Electric Cooker Disjoncteur rating

[BobDee]

Can some one explain why all cooker points seem to be rated at 32 amps even when the maximum power from EDF is 6KW? I am in the process of updating a 25 year old house and replacing the fusibles with disjoncteurs and doing my best to conform to NF C 15-100. If the cooker develops a fault, clearly the 32 amp disjonc is not going to trip when the incoming EDF breaker is rated only at 30 amps. What is the official situation if I feed the cooker via a 20 amp disjonc. Does this break the norms? The current fusible feeding the cooker is a 32 amp housing containing a 16 amp fuse. The cooker itself has a max power rating of 2.6 kW plus a single top ring of 1.5 kW, making a total max current around 18 amps. A 20 amp disjonc would be ideal here, but what would an EDF man say if it were inspected?

BobD

[Anton Redman]

EDF do not inspect. A seperate body the CONSUEL inspect but only for new builds and major new supply renovations, at present. There is going to be an isnpection like lead, asbestos etc. of the wiring pre sale but not by the CONSUEL  and there is not much feed back about how that is going to pan out in practise.

The cooker needs a independant  6mm cross section feed. The rating for acooker point is meant to support a four ring top and a conventional oven. Hence if it is a dedicated disjointer that is what they are rated at.  I agree with yuor analysis.

[Chancer]

I just checked my installation which I did following the normes and was passed by consuel, I have a 20 amp disjoncteur for the hob and a 32 amp one for the oven.

The 32 amp one is rated to protect the cabling under a fault condition (ie short circuit) and is not rated according to the power drawn by the appliance nor that available, i.e. 6 or 12 KW. The disjoncteurs in the tableau will trip very fast (less than 30 milliseconds I think) under a fault current sgnificantly their rating.

Whereas the the disjoncteur d'abonne will trip at a "sustained" current above its rating but not the momentary fault current that would trip the tableau 32 amp disjoncteur, also the differential function (RCD) has a trip or delta current of 500ma which means that the ones in your tableau (30ma delta current) should always trip first, its a bit of a belt and braces approach which in my mind makes the French system much safer.

I am sure that someone better qualified than me will give a better explanation or correct anything that I have said that is incorrect.

If you doubt whether the tableau disjoncteur will trip first you could always create a fault current[6] but at 32 amps rather you than me[:D]

 

[BobDee]

Many thanks AR and JR for the helpful replies and pointing  out the Consuel error. Just another point please.. Ideal systems seem to require at least two if not three Disjoncteur differentiels to break up different areas of the house or property. Do these devices break the circuit at the same speed as the straight disjoncteur? The present installation has only the sealed EDF breaker (30 amp rating with 500 mA diff trip) with all circuits being protected by standard cartridge fuse holders.  I quite like the idea of splitting the house wiring into 2 with each half being protected by a separate 20A Dis Dif. I dont see any point in putting in say 40A dis difs if the individule breakers would always trip first.

Regs

BobD

[Chancer]

Bob

By all means upgrade your tableau but buy a book and follow the French normes (which are very well conceived when you understand them) rather than folllowing your instinct re "splitting wiring into two".

The disjoncteur differentielles you should regard as RCD's, they will trip when there is an imbalance between phase and neutral (leak to earth conductor or to ground) of more than 30ma, the 40 amp rating is to ensure that they can carry the current demanded by the disjoncteur protected circuits.

In theory I believe that they would trip with a fault current of over 40 amps but in practice this would only be if the disjoncteur failed or there was a short on the busbar.

[BobDee]

J R

I am trying my best to follow the "Normes". I have an excellent book from Schneider that fully describes the new standards and within it shows several typical wiring systems. All seem to split the incoming supply over differing local distributions, each protected by its own disjoncteur differentiel. We only have a smallish bungalow type home and a x 2 split seems appropriate but it also seems that ideally you also split out outside wiring (gates, blinds and external power). Clearly some of this is commercial hype in that Schneider would like to sell as much hardware as possible. I have seen systems where every socket in the house is taken back to its own disjoncteur and others (still quite modern), where up to eight power sockets are fed from one breaker. Quite a minefield, especially when you are just trying to make your own home as safe as possible, but also having regard to a possible future inspection scenario if one wants to sell in years to come. Starting a new build is in many cases, easier than trying to bring a twenty five year old system up to date.

Regs

BobD

[Nick Trollope]

I believe you are confusing disjoncteurs and interrupteurs.

You installation needs a number of interrupteur differentials which is set by the size of the property (and the type of heating) - these are rated at 25, 40 or 63A. This is not a trip rating, but a current-carrying capability. They "trip" when there is an imbalance (the differential bit). A house of >100SqM with electric heating needs 5 of these (minimum). Connected to these are the disjoncteur differentials - as many as the installation needs. These are rated from 2 to 32A and are current-trip devices.

ID's and DD's do very different jobs and are both essential (mandatory in most circumstances).

