Hi all,

The other day I bought a new screwdriver set from B&Q and decided to try
it out on the nearest available screw. It turned out to be one of the
screws in the light switch in our kitchen. I noticed a strange tingling
sensation when I touched the side of the screwdriver... very mysterious...

On further investigation it seems that the earth conductors in all of my
light switches are at 120V (with respect to neutral or live - tested with
multimeter set to AC mode). However at the consumer unit, all appears to
be fine. I have a functioning RCD and it's not tripped. All the lights
work. No (obvious) dodgy wiring in any of the switches.

Before I spend weeks lifting floorboards and crawling around in the loft,
can anyone suggest a reason why this might be going on? And is there any
way to systematically track down the source of the problem? And why is it
at exactly half mains voltage?

And, as an aside, could this have anything to do with the fact that my
energy-saving lightbulbs seem to flicker every few seconds when switched
off?

Any advice would be appreciated... my electrical experience is still
fairly limited...

Thanks
Martin

In article , Martin Brook
writes
Hi all,

The other day I bought a new screwdriver set from B&Q and decided to
try it out on the nearest available screw. It turned out to be one of
the screws in the light switch in our kitchen. I noticed a strange
tingling sensation when I touched the side of the screwdriver... very
mysterious...

On further investigation it seems that the earth conductors in all of
my light switches are at 120V (with respect to neutral or live -
tested with multimeter set to AC mode). However at the consumer unit,
all appears to be fine. I have a functioning RCD and it's not tripped.
All the lights work. No (obvious) dodgy wiring in any of the switches.

Before I spend weeks lifting floorboards and crawling around in the
loft, can anyone suggest a reason why this might be going on? And is
there any way to systematically track down the source of the problem?
And why is it at exactly half mains voltage?

And, as an aside, could this have anything to do with the fact that my
energy-saving lightbulbs seem to flicker every few seconds when
switched off?

Any advice would be appreciated... my electrical experience is still
fairly limited...

Sounds like the earth wire on your lighting circuit is not connected to
earth, which is a cause for concern.

You often get 120V on a disconnected earth when some type of surge
arrestor is connected to the circuit. (It's very very high impedance, so
you don't feel a shock when you touch it, just a tingle. If you measured
it with an analogue meter rather than a digital one, the voltage would
be much lower or would disappear).

I am not sure how a surge arrestor would get onto a lighting circuit
however, unless there is a wider earthing problem in your house and the
surge arrestor equipment is on a ring main; the ring main earth is
connected to the lighting earth, but neither is connected to real earth.
--
Tim Mitchell

Martin Brook wrote:

Before I spend weeks lifting floorboards and crawling around in the loft,
can anyone suggest a reason why this might be going on? And is there any
way to systematically track down the source of the problem? And why is it
at exactly half mains voltage?

Have you checked to see if all the earths on the other circuits are
doing the same thing (even money they are as all earths should be
commoned, natch)? If so, then I'd guess you've got a faulty earthed
appliance on one of the ring mains. Go round unplugging things while
someone keeps an eye on the multimeter. My first stop would be any
television sets as although not usually earthed directly, they often
have floating chassis (there was a discussion a while back on this)
which might be electrifying the aerial cable and, from there, the earth
circuit of the house.


And, as an aside, could this have anything to do with the fact that my
energy-saving lightbulbs seem to flicker every few seconds when switched
off?

Can't see how as earth is really a non-used connection in lighting ccts.
Again, I think this has been discussed before and could be down to the
neutral side of the light being switched or a particularly high floating
neutral.

--
Scott

Where are we going and why am I in this handbasket?

In article , Martin Brook firstname.s
writes
Hi all,

The other day I bought a new screwdriver set from B&Q and decided to try
it out on the nearest available screw. It turned out to be one of the
screws in the light switch in our kitchen. I noticed a strange tingling
sensation when I touched the side of the screwdriver... very mysterious...

On further investigation it seems that the earth conductors in all of my
light switches are at 120V (with respect to neutral or live - tested with
multimeter set to AC mode). However at the consumer unit, all appears to
be fine. I have a functioning RCD and it's not tripped. All the lights
work. No (obvious) dodgy wiring in any of the switches.

