07/12/2023
Lighting Designers thwart BS7671
This is a "double insulated" lighting fitting. Noted in this technical detail by the "square within square" on the data plate.
It is relevant because it invites such widespread and almost universal abuse of it's raison d'etre. I find this with DIY’ers and electricians alike.
Lighting designers love “double insulated”. The mere act of including in their under-engineered design, a poxy teeny little white plastic box, gives them scope to avoid pennies on every fitting they put out.
The concept is straightforward in BS7671 which provides that earthing of metallic (conductive) wiring is made unnecessary ONLY when there are two separate physical layers of insulation.
For example, one layer might be the plastic used round a wiring junction (push-type or even the old fashioned “choc-bloc” screw-type). The second layer in this example would be the wincy 30mmx 8mm box thing which costs a fraction of a penny.
Inside this scrap of an enclosure, the Designers (so they imagine), expect that it will be possible to safely terminate the wiring which in the UK, might be typically up to three or more twin-earth cables with 1mm or 1.5 mm square copper. A standard junction box for this purpose might need to be 100mm x 30mm. - Even terminating ONE such clean cable is very difficult, the enclosed terminals within scarcely fit the smallest standard screwdrivers and are grossly inadequate.
So faced with this physical impossibility, nearly everyone out of sheer frustration with the stupid little piece of plastic, immediately tosses it away and reverts to robust and safe push-type or screw fittings and chucks these loose inside the metal cover plate. (What you see above is half-and half). All well and good, but the Designers have, through trivial cost-cutting for a crowded market which doesn't differentiate, and, I believe, through sheer laziness, decided it would be “double insulated”. This necessitates that none of those single-insulated cable connectors or single-insulated cable tails can come into contact with the uninsulated metal.
A very simple and costing nearly nothing get-out is an earth stud on the enclosure! (Such as you will find on every metal faced light switch).
The result of the way these are almost universally installed, is thus, instant “disqualification” of the double-insulated status. So should a cable fall out of a connector or a single-insulated cable covering become abraded, it will contact an unearthed metal enclosure, rendering it live to the touch. In an EICR, this is technically a "C2, Potentially Dangerous" condition.
This is so widely abused and so widespread that whenever I see a modern light fitting of this sort, if I’m doing an EICR inspection or a teste for a consumer unit fit, or anything, I can be 90% certain that it will be incorrectly assembled.
The only way to prevent an inevitable “Potentially dangerous” conclusion brought on by a combination of Designer laziness/cost cutting and installer frustration, is to fix it. I today removed and "mended" six light fittings recently put up by Others, just so.
I might typically ring-crimp an earth wire under a fixing screw or in any way I can see suitable. I then cross-out the square “double insulated” symbol with a marker pen. There are not many options when the designer and the customer would be displeased by me drilling the enclosure and bolting through it.
I see this with nearly all brands of “décor” light fitting where metal enclosures are used. This one is B&Q “Dar” brand, - but they all do it.
