Universal Mains Sockets - A Warning!

A service of PlugSafe

Lengon

Universal Sockets are fundamentally unsafe! 

Since Britain introduced the first mains sockets in the 1880s their use has spread around the world, and many countries have adopted sockets which are appropriate for their own electrical systems.

One of the frustrations of modern travel is the many different mains sockets now in use, but that is not going to change any time soon.  The cost and inconvenience involved in changing the electrical infrastructure of a developed country would be too great to be tolerated by its citizens, and far outweighs the inconvenience to the traveler.  The IEC is the world standards body responsible for coordinating electrical standards.  For many years the IEC attempted to find a solution to the problem of incompatible plugs, but in the end all they could do is to develop a standard for yet another new type!  The safety issues of trying to make one socket accept many different plugs were too great to have a practical solution.  The new standard, IEC 60906-1, has so far been adopted only by South Africa who will phase it in over many years.  Brazil adopted something similar, but failed to make it compliant with IEC 60906-1, totally missing the point!

In a misguided attempt to solve the problem, far eastern entrepreneurs have developed various non-standard so-called universal sockets, but they have failed to understand why this is not safe.  The example above is one of these which has been withdrawn from UK sale as having a serious risk of electric shock.  It has two sets of socket apertures, the pair at the top are intended for two pin American and European plugs, the centre and lower apertures are intended to accept various three pin earthed plugs, including UK, American, Chinese, Australian and, apparently, the 5 amp BS 546 plug which is still used in many countries.  There are many other types on the market, but all are a very bad idea! Here are some of the reasons why: 

Voltage:  A fundamental reason for not using a single plug type is that there are two very different mains voltages used in the world, the European voltage is a nominal 230 V, the American voltage is a nominal 120 V, other countries use one or other of these.  International standard IEC 60884-1 requires that a plug intended for one of these voltages may not fit into a socket intended for the other.  Universal sockets do not comply with that standard.  Plugging a 120 V appliance into a 230 V socket may result in a fire!

Polarity:  A normal mains supply consists of ‘earth’ (or ‘ground’), which is a safety connection for exposed metal parts (such as the casing of white goods); ‘neutral’, which is at approximately 0 V; and  ’line’ which is at 120 V or 230 V.  Both ‘neutral’ and ’line’ carry current, and are referred to as ‘live parts’.  The UK and the US both use polarized plugs, but whereas the UK line connection in the socket illustrated is at bottom right, the US line is at bottom left!  A switch fitted to an appliance is often in the line wire only, so it is important to make sure that the right connection is made.  Universal Sockets have the terminals marked for UK polarization, meaning that it is incorrect for some other plugs, including US plugs.  (The US also uses polarized two-pin plugs, with the neutral pin wider than the line pin, but universal sockets often accept these in either aperture, negating that safety feature as well!  Sometimes both apertures are too small to accept the wider neutral pin.)

Access to Live Parts (Plug pins):  UK plugs (and some others) have partially sleeved line and neutral pins to ensure that the metal cannot be touched when the plug is partially engaged.  Other plugs, such as the German Schuko, rely on the plug being inserted into a recessed socket.  (See picture, far right, of a Schuko plug in its recessed socket, note the side earthing contact in the upper socket.)  As universal sockets can have no recess there is nothing to prevent touching an unsleeved line pin on a partially engaged plug, as demonstrated by this Schuko plug in the Lengon socket.

Schuko recessed
Schuko in universal

Earthing:  UK and US plugs, as well as many others, use the third pin for earthing, however the German Schuko plug uses a side contact, and the French plug uses a pin projecting from the face of the socket, clearly neither of these contacts exist in a universal socket (the presence of either would prevent other plugs being used) so although the universal socket will accept both French and German plugs, neither will be earthed!  (The picture above clearly shows the side contact making no connection.)  In the event of a fault this is potentially lethal.