Before I spend weeks lifting floorboards and crawling around in the loft,
can anyone suggest a reason why this might be going on? And is there any
way to systematically track down the source of the problem? And why is it
at exactly half mains voltage?

And, as an aside, could this have anything to do with the fact that my
energy-saving lightbulbs seem to flicker every few seconds when switched
off?

Any advice would be appreciated... my electrical experience is still
fairly limited...

Thanks
Martin

It seems that the earth in your lightning circuit has come detached from
the actual earth and is now "floating" where it will because of
Capactive leakage acquire some current albeit a very small amount.

This won't trip the RCD. So somewhere there is a discontinuity between
the lighting earth and the earth on the consumer unit. Trace the wiring
through from the dist board to each fitting. Use a continuity meter and
switch all the power off before you do it if you don't have that much
experience working on electric's.

The lighting earth isn't used that much except if you have any metal
light fittings like candelabra's or such like. It must be earth just in
case some "real" leakage develops!....
--
Tony Sayer

Thanks for the reply,

On Thu, 5 Aug 2004 14:46:36 +0100, Tim Mitchell
wrote:
Sounds like the earth wire on your lighting circuit is not connected to
earth, which is a cause for concern.

You often get 120V on a disconnected earth when some type of surge
arrestor is connected to the circuit. (It's very very high impedance, so
you don't feel a shock when you touch it, just a tingle. If you measured
it with an analogue meter rather than a digital one, the voltage would
be much lower or would disappear).

I am not sure how a surge arrestor would get onto a lighting circuit
however, unless there is a wider earthing problem in your house and the
surge arrestor equipment is on a ring main; the ring main earth is
connected to the lighting earth, but neither is connected to real earth.

I'm not aware of there being any kind of surge arrestor anywhere...

Also, most of the wiring in the house seems to be fine, earth-wise. I've
already rewired two ring mains and added a new one, and everything is fine
on those. The lighting circuit is the only one I haven't touched, but
there is no voltage on the earth at the CU. So it seems to me that the
problem must be somewhere in the rest of the circuit. Which, of course,
disappears through a hole in the cellar roof.









--
Using Opera's revolutionary e-mail client: http://www.opera.com/m2/

In article , Martin Brook
writes
Thanks for the reply,

On Thu, 5 Aug 2004 14:46:36 +0100, Tim Mitchell
wrote:
Sounds like the earth wire on your lighting circuit is not connected
to earth, which is a cause for concern.

You often get 120V on a disconnected earth when some type of surge
arrestor is connected to the circuit. (It's very very high impedance,
so you don't feel a shock when you touch it, just a tingle. If you
measured it with an analogue meter rather than a digital one, the
voltage would be much lower or would disappear).

I am not sure how a surge arrestor would get onto a lighting circuit
however, unless there is a wider earthing problem in your house and
the surge arrestor equipment is on a ring main; the ring main earth
is connected to the lighting earth, but neither is connected to real earth.

I'm not aware of there being any kind of surge arrestor anywhere...

Also, most of the wiring in the house seems to be fine, earth-wise.
I've already rewired two ring mains and added a new one, and
everything is fine on those. The lighting circuit is the only one I
haven't touched, but there is no voltage on the earth at the CU. So it
seems to me that the problem must be somewhere in the rest of the
circuit. Which, of course, disappears through a hole in the cellar roof.


It might be just floating then, but you don't normally get enough
induced voltage to feel a tingle.
--
Tim Mitchell

In article ,
tony sayer wrote:
The lighting earth isn't used that much except if you have any metal
light fittings like candelabra's or such like. It must be earth just in
case some "real" leakage develops!....

I'd be more worried about metal plate switches.

--
*Born free - taxed to death *

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

In article ,
Martin Brook wrote:
So it seems to me that the problem must be somewhere in the rest of
the circuit. Which, of course, disappears through a hole in the cellar
roof.

Are all your fittings standard ceiling roses? If so it's easy enough to do
a visual check as a first step. If, however, some have been changed
because of the fittings, I'd guess the earth hasn't been looped through at
these.

