Neutral 240volt switching in France

[Speedy Builder5Participant @speedybuilder5]

Apart from wanting to be different, why would older 240volt domestic installations switch the neutral line and not the live line.  This means that lamp holders stay live whilst changing bulbs, most sockets were not and now mainly not switched although modern standards require the live to be switched.

Bob

[BazyleParticipant @bazyle]

Converted from an earlier pre national grid system where neither was earth perhaps. I think the USA 120v is also balanced so both are live but not enough to kill you quickly.
I was caught out with my school electrics in a turn of the century house perhaps initially wired for DC where there was a fuse on each side so depending on which fuse went it might all be live….

[Another JohnSParticipant @anotherjohns]

Bazyle; North America, 240v (approx) comes in, but there is a “centre tap”.

This “centre tap” is ground. At the circuit breaker panel, is where “ground” is. From the panel, there is available 120v and 240v. White wires are tied to ground at the panel. Black wires go to the 240v input from outside. Green (or bare, uninsulated) ground wires also go to the ground at the panel.

The service to the house has 2 black wires and 1 white or uninsulated ground; 3 wires come in.

So, from the circuit breaker panel you have 2 black wires, 1 white and 1 ground. The white is “Neutral”; tied to ground ONLY at the circuit breaker panel.

Across the two black wires is 240v (approx). Taking 1 black and the white gives 120v.

Appliances like clothes dryers use 240v. I believe our air conditioner is also 240v.

There should never be any current on the green ground wire, unless there is a wiring issue.

Written pre-coffee, so hopefully this makes some sense!  JohnS.

[OldironParticipant @oldiron]

From what I have seen from the French penchant for dangling wires across rooms to lights and down the side of door jambs nothing surprises me about French wiring.

Extract from DIYNOT forum maybe relevant  https://www.diynot.com/diy/threads/phase-and-neutral-france.599383/ 

“There really isn’t a rule on live – neutral – in sockets – a vaguely followed standard is a better way to view it in France. If it’s a modern installation it will be both RCD protected and double pole MCB”

[Speedy Builder5Participant @speedybuilder5]

Getting back to neutral switching, would switching the neutral produce less of an arc on make/break than Live switching ??

[Speedy Builder5]

On Speedy Builder5 Said:

Getting back to neutral switching, would switching the neutral produce less of an arc on make/break than Live switching ??

No, the neutral line carries the same current as Live, so sparks and arcs will be the same.   There’s nothing clever going on in a system that switches neutral.   It’s either a design flaw inherited from an old wiring scheme, or a mistake in a new one.

I think Bob has heritage electrics!  As only two wires are needed to supply electricity, that’s all most early distribution systems provided.  Both wires were ‘hot’ and there was no earth or neutral.   Therefore either side can be switched to control the appliance, but both have to be disconnected to make it safe to work on.

Although two wire systems work they’re inherently rather dangerous, and the large number of accidents as the system rolled out eventually forced a rethink during the late 1930s.  Two wire accidents ranged from hurty tingles to death by electrocution, not just in the home, but passers-by being zapped in the street by high-voltage faults.   And many, many electricians were caught out by two wire shortcomings, not just ordinary folk.

The answer was earthing, which improves safety a various ways.   For example, earthing one side of an AC two wire system creates a neutral return, which is safer in that merely touching it isn’t enough to cause an accident.    But earthing requires 3 expensive wires, and because these can be arranged in various combinations, what the consumer gets depends on where he lives!  The US system is not the same as the British system and both differ from the French system.   Therefore DIY electricians in the UK should avoid US based youtube advice and vice-versa.  JohnS helpfully describes the US system above:  not how British homes are wired!

A further complication is the world didn’t introduce earthing overnight and then ‘best practice’ varied over time.  On the ground today, one is likely to find a mish-mash of old and new, depending on the age of the installation and locale.   The UK is moderately aggressive at forcing change, other administrations much less so.   It appears the French retained their original 2-wire system longer than most, and then allowed it to run in parallel with the new.   Seems modern 3-pin sockets can replace ye-olde 2-pin sockets without earthing the third pin!  Very bad in my opinion because it creates the impression the consumer has the safer earthed system, when he still has the risky original, yuk.  Presumably done to appease those who hate being told by government to spend private money on what’s good for them!

I suggest Bob test his home with a French mains tester. Important to read the French instructions, because I it’s unlikely the average Brit will know what to expect of a French system, especially one that might be antique.

Possibly, Bob’s home was rewired to current French standards, but the work done badly.  Perhaps the wires in the wall are good, but live and neutral are reversed in the socket or at the consumer unit.

Can’t help with what should be done in the event Bob finds his electrics are imperfect!  ‘Do nothing’ is always an option, as is ‘fix it when opportunity arises’.    Having a heart problem would make me more inclined to upgrade sooner rather than later!

Dave

 

 

[Speedy Builder5Participant @speedybuilder5]

Thanks for that Dave, I came across this “neutral” switching whilst removing unwanted lighting circuits in a friend’s “pig stye” before demolition.

For my own home installation, I installed all circuits to the French norm NF-100 (Now revised to NF C 15-100) and had to have it inspected and certified before final connection to the meter. Note the number of sockets / lights maximum on spur circuits (ring mains not allowed). One of the more festidious parts of the inspection was to test earth connections to all taps, sinks, radiators etc and the lightning detection and “shorting” to earth equipment.

Its a 3 phase implementation and although it passed inspection, the 3 gang switch at the foot of the stairs had 2 different phases within the box (and subsequently changed).

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