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Department of Computer Science and Technology

Dr Markus Kuhn

Do not use foreign plug-adapters in floorboxes

Do not use foreign plug-adapters in floorboxes

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In February 2009, one of our PhD students plugged a UK-US plug adapter into his floorbox in the William Gates Building to connect a laptop. It instantly exploded in his hand and tripped a 40 A corridor circuit breaker that powered down nearby offices. Luckily, nobody was hurt and no data was lost.

This American-designed adapter had on its engagement surface a live metal rivet that holds the second half of the fuse. When inserted into a floorbox, this rivet touched an earthed metal screw and created a short circuit. The resulting short-circuit current detonated the fuse.

This adapter obviously does not not conform to the UK plug standard BS 1363, which forbids live metal contacts like this rivet on the engagement surface (and also requires more, e.g. insulating sleeves around the live/neutral pins).

To prevent such accidents, please follow the advice from the WGB office manual page:

  • If you need power for a mobile device (laptop, phone charger, etc.) on your desk, ask building-services for an extension strip, such that you never have to access the floorbox directly.
  • Do not use any travel adapters or plug chargers directly in the floor box. They prevent closing it, which disrupts the ventilation system.
  • If you want to use foreign 230 V equipment that has no British BS 1363 power plug with fuse, check whether it has an equipment-side IEC-320 connector (2 or 3 pole). This is standard today for most PCs and laptops worldwide. Simply get a British replacement power cord, e.g. from the suppliers listed below (sys-admin and stores sometimes also have a few on stock). This is far more convenient and reliable than using a travel plug adapter.
  • Avoid any foreign travel adapter (like the one above) that does not state that it complies with British Standard BS 1363-3. If you really need one, buy it in the UK.

Replacement power cords

UK plug to IEC 320 C7 "figure of eight" 2-pin connector:

UK plug to IEC 320 C5 "cloverleaf" 3-pin connector: