Tingle from metal lamp = dangerous?

[Lars]

My electrical theory is fair but not great. Can someone please
advise me.

I have an old Anglepoise lamp with painted metal arms and painted
metal lampshade (Anglepoise model 90). It has a two-core mains
lead. I am in the UK so this is all at 230-240 volts.

Today I touched the outside of the lampshade and got a sort of vey
mild tingle feeling which felt "odd". When I used a mains tester
screwdriver on the exposed metal (at the joint of the lampshade
and support arm) then it glowed as if the metal of the Anglepoise
lamp was live.

I unplugged the lamp and tested the resistence between the live
pin on the mains plug and some exposed metal on the lamp. I got
no resistence reading at all (i.e. it must have been a very high
resistence). I then tested the neutral pin in the same way and
got the same high resistence result.

So the lamp seems ok. But something seems to be wrong!

QUESTION: Is my lamp safe to use and could I get a shock from it
in its present condition?

QUESTION: If my lamp is unsafe then is there a repair I can do?

Thank you for any info.
Lars

-----------------

PS: Picture of Anglepoise model 90:
Loading Image...

[Bob Eager]

Post by Lars
I have an old Anglepoise lamp with painted metal arms and painted
metal lampshade (Anglepoise model 90). It has a two-core mains
lead. I am in the UK so this is all at 230-240 volts.
Today I touched the outside of the lampshade and got a sort of vey
mild tingle feeling which felt "odd". When I used a mains tester
screwdriver on the exposed metal (at the joint of the lampshade
and support arm) then it glowed as if the metal of the Anglepoise
lamp was live.
I unplugged the lamp and tested the resistence between the live
pin on the mains plug and some exposed metal on the lamp. I got
no resistence reading at all (i.e. it must have been a very high
resistence). I then tested the neutral pin in the same way and
got the same high resistence result.
QUESTION: Is my lamp safe to use and could I get a shock from it
in its present condition?

No. Yes.

Post by Lars
QUESTION: If my lamp is unsafe then is there a repair I can do?

I would guess that the insulation is failing somewhere. Your test with
the meter wasn't high voltage and didn't show it up. You need proper
equipment to do that test.

I would guess that replacing all the wiring would probably do it. It
*might* be the lamp holder, but I'd change the wiring first. If you do
replace the lampholder, it's probably a special heat resistant one
(probably ceramic).

[Rob Morley]

Post by Lars
My electrical theory is fair but not great. Can someone please
advise me.
I have an old Anglepoise lamp with painted metal arms and painted
metal lampshade (Anglepoise model 90). It has a two-core mains
lead. I am in the UK so this is all at 230-240 volts.
Today I touched the outside of the lampshade and got a sort of vey
mild tingle feeling which felt "odd". When I used a mains tester
screwdriver on the exposed metal (at the joint of the lampshade
and support arm) then it glowed as if the metal of the Anglepoise
lamp was live.
I unplugged the lamp and tested the resistence between the live
pin on the mains plug and some exposed metal on the lamp. I got
no resistence reading at all (i.e. it must have been a very high
resistence). I then tested the neutral pin in the same way and
got the same high resistence result.

That's because you were measuring it at a few volts - you need to
measure at a few hundred volts.

Post by Lars
So the lamp seems ok. But something seems to be wrong!
QUESTION: Is my lamp safe to use and could I get a shock from it
in its present condition?

Probably not very safe - you already had a mild shock from it.

Post by Lars
QUESTION: If my lamp is unsafe then is there a repair I can do?

Find the loose wire or damaged insulation and replace it.

[Sam Wormley]

Post by Lars
My electrical theory is fair but not great. Can someone please
advise me.
I have an old Anglepoise lamp with painted metal arms and painted
metal lampshade (Anglepoise model 90). It has a two-core mains
lead. I am in the UK so this is all at 230-240 volts.
Today I touched the outside of the lampshade and got a sort of vey
mild tingle feeling which felt "odd". When I used a mains tester
screwdriver on the exposed metal (at the joint of the lampshade
and support arm) then it glowed as if the metal of the Anglepoise
lamp was live.

REplace the wiring!

[Peter Parry]

Post by Lars
Today I touched the outside of the lampshade and got a sort of vey
mild tingle feeling which felt "odd".

Do you have nylon carpets?

[Mary Fisher]

Post by Lars
Today I touched the outside of the lampshade and got a sort of vey
mild tingle feeling which felt "odd". When I used a mains tester
screwdriver on the exposed metal (at the joint of the lampshade
and support arm) then it glowed as if the metal of the Anglepoise
lamp was live.

We have an Art Deco brass lamp which I can feel 'tingling'or 'trembling'
when I touch the base or the stem. The wiring has been checked and renewed
several times and it still happens - and Spouse is absolutely thorough about
doing a good job mainly to prove me wrong because he can't feel it. I can
still feel it.

I could also, once upon a time, feel the same thing from a metal electric
kettle and nobody else could. The kettle was taken away by the first child
to go to university. Over the years we lost all our electric kettles like
that which is why we're left with an ancient copper one on the gas hob, it
used to be used by Spouse's grandmother on their coal fire. But that's a
different story.

It's not a shock and it can only be felt with the lightest possible touch -
but it's very definitely there and can only be sensed when the lamp is
plugged in and the outlet switch is on. The lamp itself doesn't have to be
lit.

I've never suffered and I doubt that the OT will either. If he were going to
he would have done by now.

Mary

[Jan Panteltje]

On a sunny day (Wed, 27 Apr 2005 21:48:01 +0100) it happened "Mary Fisher"

Post by Mary Fisher

Post by Lars
Today I touched the outside of the lampshade and got a sort of vey
mild tingle feeling which felt "odd". When I used a mains tester
screwdriver on the exposed metal (at the joint of the lampshade
and support arm) then it glowed as if the metal of the Anglepoise
lamp was live.

We have an Art Deco brass lamp which I can feel 'tingling'or 'trembling'
when I touch the base or the stem. The wiring has been checked and renewed
several times and it still happens - and Spouse is absolutely thorough about
doing a good job mainly to prove me wrong because he can't feel it. I can
still feel it.
I could also, once upon a time, feel the same thing from a metal electric
kettle and nobody else could. The kettle was taken away by the first child
to go to university. Over the years we lost all our electric kettles like
that which is why we're left with an ancient copper one on the gas hob, it
used to be used by Spouse's grandmother on their coal fire. But that's a
different story.
It's not a shock and it can only be felt with the lightest possible touch -
but it's very definitely there and can only be sensed when the lamp is
plugged in and the outlet switch is on. The lamp itself doesn't have to be
lit.
I've never suffered and I doubt that the OT will either. If he were going to
he would have done by now.
Mary

It is a common case, and possibly capacitive coupling between the hot wire
and the metal frame (if no isolation problem).
The responsible things to do is use a 3 lead mains cable and plug, and connect
the ground to the metal frame.
Problem solved.
ANY other configuration will leave the possiblity of a short between a live
wire and the frame, causing the metal to become live.
When ground is connected a short will blow the fuse.

[Mary Fisher]

Post by Jan Panteltje
On a sunny day (Wed, 27 Apr 2005 21:48:01 +0100) it happened "Mary Fisher"

Post by Mary Fisher

Post by Lars
Today I touched the outside of the lampshade and got a sort of vey
mild tingle feeling which felt "odd". When I used a mains tester
screwdriver on the exposed metal (at the joint of the lampshade
and support arm) then it glowed as if the metal of the Anglepoise
lamp was live.

We have an Art Deco brass lamp which I can feel 'tingling'or 'trembling'
when I touch the base or the stem. The wiring has been checked and renewed
several times and it still happens - and Spouse is absolutely thorough about
doing a good job mainly to prove me wrong because he can't feel it. I can
still feel it.
I could also, once upon a time, feel the same thing from a metal electric
kettle and nobody else could. The kettle was taken away by the first child
to go to university. Over the years we lost all our electric kettles like
that which is why we're left with an ancient copper one on the gas hob, it
used to be used by Spouse's grandmother on their coal fire. But that's a
different story.
It's not a shock and it can only be felt with the lightest possible touch -
but it's very definitely there and can only be sensed when the lamp is
plugged in and the outlet switch is on. The lamp itself doesn't have to be
lit.
I've never suffered and I doubt that the OT will either. If he were going to
he would have done by now.
Mary

It is a common case, and possibly capacitive coupling between the hot wire
and the metal frame (if no isolation problem).
The responsible things to do is use a 3 lead mains cable and plug, and connect
the ground to the metal frame.
Problem solved.

Nope. That's what Spouse said. It now has that (he did it) and there's no
change..

Mary

[bz]

Post by Mary Fisher

Post by Jan Panteltje
On a sunny day (Wed, 27 Apr 2005 21:48:01 +0100) it happened "Mary

Post by Mary Fisher

Post by Lars
Today I touched the outside of the lampshade and got a sort of vey
mild tingle feeling which felt "odd". When I used a mains tester
screwdriver on the exposed metal (at the joint of the lampshade
and support arm) then it glowed as if the metal of the Anglepoise
lamp was live.

