Schuko
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"Schuko" (pronounced /ˈʃuːkoʊ/) is the colloquial name for a system of domestic AC power plugs and sockets that is defined as "CEE 7/4" or known unofficially as "Type F" . A Schuko plug features two round pins of 4.8 mm diameter (19 mm long, centers 19 mm apart) for the live and neutral contacts, plus two flat contact areas on the top and bottom side of the plug for protective earth (ground). Schuko sockets form a cavity into which the plug is inserted. Schuko plugs and sockets are symmetric AC connectors. They can be mated in two ways, therefore live and neutral can arrive on either pin at the consuming device. As with most types of European sockets, Schuko sockets can accept europlugs. Schuko plugs are considered a very safe design when used with Schuko sockets but they can also mate with other sockets to give an unsafe result.
"Schuko" is a short form of the German term Schutzkontakt (literally: protective contact), which simply indicates that plug and socket are equipped with protective-earth contacts (in the form of clips rather than pins). Schuko connectors are normally used on circuits with 230 V, 50 Hz, for currents up to 16 A.
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[edit] History
The Schuko system originated in Germany and goes back to a patent (DE 370538) granted in 1926 to Albert Büttner, a Bavarian manufacturer of electrical accessories. It is used today in more than 40 countries, including most of Continental and Eastern Europe.
France, Belgium, the Czech Republic, Slovakia and Poland use a type of plug and socket (CEE 7/5) with the same size and spacing of the main pins but with a male protective-earth pin on the socket instead of the earth clips and without the guiding notches at the sides. Most modern moulded-on Schuko plugs, and good-quality rewirable replacements - are a hybrid version with an extra hole ("CEE 7/7") that also accommodates the earth pin of French sockets.
CEE 7/7 has now become the de facto standard across the European Union and in many other countries that follow CENELEC standards. The only countries that do not use CEE 7/7 within in the EU are : Denmark ( DS Afsnit 107-2-D1) (From 2008, Denmark will also use CEE 7/5), Ireland (BS1363), Italy ( CEI 23-16/VII), Malta (BS1363), Cyprus (BS1363) and the United Kingdom (BS1363).
Countries that have moved away from Schuko:
- The Republic of Ireland
In the Republic of Ireland, schuko was commonly installed until the 1960s. For safety reasons and to harmonise with the UK (with which Ireland has a long standing free travel arrangement) and avoid having a different outlet type in Northern Ireland and the Republic of Ireland, The Republic standardised on BS1363 (transposed into Irish Standards as IS401 (Plug) and IS411 (Socket outlet). This standardisation in Ireland occurred at the same time as the UK was phasing out older BS546 plugs and socket outlets (which were also used in parts of Ireland). The adoption of BS1363 also eliminated a situation where by grounded schuko plugs could be connected to non-grounded outlets, or to BS546 grounded outlets without making an earth connection. The UK had similar problems, where a mixture of old 2-pin and 3-pin BS plugs created all sorts of compatibility and grounding problems. The new BS1363 standard was specifically designed to be incompatible with any existing system, thus force compliance with grounding and other safety regulations. It should also be noted that in the 1960s compatibility with other European countries was not considered to be a major issue, as travel was less frequent and people did not carry as many portable appliances.
However, in the Republic of Ireland many wiring practices remain more like Continental Europe, particularly Germany. Socket outlets (which, unlike the UK, are often unswitched) are normally fed by 16amp or 20amp radials rather than UK-style ring circuits and are required to be protected by a 30mA RCD (US Terminology: GFCI). Also, fuses and other installation equipment tends follow German DIN standards rather than British Standards.
Schuko has been completely phased out of use in Ireland and will not be encountered in hotels, businesses or private homes. The only standard in use for general residential or business use is BS1363. However, some hotels do provide a schuko outlet alongside BS1363 outlets for the convenience of European visitors. This is also safer as it avoids the use of adaptors or forcing European plugs into BS1363 outlets which have had their shutters overridden.
[edit] Safety features
When inserted into the socket, the Schuko plug covers the socket cavity (1) and establishes protective-earth connection through the earth clips (2) before the live and neutral pins (3) establish contact, thereby preventing users from touching connected pins. (Hence the Schuko system does not require partially insulated pins as used in the europlug and the British and Australian plugs.) A pair of non-conductive guiding notches (4) on the left and right side provides extra stability, enabling the safe use of large and heavy plugs (e.g. with built-in transformers or timers).
[edit] Compatibility with other plug/socket types
Schuko sockets can accept two-pin unearthed type C plugs, namely CEE 7/16 and CEE 7/17. Less safely, schuko plugs can be inserted into many two-pin unearthed sockets and into some sockets with a different form of earth connection that will not mate with the earth contacts on the schuko plug (e.g., some variants of type K). Many such sockets also lack the cavity required to prevent users from touching the pins whilst inserting the plug.
The Russian standard plug defined in GOST 7396 is similar but has 4 mm pins. Therefore, Russian plugs will fit Schuko outlets, but Schuko plugs will not fit Russian outlets. Many former Eastern bloc countries are currently undergoing a process of transition from the (10 A) GOST to the (16 A) Schuko standard.
In Italy, Argentina and Uruguay, hybrid versions of Schuko sockets are seen with an extra hole that will take the smaller variant of type L plugs. There are also hybrid Schuko sockets with three extra holes and a wider cavity that will also accept the larger variant of type L plugs.
Although Schuko sockets are unpolarized, it is recommended to wire them the same way French sockets are wired (live on left and neutral on right, when looking at the socket) for consistency and so that universal CEE 7/7 plugs will plug in polarized fashion in most cases (when the plug's female ground receptacle is on top). Unfortunately in some countries like Finland and The Netherlands there is (or was) a long-standing installation tradition of wiring Schuko and the CEE 7/17 the opposite way, with live on the right and neutral on the left. That's why if there is a need to be sure which side is live, the socket's polarity must be tested every time.
[edit] Criticism
Schuko sockets are criticised for being unpolarized by design, and also for requiring much more force to plug and unplug than other sockets, which is a problem for some physically impaired people. The IEC 60906-1 standard that addresses these problems is intended to replace Schuko sometime in future. Two IEC 60906-1 sockets can fit in the same space as one Schuko socket.
