Plugging in in Europe

[Collaro]

Sockets in Europe (I am thinking of the Schuko system) allow plugs to be inserted either way around - the earth is in contact by means of metal surrounding "clips".

Thus line and neutral are not strictly adhered to. Note that the plugs themselves are not fused.

Does anyone have any advice regarding how to plug in old equipment safely? I suppose the grounding system used (IT, TT or TN) may have a part to play in the answer.

[Lucien Nunes]

Use a 'Martindale' type socket tester that indicates which pole is live through a pattern of neons, and mark the Schuko plugs of your equipment so that you can engage the correct pin.

Schuko is non-polarised for historic reasons - it was introduced when delta supplies were prevalent in its locale, where both current-carrying conductors are lines and there is no earthed neutral present to impart any sense of polarity. The earthing system doesn't really come into this equation.

[Collaro]

aha. Thanks.
Is it possible to check using a multimeter too?

[TonyDuell]

Yes. Measure the AC voltage between each of the sockets (separately) and the earth clips. One socket will be close to earth potential (low voltage on this test), the other will be close to the full mains votlage. The first one is the neutral, the second the live.

Only try this if you are used to measuring high voltages, though. The mains can be lethal.

[TonyDuell]

Another thing you could do is make a simple tester. Wire a mains neon indicator (the common type with a built-in series resistor) between one pin and the earth contact of a Schuko plug. Mark which pin it's connected to on the outside of the plug.

Now plug it both ways round into the socket. The neon should light with it one way round. In that case the marked pin is going to the live contact on the socket.

[broadgage]

As above, but remember that in fact the supply polarity does not usually matter for portable equipment. When in Rome----!

In the more remote parts of Europe there are probably STILL a few supplies with BOTH poles live. Could be three phase 4 wire at 127/220 volt with the neutral not distributed, or could be three phase, 3 wire with 220 volts between phases.

[Collaro]

Well where I was (out in the sticks in Norway) both caused my ancient neon tester to glow - so it might be that system. When I get back there I will have to check the voltages with my mulitmeter.

I would be curious to hook up an oscilliscope to see the voltage wrt ground from both.

Hmmm.

[cmjones01]

Yes, never trust the polarity of a Schuko socket or of the French type as used here in Poland as well as other places. There are lots of double sockets here which have live and neutral opposite ways round on each of the two sockets! There also exist many sockets which will accept an earthed plug (with thick 4.8mm pins) but which don't have an earth pin, so it's entirely possible to connect an appliance which needs an earth but doesn't get one. Don't get me started on the old 2-wire system where earth and neutral are one wire all the way to the wall socket. Fun if the neutral breaks, for example because it has a joint between aluminium and copper wire attached only with insulation tape. But I digress... Be grateful for the IEE wiring regulations!

Chris

[julie_m]

I thought the Norwegian system was to have a non-earthed neutral, so that touching only the live would not give you a shock since there was no return path to Earth. Except for parasitic coupling along the distribution cables -- which was still enough to deliver an unpleasant surprise.

[broadgage]

In the past much of Norway used 3 phase 4 wire at 127/220 volts with an earthed neutral.
Most such systems have been changed to 3 phase 4 wire at 220/380 volt, again with an earthed neutral.

Some of the lower voltage systems no doubt remain. Note that standard 220 volt appliances and standard 220 volt outlets are used on either system.

I doubt that systems with an un-earthed neutral were ever very popular for public supplies. They have a number of drawbacks including still giving a lethal shock as the leakage currents can be an amp or more over say a city block.

Some hotels use single phase 230 volts with an earthed centre tap so as to give a choice of 115 volts on USA type outlets and 230 volts on European type outlets, for overseas visitors. Such a supply would not normally be direct from public mains, but would use a transformer with a single phase 380 volt primary, connected between any two phases.

[Collaro]

Originally Posted by julie_m

I thought the Norwegian system was to have a non-earthed neutral, so that touching only the live would not give you a shock since there was no return path to Earth. Except for parasitic coupling along the distribution cables -- which was still enough to deliver an unpleasant surprise.