--
*Laugh alone and the world thinks you're an idiot.

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

"Tim Mitchell" wrote in message
...
Sounds like the earth wire on your lighting circuit is not connected
to earth, which is a cause for concern.

You often get 120V on a disconnected earth when some type of surge
arrestor is connected to the circuit. (It's very very high impedance,
so you don't feel a shock when you touch it, just a tingle. If you
measured it with an analogue meter rather than a digital one, the
voltage would be much lower or would disappear).

I am not sure how a surge arrestor would get onto a lighting circuit
however, unless there is a wider earthing problem in your house and
the surge arrestor equipment is on a ring main; the ring main earth
is connected to the lighting earth, but neither is connected to real
earth.

I'm not aware of there being any kind of surge arrestor anywhere...

Also, most of the wiring in the house seems to be fine, earth-wise.
I've already rewired two ring mains and added a new one, and
everything is fine on those. The lighting circuit is the only one I
haven't touched, but there is no voltage on the earth at the CU. So it
seems to me that the problem must be somewhere in the rest of the
circuit. Which, of course, disappears through a hole in the cellar roof.



It might be just floating then, but you don't normally get enough
induced voltage to feel a tingle.

But you occasionally do through certain poor quality electronic transformers
for 12v lights. Does the OP have any of these ?

These rely on the high frequency transformer being earthed properly and if
it isn't a voltage is induced in the earth lead, albeit at a high impedance.

"Martin Brook" wrote in
news

On further investigation it seems that the earth conductors in all of
my light switches are at 120V (with respect to neutral or live -
tested with multimeter set to AC mode). However at the consumer unit,
all appears to be fine. I have a functioning RCD and it's not
tripped. All the lights work. No (obvious) dodgy wiring in any of the
switches.



What does your earth measure with respect to a "real" earth (e.g.
conductive thing in the ground, bonded water pipe, earth at the consumer
unit) ?

Boris

Dave Plowman (News) wrote:
The lighting earth isn't used that much except if you have any metal
light fittings like candelabra's or such like. It must be earth just in

I'd be more worried about metal plate switches.

I'd be inclined to measure every earth on your lighting circuit, seeing
which switches/fittings have the 120v on them and which don't. Then you
will probably be able to deduce where it is not connected.

If lucky in this process you will find the loose or missing earth. If
not you will have to do some continuity checking and disconecting of
things to deduce which cable is broken and then replace it.

On Thu, 5 Aug 2004 23:18:12 +0100, G&M wrote:


"Tim Mitchell" wrote in message
...
Sounds like the earth wire on your lighting circuit is not connected
to earth, which is a cause for concern.

You often get 120V on a disconnected earth when some type of surge
arrestor is connected to the circuit. (It's very very high impedance,
so you don't feel a shock when you touch it, just a tingle. If you
measured it with an analogue meter rather than a digital one, the
voltage would be much lower or would disappear).

I am not sure how a surge arrestor would get onto a lighting circuit
however, unless there is a wider earthing problem in your house and
the surge arrestor equipment is on a ring main; the ring main earth
is connected to the lighting earth, but neither is connected to real
earth.

I'm not aware of there being any kind of surge arrestor anywhere...

Also, most of the wiring in the house seems to be fine, earth-wise.
I've already rewired two ring mains and added a new one, and
everything is fine on those. The lighting circuit is the only one I
haven't touched, but there is no voltage on the earth at the CU. So it
seems to me that the problem must be somewhere in the rest of the
circuit. Which, of course, disappears through a hole in the cellar
roof.



It might be just floating then, but you don't normally get enough
induced voltage to feel a tingle.

But you occasionally do through certain poor quality electronic
transformers
for 12v lights. Does the OP have any of these ?

I don't have any that I'm aware of...


These rely on the high frequency transformer being earthed properly and
if
it isn't a voltage is induced in the earth lead, albeit at a high
impedance.






