location.

2) Pay a NICEIC/etc sparks to wire up a CU with one 20A radial "site supply". Not so daft, as I'll be working of a site supply initially until I get all the old cabling stripped and walls chased. But it gauls me as I've already paid the BCO the BNA fee.

3) Be naughty and pull the DNO's fuse. That however gives EDF an excuse to get involved and I still have the issues in (1) regarding the henley block.

Any advice before I open the can of worms by phoning their networks division on Monday?

Many thanks,

Tim

Reply to
Tim S
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Yes, they didn't even glance at the certificate.

If your installation looks right then I think that's what you can expect, if it looks odd the expect rules an regulations.

Reply to
dom

That's what I did. Shortly afterwards the meter was replaced (as it had been in for 15 years -- was new in 1954) with a digital one, and the fuse was re-sealed. No comment was made.

Reply to
<me9

I just pulled the fuse to change the tails from my meter to the CU. No meter reader has ever commented, and I don't think it's been re-sealed in 5 years.

To be honest, I don't think they care if you mess with the fuse / seals on the meter connections. Now if you mess with the seals on the meter *case* that's a different matter. There's no legitimate reason to do that.

Jon.

Reply to
Tournifreak

There is if installing a new CU and the tails ain't long enough.

I think the supplier would look at extremely low usage before taking any action if they saw seals tampered with and suspected dishonesty. The types who do this aren't going to be satisfied with a normal size bill. ;-)

Reply to
Dave Plowman (News)

Dave Plowman (News) coughed up some electrons that declared:

Thanks for the replies so far. Having looked at the model EIC in the back of the 17th, it's not going to be hard to complete one in an unqualified way, especially if it has one final circuit comprising 20 radial to a double socket!

I'll do an EIC for the final installation, but unless I've managed to gain a

2392 by then, I'll just attach the PIR that BC arranges to it as verification of testing.

I'm looking out for a multifunction tester presently.

We'll see what they say when I ring EDF's networks division on Monday.

Not too happy breaking seals as it gives them an excuse to be difficult later, but if it transpires that they're going to be difficult anyway, I'll probably live-work to the current henley, very very carefully with appropriate precautions. So much for safety... The state of this country is serious starting to annoy me.

I'll post their initial response back here.

Cheers

Tim

Reply to
Tim S

If you're buying new I'm quite happy with my Dilog which was significantly cheaper than the Fluke and Megger equivalents, does what it says on the tin, is calibrated (though the calibration tolerances are enough to drive a coach and horses through so it's no precision instrument) and comes with a free one/two-probe tester which I've seen badged by Fluke for best part of ton elsewhere.

Reply to
John Stumbles

Temporary supply? You do know that they won't give you PME for that? It will need to be TT'd.

And that the IEE/T have downloadable forms:

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Reply to
Andy Wade

Andy Wade coughed up some electrons that declared:

Do you know the reasoning - it seems non obvious?

Basically, the plan started as having the new CU in the correct place, fitted with incomer and one or two RCBOs, from which a temporary (in the common use of the word) fixed installation was made feeding literally one or two 13A outlets via surface clipped T&E to run power tools.

All the chasing and box sinking would be done in one hit, then each final circuit would be added. As soon as the ground socket ring was completed, the temporary RCBOs would come out and the ways used for permanent circuits.

Does this class as "temporary" in the context?

In the worst case, I can use the current CU to distribute a couple of temporary circuits, and have the new CU ready with at least a couple of permanent final circuits (most sockets and lighting downstairs), but I was hoping to clear out all the old crap at the start of the job.

Thanks - I did know the IET had them somewhere on their website, so thanks for the link.

Cheers

Tim

Reply to
Tim S

Tim S coughed up some electrons that declared:

Forget that bollocks, it's late and I drank beer and typed without reading.

PME as in TN-C-S, then I presume the reason is the same as no PME to outbuildings: certain supply faults may produce significant PD between the PME earth and local true earth. I can see that being an issue with a site supply, in the usual sense of the word, ie a muddy field full of builders and building going up.

This would be a minimal fixed installation with a short expected lifetime in an established dry building.

This is one of the things I have to check - I'm hoping it's a *good* TN-S system (it's not overhead wires, so I have a chance, but supply head was replaced 10 years back and I've heard EDF like TN-C-S). A good question to put to EDF on Monday.

Cheers

Tim

Reply to
Tim S

John Stumbles coughed up some electrons that declared:

This one?

