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

 

[Bob Eager]

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.

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]

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.

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.

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]

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!

 

[Mary Fisher]

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

 

[Joe]

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...?

 

[Mary Fisher]

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]

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.





--
bz

please pardon my infinite ignorance, the set-of-things-I-do-not-know is an
infinite set.

[email protected] remove ch100-5 to avoid spam trap

 

[Kaiser]

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.

 

[Jeff Wisnia]

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

--
Jeffry Wisnia

(W1BSV + Brass Rat '57 EE)

"As long as there are final exams, there will be prayer in public
schools"

 

[James Salisbury]

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...

 

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

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.

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

Get the wiring replaced and the bulb holder inspected.

sponix

 

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

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.

 

[Chris Lewis]

It has a two-core mains
lead.

Does it have an earth (ground) prong too?

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.

 

[Lars]

On Wed 27 Apr 2005 23:35:40, Jeff Wisnia wrote:

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?

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

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.

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).

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.

 

[Roger R]

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

 

[Dave D]

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]

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

 

[Martin Crossley]

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 = 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.

®oy