--
Using Opera's revolutionary e-mail client: http://www.opera.com/m2/

On Thu, 05 Aug 2004 17:54:56 +0100, Dave Plowman (News)
wrote:

In article ,
Martin Brook wrote:
So it seems to me that the problem must be somewhere in the rest of
the circuit. Which, of course, disappears through a hole in the cellar
roof.

Are all your fittings standard ceiling roses? If so it's easy enough to
do
a visual check as a first step. If, however, some have been changed
because of the fittings, I'd guess the earth hasn't been looped through
at
these.


Yes, they all are... forgive my ignorance, but I'm picturing a setup where
there is a junction box above each light fitting, which is why I was
expecting to be having to spend a lot of time lifting floorboards... am I
getting this completely wrong?


--
Using Opera's revolutionary e-mail client: http://www.opera.com/m2/

On Fri, 06 Aug 2004 06:42:08 GMT, Boris wrote:

"Martin Brook" wrote in
news

On further investigation it seems that the earth conductors in all of
my light switches are at 120V (with respect to neutral or live -
tested with multimeter set to AC mode). However at the consumer unit,
all appears to be fine. I have a functioning RCD and it's not
tripped. All the lights work. No (obvious) dodgy wiring in any of the
switches.



What does your earth measure with respect to a "real" earth (e.g.
conductive thing in the ground, bonded water pipe, earth at the consumer
unit) ?

Boris

As things stand, I have no easy way to measure that... _but_ at the
consumer unit, the live conductor of the lighting circuit (which
presumably is wired correctly, or the lights wouldn't be working) measures
240V with respect to real earth. So from that i'm assuming the earth in
the lighting circuit is at 120v with respect to earth.

Martin




--
Using Opera's revolutionary e-mail client: http://www.opera.com/m2/

On Fri, 06 Aug 2004 12:24:12 +0100, Mike wrote:


I'd be inclined to measure every earth on your lighting circuit, seeing
which switches/fittings have the 120v on them and which don't. Then you
will probably be able to deduce where it is not connected.

Haven't checked every fitting but it is at 120v at every switch. (Haven't
checked the pull-cord switch in the bathroom), but in terms of layout I
would expect that to be near the end of the circuit. I think this suggests
the fault is between the CU and the first ground floor light.


If lucky in this process you will find the loose or missing earth. If
not you will have to do some continuity checking and disconecting of
things to deduce which cable is broken and then replace it.


Thought so... I guess I'll be doing that then!


--
Using Opera's revolutionary e-mail client: http://www.opera.com/m2/

"Boris" wrote in message
.37...
"Martin Brook" wrote in
news

On further investigation it seems that the earth conductors in all of
my light switches are at 120V (with respect to neutral or live -
tested with multimeter set to AC mode). However at the consumer unit,
all appears to be fine. I have a functioning RCD and it's not
tripped. All the lights work. No (obvious) dodgy wiring in any of the
switches.



What does your earth measure with respect to a "real" earth (e.g.
conductive thing in the ground, bonded water pipe, earth at the consumer
unit) ?


That can be very misleading real earth "the conductive thing in the ground"-
may not be connected to your mains earth at all eg a PME installation.

It seems there are two issues here. Why is the the lighting earth not
earthed and why is it it at 120V.

First one in easy- probably a simple break or unmade connection. Check the
continuity (power off) from the lighting earth to the earth bus in the
consumer unit and the meter board. To help with the second bit, do the ring
mains and other spurs (eg cooker and shower) at the same time.

Second one is more complicated- I suspect a filter in something on the
circuit is the culprit. These filters have capacitors from L and N to earth.
If the earth is not connnected it will be at the mid-point of a 1:1
potential divider, in this case 120V. Earth the earth and all is well. The
filter isn't broken- just effectively incorrectly wired. You may be able to
isolate the fault by unpluging appliances.


--
Brian Reay
www.g8osn.org.uk
www.amateurradiotraining.org.uk
FP#898

In article ,
Martin Brook wrote:
Are all your fittings standard ceiling roses? If so it's easy enough
to do a visual check as a first step. If, however, some have been
changed because of the fittings, I'd guess the earth hasn't been
looped through at these.


