Hi,

I recently bought some converta (white plastic) sockets to convert my single
plugs to doubles as easy as possible. The instructions clearly state that
the earth terminal on the new socket should be connected to the metal wall
box, if a metal one is present, as well as obviously being connected to the
main earth wires that go into the walls. The boxes are recessed and are
flush with the walls.

There are no terminals on my wall boxes, so I just connected a piece of wire
to one of the screw holes that are not used on the box from the earth
terminal on the converta socket. I did this by wrapping the wire around the
unused screw hole. It was covered in dust and debris, so I don't really know
if it is making good contact.

I cannot understand why this is needed if the mains earth is connected and
the metal box is not exposed? Is there any major issue with what I have
done?

Thanks,

James

"James" wrote in message
...
Hi,

I recently bought some converta (white plastic) sockets to convert my
single
plugs to doubles as easy as possible. The instructions clearly state that
the earth terminal on the new socket should be connected to the metal wall
box, if a metal one is present, as well as obviously being connected to
the
main earth wires that go into the walls. The boxes are recessed and are
flush with the walls.

There are no terminals on my wall boxes, so I just connected a piece of
wire
to one of the screw holes that are not used on the box from the earth
terminal on the converta socket. I did this by wrapping the wire around
the
unused screw hole. It was covered in dust and debris, so I don't really
know
if it is making good contact.

I cannot understand why this is needed if the mains earth is connected and
the metal box is not exposed? Is there any major issue with what I have
done?

Thanks,

James



No major issues, but one thing does spring to my mind. If the metal box is
completely covered by your new boxes, then why fix an earth tag to it at
all? It might actually have been safer to leave the boxes disconnected from
any earth ground if they are not actually being used to house the working
part of the sockets. But I can't see the job, so my comments are only based
on speculations.

On Fri, 27 May 2005 05:29:38 GMT, "BigWallop"
wrote:

If the metal box is completely covered by your new boxes,

It isn't completely covered, unless it's both covered and you replace
the screws holding the cover on with insulated ones.

then why fix an earth tag to it at all?

To provide a path for a fault current, in the case of a wire coming
loose inside the box. It's not just to protect you from a live case
fault, it's to signal the occurence of this fault even before you've
touched it.

Thanks for the advice. The single sockets were not wired to the boxes from
the socket earth terminal, maybe its some new regulation thing. The single
sockets have been in since the house was built in the mid 70's.

James




"Andy Dingley" wrote in message
...
On Fri, 27 May 2005 05:29:38 GMT, "BigWallop"
wrote:

If the metal box is completely covered by your new boxes,

It isn't completely covered, unless it's both covered and you replace
the screws holding the cover on with insulated ones.

then why fix an earth tag to it at all?

To provide a path for a fault current, in the case of a wire coming
loose inside the box. It's not just to protect you from a live case
fault, it's to signal the occurence of this fault even before you've
touched it.

If you wanted a better way to sequre the arth to the back box, try buying a
cheap rivot gun and some biug rivots with loop eye fixings to rivot the
earth to the back box just did this in my house

James wrote:
Thanks for the advice. The single sockets were not wired to the boxes from
the socket earth terminal, maybe its some new regulation thing. The single
sockets have been in since the house was built in the mid 70's.

Yes, it's a 'new' recommended practice - but not that new! Thinking
changed around the mid80s, AFAIR. Previously, it was considered that the
backbox would get reasonably well earthed through the faceplate screws,
which rested in little brass cups which were solidly joined to the
metalwork of the faceplate, which included the 'wiring accessory's earth
terminal. ('Wiring accessory' is electrician-speak for switch, socket,
fused connection unit, etc.)

However, there were a few documented cases where corrosion between the
screw and the backbox increased the resistance between backbox and earth
to the point where a fault current flowed which was large enough to
cause notable heating - I think even a fire in a couple of cases - but
too low to blow the fuse/MCB. This was more likely where you had the
unfortunate combination of only one of the faceplate screws having the
brass cup and fixing to faceplate metalwork mentioned above, and that
being the side with the adjustable lug of the metal back box. (Most?
backboxes have one fixed threaded lug on one side, the other one having
some up-and-down play in it to allow the accessory to end up all
luvverly horizontal like even if the backbox is marginally skew whiff.)

Since this was publicised by the IEE and in the odd 'How To Do Sensible
Wiring' book, practice has changed to prefer a flying-lead connection
from the accessory earth terminal to the back-box's earth terminal - and
backenboxen aren allen maden withen integralen earthen terminalen. But
you'll still find older ones - like the Original Poster's - wot don't
have such a terminal. Taking a flylead and poking it hopefully into a
spare mounting hole doesn't really make a solid enough contact; it's
worth at least using a short self-tapper to secure that lead (you may
need a few mm depth of the material behind the box drilling out with a
handy masonry drill).

HTH - Stefek

Stefek Zaba wrote:

Since this was publicised by the IEE

Any reference to when and where "this was publicised by the IEE" and
quasi-officially recommended? ICBW but I don't think the NICEIC
technical manual mandates it if the mounting box is not touchable.

One situation in which this link /is/ mandated is where the incoming
earth (CPC) arrives at the box via a metal conduit, cable armour or
sheath. Then the earth connection to the accessory must be made via a
separate wire link from an earth terminal on the box to the earth
terminal of the accessory. [Reg. 543-02-07]

Of course the 'converta' sockets (WWIANF) mentioned might not have any
earth path to the box via the mounting screws, in which case the link is
a good idea.

To connect to old boxes with no earth terminal I recommend a short self
tapping screw (say No. 8) in conjunction with an insulated crimp ring
terminal on the end of the wire.

--
Andy

Andy Wade wrote:

Since this was publicised by the IEE

Any reference to when and where "this was publicised by the IEE" and
quasi-officially recommended? ICBW but I don't think the NICEIC
technical manual mandates it if the mounting box is not touchable.

I *think* I'm remembering a section in one of Trevor Marks' bookses. But
old age being what it is, ...

Stefek