Hi all,

My internet searching skills seem to be sadly lacking, so I'll
apologise if there is as easy solution I've not found.

I do a fair amount of travel abroad, and need to carry (mostly) IT
equipment, some of which is powered by wall-warts - transformers
moulded into UK plugs, so I can't simply swap mains leads. What I'd
like to do is find an in-line RCBO so that I can take an n-way
extension, chop off the plug and attach a Schuko-style plug and and
RCBO. Then I can get rid of my collection of Schuko-to-BS1363 adapters
and assorted mains leads and travel with a standard set of kit that
never needs changing.

The reason I want dual pole is that the polarity of the live and
neutral is not guaranteed with Schuko - indeed, in some double
sockets it is guaranteed they will be different.

I think I want an RCBO as, in theory, 'continental' wiring can deliver
16A quite happily, and given that the UK stuff is rated to 13A, I'd
like to put in a 10A RCBO.

I have found in-line RCDs, but no RCBOs. An alternative (probably
cheaper) approach might be to use the RCD and put in a couple of in-
line 13A fuses in the extension lead. I realise that fusing a neutral
is normally a no-no, but since I can't tell which is live and which is
neutral, it seems like the best approach. Do such things as 13A in-
line fuseholders exist? And come to that (although not relevant for
this query) in-line dual pole 13A switches? I can find single-pole
'torpedo' switches rated to 3A, but nothing higher.

Cheers,

Sid

wrote:
Hi all,

My internet searching skills seem to be sadly lacking, so I'll
apologise if there is as easy solution I've not found.

I do a fair amount of travel abroad, and need to carry (mostly) IT
equipment, some of which is powered by wall-warts - transformers
moulded into UK plugs, so I can't simply swap mains leads. What I'd
like to do is find an in-line RCBO so that I can take an n-way
extension, chop off the plug and attach a Schuko-style plug and and
RCBO. Then I can get rid of my collection of Schuko-to-BS1363 adapters
and assorted mains leads and travel with a standard set of kit that
never needs changing.

The reason I want dual pole is that the polarity of the live and
neutral is not guaranteed with Schuko - indeed, in some double
sockets it is guaranteed they will be different.

I think I want an RCBO as, in theory, 'continental' wiring can deliver
16A quite happily, and given that the UK stuff is rated to 13A, I'd
like to put in a 10A RCBO.

I have found in-line RCDs, but no RCBOs. An alternative (probably
cheaper) approach might be to use the RCD and put in a couple of in-
line 13A fuses in the extension lead. I realise that fusing a neutral
is normally a no-no, but since I can't tell which is live and which is
neutral, it seems like the best approach. Do such things as 13A in-
line fuseholders exist? And come to that (although not relevant for
this query) in-line dual pole 13A switches? I can find single-pole
'torpedo' switches rated to 3A, but nothing higher.

Cheers,

Sid

The multi-way socket strip should have a fuse, so could you just get one of
these
http://www.screwfix.com/prods/76975/

Then if your L&N is reversed, you can just unplug and re-plug the Schuko the
other way round?

Toby...

On Nov 10, 9:02*am, "Toby" wrote:
wrote:
Hi all,

My internet searching skills seem to be sadly lacking, so I'll
apologise if there is as easy solution I've not found.

I do a fair amount of travel abroad, and need to carry (mostly) IT
equipment, some of which is powered by wall-warts - transformers
moulded into UK plugs, so I can't simply swap mains leads. What I'd
like to do is find an in-line RCBO so that I can take an n-way
extension, chop off the plug and attach a Schuko-style plug and and
RCBO. Then I can get rid of my collection of Schuko-to-BS1363 adapters
and assorted mains leads and travel with a standard set of kit that
never needs changing.

The reason I want dual pole is that the polarity of the live and
neutral is not guaranteed with Schuko *- indeed, in some double
sockets it is guaranteed they will be different.

I think I want an RCBO as, in theory, 'continental' wiring can deliver
16A quite happily, and given that the UK stuff is rated to 13A, I'd
like to put in a 10A RCBO.

I have found in-line RCDs, but no RCBOs. An alternative (probably
cheaper) approach might be to use the RCD and put in a couple of in-
line 13A fuses in the extension lead. I realise that fusing a neutral
is normally a no-no, but since I can't tell which is live and which is
neutral, it seems like the best approach. Do such things as 13A in-
line fuseholders exist? And come to that (although not relevant for
this query) in-line dual pole 13A switches? I can find single-pole
'torpedo' switches rated to 3A, but nothing higher.