Originally Posted by broadgage

In the past much of Norway used 3 phase 4 wire at 127/220 volts with an earthed neutral.
Most such systems have been changed to 3 phase 4 wire at 220/380 volt, again with an earthed neutral.

Thank you for all the info about the electricity supply in Norway. I will find out what the situation is with the place I have out there.

The bottom line (pun intended ) is, if I plug in any 50s or 60s equipment, how safe am I, and what precautions should I take?

I already see the need to check if there is a line and neutral, and then ensure that the UK plug, through the adapter, is plugged in the correct way around. I also need to be sure that the "ring" I am plugging into is earthed. A lot of Norwegian houses have non-earthed power outlets - essentially for lights, chargers, etc not requiring earth. Unfortunately, plugs which indicate there is an earth connection to be made also go into them, resulting in stuff being plugged in and not being earthed .

[bluepilot]

Originally Posted by Collaro

Sockets in Europe (I am thinking of the Schuko system) allow plugs to be inserted either way around - the earth is in contact by means of metal surrounding "clips".

That's not completely true. German sockets are like that but French ones have a polarizing pin. Modern plugs fit both German and French sockets. The French ones also have covers in the socket to stop you poking things in, unlike the German ones where you have to buy an extra bit to stick over the holes.

[paulsherwin]

Live chassis equipment was intended to remain safe with 240V on the chassis, thanks to physical isolation. Modern safety regs don't consider this adequate but it shouldn't be a problem if the equipment is used sensibly. The usual warnings about young children apply of course.

Working on a live chassis set obviously requires that the chassis be at 0V, or an isolation transformer used.

Equipment expecting a protective earth connection shouldn't be used without one as this can be dangerous in the event of a fault condition.

[Collaro]

Originally Posted by bluepilot

That's not completely true. German sockets are like that but French ones have a polarizing pin. Modern plugs fit both German and French sockets. The French ones also have covers in the socket to stop you poking things in, unlike the German ones where you have to buy an extra bit to stick over the holes.

Yeah, I lived in Prague for four years many years ago and they also use the French system, so the earth forces a particular direction. It leads (another pun )to interesting boxes of bits and pieces of various systems littering my garage and hobby room!


I'm concerned about the German/Norwegian style of sockets which do allow for this rotation, and then possible safety issues with line and neutral interchange.

[julie_m]

French multiple adaptors and extension leads often have some sockets wired with the live and neutral interchanged .....

[Collaro]

Originally Posted by paulsherwin

Equipment expecting a protective earth connection shouldn't be used without one as this can be dangerous in the event of a fault condition.

This probably goes on all the time in Norway!

[G6Tanuki]

Rule #1: don't expect any predictable polarisation regarding which-pin-is-phase and which-pin-is-neutral.

Europeans [and North Americans] are quite happy to build kit that deals with either pin being 'hot' - a sensibility which the UK has been insulated [pun intended] from for far-too-long.

Example: small power-tools shipped throughout Europe with a polarisation-ambivalent 2-pin plug, and a "converter" supplied on a nation-state basis to allow it to be plugged into the local supplies.

http://uk.rs-online.com/web/p/products/8056294/

Some people will bitch that "this can allow the power-switch on the appliance to be in the neutral lead" - but is that really a probbem? In times-past we powered our appliances from 2-pin adapters plugged into bayonet lighting-outlets and the world kept on turning.

Remember that the neutral in the UK is considered a live conductor, assuming it is "safe" should never be done. It's fine swapping the leads round for less hum but not for safety.

[Tractorfan]

Hi,
Indeed, the polarity of French sockets can't be guaranteed despite them having an earth pin. We have some two gang wall sockets, and the polarity is different for each socket.
But French disjoncteurs (MCBs) are double pole devices which isolate completely on fault, as opposed to the UK variety which only break the live pole when they trip. Maybe this is the reason that continental Europe isn't as paranoid about which is phase (live) or neutre (neutral).
Just my two centimes worth.
Cheers, Pete

[Maarten]

Originally Posted by Collaro

I would be curious to hook up an oscilliscope to see the voltage wrt ground from both.

Make sure to use a CAT-rated scope for that or your finds might be quite interesting (and possibly expensive).