help to wire a dimmer switch

[ban-all-sheds]

http://www.youtube.com/watch?v=3GRm_35rHlo

Just testing the new feature..

 

[martinxxxxxx]

How does it add anything?

This is not extraneous metal,so surely does not need be bonded.

I would of supposed belt and braces are well catered for by virtue of the two retaining screws.

Have I missed some regulation at all?

I would call the metal backbox an exposed conductive part, which could become live due to failure of primary insulation. Although it would normally be linked to the switch via screws, this is not the case when an accessory is off the wall for servicing, so many people (myself included) also use a short strap to link backbox and accessory earth terminals. For the 30 seconds it takes, you might as well do it.

And it is not normally exposed either