A cooker outlet should be fed with a 32A DD - regardless of the setting of the EDF breaker, for the reasons that JR states above. A typical large installation can contain 5 IDs and (perhaps) 30 DD's (plus various other control devices), so I'd suggest that your interperetation that Schneider are producing commercial hype is.... specious?

Use an electrician!

[BobDee]

Hi Nick and others.

Point taken, a confusion of terms. I dont think Nick that you mean that every device is fed via a disjoncteur differentiel, Surely just a straight disjoncteur. As far as I can see you normally only use Disjoncteur Differentiels on specialist devices such as freezers, pool pumps etc. This is based on the examples shown in the Schneider Electric catalogue.

My question was given that a disjoncteur differentiel is a combined out of balance detector and current trip device, would using them to feed a series of normal disjoncteurs be allowable instead of an Interrupteur Differentiel? I realise that is not the way to put in a new installation, but what I have at the moment is just twelve fuses fed directly from the EDF breaker.

This property has suffered greatly over the years at the hands of "Electricians" and with out doubt, there a good guys out there but I would like myself to get as fuller understanding of the system as possible.

My background is in radio and computer / electronic engineering and consider myself capable of safe electrical work, but understanding all the French regs is another matter. I have to say though. I am getting a heathy respect for French practices other than the insistance of double pole switching everywhere.

 

BobD     

[Nick Trollope]

Sorry Bob, but either I am misunderstanding you, or you indeed are confused.

Buy yourself a book - L'installation Electrique is one ofthe best and look at the pictures if you can't read the text.

There are ID's (big breakers, earth trip/imbalance detectors) and there are DD's (little breakers, current trip). I've no idea what an "ordinary" disjoncteur is, but I know that you need lots of DDs and several IDs.

The regs are the regs. They are not up for negotiation and you either understand them or you don't - there really is no "middle ground". Also, I can't see why you would object to double pole switching - apart from on cost grounds, of course!

Find yourself a decent electrician! Bear in mind that, from next March, electrical inspections will become part of the house sales/rental package.

[BobDee]

Hi Nick,  me again!

I reckon this is probably a hair splitting exercise and ideally a glass of wine or two is needed to oil the discussion.

Disjoncteur (D?)= Circuit breaker. Viz Legrand 060 20 or Merlin Gerin 16727. This definition from any dictionary or indeed the glossary at the head of this forum.

Disjoncteur Differentiel (DD) = Circuit Breaker with built in sensor to detect unequal current flow in phase and neutral wires. Trips on over current or out of balance current.

Interrupter Differentiel (ID) = Switch that trips on detection of unequal current flow in phase and neutral wires. Does not trip on excessive current.

One of the most useful ways I have found for sorting all this out is to type the words above into EBAY France and see what comes up.. Pictures as well!

I have no problem at all with the "Norms", indeed I am coming to love reading them, but my situation is I am sure typical of so many. An old house that is not unsafe, but not conforming to the standards of a new build. If I want to add say an extra power point (we have been here before), I assume if I call a French electrician in to do this, he will not condemn the existing old but safe installation. He will make the addition using equivalent materials. All the hard ware shops are brimming full of "Fusibles" and complete distribution systems that dont meet NF C 15-100. Someone somewhere uses all this stuff.

On the 2 pole / 1 pole stuff, its just interesting that the old Fusible system only had one fuse in the live phase leg yet both P&N are broken when the fuse holder is pulled. Cant see the logic here. I dont think the UK records millions of deaths throgh commoning all the neutrals together. (Old chestnut here. Best not go down this road!)

Just a point on the forthcoming inspection system. We have just been inspected re our Fosse Septique. Twenty five years old but passed muster with "Not conforming but satisfactory" I suspect a lot of electrical inspections will be the same. How many French houses fully confirm to the new electrical standards? I would guess less than 5%. 

BobD

 

 

[BobDee]

Just a thank you to those you responded to my original question. Through being obliged to dig a bit deeper and noting the comments to my original post, I learnt a lot and will proceed with my upgrade armed with some extra knowledge. Incidently, the Schneider (Merlin Gerin) publication on the new norms is most useful. I think you have to write to them to get it for free.

Regs

BobD

[bejay]

Bob

You are of course quite correct in your definitions of disjoncters and interrupters.

JR is right to say that a that a 32A breaker is used to protect the installed wiring. For a cooker this is a mixture of tradition and futureproofing. Cooker power requirements  can change over the years and indeed in a new property an electrician may well not know what particular device will be connected. Also the level of power supplied to a property can be altered wihin the EDF main switch, Which will trip first depends on the designed disconnection times of the two units rather than the actual current. It should be the 32A trip because it is not a safe situation if the main trip disconnects for a single fault.

For anybody who is familiar with UK electrical systems there are two fundamental differences in the existing French systems Firstly in France the earth systems are the responsibility of the customer whereas the UK system its very largely supplied by the supplying utility, secondly, there is, for good reasons, a very great insistence on observing correct polarity in domestic wiring. This has not been so in Europe.

The French regulations reflects these two facts in their use of IDs and double pole isolation. They have to start from where thay're  at !

bj