Yes, they all are... forgive my ignorance, but I'm picturing a setup
where there is a junction box above each light fitting, which is why I
was expecting to be having to spend a lot of time lifting
floorboards... am I getting this completely wrong?

If you unscrew the cover from a 'standard' ceiling rose, you'll expose the
connections. The earth wires are pretty obvious - if they exist. For some
reason, I've often seen them cut off.

--
*Growing old is inevitable, growing up is optional *

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

"Martin Brook" wrote in message ...
On Thu, 5 Aug 2004 14:46:36 +0100, Tim Mitchell
wrote:

Sounds like the earth wire on your lighting circuit is not connected to
earth, which is a cause for concern.


Also, most of the wiring in the house seems to be fine, earth-wise. I've
already rewired two ring mains and added a new one, and everything is fine
on those. The lighting circuit is the only one I haven't touched, but
there is no voltage on the earth at the CU. So it seems to me that the
problem must be somewhere in the rest of the circuit. Which, of course,
disappears through a hole in the cellar roof.


This does beg the q what did you connect the other meter lead to in
each case? But assuming for a mo that you used the same point at all
times, and that piont was really earthed, you likely have lost an
earth connection somewhere in lighting cct.

It matters if you have fittings needing earth - of course that does
include plastic switches which have metal screws.

Regards, NT

"Brian Reay" wrote in
:


That can be very misleading real earth "the conductive thing in the
ground"- may not be connected to your mains earth at all eg a PME
installation.


Agreed, but surely you wouldn't get 120 volts? Unless your electricity
suppliers neutral had a fault...


It seems there are two issues here. Why is the the lighting earth not
earthed and why is it it at 120V.

First one in easy- probably a simple break or unmade connection. Check
the continuity (power off) from the lighting earth to the earth bus in
the consumer unit and the meter board. To help with the second bit,
do the ring mains and other spurs (eg cooker and shower) at the same
time.

Second one is more complicated- I suspect a filter in something on
the circuit is the culprit. These filters have capacitors from L and N
to earth. If the earth is not connnected it will be at the mid-point
of a 1:1 potential divider, in this case 120V. Earth the earth and
all is well. The filter isn't broken- just effectively incorrectly
wired. You may be able to isolate the fault by unpluging appliances.



That sounds entirely reasonable. The tingling noted by the OP would be as a
result of current through filter caps.

Boris

"Brian Reay" wrote in message ...
"Boris" wrote in message
.37...
"Martin Brook" wrote in
news

That can be very misleading real earth "the conductive thing in the
ground"- may not be connected to your mains earth at all eg a PME
installation.

Incoming "conductive things" like water pipes should of course be firmly
bonded to the PME terminal (main bonding). Network faults apart - and these
would usually clear in a matter of seconds - the PME earth shouldn't be more
than a volt or three adrift of the local 'true' ground.

It seems there are two issues here. Why is the the lighting earth not
earthed and why is it it at 120V.

It is at ~120 V _because_ the connection to the main earth terminal is
either absent or broken. (There's a lot to be said for Occam's razor, you
know.)

Second one is more complicated- I suspect a filter in something on
the circuit is the culprit. These filters have capacitors from L and
N to earth. If the earth is not connnected it will be at the mid-
point of a 1:1 potential divider, in this case 120V. Earth the earth
and all is well. The filter isn't broken- just effectively
incorrectly wired.

No need to postulate a filter: the capacitance in the wiring is quite enough
to produce the effect described. T&E cable will have roughly equal
capacitance between L and E and N and E. If the earth wire (CPC, strictly)
is left floating then a high-impedance meter will measure 120 V AC on it,
due to the capacitive divider principle that you describe. The few
microamps of leakage through your body (and its own capacitance to earth)
that you'd get when touching the CPC in these circumstances is quite enough
to produce a tingle.

On a lighting circuit like this I'd expect to see almost exactly half-mains
voltage when all the lights are switched off, with the voltage rising as
lights are switched on (because in the switch-drops sections both L and SL
conductors are 'live' when the light is on and all the capacitance in such
section is now between L and E, IYSWIM).

Could this whole thing be a simple case of incompetent extension(s) to an
old unearthed lighting circuit - somebody adding new wiring and accessories
and having nothing to connect the CPC to?