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dilog's website is partly knackered so I can't download the manual (if I could anyway).

Do you recall if the supplied test leads are fused?

The freebie volt tester is worth having. It's on TLC's website so I'll nip into my local branch and see if they have one I can look at.

Cheers

Tim

Reply to
Tim S

And - key point - no main bonding present, possibly because the water and gas pipes aren't yet in place. I guess that if you have the main services bonded and aren't going to disturb them then they should be able to give you a TN-x earth, even though the final circuit arrangements are temporary. You'll have to ask them, but don't be surprised if they say "no, it must be TT" because what you're proposing isn't on their standard menu of supply types.

In any case it's no big deal. When I re-wired here I knocked up a temporary supply board - four old surface mount double sockets, a 1-way Wylex switch-fuse with 30 A fuse and a 30 mA RCD. The temporary earth was a length of 22 mm water pipe bashed in the ground and brought in via a hole drilled in a wooden window frame. Eastern Electricity, as then was, were quite happy to connect this. As rewiring proceeded I temporarily teed off the temporary tails to feed the new CU. When ready for proper connection of the new tails I removed the makeshift feed arrangement, left my test equipment lying conspicuously about and called out 'the board' again. They connected the new installation up, including TN-S earth, with no quibbles or awkward questions at all.

Reply to
Andy Wade

I would also look at the Megger MFT 1552 for about 60 more, it is well regarded and might have a better resale value later.

Fused test leads are worth it, and typically quite expensive.

Alternatively, you could hire a meter when ready and spend the saving on going all RCBOs or a triple RCD wide CU.

-- DB.

Reply to
dorothybradbury

Andy Wade coughed up some electrons that declared:

Thanks Andy. Round at the house again today. Strewth, the state of the wiring in the roof spaces - mice have been busy, not surprised the lighting circuit failed given various bits of 1mm and 1.5mm that have been munched through. Yes the relevant fuses are removed...

I digress... A third option would be to have the CU by the front door, where the wall sets back 20mm and build a wiring cupboard to enclose it. Get EDF to relocate the supply head and meter there. I'll ask them how much that'll be (not cheap I know) but looking like an elegant solution. People expect CU's in halls, the ceiling accesses probably the best bit of roof void for wiring and a floor-ceiling wiring cupboard would leave plenty of room for SWA termination, from cables going outside. I'd put a duct in leading to a pit outside for future expansion.

Ah, the endless choices available when fixing a knackered house.[1]

Couple of questions:

1 Are there any issues with a main bond around 15 meters long to reach the gas and water incoming services from the proposed MET position? I assume it is sized to achieve a certain impedance? (Haven't got that far through the wiring regs yet). 2 Are there any restrictions on the flammability of a board the CU + accessories are fixed to. I was thinking of lining the back of such a cupboard with ply? I know there is an issue with old open backed equipment.

BTW, did you bother with a 100mA time-delayed RCCB for your temporary TT system (bit pointless with a single final circuit I know).

Cheers

Tim

[1] On the plus side, SWMBO and I thrashed out the design mods to the rest of the house this afternoon. Practically ready to see the BCO now, who was most amenable to a personal chat pre-BNA when I spoke to him last week. Interesting to see if he puts the kibosh on any of our plans...
Reply to
Tim S

Building control may wish to see the installation form time to time but in all likelihood, they'll simply ask to see the EIC. They may ask if your part P registered. Make it clear that you know more than the BCO about domestic electric installation, and wave the test results under their nose. The important thing it to emit all the signs of competence, becaus that is the reality.

AKAIK there is nowhere on the EIC which requires that a "guild" registration number is written down. [1]

So get yourself the right test gear and complete the EIC and sign it, obviously you'll be designing, installing, inspecting and testing it yourself.

If the incomer and meter are in a suitable place then you won't even need to bother EDF. The only way EDF will need to be involved is if you are wanting the incomer, cut-out and/or meter relocated.

[1] This is different to say a Gas Safety Certificate or Boiler Commissioning Page.
Reply to
Ed Sirett

Hi Ed,

Ed Sirett coughed up some electrons that declared:

At the moment, there's a lot of flux in the plans. As the plans for the electrical systems stabilise, I'll be doing a formal design which I plan to hand over to the BCO. Essentially a page for each final circuit, demonstrating that grouping, derating factors and calculated loop impedances are tolerable for the chosen cable CSA. Another for earthing/bonding arrangements and one for submain and protection, if relevant (I may be happier getting an engineer's opinion on that, akin to a beam calc for structural work.)