Cheers,

Sid

The multi-way socket strip should have a fuse, so could you just get one of
thesehttp://www.screwfix.com/prods/76975/

Then if your L&N is reversed, you can just unplug and re-plug the Schuko the
other way round?

Toby...

or fit 3 neons into the multiway socket to do the same job. Much
neater. Then you just want an RCD.


NT

wrote:

I think I want an RCBO as, in theory, 'continental' wiring can deliver
16A quite happily, and given that the UK stuff is rated to 13A, I'd
like to put in a 10A RCBO.

I have found in-line RCDs, but no RCBOs. An alternative (probably
cheaper) approach might be to use the RCD and put in a couple of in-
line 13A fuses in the extension lead. I realise that fusing a neutral
is normally a no-no, but since I can't tell which is live and which is
neutral, it seems like the best approach. Do such things as 13A in-
line fuseholders exist? And come to that (although not relevant for
this query) in-line dual pole 13A switches? I can find single-pole
'torpedo' switches rated to 3A, but nothing higher.

There is no point in fusing both live and neutral since only one will
blow on an overload, and you won't know which. The one 13A fuse will
serve to limit the maximum current, hence you can skip the RCBO bit of
the requirement, and just go for a RCD.

NT's suggestion of neons is quite a simple and effective way to check
the polarity. One between each side of the supply and earth should tell
you what you need to know (you could leave the existing neon found in
most 4 way leads as a "power good" indicator, and then add another
betwixt neutral and earth as a "polarity reversed" one)


--
Cheers,

John.

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

On Nov 10, 10:16*am, John Rumm wrote:
wrote:
I think I want an RCBO as, in theory, 'continental' wiring can deliver
16A quite happily, and given that the UK stuff is rated to 13A, I'd
like to put in a 10A RCBO.

I have found in-line RCDs, but no RCBOs. An alternative (probably
cheaper) approach might be to use the RCD and put in a couple of in-
line 13A fuses in the extension lead. I realise that fusing a neutral
is normally a no-no, but since I can't tell which is live and which is
neutral, it seems like the best approach. Do such things as 13A in-
line fuseholders exist? And come to that (although not relevant for
this query) in-line dual pole 13A switches? I can find single-pole
'torpedo' switches rated to 3A, but nothing higher.

There is no point in fusing both live and neutral since only one will
blow on an overload, and you won't know which. The one 13A fuse will
serve to limit the maximum current, hence you can skip the RCBO bit of
the requirement, and just go for a RCD.

NT's suggestion of neons is quite a simple and effective way to check
the polarity. One between each side of the supply and earth should tell
you what you need to know (you could leave the existing neon found in
most 4 way leads as a "power good" indicator, and then add another
betwixt neutral and earth as a "polarity reversed" one)

--
Cheers,

John.

Or one neon only as a polarity reverse warning. But can you always
rely on a good earth?


NT

In article
,
wrote:
I do a fair amount of travel abroad, and need to carry (mostly) IT
equipment, some of which is powered by wall-warts - transformers
moulded into UK plugs, so I can't simply swap mains leads. What I'd
like to do is find an in-line RCBO so that I can take an n-way
extension, chop off the plug and attach a Schuko-style plug and and
RCBO. Then I can get rid of my collection of Schuko-to-BS1363 adapters
and assorted mains leads and travel with a standard set of kit that
never needs changing.

The reason I want dual pole is that the polarity of the live and
neutral is not guaranteed with Schuko - indeed, in some double
sockets it is guaranteed they will be different.

Doesn't make a scrap of difference to any of your likely equipment. I
can't think of any appliances where swapping line and neutral would cause
problems with either operation or safety. So just use an RCD fused at an
appropriate level. A Schuko plug in one would be ideal.

--
*I don't know what your problem is, but I'll bet it's hard to pronounce

Dave Plowman London SW
To e-mail, change noise into sound.

wrote:

Or one neon only as a polarity reverse warning. But can you always
rely on a good earth?

Depends on the sort of place you are plugging it into I suppose. Have
another from live to neutral if in doubt.

--
Cheers,

John.