We have an Art Deco brass lamp which I can feel 'tingling'or
'trembling' when I touch the base or the stem. The wiring has been
checked and renewed several times and it still happens - and Spouse is
absolutely thorough about
doing a good job mainly to prove me wrong because he can't feel it. I
can still feel it.
I could also, once upon a time, feel the same thing from a metal
electric kettle and nobody else could. The kettle was taken away by the
first child to go to university. Over the years we lost all our
electric kettles like that which is why we're left with an ancient
copper one on the gas hob, it used to be used by Spouse's grandmother
on their coal fire. But that's a different story.
It's not a shock and it can only be felt with the lightest possible touch -
but it's very definitely there and can only be sensed when the lamp is
plugged in and the outlet switch is on. The lamp itself doesn't have to
be lit.
I've never suffered and I doubt that the OT will either. If he were going to
he would have done by now.
Mary

It is a common case, and possibly capacitive coupling between the hot
wire and the metal frame (if no isolation problem).
The responsible things to do is use a 3 lead mains cable and plug, and connect
the ground to the metal frame.
Problem solved.

Nope. That's what Spouse said. It now has that (he did it) and there's
no change..

Then it is probably not being plugged into a properly grounded outlet.

At the very least, you should have him install a GFI outlet in the place
that the lamp is used. Better is to make sure that the safety ground on
the outlet really has a good, low impedence run to the main breaker box.

Of course, he may have failed to properly connect the safety ground to the
metal parts of your lamp. :)

[b***@meeow.co.uk]

Post by Lars
Today I touched the outside of the lampshade and got a sort of vey
mild tingle feeling which felt "odd". When I used a mains tester
screwdriver on the exposed metal (at the joint of the lampshade
and support arm) then it glowed as if the metal of the

Anglepoise

Post by Lars
lamp was live.

Once had lots of problems like this, and when i got a shock off the
earth I did something about it. It turned out lots of the various earth
connections around the house were just copper cable twisted together,
so of course the joints had gone high R over time. Also the earth rod
was disconnected, so there was no E anywhere anyway. Just glad there
was no shower.


NT

[Palindr☻me]

Post by Mary Fisher

Post by Jan Panteltje
On a sunny day (Wed, 27 Apr 2005 21:48:01 +0100) it happened "Mary Fisher"

Post by Lars
Today I touched the outside of the lampshade and got a sort of vey
mild tingle feeling which felt "odd". When I used a mains tester
screwdriver on the exposed metal (at the joint of the lampshade
and support arm) then it glowed as if the metal of the Anglepoise
lamp was live.

It is a common case, and possibly capacitive coupling between the hot wire
and the metal frame (if no isolation problem).
The responsible things to do is use a 3 lead mains cable and plug, and connect
the ground to the metal frame.
Problem solved.

Nope. That's what Spouse said. It now has that (he did it) and there's no
change..

Following fitting the earth connection, does it tingle even
when switched off at the wall socket?

If so , it sounds like you are discharging a static charge
into the lamp, rather than getting a charge from it.
Touching something that is earthed (eg wall radiator)
shortly before touching the lamp should prove/disprove this.
But don't touch the two at the same time until you have had
the lamp professionally tested for safety - I wouldn't have
trusted my hublet with anything electrical..

[Kaiser]

Post by Mary Fisher

Post by Jan Panteltje
On a sunny day (Wed, 27 Apr 2005 21:48:01 +0100) it happened "Mary Fisher"

Post by Mary Fisher

Post by Lars
Today I touched the outside of the lampshade and got a sort of vey
mild tingle feeling which felt "odd". When I used a mains tester
screwdriver on the exposed metal (at the joint of the lampshade
and support arm) then it glowed as if the metal of the Anglepoise
lamp was live.

We have an Art Deco brass lamp which I can feel 'tingling'or 'trembling'
when I touch the base or the stem. The wiring has been checked and renewed
several times and it still happens - and Spouse is absolutely thorough about
doing a good job mainly to prove me wrong because he can't feel it. I can
still feel it.
I could also, once upon a time, feel the same thing from a metal electric
kettle and nobody else could. The kettle was taken away by the first child
to go to university. Over the years we lost all our electric kettles like
that which is why we're left with an ancient copper one on the gas hob, it
used to be used by Spouse's grandmother on their coal fire. But that's a
different story.
It's not a shock and it can only be felt with the lightest possible touch -
but it's very definitely there and can only be sensed when the lamp is
plugged in and the outlet switch is on. The lamp itself doesn't have to be
lit.
I've never suffered and I doubt that the OT will either. If he were going to
he would have done by now.
Mary

It is a common case, and possibly capacitive coupling between the hot wire
and the metal frame (if no isolation problem).
The responsible things to do is use a 3 lead mains cable and plug, and connect
the ground to the metal frame.
Problem solved.

Nope. That's what Spouse said. It now has that (he did it) and there's no
change..

In that case it may be advisable to check that your 13amp socket has a good
earth.

[Jan Panteltje]

On a sunny day (Wed, 27 Apr 2005 22:20:56 +0100) it happened "Mary Fisher"

Post by Mary Fisher

Post by Jan Panteltje
On a sunny day (Wed, 27 Apr 2005 21:48:01 +0100) it happened "Mary Fisher"

Post by Mary Fisher

Post by Lars
Today I touched the outside of the lampshade and got a sort of vey
mild tingle feeling which felt "odd". When I used a mains tester
screwdriver on the exposed metal (at the joint of the lampshade
and support arm) then it glowed as if the metal of the Anglepoise
lamp was live.

We have an Art Deco brass lamp which I can feel 'tingling'or 'trembling'
when I touch the base or the stem. The wiring has been checked and renewed
several times and it still happens - and Spouse is absolutely thorough about
doing a good job mainly to prove me wrong because he can't feel it. I can
still feel it.
I could also, once upon a time, feel the same thing from a metal electric
kettle and nobody else could. The kettle was taken away by the first child
to go to university. Over the years we lost all our electric kettles like
that which is why we're left with an ancient copper one on the gas hob, it
used to be used by Spouse's grandmother on their coal fire. But that's a
different story.
It's not a shock and it can only be felt with the lightest possible touch -
but it's very definitely there and can only be sensed when the lamp is
plugged in and the outlet switch is on. The lamp itself doesn't have to be
lit.
I've never suffered and I doubt that the OT will either. If he were going to
he would have done by now.
Mary

It is a common case, and possibly capacitive coupling between the hot wire
and the metal frame (if no isolation problem).
The responsible things to do is use a 3 lead mains cable and plug, and connect
the ground to the metal frame.
Problem solved.

Nope. That's what Spouse said. It now has that (he did it) and there's no
change..
Mary

Well, I was in this house once, where they also earthed the stuff, but it
then turned out the earth (I had to install some equipment there) was not
connected to anything, it was originally connected to water pipes, but
somebody had just cut the wire.
You (he) can test if earth is there with say a 40 W lightbulb between earth and
live. It should light.
Then test between live and your lamp frame, it should light too.
The only alternative is that you pick up something from the floor (bad wiring
conductive carpet), anything goes.

[Joe]

Post by Lars
My electrical theory is fair but not great. Can someone please
advise me.
I have an old Anglepoise lamp with painted metal arms and painted
metal lampshade (Anglepoise model 90). It has a two-core mains
lead. I am in the UK so this is all at 230-240 volts.
Today I touched the outside of the lampshade and got a sort of vey
mild tingle feeling which felt "odd". When I used a mains tester
screwdriver on the exposed metal (at the joint of the lampshade
and support arm) then it glowed as if the metal of the Anglepoise
lamp was live.
I unplugged the lamp and tested the resistence between the live
pin on the mains plug and some exposed metal on the lamp. I got
no resistence reading at all (i.e. it must have been a very high
resistence). I then tested the neutral pin in the same way and
got the same high resistence result.
So the lamp seems ok. But something seems to be wrong!
QUESTION: Is my lamp safe to use and could I get a shock from it
in its present condition?
QUESTION: If my lamp is unsafe then is there a repair I can do?

It's probably just capacitive leakage between the live wire and the
metal, and is unlikely to be serious, but what is serious is that the
metal isn't earthed. The resistance measurements aren't completely
reliable, as presumably they were made with a low-voltage source rather
than a few hundred volts, but they do suggest there isn't a direct short
of wire to metal.

You shouldn't have any appliance with exposed metal parts which are not
earthed. Such an appliance needs three-core cable and all of the metal
parts well earthed. In an anglepoise, in particular, there will be mains
wires flexing every time the lamp is moved. Eventually the insulation
will crack, and a wire will touch the metal body. You really want a good
earth at this point.

I would recommend fitting a three-core cable, making sure the plug fuse
is correct (almost certainly three amps) rather than the default 13 amp
one that came with the plug. Again, particularly with an anglepoise, it
would not be safe to assume that all the metalwork is in good electrical
contact and that earthing at the cable entry point would provide a good
connection at the shade.

