Earthing back boxes and socket outlets

[mike]

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. 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?
Is this something new? Or something cheap?

[polygonum]

I thought that each connection had to be made separately, and relying on
the faceplate being in contact with the back box was a no-no. Even if,
as in the MK case, it might actually be connected.

--
Rod

[fred]

In article
<8fbbafaf-23a9-493e...@fw24g2000vbb.googlegroups.com>,
mike <mike...@yahoo.com> writes

If we simplify the situation by assuming a surface mounted plastic
patress then we have exposed metal parts (fixing screws) that can
readily come into contact with the basic insulation on the conductors
(the brown and blue cores) when the box is assembled.

Rules are that exposed metal parts need to be separated from live
conductors by 2 layers of insulation (double insulated)[1] or if there
is only one layer of insulation be earthed.

Given that, I can't see how these parts can be compliant.

Given the supplier I am not that shocked<g>, it wouldn't be the first
time a buyer has bought on cost only to be bitten in the arse when they
find out they have worthless shit in the warehouse.

Oooh, pass me another budget lasagne Neddy . . . .

[1] Special case of reinforced insulation set aside for this example
--
fred
it's a ba-na-na . . . .

[John Rumm]

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...

> 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.

> Is this something new? Or something cheap?

No and yes.



--
Cheers,

John.

/=================================================================\
| Internode Ltd - http://www.internode.co.uk |
|-----------------------------------------------------------------|
| John Rumm - john(at)internode(dot)co(dot)uk |
\=================================================================/

[Dave Plowman (News)]

In article
<8fbbafaf-23a9-493e...@fw24g2000vbb.googlegroups.com>,

It's best practice to run an earth wire between the socket and earth
terminal on a metal back box. That's why it's there.

--
*Cleaned by Stevie Wonder, checked by David Blunkett*

Dave Plowman da...@davenoise.co.uk London SW
To e-mail, change noise into sound.

[Lobster]

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?

--
David

[John Rumm]

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

[charles]

In article <SIATs.100226$qT2....@fx05.fr7>,

If the socket happend to be be hanging loose, how do you get earth
continuity?

--
From KT24

Using a RISC OS computer running v5.18

[mike]

On Feb 15, 10:29 pm, John Rumm <see.my.signat...@nowhere.null> wrote:
> On 15/02/2013 20:15, mike wrote:

> > 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.

So "no" in theory but "yes" in practice because there will inevitably
be cases where people connect it to the back box earth.

> 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.

If everything is reliably earthed via the socket screw in the
situation you describe, how would it be any less reliable if the earth
were connected to the back box rather than the face plate?

[ARW]

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

[Arfa Daily]

"Lobster" <davidlobs...@hotmail.com> wrote in message
news:SIATs.100226$qT2....@fx05.fr7...

With the 'main' earth connection in the circuit being the earth pin on the
socket face, I can't imagine that anyone in their right mind would not make
this the primary connection point for the safety earth wire(s). It would be
madness to try to use the (sometimes present) faceplate fixing screw earth
straps 'backwards' - that is to try to make the socket's primary earth
*from* the backbox via the screws. If those screws were the slightest bit
loose, or corroded, the earth could be almost totally ineffective.

In a correct installation, the possibility of the faceplate screws becoming
live is pretty damn small anyway, and almost non-existent if the backbox is
plastic. Never-the-less, if the backbox is metal, I would always run a
secondary flying earth wire to the earth terminal that is always present in
such boxes, and then the faceplate screws would be earthed anyway, courtesy
of the fact that they are screwed into the earthed backbox. In my opinion,
within practical constraints, 'belt and braces' is good when it comes to
electrics ...

Arfa

[John Rumm]

The circuit earth wires are always connected directly to the socket. So
even with the socket completely disconnected from its backbox (which may
be plastic remember), it still is both earthed, and providing earth
continuity.

[John Rumm]

Indeed, I did wonder if some suggestions here were suggesting this back
to front connection scheme!

About the only time I can envisage something similar to that being
"normal" would be on a wiring system that relies on with cable sheath
(e.g. MICC) or conduit to provide the CPC. However even there one ought
to be using a banjo tag or similar on the gland to connect the socket
earth, rather than the earth tag on the box.

