Consumer Unit Blanking Plates

And to confuse matters some clip on front covers for sockets are not earthed either…

Decorative covers on sockets etc. would usually be separated from live parts by reinforced insulation (i.e. the insulating body of the socket housing).

I guess the worry is that blanks on a CU might come into contact with wiring with only basic insulation. The obvious answer is to ask the manufacurer. I've not used any of these metallic blanks yet, so not sure of the exact design, but might suspect that normally wiring wouldn't come particularly near to them - terminals of MCBs etc would normally be considerably higher (or lower) than the opening and it would be unusual to run wiring in front of the DIN rail - so the manufacturer might consider than the blanks not to be liable to become live even if basic insulation failed. That might be different if there were good cause to run wiring to something immediately behind the blank - e.g. DIN rail mounted terminals - but then most CU manufacturers don't supply such things as part of their CU range so you'd be back to the old chestnut about using components not specified by the manufacturer so you become responsible for the assembly and type testing etc. 

   - Andy.

perspicacious: 
 

For example, for the same reason, great care is taken to ensure that socket fronts and boxes are earthed. 

So long as one of the metal box fixing lugs is fixed, ie not the adjustable side, there is no requirement to “tail back” from the socket-outlet to the metal box.

Regards

BOD

Except where 543.2.7 applies.

Z.

Qbit: 
 

Chris Pearson

Precisely: the fixed lug is used to earth the box via the screws.  Any metal front at risk will be earthed by the screw and/or internal design connection.  I.e. significant effort to ’deadfront’.  

We can't rely on a socket fixing screw for a reliable earth connection to its back box, as it might come loose with socket use. Also, is a metal back box sunk into a wall an “exposed conductive part?”

I recently installed a new all R.C.B.O. consumer unit for a local customer. The metal board had an earth tail from the front cover to the earth terminal. A blighter if you forget it's there and wonder at just what is holding the cover back when you try to remove it. No blanks, all R.C.B.O.s.

Z.

perspicacious: 
 

For example, for the same reason, great care is taken to ensure that socket fronts and boxes are earthed. 

So long as one of the metal box fixing lugs is fixed, ie not the adjustable side, there is no requirement to “tail back” from the socket-outlet to the metal box.

Regards

BOD

If the fixing screws are slackened off (say when decorating for instance then not subsequently tightened) or are replaced with nylon screws (I did wonder why on earth when I saw this! I always earth tail metal backboxes