Posts Tagged ‘Inferior Standards’

Edison Screw Fittings – why do we tolerate them?

January 30th, 2009 No comments

The lamp in the bathroom just went pop – No problem except once I opened the fitting, I find it’s an Edison Screw (ES) type for which I don’t have a spare. I’m guessing that the previous owner installed this light fitting themselves.

Bayonet CapWhy, when we already have a superior standard in the form of the Bayonet Cap (BC) fitting, do we allow Edison screw type fittings to be sold in this country?

  • On a BC fitting Both Live and Neutral are connected at the base with the cap safely connected to earth, but ES uses the cap as part of the circuit. It is not uncommon for the pendant flex to be wired with live and neutral reversed. With ES, this makes the cap live while on BC, polarity is irrelevant and the hazard is avoided;
  • If an ES lamp is not screwed in tightly enough, the live connection can work loose, leading to high resistance and localised heating. It can also cause the lamp to flicker shortening its life. This cannot happen with a BC fitting.
  • ES is bulkier than BC, partly owing to the requirement to shroud the metal receptacle. The BC receptacle, being earthed, does not require shrouding.

The problem lies partly with retailers such as Ikea – Rather than selling fittings with a standard BC lampholder, they choose to impose ES fittings which are usually made abroad. This also means that the lampshades they sell will not fit standard BC lampholders as the ring is made for the larger ES lampholder and a separate adapter ring is required.

Although the same thing would not happen with socket outlets, inferior standards for sockets in other countries has already caused a hazard to materialise in the UK.
BS1363 Socket showing shuttersUnlike the majority of foreign socket outlets, the UK BS1363 standard for socket outlets is designed with shutters to prevent the insertion of objects into the socket. Other countries have had to resort to the use of plastic ‘safety socket covers’ to prevent children inserting foreign objects into unprotected live sockets. Unfortunately, several toy manufacturers have marketed a UK version of these socket-covers, which are not only unnecessary but whose use can actually negate the safety features of the BS1363 sockets creating a very real hazard.