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

On 10 Nov, 11:29, John Rumm wrote:
wrote:
Or one neon only as a polarity reverse warning. But can you always
rely on a good earth?

Depends on the sort of place you are plugging it into I suppose. Have
another from live to neutral if in doubt.

I can't always rely on a good earth, unfortunately. Do socket testers
reliably indicate live and neutral reversal if there is no earth? I
don't quite see how. If so, using the socket tester in the extension
sockets is inspired - thank-you.

I already have in-line RCDs, so I think a trip to Screwfix (I have one
within walking distance) is in order for a socket tester and another
multi-way extension.

I prefer to use an in-line RCD as it is more versatile that the
moulded-plug variety - I've often found sockets where it is not
possible to plug in a moulded-plug RCD or wall-wart - e.g. the sockets
found under floor plates in conference and/or meeting rooms, or
sockets with furniture or decor in the way - having a small right
angle Schuko is essential in such cases.

Many thanks for all the replies.

Sid

wrote:
On 10 Nov, 11:29, John Rumm wrote:
wrote:
Or one neon only as a polarity reverse warning. But can you always
rely on a good earth?
Depends on the sort of place you are plugging it into I suppose. Have
another from live to neutral if in doubt.

I can't always rely on a good earth, unfortunately. Do socket testers
reliably indicate live and neutral reversal if there is no earth? I

You would have to query the manufacturer. Most of them state they can't
detect a neutral earth transposition, but handle the remainder of the
faults. However they can oly usually show one fault at a time, so it may
well be that the lack of earth would be flagged as the first fault, and
you would not get to see the polarity reversal fault until after
clearing the first one.

don't quite see how. If so, using the socket tester in the extension
sockets is inspired - thank-you.

I was thinking of just adding "mains ready" neons to a trailing socket
rather than using a full blown plug in tester. However that would also
do the job.



--
Cheers,

John.

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

"Dave Plowman (News)" wrote in message
...
In article
,
wrote:
I do a fair amount of travel abroad, and need to carry (mostly) IT
equipment, some of which is powered by wall-warts - transformers
moulded into UK plugs, so I can't simply swap mains leads. What I'd
like to do is find an in-line RCBO so that I can take an n-way
extension, chop off the plug and attach a Schuko-style plug and and
RCBO. Then I can get rid of my collection of Schuko-to-BS1363 adapters
and assorted mains leads and travel with a standard set of kit that
never needs changing.

The reason I want dual pole is that the polarity of the live and
neutral is not guaranteed with Schuko - indeed, in some double
sockets it is guaranteed they will be different.

Doesn't make a scrap of difference to any of your likely equipment. I
can't think of any appliances where swapping line and neutral would cause
problems with either operation or safety. So just use an RCD fused at an
appropriate level. A Schuko plug in one would be ideal.

yay, someone with sense replies

i'd imagine 99% of his wall warts dont need an earth, and as for polarity,
why would they care, if you had the shuko version it could be plugged in
either way round, so why does having a 13 amp plug on it make it 'special'


as for the rcd.... almost all wall warts have some sort of protection built
in, and any power you can be exposed to will be after the wart, so will be
low voltage prolly DC, so the rcd wont do owt anyway.

just make up an extension with a dual country shuko on it (with the earth
strips for germany, and the hole for the earth pin for france) and your
covered for most places in europe, caravan shops should sell the dual earth
plug if your really stuck, but of course if you never want to plug into
french power, then dont bother and get a plain old german shuko, (btw, even
tho frances shuko's are polorised, they rarely wire the sockets up with any
polarity consistancy)

wrote in message
...
Hi all,

My internet searching skills seem to be sadly lacking, so I'll
apologise if there is as easy solution I've not found.

I do a fair amount of travel abroad, and need to carry (mostly) IT
equipment, some of which is powered by wall-warts - transformers
moulded into UK plugs, so I can't simply swap mains leads. What I'd
like to do is find an in-line RCBO so that I can take an n-way
extension, chop off the plug and attach a Schuko-style plug and and
RCBO. Then I can get rid of my collection of Schuko-to-BS1363 adapters
and assorted mains leads and travel with a standard set of kit that
never needs changing.

The reason I want dual pole is that the polarity of the live and
neutral is not guaranteed with Schuko - indeed, in some double
sockets it is guaranteed they will be different.

I think I want an RCBO as, in theory, 'continental' wiring can deliver
16A quite happily, and given that the UK stuff is rated to 13A, I'd
like to put in a 10A RCBO.

I have found in-line RCDs, but no RCBOs. An alternative (probably
cheaper) approach might be to use the RCD and put in a couple of in-
line 13A fuses in the extension lead. I realise that fusing a neutral
is normally a no-no, but since I can't tell which is live and which is
neutral, it seems like the best approach. Do such things as 13A in-
line fuseholders exist? And come to that (although not relevant for
this query) in-line dual pole 13A switches? I can find single-pole
'torpedo' switches rated to 3A, but nothing higher.

Cheers,

Sid

You can buy a UK Extension and fit a Schuko lead to it. I say a Schuko
Lead, because I don't know of any UK supplier that will just have the plugs.
They have to be moulded to the appliance lead the same as the UK now. But
you can probably buy a Schuko kettle (clover) lead for around 4 or 5 pounds.

Remove the UK setup on the extension and fit the new Schuko lead in its
place. You're working with the same AC (or as near as damn it) as we do in
the UK. Either way round, it has to work. Even your small PSU's. Now you
have a Schuko plug to 13 amp fused UK two, three, four, five, six, seven or
eight way extension socket.

Schuko appliance leads are sold only in the earthed version in the UK. Our
regulations make it mandatory for the leads sold in the UK to be earthed.
:-)

Good luck with it.

In article ,
writes:

I do a fair amount of travel abroad, and need to carry (mostly) IT
equipment, some of which is powered by wall-warts - transformers
moulded into UK plugs, so I can't simply swap mains leads. What I'd
like to do is find an in-line RCBO so that I can take an n-way
extension, chop off the plug and attach a Schuko-style plug and and
RCBO. Then I can get rid of my collection of Schuko-to-BS1363 adapters
and assorted mains leads and travel with a standard set of kit that
never needs changing.

One comment I'd make is that RCD's are fragile devices and usually
fail unsafe. If you have one as part of portable equipment, make
sure you always test it when you are setting up, and at frequent
intervals whilst in use. Otherwise, you will be unaware when it's
been dropped and no longer trips off. For this reason, I never
buy the type which is built in to a plug. People treat them like
plugs in terms of dropping, bashing, kicking, etc, and they don't
survive that.

--
Andrew Gabriel
[email address is not usable -- followup in the newsgroup]

In article ,
Andrew Gabriel wrote:
One comment I'd make is that RCD's are fragile devices and usually
fail unsafe. If you have one as part of portable equipment, make
sure you always test it when you are setting up, and at frequent
intervals whilst in use. Otherwise, you will be unaware when it's
been dropped and no longer trips off. For this reason, I never
buy the type which is built in to a plug. People treat them like
plugs in terms of dropping, bashing, kicking, etc, and they don't
survive that.

We use loads of them for location filming and they seem to survive quite
well.

--
*Why isn't there mouse-flavoured cat food?

Dave Plowman London SW
To e-mail, change noise into sound.

On Mon, 10 Nov 2008 12:36:48 -0000, gazz wrote:

i'd imagine 99% of his wall warts dont need an earth, and as for
polarity, why would they care,

Agreed, most wall warts are double insulated and earth less.

I think the OP was concerned about single pole switching in a system were
polarity is not fixed. ie the trip goes but equipment is still live. In
the "heat of the moment" it is all to easy to forget to unplug apparently
dead kit before working on the fault.

But aren't some continental sockets earthless and/or have a bi-phase
supply? Which poses some interesting questions regarding the KISS plugin
tester and rotate the plug approach.

--
Cheers
Dave.

On 10 Nov, 14:53, (Andrew Gabriel) wrote:
In article ,
* * * * writes:



What I'd
like to do is find an in-line RCBO so that I can take an n-way
extension, chop off the plug and attach a Schuko-style plug and and
RCBO. Then I can get rid of my collection of Schuko-to-BS1363 adapters
and assorted mains leads and travel with a standard set of kit that
never needs changing.

One comment I'd make is that RCD's are fragile devices and usually
fail unsafe. If you have one as part of portable equipment, make
sure you always test it when you are setting up, and at frequent
intervals whilst in use. Otherwise, you will be unaware when it's
been dropped and no longer trips off. For this reason, I never
buy the type which is built in to a plug. People treat them like
plugs in terms of dropping, bashing, kicking, etc, and they don't
survive that.

Would a power strip with a built in RCD help?
http://www.olson.co.uk/fused_rcd.htm "panel mounted fuse holder and
30mA RCD"

They also do them with individually fused sockets
http://www.olson.co.uk/power_strip.htm

Or bespoke with a range of options, though that might be pricy.
"Customer specified sockets, including combinations of different
sockets
UK 13A (BS1363), IEC320 C13 10A, IEC320 C19, IEC309 16A and 32A, USA,
German, French, Swiss, Italian, Neutrik, Electrak
Customer specified options such as switches, circuit breakers, fuses,
neon indicators, meters, rf filters, sequential start timers"

Thanks Andrew, thanks Owain.

I should have looked at Olsen - I've specified them in datacentres
often enough, usually bespoke. I've not been the one paying.

I usually test RCDs pretty much every time I energise them - just got
into the habit. Perhaps I've been lucky, but I've not had one fail
yet. I take the point about being fragile, 'though. Knocking about in
checked baggage is not the most benign of environments. Anything
brittle gets double wrapped in bubble wrap, and I make sure the
suitcase is stuffed to prevent rattling about. A friend of mine told
me to pack as if the suitcase were to be thrown from the second storey
of a building, which seems to work, and having often watched baggage
handlers load and unload, I see what luggage gets put through.

Sid

On 10 Nov, 15:31, "Dave Liquorice"
wrote:
On Mon, 10 Nov 2008 12:36:48 -0000, gazz wrote:
i'd imagine 99% of his wall warts dont need an earth, and as for
polarity, why would they care,

Agreed, most wall warts are double insulated and earth less.

I think the OP was concerned about single pole switching in a system were
polarity is not fixed. ie the trip goes but equipment is still live. In
the "heat of the moment" it is all to easy to forget to unplug apparently
dead kit before working on the fault.

But aren't some continental sockets earthless and/or have a bi-phase
supply? Which poses some interesting questions regarding the KISS plugin
tester and rotate the plug approach.

Dave - you are reading my mind. As I get older, the chances of me
forgetting to isolate before investigating the fault get higher. You
could say from a Darwin Award point of view, it would serve me right,
but alas, I'm too old to qualify.

As for continental sockets, you are quire right, and what would be
regarded in the UK as dangerous practices abound. In Italy, I came
across a multi-way CEE 7/7 trailing adaptor wired into a CEE 7/16 plug
(hidden away behind a filing cabinet), which was powering everything
in a meeting room - including the (very hot) projector and multiple
laptops. Similarly, in Denmark, a multiway CEE 7/7 serving several
other multiway adapters.

Norway has many CEE 7/17 sockets in older buildings (Like Schuko, but
no earth slides or pins), which is problematic as many higher power
laptop power transformers supplied in the UK seem to want functioning
earths - they are certainly wired as such.

I think bi-phase is/was used a lot in Scandinavia and Germany.

Like many things, this seems to get more complicated the more I look
at it. At least I don't (yet) travel to the USA.

As life goes on, I keep on finding more things to be ignorant about!

Regards,

Sid

On Nov 10, 12:13*pm, wrote:
On 10 Nov, 11:29, John Rumm wrote: wrote:
Or one neon only as a polarity reverse warning. But can you always
rely on a good earth?

Depends on the sort of place you are plugging it into I suppose. Have
another from live to neutral if in doubt.

I can't always rely on a good earth, unfortunately.

Then you need the full set of 3 neons, as used in plug-in testers.


Do socket testers
reliably indicate live and neutral reversal if there is no earth?

They're just 3 neons, L-N, N-E, E-L. So they'd indicate all wasnt
right, but cant tell you exactly whats going on if there are 2
simultaneous faults.


NT

On Mon, 10 Nov 2008 09:53:48 -0800 (PST), wrote:

They're just 3 neons, L-N, N-E, E-L. So they'd indicate all wasnt
right, but cant tell you exactly whats going on if there are 2
simultaneous faults.

One "fault" could be no earth at the socket... And being neons you may
still get illumination, via leakage, in the abscence of a real earth. Or
the "delta" connected neons would make the floating earth point rise to
50% of the L-N voltage which would provide enough volts for the neons to
light at a lower level compared to the one L-N but that might not be
particulary obvious.

I wonder of the better quality plugin testers use LEDs and high voltage
zeners?

--
Cheers
Dave.

On Nov 10, 6:54*pm, "Dave Liquorice"
wrote:
On Mon, 10 Nov 2008 09:53:48 -0800 (PST), wrote:
They're just 3 neons, L-N, N-E, E-L. So they'd indicate all wasnt
right, but cant tell you exactly whats going on if there are 2
simultaneous faults.

One "fault" could be no earth at the socket... And being neons you may
still get illumination, via leakage, in the abscence of a real earth. Or
the "delta" connected neons would make the floating earth point rise to
50% of the L-N voltage which would provide enough volts for the neons to
light at a lower level compared to the one L-N but that might not be
particulary obvious.

I wonder of the better quality plugin testers use LEDs and high voltage
zeners?

Yes, both neons light, the fault shows up.


NT

On Nov 10, 3:31*pm, "Dave Liquorice"
wrote:
On Mon, 10 Nov 2008 12:36:48 -0000, gazz wrote:
i'd imagine 99% of his wall warts dont need an earth, and as for
polarity, why would they care,

Agreed, most wall warts are double insulated and earth less.

I think the OP was concerned about single pole switching in a system were
polarity is not fixed. ie the trip goes but equipment is still live. In
the "heat of the moment" it is all to easy to forget to unplug apparently
dead kit before working on the fault.

But aren't some continental sockets earthless and/or have a bi-phase
supply? Which poses some interesting questions regarding the KISS plugin
tester and rotate the plug approach.

with a groundless supply, all 3 neons will light

Appliances dont care a whatsit about polarity, earth, fusing or RCD.
Its people getting electrocuted or burnt by faulty appliances that
care.


NT

On Mon, 10 Nov 2008 08:59:26 -0800 (PST), wrote:

Like many things, this seems to get more complicated the more I look
at it. At least I don't (yet) travel to the USA.

I don't think you will find a single system that will be "safe" or give
correct indications under all circumstances. You just have to be
pragmatic, like use a plugin tester and rotate the plug if the tester
indicates a reversal. Not forgetting to check again after the plug
rotation and being aware of the limitations of the plugin tester.

As life goes on, I keep on finding more things to be ignorant about!

One should never stop learning, I'm reading "In Search of Schrodinger's
Cat" by John Gribbin. Now I don't stand a cat in hells chance, let alone
in a box, of really understanding quantum theory but it doesn't stop me
getting some knowledge of the very basics. It's an old book now, 1985, I
wonder what developments there have been in the last 20 year? And is there
similar book about covering them?

--
Cheers
Dave.

On Mon, 10 Nov 2008 08:59:26 -0800 (PST), wrote:

Norway has many CEE 7/17 sockets in older buildings (Like Schuko, but
no earth slides or pins), which is problematic as many higher power
laptop power transformers supplied in the UK seem to want functioning
earths - they are certainly wired as such.

The earth on some laptop and similar PSU's is for interference
reduction. Switched mode power supplies can generate a lot of radio
frequency noise and some filter designs to prevent interference
require an earth. It has no safety function.

On 12 Nov, 10:12, Peter Parry wrote:
On Mon, 10 Nov 2008 08:59:26 -0800 (PST), wrote:

The earth on some laptop and similar PSU's is for interference
reduction. *Switched mode power supplies can *generate a lot of radio
frequency noise and some filter designs to prevent interference
require an earth. *It has no safety function.

Thank-you. I didn't know that.

I'm not trying to say you are generally wrong, but the Dell PA-12 65
Watt I have in my hands now has an earth connection. There is no
'nested squares' double insulation mark on it among the profusion of
conformance marks. It also says:

CAUTION: FOR USE WITH INFORMATION TECHNOLOGY EQUIPMENT ONLY.
UTILISER AVEC DU MATERIEL INFORMATIQUE SEULEMENT
DAS NETZEIL DARF NUR IN VERBINDUNG MIT
GERATEN NACH EN 60950 VERWENDET WERDEN
Apparatet skal tilkoples jordet stikkontakt
Apparaten skal an slutas till jorolat uttag.
Chinese

I'm not sure of the German, but EN 60950 is a standard maintained by
CEN (European Committee for Standardization) and CENELEC (European
Committee for Electrotechnical Standardization), entitled "Safety of
information technology equipment". I can't find a free copy on the
web, but this gives some idea as to the contents:

http://www.bsigroup.com/en/Standards...N-60950-12006/

The Danish/Norwegian and Swedish both specify it should only be
connected to earthed sockets. I've no idea what the Chinese says.