Access to Live Parts (Socket Contacts):  The live pins of American plugs (and some others) are closely spaced (12.7 mm centres) when compared to UK plugs (22.2 mm centres).  The overall width of a US plug is normally in the range 22 - 25 mm, the minimum distance between the edges of socket apertures to accept a UK plug is 29 mm, thus it will always be the case that a US plug inserted into a socket which will also accept UK plugs will leave the socket apertures dangerously exposed on either side.  This  allows plenty of space for a child to poke objects such as this paper clip into the live contacts

Note also the voltage rating tag on this American cord, as is normal for this type it is rated at 125 Volts only.  It is not suitable for connection to a 230 V socket!

If you want to use an American appliance which is rated for use at 230 Volts also, make sure you use a power cord suitable for 230V.

US plug in universal

Fusing:  The system of wiring used in the UK (called a ‘ring circuit’) includes 32 Amp protection for the fixed wiring and requires that there be an appropriately sized fuse in the plug which will prevent the flexible appliance cord overheating and catching fire in the case of a short circuit.  Other countries use a radial system and rely on the protection (typically 16 Amp) for the fixed wiring to protect the flexible cord (which is fine for some appliance cords, but of doubtful value for lightweight cords such as those used with Europlugs).  A universal socket will, by definition, accept non-BS 1363 unfused plugs so when connected to a UK ring circuit the flexible cord is not adequately protected.

Shutters:  UK standards require that pin apertures are shuttered, the shutters being operated either by insertion of the earth pin or by simultaneous insertion of two or more pins.

Some universal sockets have no shutters, such as this one.  Others have inadequate shutters which can be opened by pressing a pin or other object into the line aperture alone.  This is completely unacceptable and potentially lethal.

Dogong
Paper clip

Poor contact: Sockets are normally designed to make the maximum electrical contact with the pins of the plug. Because the contacts in a universal socket are designed to accept a variety of sizes and shapes they are seriously compromised, often doing little more than touching at a couple of points.  A poor contact will result in arcing and/or overheating with the potential of fire.

Insufficient mechanical stability:  One of the functions of a socket is to securely hold the plug, but the overlarge apertures and poor contacts in a universal socket prevent this from happening.  In addition, some plug types (such as the German Schuko) rely on the socket recess for additional stability, but universal sockets have no recess.

Under-rated for most plugs:  Universal sockets do not have a standard current rating, they often claim to be rated at 10 A, but most plugs are rated at higher currents, eg 13 A (UK), 15 A (US) and 16 A (French and German), a plug should only be used in a socket which has a compatible current rating.

Mis-inserted schuko
Mis-inserted europlug

Plugs can be mis-inserted (1):  The overlarge apertures of a universal socket allows some plugs such as the Europlug and Schuko to be inserted into the wrong contacts, eg between line and earth.  This is illustrated above.

Oversize aperture 2 Oversize aperture 3
Oversize aperture 1

Plugs can be mis-inserted (2):  The overlarge apertures will also allow a BS 1363 earth pin to be inserted into the line aperture of a universal socket!.  The left hand picture shows a power pin inserted into the neutral aperture, and an earth pin inserted into the line aperture.  The apertures are so wide because they are designed to accomodate a BS 1363 plug (which defines the outer extremities) as well as a US NEMA plug (which defines the inner extremities).  It can be clearly seen that the aperture width is more than enough to accomodate a BS 1363 earth pin.  The centre picture is of a universal socket designed for an equipent panel, if this is mounted near to the edge of the panel then there is nothing to prevent the plug being inserted into the line aperture.  The right hand picture shows a cheap, ubiquitous and illegal Chinese universal adaptor which facilitates the same dangerous situation.

The Plugs and Sockets, etc. (Safety) Regulations 1994 control the selling of mains sockets in the UK.  Universal sockets do not meet the requirements specified, and it is therefore not legal to supply them in the UK.  Electrical Safety First (formerly the Electrical Safety Council) has commissioned a detailed report which describes the problems with universal sockets.

PlugSafe continues to identify illegal offerings of universal sockets on UK websites, and works with Trading Standards to have such listings removed.  An example of a withdrawn socket can be found on the EU RAPEX list here.

universal email
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