> In a correct installation, the possibility of the faceplate screws
> becoming live is pretty damn small anyway, and almost non-existent if
> the backbox is plastic. Never-the-less, if the backbox is metal, I would
> always run a secondary flying earth wire to the earth terminal that is
> always present in such boxes, and then the faceplate screws would be
> earthed anyway, courtesy of the fact that they are screwed into the
> earthed backbox. In my opinion, within practical constraints, 'belt and
> braces' is good when it comes to electrics ...

No harm in that...

The screws themselves probably represent relatively little risk - even
if you could make contact to them, the contact area is small and would
be very difficult to maintain contact with under shock conditions
(rather like trying to electrocute yourself in a BC lamp holder!)

Obviously on a metal clad faceplate, the issue becomes more significant.

[ARW]

Dave Plowman (News) wrote:
> In article
> <8fbbafaf-23a9-493e...@fw24g2000vbb.googlegroups.com>,
> mike <mike...@yahoo.com> 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. 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? Is this something new? Or something cheap?
>
> It's best practice to run an earth wire between the socket and earth
> terminal on a metal back box. That's why it's there.

Best practice and electricians? Pull the other one:-).

I fit the flyleads in older houses where there are damp problems and where
the spec says I have to.

Any competent DIYer should be fitting the flylead as they are not on price.

The sockets in question were brought to the attention of this group last
year by SteveWalker. They are Toolstation's "Contractor Pack", marked HLM.



--
Adam

[John Rumm]

On 16/02/2013 09:21, mike wrote:
> On Feb 15, 10:29 pm, John Rumm <see.my.signat...@nowhere.null> wrote:
>> On 15/02/2013 20:15, mike wrote:
>
>>> 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.
>
> So "no" in theory but "yes" in practice because there will inevitably
> be cases where people connect it to the back box earth.

Excluding cases conduit/sheath/armour earthing is in use it seems
relatively unlikely - its not as if its any easier to connect two wires
to the box and four to the socket... I have seen countless examples of
no flying lead betwixt socket and box, but don't recall ever seeing the
being being used at a primary connection point.

>> 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.
>
>
> If everything is reliably earthed via the socket screw in the
> situation you describe, how would it be any less reliable if the earth
> were connected to the back box rather than the face plate?

Because in reality its a less reliable connection...

While not desirable, an unearthed backbox is unlikely to kill you, but
an unearthed socket might.

Imagine a situation where some one is decorating and has release socket
screws to get paper etc behind the faceplate. Anything plugged into that
socket *must* still be earthed, but whether the box still is in those
circumstances is less important.

[Frank Erskine]

On Sat, 16 Feb 2013 01:21:13 -0800 (PST), mike <mike...@yahoo.com>
wrote:

Very often the earth lug on the back box isn't large enough to take
three 2.5mm wires.

--
Frank Erskine

[Dave Plowman (News)]

In article <kfnuhd$b45$1...@dont-email.me>,

ARW <adamwa...@blueyonder.co.uk> wrote:
> > It's best practice to run an earth wire between the socket and earth
> > terminal on a metal back box. That's why it's there.

> Best practice and electricians? Pull the other one:-).

;-) But if I were an electrician I'd make sure the terminal screws were
left loose to.

> I fit the flyleads in older houses where there are damp problems and
> where the spec says I have to.

> Any competent DIYer should be fitting the flylead as they are not on
> price.

Quite.

> The sockets in question were brought to the attention of this group last
> year by SteveWalker. They are Toolstation's "Contractor Pack", marked
> HLM.

Seems they saved 0.0001p by not running the earth strip to the screw holes.

--
*Middle age is when work is a lot less fun - and fun a lot more work.

[ARW]

Dave Plowman (News) wrote:
> In article <kfnuhd$b45$1...@dont-email.me>,
> ARW <adamwa...@blueyonder.co.uk> wrote:
> > > It's best practice to run an earth wire between the socket and
> > > earth terminal on a metal back box. That's why it's there.
>
> > Best practice and electricians? Pull the other one:-).
>
> ;-) But if I were an electrician I'd make sure the terminal screws
> were left loose to.

That's not always true. Sometimes they overtighten the screws to see if they
can snap off half of the screws head. It's a fine balancing act to decide
which one to do.

