Those Frenchies....slightly OT....earth bonding

Let's just say there is no point in expecting UK electrical safety standards anywhere outside the UK.

Christian.

Last French hotel I saw had bare live connections in the room.

However as far as danger goes, deaths per annum from missing bathroom bonding are less than 1 in UK, so its hard to conclude that its a real safety issue.

NT

I once found an interesting situation, on a campsite in the Dordogne. After complaints that "My hairdryer makes a funny noise." I took my multimeter and checked. Earth to pin 1: 220V. Earth to pin 2: 220V. Pin 1 to pin 2: 380V. They had actually managed to get two phases onto the sockets. Fortunately there were some sockets without an earth pin which were at 220V.

I decided that, since my technical French was about as advanced as I presumed the proprietor's grasp of vector theory to be, there was little I could do, besides keep well clear.

Chris

Bonding - Its what happens when the cable manufacturers are given a place on the wiring regs commitees. Hands up those who remember all the bits of green yellow on show after the 15th edition came into effect I'll bet the copper sales went through the roof around that time.

Why would a little fact like that stop the ODPM introducing a whole suite of extra building regs ? Expect the Federation Of Bathroom Earth Bonders to have exclusive rights to self-certifying such connections.

A friend in France has a new, single phase 18 KW supply and it came with a 500 mA master RCCD - not sure how much protection that gives against unpleasant shocks !!

Nick

None, it's to protect the wiring not the user.

It isn't designed to. It is purely to provide disconnection in the event of an earth fault where the supplier can't guarantee a supply earth of sufficiently low earth loop impedence. In this situation in the UK, we tend to fit a 100mA time delay device that is guaranteed to discriminate with any immediate action 30mA devices on the circuits themselves. However, I can't see why a 500mA time delay device wouldn't comply as well, except that they're probably difficult to get hold of and it means that your earth rod has to have (and maintain) a lower impedence.

Christian.

It also protects the user from shocks resulting from indirect contact.

How do you reckon that then?.....

See the much longer post after mine which explains it more fully.

Funny but for some reason I didn't receive that post!.

Its still somewhat debatable as to does it actually protect the wiring. Assuming that theres a live-neutral short then it wouldn't be able to do anything about that.

Assume a neutral-earth (supplier provided) short then that's really not a problem but the only fault situation is a live-earth short but if the earth itself is duff then the local earth is going to rise to "whatever" voltage above earth, so yes the RCD would trip but the wiring would hardly be affected, the supplier fuse should then rupture provided sufficient current flows ands of course the supplier fuse must be there in case of a live-neutral short.

So seems to me to be a bit pointless really?.....

The problem is that a short circuit between live and earth would not produce enough to blow the MCB, as the earth loop impedence is too high to draw enough current. Unfortunately, the current is likely to be large enough to cause wiring damage in the immediate vicinity of the short circuit, which is likely to get very hot as the short circuit connection is unlikely to be very solid.

Also, it limits the period at which elevated voltages appear on the local earth. If there is no RCD device and poor earth loop impedence, the installation earth potential will rise to line voltage.

Christian.

In article , Christian McArdle writes

Well this seems to be an odd way of going about power supply. So if there is a fault and the earth rises above what it ought be, then surely on that circuit, fault side of the consumer unit, there should be a fuse or MCB that will protect the wiring thus affected?. Using an RCD is a very strange way of going about it...

Well yes it could, but this isn't a wiring protection issue, this is a safety angle now and a 1/2 amp RCD isn't my idea of safety.

Anyway we've just bought a French gaff so that's one thing on the check list for starters!, and No I didn't inspect the place she did when SWISNTGOINGTOBEOBEYED signed up for it.

I said when your over there, just get some particulars on some places not buy the bl**dy place!

But that's another story...

But the current drawn may be below that of the circuit rating, so a fuse or MCB is not appropriate. Instead, an RCD is used.

But the 0.5A RCD is to replace the protection offered by the circuit MCB for earth faults. Surely a 0.5A RCD is safer than a 32A MCB when it comes to protecting against earth leakage?

Should additional protection against shock be required, then the individual circuits (or a group of them) should be protected by 30mA RCDs. This is a separate issue. You certainly don't install whole installation 30mA RCDs any more, as they are more dangerous than no protection at all. However, given the choice between a 32A MCB and a 0.5A RCD for earth protection on an installation with poor earth loop impedence, I know which I would prefer, particularly if the 0.5A is time delayed.

Christian.

In article , Christian McArdle writes

So the wiring can't handle the current that the MCB is rated at?...

Odd way to go about things..Still they are French;(

Debatable but if i were to be in on the receiving end I'd prefer a 30 ma one thanks..

What in case the lights go out?..

Still seems rather poor engineering anyway. Having just bought a gaff in France, I'll check this out!...

It is the area that is short circuiting that can't cope with the current. That area will be very hot and a probable fire hazard. The general circuit cable in good condition will be fine.

The same principles inform the UK regulations. In the event of a short circuit between live and earth, a protective device should operate. In the event that the earth provides a bad path for current such that the short circuit won't be enough to operate the MCB, then an RCD is used to measure the actual earth leakage. As earth leakage should be low anyway, it can operate at a much lower level than the circuit MCB, which has to pass genuine current too.

The system that you described would pass UK regulations, provided that the RCD had a time delay and certain specified circuits had 30mA RCDs.

Christian.