For maximum safety, I would replace the existing internal wiring. If
it's really old, then it may have deteriorated significantly,
particularly in the hot area. Probably any paint at the lamp joints will
have worn away long since, but I'd consider using star washers on the
joints and linking around the 'elbows' of the lamp with wires to solder
tags screwed down over the washers. That way, the shade, the part most
likely to be touched, should have good earth continuity.

Maybe you can go on using it as it is for decades more without incident.
Are you feeling lucky...?

[s--p--o--n--i--x]

Post by Joe
You shouldn't have any appliance with exposed metal parts which are not
earthed. Such an appliance needs three-core cable and all of the metal
parts well earthed. In an anglepoise, in particular, there will be mains
wires flexing every time the lamp is moved. Eventually the insulation
will crack, and a wire will touch the metal body. You really want a good
earth at this point.

If it's the sort of anglepoise lamp I'm thinking of it will be double
insulated.

Whilst it would be sensible to earth the thing, it will need 'cross
bonding' across the hinged joints.

[Bill Woods]

Post by s--p--o--n--i--x
If it's the sort of anglepoise lamp I'm thinking of it will be
double insulated.

What does "double insulated" mean in actual practice?

Post by s--p--o--n--i--x
Whilst it would be sensible to earth the thing, it will need
'cross bonding' across the hinged joints.

[Pop]

Basically, Double insulated is a little misleading, but
in UL/CSA parlance, it means that the internal wiring
is such that it would take TWO faults to occur, either
of which would stop the product from working, before
anything could become electrically dangerous to the
user. Usage conditions are also taken into account.
Among other things it also means that there cannot
be any exposed metal on the product. ALL exposed metal
must be grounded, which become a non-essential in
double insulated products.

It also means it doesn't need a third "prong", and the
blades do not have to be polarized on the two-blade
plug, and it does not need a 3-hole outlet.

Pop

Post by Bill Woods

Post by s--p--o--n--i--x
If it's the sort of anglepoise lamp I'm thinking of
it will be
double insulated.

What does "double insulated" mean in actual practice?

Post by s--p--o--n--i--x
Whilst it would be sensible to earth the thing, it
will need
'cross bonding' across the hinged joints.

[daestrom]

Basically, Double insulated is a little misleading, but in UL/CSA
parlance, it means that the internal wiring is such that it would take TWO
faults to occur, either of which would stop the product from working,
before anything could become electrically dangerous to the user. Usage
conditions are also taken into account.
Among other things it also means that there cannot be any exposed metal
on the product. ALL exposed metal must be grounded, which become a
non-essential in double insulated products.
It also means it doesn't need a third "prong", and the blades do not have
to be polarized on the two-blade plug, and it does not need a 3-hole
outlet.

Not entirely true. The classic example is a double-insulated inexpensive
power drill. The chuck that holds the bit is metal, and is not grounded.
The tool does not have a third prong grounding conductor. But it meets the
definition of double-insulated because the chuck is insulated from the motor
by nylon gear-drive. And the windings on the motor are, of course,
insulated from the motor frame. So it would take two faults, just as you
said. It has no third prong, also as you said. But the exposed metal parts
are *not* necessarily grounded.

daestrom

[m***@UNLISTED.com]

On Sat, 14 May 2005 16:09:03 GMT, "daestrom"

Post by daestrom

Basically, Double insulated is a little misleading, but in UL/CSA
parlance, it means that the internal wiring is such that it would take TWO
faults to occur, either of which would stop the product from working,
before anything could become electrically dangerous to the user. Usage
conditions are also taken into account.
Among other things it also means that there cannot be any exposed metal
on the product. ALL exposed metal must be grounded, which become a
non-essential in double insulated products.
It also means it doesn't need a third "prong", and the blades do not have
to be polarized on the two-blade plug, and it does not need a 3-hole
outlet.

Not entirely true. The classic example is a double-insulated inexpensive
power drill. The chuck that holds the bit is metal, and is not grounded.
The tool does not have a third prong grounding conductor. But it meets the
definition of double-insulated because the chuck is insulated from the motor
by nylon gear-drive. And the windings on the motor are, of course,
insulated from the motor frame. So it would take two faults, just as you
said. It has no third prong, also as you said. But the exposed metal parts
are *not* necessarily grounded.
daestrom

So they put in nylon gears, which we all know have a very limited life
span, instead of using reliable gears and adding a grounded cord.
That's just plain stupidity at it's worse. Also the reason I am
always looking for the old solid metal drills at garage sales. Not to
mention that most new drills have those keyless chucks, and I
absolutely despise those useless pieces of shit.

I'd much rather spend the extra dollar or two for the steel gears and
grounded cord.

I bought a portable jig saw (saber saw) 2 years ago. It had plastic
or nylon gears. I used it maybe 2 hours at most cutting plywood and
such. Then I inserted a metal cutting blade and started to cut a
piece of steel barn siding. I was cutting the length of the steel or
about 8 feet. That stuff is only 22 gauge or thereabouts. I cut
about 2 feet when the saw stopped cutting, but the motor was still
running. I opened the saw to find the nylon gears completely
stripped. After a big hassle, I was able to get the thing replaced
thru the warranty, but as far as I am concerned, it's pretty much a
useless tool, since I know as soon as I use it for anything more than
cutting some balsa wood, the new one will strip too. Just more
inferior crap sold by Black & Decker.

Mark

[Stephen B.]

<SNIP>

Post by m***@UNLISTED.com

Post by daestrom
Not entirely true. The classic example is a double-insulated inexpensive
power drill. The chuck that holds the bit is metal, and is not grounded.
The tool does not have a third prong grounding conductor. But it meets the
definition of double-insulated because the chuck is insulated from the motor
by nylon gear-drive. And the windings on the motor are, of course,
insulated from the motor frame. So it would take two faults, just as you
said. It has no third prong, also as you said. But the exposed metal parts
are *not* necessarily grounded.
daestrom

So they put in nylon gears, which we all know have a very limited life
span, instead of using reliable gears and adding a grounded cord.
That's just plain stupidity at it's worse. Also the reason I am
always looking for the old solid metal drills at garage sales. Not to
mention that most new drills have those keyless chucks, and I
absolutely despise those useless pieces of shit.
I'd much rather spend the extra dollar or two for the steel gears and
grounded cord.
I bought a portable jig saw (saber saw) 2 years ago. It had plastic
or nylon gears. I used it maybe 2 hours at most cutting plywood and
such. Then I inserted a metal cutting blade and started to cut a
piece of steel barn siding. I was cutting the length of the steel or
about 8 feet. That stuff is only 22 gauge or thereabouts. I cut
about 2 feet when the saw stopped cutting, but the motor was still
running. I opened the saw to find the nylon gears completely
stripped. After a big hassle, I was able to get the thing replaced
thru the warranty, but as far as I am concerned, it's pretty much a
useless tool, since I know as soon as I use it for anything more than
cutting some balsa wood, the new one will strip too. Just more
inferior crap sold by Black & Decker.
Mark

Nylon gears can last for decades of use when not abused. Jigsaws are not the
best choice for cutting 22 gauge steel. Tin snips or nibblers are a much
better choices. For a saw blade to work most efficiently, the material must
be significantly thicker than the pitch of the blade. When cutting thicker
material the teeth lower on the blade hold the saw away from the material
being cut. Without these lower teeth in contact, every time a tooth of your
saw hit caught on the bottom of the sheet-metal, it sent a major shock
straight up the transmission.

Maybe you have to buy the stuff not in the bargain bin. I like my old Black
and Decker drill, but if I ever start doing serious work, I would buy a new
one that is lighter more efficient and more powerful.

[m***@UNLISTED.com]

Post by Bill Woods

Post by s--p--o--n--i--x
If it's the sort of anglepoise lamp I'm thinking of it will be
double insulated.

What does "double insulated" mean in actual practice?

Post by s--p--o--n--i--x
Whilst it would be sensible to earth the thing, it will need
'cross bonding' across the hinged joints.

Double insulated means they wrapped TWO layers of electrical tape
around all bare wires, not just one. That also means the item cost $5
more than if they has only wrapped the wires once.

As to the OP, you mean you still didn't fix that lamp. You posted
about it about 2 or 3 months ago. Apparently you have not used the
lamp or we would have heard about your funeral by now.

It always amazes me that people will risk their life for a lousy
dollars worth of wire and 20 minutes of time, and probably spent an
hour posting a message about it.

Mark

[b***@meeow.co.uk]

Post by Bill Woods
What does "double insulated" mean in actual practice?

I guess its a derivative of the literal term. There are 2 layers of
insulation between live and metal casing or user, wire ends are cable
tied together so that if one comes out it doesnt wander far enough to
touch anything dangerous, and the insulation test v is much higher. No
earth connection is used.

Thats the meant-to. In practice there are plenty of [[]] products that
do not meet the above at all, japanese stereos and spotlights
especially.


NT

[The Natural Philosopher]

Post by b***@meeow.co.uk

Post by Bill Woods
What does "double insulated" mean in actual practice?

I guess its a derivative of the literal term. There are 2 layers of
insulation between live and metal casing or user, wire ends are cable
tied together so that if one comes out it doesnt wander far enough to
touch anything dangerous, and the insulation test v is much higher. No
earth connection is used.
Thats the meant-to. In practice there are plenty of [[]] products that
do not meet the above at all, japanese stereos and spotlights
especially.
NT

Originally it meant a transformer with not only insulated wire, but an
actual sheet of something insulating between primary and secondary.
I think it then gort extended to the above specs.

[Palindr☻me]

Post by Lars
My electrical theory is fair but not great. Can someone please
advise me.
I have an old Anglepoise lamp with painted metal arms and painted
metal lampshade (Anglepoise model 90). It has a two-core mains
lead. I am in the UK so this is all at 230-240 volts.
Today I touched the outside of the lampshade and got a sort of vey
mild tingle feeling which felt "odd". When I used a mains tester
screwdriver on the exposed metal (at the joint of the lampshade
and support arm) then it glowed as if the metal of the Anglepoise
lamp was live.
I unplugged the lamp and tested the resistence between the live
pin on the mains plug and some exposed metal on the lamp. I got
no resistence reading at all (i.e. it must have been a very high
resistence). I then tested the neutral pin in the same way and
got the same high resistence result.
So the lamp seems ok. But something seems to be wrong!
QUESTION: Is my lamp safe to use and could I get a shock from it
in its present condition?
QUESTION: If my lamp is unsafe then is there a repair I can do?

There are several potential causes. IMHO, the lampholder
would be the prime suspect. Over many years of being baked
by the proximity of the lamp below it, the surface can
degrade and allow a minute leakage current to flow. This can
be made worse by dust/dirt getting into small cracks.

A normal multimeter type tester is not a lot of use for
testing for leakage - that is why electrical safety testing
is done using special testers energised at 250 or 500 v.

If it was a three wire cable, this very small leakage
current would have a return path. The leakage current would
have to increase to a point where the RCD/ELCB tripped, if
fitted, or the plugtop fuse blows. That could take many
years. No tingle though.

With a two wire cable, the leakage current will be able to
increase with time until it trips the RCD/ELCD via the
person touching the exposed metalwork. The RCD/ELCB should
mean that this will probably not be fatal. Without one
fitted, the current will rise to a point where it is high
enough and flows for long enough to easily be fatal - it is
then Russian Roulette as to whether it kills or not.

So, basically, you can ignore this and hope that the leakage
grows only slowly. If you have an RCD/ELCB, probably no one
will die if your hopes prove optimistic. If you don't have
one, then you are playing for pretty large stakes..

So, your options are:

Test the lamp using a proper insulation tester. You may find
that the lab tech in the electrical engineering department
of a local university will do this for you for the cost of a
beer. The lamp may actually be fine as some people are able
to detect leakage currents way lower than anything demanded
by the rules.

Fit an RCD/ELCB at the supply or replace the consumer unit
with a split box - if not already fitted.

Replace the cable with a three wire one and connect the
earth wire to the metalwork. That should stop the tingle. If
the insulation iof the lampholder does deteriorate further
then all that should happen is the RCD/ELCB will trip.

Replace the lampholder in the assembly with a new one. I
have managed to fit a standard ceiling lampholder to an
Anglepoise in the past. You may be able to get hold of the
genuine article.

[Jeff Wisnia]

Post by Lars
My electrical theory is fair but not great. Can someone please
advise me.
I have an old Anglepoise lamp with painted metal arms and painted
metal lampshade (Anglepoise model 90). It has a two-core mains
lead. I am in the UK so this is all at 230-240 volts.
Today I touched the outside of the lampshade and got a sort of vey
mild tingle feeling which felt "odd". When I used a mains tester
screwdriver on the exposed metal (at the joint of the lampshade
and support arm) then it glowed as if the metal of the Anglepoise
lamp was live.
I unplugged the lamp and tested the resistence between the live
pin on the mains plug and some exposed metal on the lamp. I got
no resistence reading at all (i.e. it must have been a very high
resistence). I then tested the neutral pin in the same way and
got the same high resistence result.
So the lamp seems ok. But something seems to be wrong!
QUESTION: Is my lamp safe to use and could I get a shock from it
in its present condition?
QUESTION: If my lamp is unsafe then is there a repair I can do?
Thank you for any info.
Lars
-----------------

The two questions I haven't noticed anyone asking you directly are these:

What are you standing or sitting on and/or touching when you feel that
tingle?

And, what is the "cold end" of the "screwdriver" mains tester connected
to when you see it lighting?

If you can reasonably feel that your body is well insulated from ground
when you feel that tingle, like you are standing on dry carpeting on a
wooden floor inside a house, then I'll put my chips in with the folks
who say you are probably just feeling a capacitivly coupled ac current
flowing between the hot lead in the lamp and the lamp's metal body which
is then charging and discharging your body's capacitance.

How about trying this? connect a wire to a known ground, get the
smallest wattage 240 volt bulb you can find, unplug the lamp and connect
that bulb beween the metal lamp body and the grounded wire. Then plug
the lamp back in.

Does the bulb light, with the lamp either off or on? If it doesn't, then
the current flow (in amps) is less than the wattage of the bulb divided
by 240.

If it does light, you DO have a dangerous condition of deteriorated
insulation or some other conductive path within the lamp, STOP and get
it fixed.

If the test bulb doesn't light, replace it with an ac ammeter set to a
range higher than that bulb would draw at 240 volts and then switch to
lower ranges until you can measure the "leakage" current. I'm betting
you'll find it will be less than a milliampre, and is likely
capacitively coupled.

While it's nice to hear that all metal bodied lamps ought to have a
direct connection from their metal parts to ground through a three wire
cord and appropriate plugs and recepticals, that is certainly the
exception rather than the rule for household use in the USA. I've got
all sorts of metal bodied lamps in my home, all of them purchased new,
some as recently as last year, and not one of them came equipped with a
three wire cord.

In fact, I've installed capacitive "touch switch" multi level dimmers in
four of those lamps, using their bodies as the sensing elements. I
couldn't do that if we had to ground the lamp bodies.

Let us know what you find,

Jeff

[stretch]

Use a Megohmmeter (Insulation tester) between the wiring and the metal
on the lamp. Some Air Conditioning contractors (Like Me) use them to
test compressor motors. An electrician may have one also. If that
tests OK, then it is probably capacitive coupling and not a problem.

Stretch

[Lars]

Post by Jeff Wisnia
The two questions I haven't noticed anyone asking you directly
What are you standing or sitting on and/or touching when you
feel that tingle?

I am standing on a carpet on the third floor of a building. The
carpet is 80% wool and presumably the 20% is polyester.

Post by Jeff Wisnia
And, what is the "cold end" of the "screwdriver" mains tester
connected to when you see it lighting?

I myself am touching the "cold end" of the screwdriver mains tester
with my finger.

Post by Jeff Wisnia
If you can reasonably feel that your body is well insulated from
ground when you feel that tingle, like you are standing on dry
carpeting on a wooden floor inside a house, then I'll put my
chips in with the folks who say you are probably just feeling a
capacitivly coupled ac current flowing between the hot lead in
the lamp and the lamp's metal body which is then charging and
discharging your body's capacitance.
How about trying this? connect a wire to a known ground, get the
smallest wattage 240 volt bulb you can find, unplug the lamp and
connect that bulb beween the metal lamp body and the grounded
wire. Then plug the lamp back in.
Does the bulb light, with the lamp either off or on? If it
doesn't, then the current flow (in amps) is less than the
wattage of the bulb divided by 240.
If it does light, you DO have a dangerous condition of
deteriorated insulation or some other conductive path within the
lamp, STOP and get it fixed.
If the test bulb doesn't light, replace it with an ac ammeter
set to a range higher than that bulb would draw at 240 volts and
then switch to lower ranges until you can measure the "leakage"
current. I'm betting you'll find it will be less than a
milliampre, and is likely capacitively coupled.

Could I not use an ammeter inthe first place rather than a test bulb
given that a fully-lit 100 W bulb would have a current flow of approx
0.4 A (= 100 watts/240 volts).

Post by Jeff Wisnia
While it's nice to hear that all metal bodied lamps ought to
have a direct connection from their metal parts to ground
through a three wire cord and appropriate plugs and recepticals,
that is certainly the exception rather than the rule for
household use in the USA. I've got all sorts of metal bodied
lamps in my home, all of them purchased new, some as recently as
last year, and not one of them came equipped with a three wire
cord.

My experience is the same as yours in that I have many 2-core only
appliances with metal bodies which seem designed specifically to be
2-core. Often their label refers to "double insulated" - whatever
that may be.

Post by Jeff Wisnia
In fact, I've installed capacitive "touch switch" multi level
dimmers in four of those lamps, using their bodies as the
sensing elements. I couldn't do that if we had to ground the
lamp bodies.
Let us know what you find,

[Palindr☻me]

Post by Lars
My experience is the same as yours in that I have many 2-core only
appliances with metal bodies which seem designed specifically to be
2-core. Often their label refers to "double insulated" - whatever
that may be.

In double insulated equipment the basic protection is
afforded by the first layer of insulation. If the basic
protection fails then supplementary protection is provided
by a second layer of insulation preventing contact with live
parts.

You *know* it makes sense to get all portable electrical
equipment tested regularly and properly using a
purpose-designed Portable Appliance Tester.

[Jeff Wisnia]

Post by Lars

Post by Jeff Wisnia
The two questions I haven't noticed anyone asking you directly
What are you standing or sitting on and/or touching when you
feel that tingle?

I am standing on a carpet on the third floor of a building. The
carpet is 80% wool and presumably the 20% is polyester.

Post by Jeff Wisnia
And, what is the "cold end" of the "screwdriver" mains tester
connected to when you see it lighting?

I myself am touching the "cold end" of the screwdriver mains tester
with my finger.

Post by Jeff Wisnia
If you can reasonably feel that your body is well insulated from
ground when you feel that tingle, like you are standing on dry
carpeting on a wooden floor inside a house, then I'll put my
chips in with the folks who say you are probably just feeling a
capacitivly coupled ac current flowing between the hot lead in
the lamp and the lamp's metal body which is then charging and
discharging your body's capacitance.
How about trying this? connect a wire to a known ground, get the
smallest wattage 240 volt bulb you can find, unplug the lamp and
connect that bulb beween the metal lamp body and the grounded
wire. Then plug the lamp back in.
Does the bulb light, with the lamp either off or on? If it
doesn't, then the current flow (in amps) is less than the
wattage of the bulb divided by 240.
If it does light, you DO have a dangerous condition of
deteriorated insulation or some other conductive path within the
lamp, STOP and get it fixed.
If the test bulb doesn't light, replace it with an ac ammeter
set to a range higher than that bulb would draw at 240 volts and
then switch to lower ranges until you can measure the "leakage"
current. I'm betting you'll find it will be less than a
milliampre, and is likely capacitively coupled.

Could I not use an ammeter inthe first place rather than a test bulb
given that a fully-lit 100 W bulb would have a current flow of approx
0.4 A (= 100 watts/240 volts).

The reason I suggested using a small bulb rather than a meter is this.

Just in case you DO have a dead short between the "hot" side of your 240
volt supply and the metal body of the lamp, then connecting that
grounded wire I suggested directly to the lamp body through an ammeter
would cause one heck of a lot more current than the 0.4 A you mention,
possibly enough to damage the meter before the fuse or breaker opened,
unless the meter was set to something like a 400 amp range. Capiche?

Post by Lars

Post by Jeff Wisnia
While it's nice to hear that all metal bodied lamps ought to
have a direct connection from their metal parts to ground
through a three wire cord and appropriate plugs and recepticals,
that is certainly the exception rather than the rule for
household use in the USA. I've got all sorts of metal bodied
lamps in my home, all of them purchased new, some as recently as
last year, and not one of them came equipped with a three wire
cord.

My experience is the same as yours in that I have many 2-core only
appliances with metal bodies which seem designed specifically to be
2-core. Often their label refers to "double insulated" - whatever
that may be.

And I've recently read that common consumer "pop-up" toasters don't have
three wire cords and grounded cases because people often stick tableware
in them trying to remove a stuck piece of bread. If those metal
implements shorted a toaster element to a grounded case, the element
could burn out.

They rely instead on the presence of GFCI protected outlets to keep
foolish people from electrocuting themselves while doing that. GFCIs
have been required by code for kitchen outlets in the US for many years now.

Post by Lars

Post by Jeff Wisnia
In fact, I've installed capacitive "touch switch" multi level
dimmers in four of those lamps, using their bodies as the
sensing elements. I couldn't do that if we had to ground the
lamp bodies.
Let us know what you find,

Jeff

[Chris Lewis]

Post by Jeff Wisnia
The reason I suggested using a small bulb rather than a meter is this.
Just in case you DO have a dead short between the "hot" side of your 240
volt supply and the metal body of the lamp, then connecting that
grounded wire I suggested directly to the lamp body through an ammeter
would cause one heck of a lot more current than the 0.4 A you mention,
possibly enough to damage the meter before the fuse or breaker opened,
unless the meter was set to something like a 400 amp range. Capiche?

The meter would probably _still_ explode.

I saw the result of someone mistaking a 100A DC ammeter for an AC
voltmeter, and sticking the probes in a 120V socket. Not pretty.
Yup, the breaker tripped. But the meter innards had vaporized,
and the industrial grade receptacle was destroyed.

Shouldn't put an ammeter across anything that could even remotely
have line potential across it unless there's some sort of limiter
(ie: lightbulb) in the way. Intermittent short => kaboom!

Post by Jeff Wisnia
And I've recently read that common consumer "pop-up" toasters don't have
three wire cords and grounded cases because people often stick tableware
in them trying to remove a stuck piece of bread. If those metal
implements shorted a toaster element to a grounded case, the element
could burn out.

True, but more importantly, if the toaster is grounded, and you stick
a knife into it to clear out a piece of bread, where's your other
hand? On the toaster!

-> Toasted user, not toasted bread.

[Sbharris[atsign]ix.netcom.com]

Post by Lars
I unplugged the lamp and tested the resistence between the live

pin on the mains plug and some exposed metal on the lamp. I got
no resistence reading at all (i.e. it must have been a very high
resistence). I then tested the neutral pin in the same way and
got the same high resistence result. <<

Many appliences ground the outside of metal appliance, which means it
should be in electrical contact with your neutral pin. Which means THAT
resistance should have been LOW (zero). This is a measure to prevent
shock, in case something inside the appliance should contact that outer
case (which would then blow your fuse instead of making the case "hot",
and leave it as a safety hazard in case you should grab it in one hand,
and something else that goes to ground in the other).

If you can follow the grounded pin inside your lamp, you should see
that it ends SOMEWHERE. Probably it goes to the metal screw fitting of
the bulb. If you really want to make your lamp safer, you can run a
wire from that to the metal arms somewhere. Then you can't ever shock
yourself by grabbing it.

Caution--- it's only safe to do this if your 2-pole plug is polarized
so it can't be put into the wall, in reverse. I have no idea what UK
plugs look like, so you'll have to tell me if this is true. From your
description it sounds as though it is.

SBH

[James Salisbury]

Post by Lars

Post by Lars
I unplugged the lamp and tested the resistence between the live

pin on the mains plug and some exposed metal on the lamp. I got
no resistence reading at all (i.e. it must have been a very high
resistence). I then tested the neutral pin in the same way and
got the same high resistence result. <<
Many appliences ground the outside of metal appliance, which means it
should be in electrical contact with your neutral pin. Which means THAT
resistance should have been LOW (zero). This is a measure to prevent
shock, in case something inside the appliance should contact that outer
case (which would then blow your fuse instead of making the case "hot",
and leave it as a safety hazard in case you should grab it in one hand,
and something else that goes to ground in the other).
If you can follow the grounded pin inside your lamp, you should see
that it ends SOMEWHERE. Probably it goes to the metal screw fitting of
the bulb. If you really want to make your lamp safer, you can run a
wire from that to the metal arms somewhere. Then you can't ever shock
yourself by grabbing it.
Caution--- it's only safe to do this if your 2-pole plug is polarized
so it can't be put into the wall, in reverse. I have no idea what UK
plugs look like, so you'll have to tell me if this is true. From your
description it sounds as though it is.
SBH

Hi,

We don't have 2 pin in the uk for 99.9% of appliances. We have a fused 3 pin
plug, earths must always be used as earths, neutrals as neutrals as far as
appliances are concerned...

[Roger R]

Post by Lars

Post by Lars
I unplugged the lamp and tested the resistence between the live

pin on the mains plug and some exposed metal on the lamp. I got
no resistence reading at all (i.e. it must have been a very high
resistence). I then tested the neutral pin in the same way and
got the same high resistence result. <<
Many appliences ground the outside of metal appliance, which means it
should be in electrical contact with your neutral pin.

No, No, No.
Modern appliances with exposed metal parts will be connected to Earth.
This means it should be in contact with the EARTH pin.
NEVER connect exposed metal parts to neutral.

It may appear that the neutral wire has no voltage but this is not so. If a
short is placed between earth and neutral the RCD in your consumer unit will
trip. If it doesn't there is an earth fault. Get it seen to.

Roger

[Palindr☻me]

Post by Roger R

Post by Lars

Post by Lars
I unplugged the lamp and tested the resistence between the live

pin on the mains plug and some exposed metal on the lamp. I got
no resistence reading at all (i.e. it must have been a very high
resistence). I then tested the neutral pin in the same way and
got the same high resistence result. <<
Many appliences ground the outside of metal appliance, which means it
should be in electrical contact with your neutral pin.

No, No, No.
Modern appliances with exposed metal parts will be connected to Earth.
This means it should be in contact with the EARTH pin.
NEVER connect exposed metal parts to neutral.
It may appear that the neutral wire has no voltage but this is not so. If a
short is placed between earth and neutral the RCD in your consumer unit will
trip. If it doesn't there is an earth fault. Get it seen to.

This may help:

http://www.tlc-direct.co.uk/Book/5.6.1.htm

[Sbharris[atsign]ix.netcom.com]

No, No, No. Modern appliances with exposed metal parts will be

connected to Earth. <<

We're not talking about a modern appliance, is the problem. We're
talking about how to make an antique a little safer.

This means it should be in contact with the EARTH pin. NEVER connect

exposed metal parts to neutral. <<

You can if you like. It will trip your RCD (residual current device),
if you have one, but not everybody does. These thingsa are called GFI
(ground fault interruptor) devices in the US. But if you don't have one
of these in your house, or on the circuit in question, then it does no
damage for neutral to touch ground in the lamp or whatever. And it may
make the lamp safer.

It may appear that the neutral wire has no voltage but this is not

so.<<

That depends. Actually, it is so, UNLESS you have an RCD/GFI, which
places a small voltage between neutral and ground as they exit the RCD
device. After all, the ground and neutral are connected together in the
service panel, so there's no difference between them unless the RCD,
connected after the panel, puts it there. The purpose of this small
voltage is so the RCD can detect a ground-neutral "fault" (one where
the neural wire has touched the gound inside your lamp or other
appliance) and trip when that happens. The reason RCDs do this is
because having the neutral touch ground makes the major feature of the
RCD (the ability to tell if more current is flowing in the hot wire
than in the neutral, signaling an extra path to ground which may be you
being electrocuted) inoperative. So the RCD is designed to shut off the
power if its sensing function (which requires a separate neutral and
ground path as they exit the device) is compromised and it becomes
"blind" and unable to perform its function. But again, if you don't
have an RCD in the first place, none of this applies. YOU don't care if
the ground touches neural in your old lamp UNLESS you have an RCD/GFI
to trip in the first place.

If a short is placed between earth and neutral the RCD in your

consumer unit will trip.<<

Yes, but again, if you don't have an RCD, it won't. So you don't care.
If you don't have an RCD it's better to have a grounded device outer
casing, at least, rather than have one that floats. The latter is a
shock hazard if internally it should touch the wrong wire and become
hot. But if the casing is connected to neutral at least, then you have
a chance that a hot wire contacting it will trip your fusebox, which is
a poor man's GFI. All this assumes, of course, that you have only 2
wire plugs, which are polarized. These still exist many places in the
US. I was assuming that this antique lamp had this design, but it
doesn't sound like it. If not, then obviously the 3rd (ground/earth)
wire must be followed to make sure it contacts the lamp casing instead.

If it doesn't there is an earth fault. Get it seen to. <

You say, if a short between earth and neutral doesn't make your RCD
trip then there is an Earth fault??? Sorry, that doesn't make sense.
If it doesn't, then it means your RCD isn't working.

Anyway, this guy sounds like he has an old lamp with a polarized 2 pin
plug, and no ground pin. The lamp is apparently designed with a
floating casing, so that neigher hot or neutral connect to the metal
arms of the lamp. Do I have the correct impression?

SBH

[Dave Stanton]

That depends. Actually, it is so, UNLESS you have an RCD/GFI, which places
a small voltage between neutral and ground as they exit the RCD device.
After all, the ground and neutral are connected together in the service
panel, so there's no difference between them unless the RCD, connected
SBH

Sorry, you don't know much about UK mains distribution do you ?.

The neutral wire in the UK is connected to ground only at the sub station
under normal situations and nowhere else. Therefore it can be at a
different potential to true ground.

You really should not begiving advice in a UK ng about a electrical system
which you clearly have no first hand experience of.

Dave

[Alistair Riddell]

Post by Dave Stanton

That depends. Actually, it is so, UNLESS you have an RCD/GFI, which places
a small voltage between neutral and ground as they exit the RCD device.
After all, the ground and neutral are connected together in the service
panel, so there's no difference between them unless the RCD, connected
SBH

Sorry, you don't know much about UK mains distribution do you ?.
The neutral wire in the UK is connected to ground only at the sub station
under normal situations and nowhere else. Therefore it can be at a
different potential to true ground.

Actually, in a TN-C-S supply, which is pretty common nowadays, they are
connected together in the service head (grey box with big fuse in it
belonging to the electricity co. next to the customers' meter).

[Bob Eager]

Post by Dave Stanton
The neutral wire in the UK is connected to ground only at the sub station
under normal situations and nowhere else. Therefore it can be at a
different potential to true ground.

I agre with your comment about him not knowing much about UK mains. But
in a PME (TN-C-S) situation, neutral and earth are connected together
much closer than that - at the cutout (incoming cable connection).

[Dave Stanton]

Post by Dave Stanton
The neutral wire in the UK is connected to ground only at the sub
station under normal situations and nowhere else. Therefore it can be at
a different potential to true ground.

I agre with your comment about him not knowing much about UK mains. But in
a PME (TN-C-S) situation, neutral and earth are connected together much
closer than that - at the cutout (incoming cable connection).

Yes I know I was'nt 100% correct, but did'nt want to cloud what is
becoming quite a serious case of incorrect and dangerous info.

Dave

[Sbharris[atsign]ix.netcom.com]

What's in a name? Ahem, I called it a "service panel," and you two call
it a "service head," or a "cutout." But it's the same place in the
system. The laws of physics don't differ in the UK, and I would hope
good electrical wiring practices (practises?) therefore don't differ
much either. Nothing you've said so far convinces me otherwise.

SBH

[Bob Eager]

On Fri, 29 Apr 2005 21:25:17 UTC, "Sbharris[atsign]ix.netcom.com"

Post by Sbharris[atsign]ix.netcom.com
What's in a name? Ahem, I called it a "service panel," and you two call
it a "service head," or a "cutout." But it's the same place in the
system.

Fine. But then it wasn't you I was disagreeing with.

[Richard Tobin]

Post by Dave Stanton
You really should not begiving advice in a UK ng about a electrical system
which you clearly have no first hand experience of.

The article was posted to several newsgroups, only one of which is
uk-specific. It's quite likely that readers won't notice that.

-- Richard

[bz]

Post by Sbharris[atsign]ix.netcom.com
an RCD/GFI, which
places a small voltage between neutral and ground as they exit the RCD
device. After all, the ground and neutral are connected together in the
service panel, so there's no difference between them unless the RCD,
connected after the panel, puts it there.

You are so wrong!!!!!

Post by Sbharris[atsign]ix.netcom.com
The purpose of this small
voltage is so the RCD can detect a ground-neutral "fault" (one where
the neural wire has touched the gound inside your lamp or other
appliance) and trip when that happens. The reason RCDs do this is
because having the neutral touch ground makes the major feature of the
RCD (the ability to tell if more current is flowing in the hot wire
than in the neutral, signaling an extra path to ground which may be you
being electrocuted) inoperative. So the RCD is designed to shut off the
power if its sensing function (which requires a separate neutral and
ground path as they exit the device) is compromised and it becomes
"blind" and unable to perform its function. But again, if you don't
have an RCD in the first place, none of this applies. YOU don't care if
the ground touches neural in your old lamp UNLESS you have an RCD/GFI
to trip in the first place.

The GFI does not work that way. The ones I have seen use a small toroidial
transformer to sample the current flow in the hot and neutral lines. (Some
also sample the safety ground and trip if there is any flow there).

The circuit is a balanced bridge as long and the current in the hot line is
equal to the current in the neutral line, the GFI does not trip.

If there is an imbalance, it implies that some current is flowing through
something OTHER than the designed load and that current is going to a
different neutral or to earth ground.

You can still get electrocuted if you have one lamp that has the hot
shorted to the frame and you touch that and another device that has neutral
connected to the frame. If both were on the same GFI protected circuit, you
would NOT trip the GFI.

NEVER connect the neutral to the frame of any device because you defeat the
GFI when you do this. Frame always connects to safety ground.

Your advices would also make the device deadly if it is ever used in an
older house with two wire plugs and someone plugs it in backwards.

Never connect neutral to the frame.

[ehsjr]

Post by bz

Post by Sbharris[atsign]ix.netcom.com
an RCD/GFI, which
places a small voltage between neutral and ground as they exit the RCD
device. After all, the ground and neutral are connected together in the
service panel, so there's no difference between them unless the RCD,
connected after the panel, puts it there.

You are so wrong!!!!!

Post by Sbharris[atsign]ix.netcom.com
The purpose of this small
voltage is so the RCD can detect a ground-neutral "fault" (one where
the neural wire has touched the gound inside your lamp or other
appliance) and trip when that happens. The reason RCDs do this is
because having the neutral touch ground makes the major feature of the
RCD (the ability to tell if more current is flowing in the hot wire
than in the neutral, signaling an extra path to ground which may be you
being electrocuted) inoperative. So the RCD is designed to shut off the
power if its sensing function (which requires a separate neutral and
ground path as they exit the device) is compromised and it becomes
"blind" and unable to perform its function. But again, if you don't
have an RCD in the first place, none of this applies. YOU don't care if
the ground touches neural in your old lamp UNLESS you have an RCD/GFI
to trip in the first place.

The GFI does not work that way.

A GFCI works, in part, as you describe below.
In addition, it detects a ground/neutral short
as described at the following url:
http://www.codecheck.com/gfci_principal.htm
I believe that function is what the poster was
referring to.

Ed

The ones I have seen use a small toroidial

Post by bz
transformer to sample the current flow in the hot and neutral lines. (Some
also sample the safety ground and trip if there is any flow there).
The circuit is a balanced bridge as long and the current in the hot line is
equal to the current in the neutral line, the GFI does not trip.
If there is an imbalance, it implies that some current is flowing through
something OTHER than the designed load and that current is going to a
different neutral or to earth ground.
You can still get electrocuted if you have one lamp that has the hot
shorted to the frame and you touch that and another device that has neutral
connected to the frame. If both were on the same GFI protected circuit, you
would NOT trip the GFI.
NEVER connect the neutral to the frame of any device because you defeat the
GFI when you do this. Frame always connects to safety ground.
Your advices would also make the device deadly if it is ever used in an
older house with two wire plugs and someone plugs it in backwards.
Never connect neutral to the frame.

[Sbharris[atsign]ix.netcom.com]

Post by ehsjr
A GFCI works, in part, as you describe below.

In addition, it detects a ground/neutral short
as described at the following url:
http://www.codecheck.com/gfci_­principal.htm
I believe that function is what the poster was
referring to. <<

Correct. Modern GFI's really have two parts. The main one keeps you
from killing yourself, by cutting off current when you have a hot to
ground current. The active SECOND part (a second toroid) allows the
device to detect ground-neutral faults, so it can trip then, when its
sensing function has been compromised.

SBH

[bz]

Post by ehsjr

Post by ehsjr
A GFCI works, in part, as you describe below.

In addition, it detects a ground/neutral short
http://www.codecheck.com/gfci_­principal.htm
I believe that function is what the poster was
referring to. <<
Correct. Modern GFI's really have two parts. The main one keeps you
from killing yourself, by cutting off current when you have a hot to
ground current. The active SECOND part (a second toroid) allows the
device to detect ground-neutral faults, so it can trip then, when its
sensing function has been compromised.

Look again. See the two wires going through the core? [ignore the test
line]

Each of those wires serves as the primary of a transformer.

As long as the SAME current flows in BOTH of those wires, they cancel each
other out. No current is induced into the secondary.

An imbalance in the current in those wires can be due to MORE current
flowing in EITHER of them than in the other.

An imbalance will trip the GFI.

Notice, there is NO second circuit to detect ground/neutral shorts. It is
an imbalance in current that trips the GFI.

The GFI depends on the current through BOTH wires being equal.

[ehsjr]

Post by bz

Post by ehsjr

Post by ehsjr
A GFCI works, in part, as you describe below.

In addition, it detects a ground/neutral short
http://www.codecheck.com/gfci_­principal.htm
I believe that function is what the poster was
referring to. <<
Correct. Modern GFI's really have two parts. The main one keeps you
from killing yourself, by cutting off current when you have a hot to
ground current. The active SECOND part (a second toroid) allows the
device to detect ground-neutral faults, so it can trip then, when its
sensing function has been compromised.

Look again. See the two wires going through the core? [ignore the test
line]
Each of those wires serves as the primary of a transformer.
As long as the SAME current flows in BOTH of those wires, they cancel each
other out. No current is induced into the secondary.
An imbalance in the current in those wires can be due to MORE current
flowing in EITHER of them than in the other.
An imbalance will trip the GFI.
Notice, there is NO second circuit to detect ground/neutral shorts. It is
an imbalance in current that trips the GFI.
The GFI depends on the current through BOTH wires being equal.

He does not need to look again. He has it
right. Go read the url.

No one is disputing the imbalance detection.

The poster is discussing the *additional* circuitry
that is used to enable a GFI to detect a
downstream short between neutral and ground.

Ed

[bz]

Post by ehsjr

Post by bz

Post by ehsjr

Post by ehsjr
A GFCI works, in part, as you describe below.

In addition, it detects a ground/neutral short
http://www.codecheck.com/gfci_­principal.htm
I believe that function is what the poster was
referring to. <<
Correct. Modern GFI's really have two parts. The main one keeps you
from killing yourself, by cutting off current when you have a hot to
ground current. The active SECOND part (a second toroid) allows the
device to detect ground-neutral faults, so it can trip then, when its
sensing function has been compromised.

Look again. See the two wires going through the core? [ignore the test
line]
Each of those wires serves as the primary of a transformer.
As long as the SAME current flows in BOTH of those wires, they cancel
each other out. No current is induced into the secondary.
An imbalance in the current in those wires can be due to MORE current
flowing in EITHER of them than in the other.
An imbalance will trip the GFI.
Notice, there is NO second circuit to detect ground/neutral shorts. It
is an imbalance in current that trips the GFI.
The GFI depends on the current through BOTH wires being equal.

He does not need to look again. He has it
right. Go read the url.
No one is disputing the imbalance detection.
The poster is discussing the *additional* circuitry
that is used to enable a GFI to detect a
downstream short between neutral and ground.

You are correct.
I was wrong.

I missed seeing the other drawings, further down the page.
My mistake.

[Sbharris[atsign]ix.netcom.com]

Look you simply don't understand the things completely. Rather than
argue with me, I recommend you educate yourself.

http://www.codecheck.com/gfci_principal.htm

SBH

[Bob Eager]

On Fri, 29 Apr 2005 21:44:35 UTC, "Sbharris[atsign]ix.netcom.com"

Post by Sbharris[atsign]ix.netcom.com
Look you simply don't understand the things completely. Rather than
argue with me, I recommend you educate yourself.
http://www.codecheck.com/gfci_principal.htm

The fact that he can't spell 'principle' rather reduces its
credibility...

[Sbharris[atsign]ix.netcom.com]

Post by Sbharris[atsign]ix.netcom.com
Look you simply don't understand the things completely. Rather than
argue with me, I recommend you educate yourself.
http://www.codecheck.com/gfci_­principal.htm

Post by Bob Eager
The fact that he can't spell 'principle' rather reduces its

credibility... <<

COMMENT:

[1] Since this isn't an essay on use of English, but a tutorial in
electrical engineering, I would say not.

[2] Actually, it's impossible to tell if he misspelled "principle"
unless you know that was the word he intended. For all you know, the
.htm file is is the principal one the author uses for explaining
GFCI's.

SBH

[Mary Fisher]

Post by Bob Eager
On Fri, 29 Apr 2005 21:44:35 UTC, "Sbharris[atsign]ix.netcom.com"

Post by Sbharris[atsign]ix.netcom.com
Look you simply don't understand the things completely. Rather than
argue with me, I recommend you educate yourself.
http://www.codecheck.com/gfci_principal.htm

The fact that he can't spell 'principle' rather reduces its
credibility...

<VBG>

Mary

Post by Bob Eager
--
Bob Eager

[bz]

Post by Sbharris[atsign]ix.netcom.com
Look you simply don't understand the things completely. Rather than
argue with me, I recommend you educate yourself.

Educate yourself.

Your explanation of how the RCD/GFI works "an RCD/GFI, ...places a small
voltage between neutral and ground ....The purpose of this small voltage is
so the RCD can detect a ground-neutral "fault"...." is wrong. Dead wrong.

The GFI does NOT depend on a voltage difference to sense the fault, it
depends on unbalanced current flow, as I said. See the current transformer
in the drawing in your reference?

Post by Sbharris[atsign]ix.netcom.com
http://www.codecheck.com/gfci_principal.htm

See the two current carrying wires going through the core? As long as the
current in those is equal, they cancel each other out and there is no
current induced in the secondary that feeds the 'sensor circuit'.

You gave dangerous advice when you said:

[quote]
.... But if the casing is connected to neutral at least, then you have
a chance that a hot wire contacting it will trip your fusebox, which is
a poor man's GFI.
[unquote]
even with the caveats you gave.

Never wire the neutral to the case.
Case to safety ground or be sure to float the case.

Neutral to case can kill you even with a GFI!!!!
1) If a hot case on one item and the neutral case on the other are plugged
into the same GFI protected circuit, there will be NO ground fault if you
contact both.

2) If a an old, non polar outlet is encountered or a miswired outlet (they
do happen) and 'neutral' is actually 'hot'

[bz]

Post by bz
Educate yourself.

My appologies. I read a bit further in the article and see the second
circuit. The GFIs I have taken apart did NOT have two torroids.

I was wrong. Sorry. Please accept my humble appology.

(I still think that connecting neutral to case is dangerous, however)

[Martin Crossley]

Post by Lars

Post by Lars
I unplugged the lamp and tested the resistence between the live

pin on the mains plug and some exposed metal on the lamp. I got
no resistence reading at all (i.e. it must have been a very high
resistence). I then tested the neutral pin in the same way and
got the same high resistence result. <<
Many appliences ground the outside of metal appliance, which means it
should be in electrical contact with your neutral pin. Which means
THAT resistance should have been LOW (zero). This is a measure to
prevent shock, in case something inside the appliance should contact
that outer case (which would then blow your fuse instead of making
the case "hot", and leave it as a safety hazard in case you should
grab it in one hand, and something else that goes to ground in the
other).
If you can follow the grounded pin inside your lamp, you should see
that it ends SOMEWHERE. Probably it goes to the metal screw fitting of
the bulb. If you really want to make your lamp safer, you can run a
wire from that to the metal arms somewhere. Then you can't ever shock
yourself by grabbing it.
Caution--- it's only safe to do this if your 2-pole plug is polarized
so it can't be put into the wall, in reverse. I have no idea what UK
plugs look like, so you'll have to tell me if this is true. From your
description it sounds as though it is.
SBH

1.Please look up UK plugs (British Standard BS1363) on the web,
or any more reliable reference.
2.Please imagine, or establish using diagrams, what would happen if
the neutral in the flex. broke or became disconnected in the plug,
if connected as you recommended.
3.Genuine Anglepoise lampholders were not Edison screw fitting.

[Roy Q.T.]

Maybe * but~>

Such fuss over a simple desk/table top lamp:

I'd plug it in, attach one of my meter leads to it with an alligator
clip, and test it to earth/ground moving it around some., if it read any
significant voltage I'd disassemble it and inspect it for shorts, it's
either in the switch, the bulb wiring... if the wiring is frayed or worn
out at any point =3D I'd strip it and rewire it.

If no voltage to ground was present I'd chalk it down to static
discharge and watch my friction and touching metal objects more
conscientiously.

If that is too much work or trouble: given the dull looking old lamp
type it is, (sorry if it has any emotional sig) I'd toss it in the
garbage and enjoy the more modern trouble free lamps available.

=AEoy

[Phil Scott]

Post by Lars
My electrical theory is fair but not great. Can someone

please

Post by Lars
advise me.
I have an old Anglepoise lamp with painted metal arms and

painted

Post by Lars
metal lampshade (Anglepoise model 90). It has a two-core

mains

Post by Lars
lead. I am in the UK so this is all at 230-240 volts.
Today I touched the outside of the lampshade and got a sort

of vey

Post by Lars
mild tingle feeling which felt "odd". When I used a mains

tester

Post by Lars
screwdriver on the exposed metal (at the joint of the

lampshade

Post by Lars
and support arm) then it glowed as if the metal of the

Anglepoise

Post by Lars
lamp was live.
I unplugged the lamp and tested the resistence between the

live

Post by Lars
pin on the mains plug and some exposed metal on the lamp. I

got

Post by Lars
no resistence reading at all (i.e. it must have been a very

high

Post by Lars
resistence). I then tested the neutral pin in the same way

and

Post by Lars
got the same high resistence result.
So the lamp seems ok. But something seems to be wrong!
QUESTION: Is my lamp safe to use and could I get a shock

from it

Post by Lars
in its present condition?
QUESTION: If my lamp is unsafe then is there a repair I can

do?

Post by Lars
Thank you for any info.
Lars

Its not safe... how good your meter is and how good you are
using are open to question..but the tingle is proof positive
you have some degree of short or current leak in the lamp
wiring to the lamp base metal. Rewire it.


Phil Scott

Post by Lars
-----------------
http://www.anglepoise.com/timeline/model_90.jpg

[G***@heaven.com]

Wire is cheaper than a coffin and funeral.

Post by Lars
My electrical theory is fair but not great. Can someone please
advise me.
I have an old Anglepoise lamp with painted metal arms and painted
metal lampshade (Anglepoise model 90). It has a two-core mains
lead. I am in the UK so this is all at 230-240 volts.
Today I touched the outside of the lampshade and got a sort of vey
mild tingle feeling which felt "odd". When I used a mains tester
screwdriver on the exposed metal (at the joint of the lampshade
and support arm) then it glowed as if the metal of the Anglepoise
lamp was live.
I unplugged the lamp and tested the resistence between the live
pin on the mains plug and some exposed metal on the lamp. I got
no resistence reading at all (i.e. it must have been a very high
resistence). I then tested the neutral pin in the same way and
got the same high resistence result.
So the lamp seems ok. But something seems to be wrong!
QUESTION: Is my lamp safe to use and could I get a shock from it
in its present condition?
QUESTION: If my lamp is unsafe then is there a repair I can do?
Thank you for any info.
Lars
-----------------
http://www.anglepoise.com/timeline/model_90.jpg

[s--p--o--n--i--x]

Post by Lars
QUESTION: Is my lamp safe to use and could I get a shock from it
in its present condition?

Certainly not safe. It sounds like the insulation is breaking down
under mains voltage.

Post by Lars
QUESTION: If my lamp is unsafe then is there a repair I can do?

Get the wiring replaced and the bulb holder inspected.

sponix

[Chris Lewis]

Post by Lars
It has a two-core mains
lead.

Does it have an earth (ground) prong too?

Post by Lars
Today I touched the outside of the lampshade and got a sort of vey
mild tingle feeling which felt "odd". When I used a mains tester
screwdriver on the exposed metal (at the joint of the lampshade
and support arm) then it glowed as if the metal of the Anglepoise
lamp was live.

If you get a continuous tingle, then it's _highly_ unlikely to
be a capacitive/inductive/static leak (as others have suggested).

Last time I touched a device and got a minor tingle, repeating
that test while holding on to something grounded was something
I'm not going to repeat. That hurt! Dumb me. At least
we're only 120V...

You say "old", and the picture shows that the wiring in the
lamp is being moved whenever you adjust the lamp. Possibly
abraded and the conductors may now be intermittently contacting
the frame.

I recommend removing the wiring and inspecting both it and
the lamp socket as others have suggested. The socket may need
cleaning. If you see worn spots in the wiring, replace it.

If you don't see any obvious worn spots, now you really worry
about the fixture.

Measuring resistance won't be particularly reliable, fancy
equipment or not, because if you have a bare spot on the wiring
in the arms, the slightest bit of movement may break/make the
connection.

[Dave D]

Post by Lars
My electrical theory is fair but not great. Can someone please
advise me.
I have an old Anglepoise lamp with painted metal arms and painted
metal lampshade (Anglepoise model 90). It has a two-core mains
lead. I am in the UK so this is all at 230-240 volts.
Today I touched the outside of the lampshade and got a sort of vey
mild tingle feeling which felt "odd". When I used a mains tester
screwdriver on the exposed metal (at the joint of the lampshade
and support arm) then it glowed as if the metal of the Anglepoise
lamp was live.

I'd strip it down and check it thoroughly, and if you're still not happy,
destroy and dispose of it safely. Better still, pass it on to trading
standards in case it has a design flaw.

I must point out though that it is rare for UK approved double insulated
appliances to fail and present a shock hazard. If you find a design fault
which could have contributed to the case becoming live, be sure to report it
to trading standards so it can be investigated.

Is it a constant tingling feeling or a momentary minor jolt? It's very
common to get static discharges to metal appliances, but there's also an odd
gentle 'vibrating' or 'buzzing' sensation which can sometimes be felt
touching the metalwork of double insulated appliances. These are perfectly
harmless phenomena.

Dave

[Mary Fisher]

Post by Dave D
Is it a constant tingling feeling or a momentary minor jolt? It's very
common to get static discharges to metal appliances, but there's also an
odd gentle 'vibrating' or 'buzzing' sensation which can sometimes be felt
touching the metalwork of double insulated appliances. These are perfectly
harmless phenomena.

Ah! Thank you :-)

That's exactly the effect from my art deco lamp but everyone else seems to
think it needs seeing to. It has been seen to.

Mary

Post by Dave D
Dave

[Dimitrios Tzortzakakis]

Lars,
to check the leak resistance of mains circuits you need a special
"megger"meter.This is usually in the range of Mohms, so usually a normal
multimeter shows infinite resistance (sometimes modern digital ones are
capable of measuring this resistance).It's very dangerous to use something
that gives you (even) a slight shock.If you find it's too much money to have
it professionaly repaired (maybe a worn out cable that touches the frame?)
then better trash it, than put your life in danger.

--
Tzortzakakis Dimitrios
major in electrical engineering, freelance electrician
FH von Iraklion-Kreta, freiberuflicher Elektriker
dimtzort AT otenet DOT gr

Post by Lars
My electrical theory is fair but not great. Can someone please
advise me.
I have an old Anglepoise lamp with painted metal arms and painted
metal lampshade (Anglepoise model 90). It has a two-core mains
lead. I am in the UK so this is all at 230-240 volts.
Today I touched the outside of the lampshade and got a sort of vey
mild tingle feeling which felt "odd". When I used a mains tester
screwdriver on the exposed metal (at the joint of the lampshade
and support arm) then it glowed as if the metal of the Anglepoise
lamp was live.
I unplugged the lamp and tested the resistence between the live
pin on the mains plug and some exposed metal on the lamp. I got
no resistence reading at all (i.e. it must have been a very high
resistence). I then tested the neutral pin in the same way and
got the same high resistence result.
So the lamp seems ok. But something seems to be wrong!
QUESTION: Is my lamp safe to use and could I get a shock from it
in its present condition?
QUESTION: If my lamp is unsafe then is there a repair I can do?
Thank you for any info.
Lars
-----------------
http://www.anglepoise.com/timeline/model_90.jpg