If the earth provides no safety function (just RF screening), then
shouldn't it be double insulated, and say so? I have an example of a
three-pin wall-wart which has a metal earth pin, and also the double
insulated symbol (It's a standard transformer, non switched mode (by
the weight) used for powering a four port LAN switch).

Cheers,

Sid

wrote in message
...
On 12 Nov, 10:12, Peter Parry wrote:
On Mon, 10 Nov 2008 08:59:26 -0800 (PST), wrote:

The earth on some laptop and similar PSU's is for interference
reduction. Switched mode power supplies can generate a lot of radio
frequency noise and some filter designs to prevent interference
require an earth. It has no safety function.

Thank-you. I didn't know that.

I'm not trying to say you are generally wrong, but the Dell PA-12 65
Watt I have in my hands now has an earth connection. There is no
'nested squares' double insulation mark on it among the profusion of
conformance marks. It also says:

CAUTION: FOR USE WITH INFORMATION TECHNOLOGY EQUIPMENT ONLY.
UTILISER AVEC DU MATERIEL INFORMATIQUE SEULEMENT
DAS NETZEIL DARF NUR IN VERBINDUNG MIT
GERATEN NACH EN 60950 VERWENDET WERDEN
Apparatet skal tilkoples jordet stikkontakt
Apparaten skal an slutas till jorolat uttag.
Chinese

I'm not sure of the German, but EN 60950 is a standard maintained by
CEN (European Committee for Standardization) and CENELEC (European
Committee for Electrotechnical Standardization), entitled "Safety of
information technology equipment". I can't find a free copy on the
web, but this gives some idea as to the contents:

http://www.bsigroup.com/en/Standards...N-60950-12006/

The Danish/Norwegian and Swedish both specify it should only be
connected to earthed sockets. I've no idea what the Chinese says.

If the earth provides no safety function (just RF screening), then
shouldn't it be double insulated, and say so? I have an example of a
three-pin wall-wart which has a metal earth pin, and also the double
insulated symbol (It's a standard transformer, non switched mode (by
the weight) used for powering a four port LAN switch).

Cheers,

Sid

And some earthed switching supplies have an earth pin only to protect the
mains supply in to the box, but stop at connecting to any metal shielding
that prevents RF interference. In cases where the nylon case is penetrated
by a metal chair leg Etc. while you use the IT equipment attached to it, it
pops the fuse in the plug. But that's mostly on PSU's that have a trailing
mains lead..

On Wed, 12 Nov 2008 04:08:58 -0800 (PST), wrote:


I'm not trying to say you are generally wrong, but the Dell PA-12 65
Watt I have in my hands now has an earth connection. There is no
'nested squares' double insulation mark on it among the profusion of
conformance marks.

There won't be as it isn't double insulated.

If the earth provides no safety function (just RF screening), then
shouldn't it be double insulated, and say so? I have an example of a
three-pin wall-wart which has a metal earth pin, and also the double
insulated symbol (It's a standard transformer, non switched mode (by
the weight) used for powering a four port LAN switch).

The metal earth pin in your conventional PSU won't have any connection
and the device will be double insulated. In a PSU using a filter
which requires an earth it isn't usually screened but has two
capacitors going to earth one from each line so it isn't double
insulated. The output is still isolated from the input though so
there is no risk to the user. With the earth disconnected the earth
connection on a filtered supply will rise to half the mains voltage
but with negligible current capacity - the most you will get is a
slight tingle as you touch it.

On 12 Nov, 16:44, Peter Parry wrote:
..

The metal earth pin in your conventional PSU won't have any connection
and the device will be double insulated. In a PSU using a filter
which requires an earth it isn't usually screened but has two
capacitors going to earth one from each line so it isn't double
insulated. The output is still isolated from the input though so
there is no risk to the user. With the earth disconnected the earth
connection on a filtered supply will rise to half the mains voltage
but with negligible current capacity - the most you will get is a
slight tingle as you touch it.

Thank-you for the follow-up and clarification. Much appreciated.

Regards,

Sid.