French Wiring Regulations-Residential Installation-Single Phase,240V AC Supply

We are currently upgrading and modernising the electrical installation in our 1960 French house. We started by replacing the fixed fuse box (two separate units in different downstairs locations with GE consumer units each with a bank of 8 MCBs and RCD. The house is on three levels, the attic rooms proved to be quite straight forward as a completely new set of power and lighting circuits could be installed and are compliant with French regulations, ie cable sizes, trunking protection, legrand socket outlets and switches. The second level is more problematic, as existing cables for lighting, power mostly run under the landing floor within the aperture of hollow blocks and concrete beams. The floor surface above is Italian marble slabs, in perfect order. Below, the ceilings are mortar.

On inspection, the existing cables which lie within the first floor cavities (below the marble floor) have a pvc outer coating with a metal sheaf as armour, and are either 2, 3 or 4 cored solid aluminium stranded conductors, the individual cores are either 1.5 or 2.5mm diameter dependent on use). Although the cables are in excellent condition along their length, where the individual strands emerge for joints to CUs, switch units, sockets, etc the rubber/pvc insulation of each stranded conductor has completely disintegrated with age, hence the need for repair or replacement. As there are at least 6 or 7 individual cable runs within the landing floor it has proved difficult to extract them as they are firstly very stiff and don't bend easily, and also have been jammed between blocks and fissures when the house was built so will not withdraw. We obviously don't want to run the risk of compromising the support to the marble floor above by hacking away at the ceiling below to gain access.
Has anyone had experience of whether it is acceptable to leave this type of cabling in situ, whilst upgrading all other circuits in the house? Also, is their a definitive set of French standards which say what is acceptable and what isn't acceptable based on technical limitations with solid core aluminium cables? Asking French electricians is one way forward, but the answer will more than likely be subjective and may be guided by financial consideration. Surely this type of cabling is widely used in French houses of an equivalent age, so any input/guidance is greatly appreciated.
John & Fiona

Can't answer you question but your GE consumer units 8 way? Sounds UK? UK breakers are single pole, French Normes are double pole.

Thanks for your reply John. I have actually double checked each CU. There are in fact 9MCBs and one RCD in each of the two CU boxes. There are all double pole as per the french norm.Perhaps you misunderstood my terminology regarding 8 way. The boxes were in fact fitted by a french electrician. Thanks once again.

No worries Fiona, just checking. There was an English guy not far from me who installed UK (CE marked ) CU's don't think the box is the issue but filled it with single pole breakers.

Hopefully someone with more in depth knowledge will answer your question as i would like to hear the out come to.

You don't say if you are planning / hoping to use the old cables again. Yes leave them in situ, cut them off at the ends, and push down into the floor and a smear of mortar over the top. Run your new cables on the ceiling in mini trunking or corrugated conduit if you can hide it and drill up to connect to the fittings. I wouldn't recommend using them again. You answered your own question really.

'the rubber/pvc insulation of each stranded conductor has completely disintegrated with age, hence the need for repair or replacement'

My understanding is that if you're doing a 'complete' renovation the elec installation will have to be inspected and passed by the Consuel, for a fee, before you can connect up and will have to be 100% up to the latest normes. However, if like us you're only doing a partial renovation that doesn't need an inspection before you reconnect then you can legitimately get away with parts of the installation to the older normes, which presumably the aluminium conductors met (or maybe still meet for specific applications).

However aluminium does not carry the same current for a particular size of conductor as a copper one, and the standard sizes of 1.5 for lighting and 2.5 for power will not carry anything like as much current as copper for the respective uses. So number of points per circuit would have to be significantly lower than in the normes for copper and, as you've noticed, it is much stiffer than copper so tends to be brittle and crack. All these give rise to fire risk and perhaps overloading / overheating is what's caused disintegration of the insulation where it emerges in a fitting. (This was the cause of our bare wires feeding the old main fuses we had here.)

Aluminuim is still used and cables are still sold here to the current norme codes - eg. Cable U-1000 AR2V but they are mostly huge sizes for major power distributionrather than domestic installations.

(Ours is 3-phase 18kVa 400V split into 3 separate 230V single phase subsystems around the house and outbuildings - balancing nightmare, and the commune electricity supplier refuses to update and improve the supply feed, including the currently non-norme position of the first main switch, even if we pay for it all!)

I've not found a readable definitive list of all the acceptable possibilities of the elec normes, but rate the best (imo) book on the subject, 'L'installation électrique' by Gallauziaux & Fedullo. They don't mention ally - though they do say 'généralement en cuivre' - generally copper - so presumably other metals are permitted, though I've never met aluminium and personally wouldn't trust it.

A key point may be whether all the runs have earth conductors included. I've had to run earths to all my upstairs sockets as they were all 2-pole, but fortunately they're all fed in reasonable size gaine from the loft down the walls in copper that will meet the current normes. If you've got to get new earths to all the points you'll need to start again on that floor anyway.

Sorry, but I think you'll have to bite the bullet and find a way of replacing it all. Good luck.

Well, I would ask both a French Electrician(s), and (if you can) a 'qualified in France' Brit Electrician, that way you will as it stands if it is safe.

Must admit to not being familiar with Aluminium cabling for Mains, are you sure its Aluminium all the way through and not just tinned at the ends ?. Was 'Armoured' PVC coated Aluminium cable available in the 60's, especially solid core stuff ? 2.5mm (better known as 5mm csa) depending on installation, can easily carry up to 40Amps at which point I would have thought it would be getting quite warm.

Alternatively if the under floor cabling is a later fitment, is it possible to find who fitted it and why. They might also have a plan of the cable routes and sizing (although that's somewhat optimistic).

Not wishing to upset John, but as I understand it an installation that has been properly designed, installed, and fitted with single pole breakers will be totally safe and work fine. The (French electrician installed) system I inherited used single pole fuses with common neutral and earth rails, and ran without issue. It was just such a mess with the likes of Yellow/Green earth cable used for the incoming mains feed to the fuses that demanded I upgraded it.

The problem in France (and certain other EU countries) is that they can connect anything to anything, use any colour going, and hopefully won’t kill anyone, hence double pole breakers can then come into their own as a safety essential.

All that said, please consult an approved electrician.

We both would like to thank all those who have replied, and there are some very useful points which have been made. In partiular, the technical reference provided by Rhys Williams is a definite purchase in the near future. Our main worry has been to determine whether the old cables will actually need replacement, bearing in mind the amount of labour/cost involved. An ex french electrician who has worked in industry identified the type of cable as one which is routinely used in plant/industrial applications rather than domestic. Whilst we were closely examing the exposed ends of one cable previously removed, we removed the oxidised layer of the core and to our amazement a bright copper lustre appeared. So now the buried cables can remain in place and are up to norm, if not above norm due to their mechanical protection. In switch boxes, within the CUs and in wall sockets where the core insulation has degraded, these sections can be cut out and replaced with new 1.5 size as appropriate. We think the hold up and confusion as to how to proceed safely with our project is now substantially resolved and just would like to thank once again all those who offered help and advice. J&F

Glad it's turned out better than you expected Fiona.

Tony not going to get upset except by my own wiring mess that I have inherited. It's on old cartridge fuses, so the same as yours single pole fuses cos you can't have a double pole fuse unless you have two fuses on each circuit. The NORMES are for double pole breakers, yes the UK have single pole and its safe. Funny how the UK and Germany are the only countries that have embraced the EU spec cable harmonisation (colouring). I am not normally phased going into a consumer unit (pun intended) but I alwas take a deep breath when I am at the French house.