John Rumm wrote:
On 16/02/2013 00:50, Lobster wrote:
On 15/02/2013 22:29, John Rumm wrote:
On 15/02/2013 20:15, mike wrote:
Just came to fit some socket outlets from Toolstation and
realised the faceplate screws aren't connected to earth.

They're the top ones in this pic:

http://i46.tinypic.com/9glo1z.jpg

Older MK version with earth connection is below.


I thought all sockets followed the MK pattern with the result
that using either the earth connection on the faceplate or the
earth connection in the back box would result in everything
being connected to earth.

As you have seen, not always...

Don't think I've ever seen them before - I always assumed the
earthed screw holes were mandatory

But if someone made the earth connection to the back box on
the Toolstation version, any connected appliance (double
insulation and plastic earth prongs aside) wouldn't be earthed.
Is that right?

No, because the circuit earth wires will always be connected to
the earth terminal on the socket face plate. You would not simply
terminate the circuit earth wires on the backbox and rely on that
to make an earth connection to the backbox.

With a "normal" socket that has earthed screw holes the reverse
situation is allowable - i.e. you can re;y on them to earth the
backbox (assuming it has at least one fixed tag), however good
practice would suggest adding a separate fly lead between circuit
terminal and the earth terminal on the back box.

So, if you have sockets with earthed screw holes does that mean you
actually don't need the fly lead twixt socket and backbox? I
thought it must be a belt-and-braces thing or something, but didn't
think you could just do away with the flylead?

IIUC, so long as the box has at least one fixed lug, then you can do
without the discrete fly lead.

If the socket has just one earthed eyelet and this is at the adjustable lug
side of the backbox then you also need to fit the flylead.

--
Adam