> > I fit the flyleads in older houses where there are damp problems and
> > where the spec says I have to.
>
> > Any competent DIYer should be fitting the flylead as they are not on
> > price.
>
> Quite.
>
> > The sockets in question were brought to the attention of this group
> > last year by SteveWalker. They are Toolstation's "Contractor Pack",
> > marked HLM.
>
> Seems they saved 0.0001p by not running the earth strip to the screw
> holes.

I would not normally buy electrical stuff from Toolstation. Steve Walkers
post guaranteed that I would avoid those sockets should I ever have to buy
from there.

--
Adam

[Dave Plowman (News)]

In article <kfo5g4$e1o$1...@dont-email.me>,

ARW <adamwa...@blueyonder.co.uk> wrote:
> I would not normally buy electrical stuff from Toolstation. Steve
> Walkers post guaranteed that I would avoid those sockets should I ever
> have to buy from there.

For myself, I tend to buy the fittings I like the look of, since you're
likely to have to look at them for a long long time. Which usually means
not the cheapest I can find. ;-)

--
*Letting a cat out of the bag is easier than putting it back in *

[ARW]

Dave Plowman (News) wrote:
> In article <kfo5g4$e1o$1...@dont-email.me>,
> ARW <adamwa...@blueyonder.co.uk> wrote:
> > I would not normally buy electrical stuff from Toolstation. Steve
> > Walkers post guaranteed that I would avoid those sockets should I
> > ever have to buy from there.
>
> For myself, I tend to buy the fittings I like the look of, since
> you're likely to have to look at them for a long long time. Which
> usually means not the cheapest I can find. ;-)

That's how I choose my girlfriends.

--
Adam

[mike]

On Feb 16, 12:45 pm, John Rumm <see.my.signat...@nowhere.null> wrote:
> On 16/02/2013 09:21, mike wrote:

> > If everything is reliably earthed via the socket screw in the
> > situation you describe, how would it be any less reliable if the earth
> > were connected to the back box rather than the face plate?
>
> Because in reality its a less reliable connection...
>
> While not desirable, an unearthed backbox is unlikely to kill you, but
> an unearthed socket might.
>
> Imagine a situation where some one is decorating and has release socket
> screws to get paper etc behind the faceplate. Anything plugged into that
> socket *must* still be earthed, but whether the box still is in those
> circumstances is less important.

I had thought of that situation and I take your point but, in
fairness, you have introduced three further variables into the
situation. Firstly, someone takes the socket off the wall; secondly,
they plug something into it; thirdly, whatever is plugged in has a
metal earth prong and needs an earth connection.

In the case of a socket screwed to the wall properly with the MK style
earth connection to the mounting screws, if it provides a "reliable"
earth to the mounting box it would necessarily have to work equally
reliably to the earth terminal. I'm surprised the MK style earth
connection isn't mandated but, as Adam has pointed out in another
thread:

'From BS 1363-2 1995 (Specification of 13A switched and unswitched
socket outlets)
10.3 If means are provided for electrically bonding the mounting box
to the earthing circuit of the socket-outlet
by means of the fixing screws the connection between the screw and the
earthing terminal shall be of low resistance.
Note the use of the word "if".'

... so the Toolstation sockets are just built-to-save-a-penny crap
that sneak in under the wire.

As for saying that, in practice, no-one would use the mounting box
earth, you've surely seen work infinitely worse than that.

I've just replaced a lighting circuit where a "professional"
electrician had managed to cram sixteen cables and three connector
blocks into one 30-amp junction box and, when he ran out of room for
screwed connections, twisted wires together and wrapped them in
insulation tape. It was like a rat's nest up a fish's arsehole. The
earth wires that hadn't simply been cut off were twisted together
unsheathed outside the junction box, the lid of which had been refixed
at a jaunty angle with a woodscrew.

Compared to that kind of workmanship, the mounting box earth seems
like the height of British standards.