Concur, I've had a good look.

This is the floating in the ether. Right now, I have a weird arrangement. ASCII art time:

Roof ============ Soffit line ====================== | | | | Side Wall | | | | < 2" plastic pipes | | | | < carrying final circuits | | | | < into roof space -------------- -------------- | EDF box | | | | | | Main CU | | Meter |-------| | | | Tails| Henley | | |-------| | | Supply | | Random | | Head | | Extra Fuses| -------------- -------------- | |Main |Incomer | | | | | Ground

I'm not sure why the CU is outside, not something I agree with irrespective of regs.

So, Options:

1) is new CU inside house behind EDF box. Not the best siting option and EDF needed to move and extend tails in order to lose external CU box (it's a genuine 2nd EDF box bought off them by the previous occupier). Otherwise I could run new tails from the current henley, not so neat because I've got an entire meter box for one connector block.

2) Move supply round by front door. EDF are quite good at moleing without vast amounts of destruction, but it's gonna cost me, a lot I would think. At the technical level this is the best solution. But it's also the option that probably gives them most scope to whine.

3) Put the CU where I want and run a BS88-2 fused submain with switch-fuse and SWA terminator box in 2nd cabinet. Looking like 25mm2 SWA will be required, absolute minimum and that's hellishly heavy stuff, especially in 3 core which I may well need to keep loop impedances low. I've done the calcs for the submain vis-a-vis BS88-2 in isolation, but I really need to do some worst case final circuit calcs to make sure volt drop and tripping times at each level remain in spec. Can keep EDF fully out of the loop, legitimately which is a bonus. Technically, is either a prudent alternative to moving the supply head or a very involved way to avoid technicalities.

Think I shall be free and frank with the on Monday WRT to it being a building control job. They might be OK about it, we'll see.

It's embarrasing. SWMBO formed a kitchen and 2 bathroom plans in a 10th of the time it's taking me to decide where to put the CU. :~|

Out of interest, what happens if one has a boiler with no Commissioning page. Is this a "gas thing" or a "Part L" thing or both?

Cheers

Tim

Reply to
Tim S

snipped-for-privacy@dorothybradbury.co.uk coughed up some electrons that declared:

That looks like a nice instrument, 1000V test which I heard is useful on pyro. I saw some issues with tripping 6A MCBs, although it's apparantly fixed via an upgrade: something to note if buying second hand.

I think this is a test instrument I'd like to own. The wiring will not be completed in one sitting - various extra (external) circuits will be added later.

I am going to use RCBOs throughout. Considering SPSN (DP) modules and a suitable board with L/N busbar - neatens it up a lot not having all the neutral tails and DP isolation is nice, though not required. MEM do such a board, but only to 8-ways - at this rate I'll need two stacked - upto around 10-11 final circuits.

If anyone has any recommendations for a CU, I'd like to hear them.

My primary considerations are:

1) Lots of space, no cramped wiring. 2) RCBOs that have visual indication of earth trip vs overload trip. 3) (Nice but not essential) DP board 4) >=14 final circuits, preferably off a single incoming isolator.

Cheers

Tim

Reply to
Tim S

No, provided that the route is sensible wrt mechanical damage of the conductor, etc.

No, sizing is all on CSA: not less then half the size required for the earthing conductor for TN-S, or according to Table 54.8 for PME. The latter sizes the bonding as a function of the supply neutral size - 10 mm^2 for a neutral not exceeding 35 mm^2 covers almost all domestic supplies.

There is a /recommendation/in GN3 that the measured resistance when tested for continuity should be < 0.05 ohm. That allows you 27 m of 10 mm^2 copper at 1.83 milliohm/m without any controversy.

Not for modern equipment which is all totally enclosed.

That's n/a - there were no fixed equipment circuits, only sockets for which a 30 mA fast RCD is required.

Reply to
Andy Wade

Andy Wade coughed up some electrons that declared:

Cheers Andy :)

Reply to
Tim S

Have you considered using 25 mm^2 split-concentric service cable (BS

7870) for this? It's smaller and more flexible than SWA, has a 16 mm^2 copper earth and doesn't need big brass glands. It's commonly used for service distribution circuits in blocks of flats, from a common intake or meter room to the individual flats.
Reply to
Andy Wade

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