--
Andy

In article ,
Andy Wade wrote:
Could this whole thing be a simple case of incompetent extension(s) to
an old unearthed lighting circuit - somebody adding new wiring and
accessories and having nothing to connect the CPC to?

I never cease to be surprised how many DIY bodges leave out the earth.
Perhaps because things 'work' without it?

A physics teacher friend ran a lighting circuit from the CU into a new
garage at an old house. The house lighting wiring was pretty old, with no
earth, but the consumer unit had been changed when rings were installed
and was properly earthed etc.

I was mildly surprised to find it wasn't earthed - with the ec cut off. He
reckoned if it wasn't needed in the rest of the house, why bother with it
now...

--
*Re-elect nobody

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

On 7 Aug 2004 12:08:08 GMT, (Huge) strung together
this:

Errr, I thought one shouldn't run the house earth into an outbuilding?

It depends.
--

SJW
A.C.S. Ltd

In article ,
Huge wrote:
I was mildly surprised to find it wasn't earthed - with the ec cut off.
He reckoned if it wasn't needed in the rest of the house, why bother
with it now...

Errr, I thought one shouldn't run the house earth into an outbuilding?
Perhaps that's just for {mumble} (I'd call it PME, but WTF)
installations, like what we've got.

It wasn't an outbuilding, but a lean to. IIRC, it's the distance from the
main earth point that matters (and the size of the cable)

--
*A fine is a tax for doing wrong. A tax is a fine for doing well.

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

"Dave Plowman (News)" wrote in message
...

It wasn't an outbuilding, but a lean to. IIRC, it's the distance from
the main earth point that matters (and the size of the cable)

No, distance doesn't have much to do with it: it's whether it's practicable
to apply the equipotential zone concept in the remote installation (see
http://www.google.com/groups?selm=01c1a135%244dc3c9e0%24LocalHost%40dog4 0
for an example from a previous discussion). The existence of any sort of
'damp floor' conditions suggests that an 'exported' PME earth is
inadvisable.

Where an exported earth is used, local bonding of any incoming services in
the outbuilding is essential. When it comes to "the size of the cable" you
must ensure (as always) that disconnection time and earth fault loop
impedance requirements are met, bearing in mind the type of fusing, etc.

--
Andy

"Andy Wade" wrote in message
...
"Dave Plowman (News)" wrote in message
...

It wasn't an outbuilding, but a lean to. IIRC, it's the distance from
the main earth point that matters (and the size of the cable)

No, distance doesn't have much to do with it: it's whether it's
practicable
to apply the equipotential zone concept in the remote installation (see

http://www.google.com/groups?selm=01c1a135%244dc3c9e0%24LocalHost%40dog4 0
for an example from a previous discussion). The existence of any sort of
'damp floor' conditions suggests that an 'exported' PME earth is
inadvisable.

Which does raise the question, why do old rural houses with inherently
slightly damp stone floors usually have PME in them ? Ours had a quite
noticable tingly 40volts from 'earth' to 'ground'.

In message , "Dave Plowman (News)"
writes

A physics teacher friend ran a lighting circuit from the CU into a new
garage at an old house. The house lighting wiring was pretty old, with no
earth, but the consumer unit had been changed when rings were installed
and was properly earthed etc.

I was mildly surprised to find it wasn't earthed - with the ec cut off. He
reckoned if it wasn't needed in the rest of the house, why bother with it
now...


Physics teachers!!!! PPHHHAAAAAAAA
When I was at school 30+ years ago my physics teacher had a small
cruiser, boat, that he wired spot lights on using bell wire. Well it was
only 12V wasn't it. The whole lot went up in smoke when he turned them
on.
--
Bill

replying to Andy Wade, Iain wrote:
I had same problem. Different voltage readings. But nonetheless the solution
was the same. Reconnect the broken earth connection in one of the ceiling
roses. Thanks for the ideas here. Sorted in half hour after reading your post.
Spent hours writing down values before.

--
for full context, visit https://www.homeownershub.com/uk-diy...20v-94971-.htm