[John Rumm]

On 16/02/2013 15:10, mike wrote:
> On Feb 16, 12:45 pm, John Rumm <see.my.signat...@nowhere.null> wrote:
>> On 16/02/2013 09:21, mike wrote:
>
>>> If everything is reliably earthed via the socket screw in the
>>> situation you describe, how would it be any less reliable if the earth
>>> were connected to the back box rather than the face plate?
>>
>> Because in reality its a less reliable connection...
>>
>> While not desirable, an unearthed backbox is unlikely to kill you, but
>> an unearthed socket might.
>>
>> Imagine a situation where some one is decorating and has release socket
>> screws to get paper etc behind the faceplate. Anything plugged into that
>> socket *must* still be earthed, but whether the box still is in those
>> circumstances is less important.
>
> I had thought of that situation and I take your point but, in
> fairness, you have introduced three further variables into the
> situation. Firstly, someone takes the socket off the wall; secondly,
> they plug something into it; thirdly, whatever is plugged in has a
> metal earth prong and needs an earth connection.

Indeed and I was really just highlighting that the primary earth
connection are supposed to be to the socket and illustrating a situation
were it could make a difference.

> In the case of a socket screwed to the wall properly with the MK style
> earth connection to the mounting screws, if it provides a "reliable"
> earth to the mounting box it would necessarily have to work equally
> reliably to the earth terminal. I'm surprised the MK style earth
> connection isn't mandated but, as Adam has pointed out in another
> thread:
>
> 'From BS 1363-2 1995 (Specification of 13A switched and unswitched
> socket outlets)
> 10.3 If means are provided for electrically bonding the mounting box
> to the earthing circuit of the socket-outlet
> by means of the fixing screws the connection between the screw and the
> earthing terminal shall be of low resistance.
> Note the use of the word "if".'

I suppose playing devil's advocate, you could argue that its becoming
less critical rather than more, as more installations are done with
insulated backboxes (i.e. dry lining ones) these days.

> ... so the Toolstation sockets are just built-to-save-a-penny crap
> that sneak in under the wire.
>
> As for saying that, in practice, no-one would use the mounting box
> earth, you've surely seen work infinitely worse than that.

I have seen plenty of crap work, just never seen an install where the
primary connection has been made to the box.

Daft situations like a ring (or worse a radial) where one earth is taken
to the socket and the other to the box - with a result of loss of earth
continuity if the faceplate is removed or a connection goes high
impedance (more likely where the screwed connection is between
dissimilar metals and the screw pressure does not make the contact point
gas tight)

> I've just replaced a lighting circuit where a "professional"
> electrician had managed to cram sixteen cables and three connector
> blocks into one 30-amp junction box and, when he ran out of room for
> screwed connections, twisted wires together and wrapped them in
> insulation tape. It was like a rat's nest up a fish's arsehole. The
> earth wires that hadn't simply been cut off were twisted together
> unsheathed outside the junction box, the lid of which had been refixed
> at a jaunty angle with a woodscrew.

Mmmm yummy ;-)

> Compared to that kind of workmanship, the mounting box earth seems
> like the height of British standards.

In relative terms quite possibly, but it still does not make it good or
sensible practice.

[SteveW]

Thank you, I was just about to search for my original post, but I'll not
bother now!

SteveW

[Windmill]

Most of the sockets I've seen which were wired relatively recently have
a squashed-flat loop in the earth wire to allow it to fit into the back
box terminal, but the wire then continues on to the earth terminal on the
socket.
All one piece of wire so less risk of an open earth connection if there
are loosely-fastened screws in back box and/or faceplate.
I had assumed that was more or less a standard for a professional
installation.

--
Windmill, Til...@Nonetel.com Use t m i l l
J.R.R. Tolkien:- @ O n e t e l . c o m
All that is gold does not glister / Not all who wander are lost

[Dave Plowman (News)]

In article <MICow...@freebie.onetel.net.uk>,

Windmill <spam-n...@Onetel.net.uk.invalid> wrote:
> Most of the sockets I've seen which were wired relatively recently have
> a squashed-flat loop in the earth wire to allow it to fit into the back
> box terminal, but the wire then continues on to the earth terminal on the
> socket.
> All one piece of wire so less risk of an open earth connection if there
> are loosely-fastened screws in back box and/or faceplate.
> I had assumed that was more or less a standard for a professional
> installation.

Sounds like a rather fiddly way to do it. And slightly wasteful of cable -
for those who worry about such things. ;-)

I bought a 100m reel of 1.5 single green/yellow many many years ago just
for this, and I'd expect it to see me out. ;-) But you can usually rescue
some earth from cut-offs of the TW&E - and of course you will already have
the sleeving.

--
*When cheese gets its picture taken, what does it say? *