Tweaking some lighting, I turned off the mcb for the LX circuit and
opened a pendant fitting. Double-checked with a neon 'driver - not live,
is says. Unscrewed one of the neutrals. As I do so it sparks quite
impressively. Why?

(I chickened out and turned off the whole house supply in the end. Wife
really enjoyed that on a Sunday evening...)

It was a pretty common pendant arrangement - four cables - incoming
L/N/E feed. Outgoing feed. Cable to switch. Cable for pendant fitting.


A spark must means there's current flowing - but where from? I did
wonder whether the 12v transformers for the halogens might have caused
it?

Neon driver! Bin it! They are the work of the devil and about as
reliable as a Politician. IMHO you have either isolated the wrong
circuit or you may have a borrowed neutral. Either way...get help I feel
that you may need it.


--
Posted via Mailgate.ORG Server - http://www.Mailgate.ORG

In article ,
says...
Tweaking some lighting, I turned off the mcb for the LX circuit and
opened a pendant fitting. Double-checked with a neon 'driver - not live,
is says. Unscrewed one of the neutrals. As I do so it sparks quite
impressively. Why?

(I chickened out and turned off the whole house supply in the end. Wife
really enjoyed that on a Sunday evening...)

It was a pretty common pendant arrangement - four cables - incoming
L/N/E feed. Outgoing feed. Cable to switch. Cable for pendant fitting.


A spark must means there's current flowing - but where from? I did
wonder whether the 12v transformers for the halogens might have caused
it?


There is current returning through that neutral block from one of the
other lights upstream of that fitting. Disconnect the neutrals, and one
will be at 0v (near enough), and the other will be live, as there's no
voltage drop across the 'on' light, because no current flows. I learned
very early on that you can get quite a belt from a neutral that way!

In article ,
says...
In article ,
says...
Tweaking some lighting, I turned off the mcb for the LX circuit and
opened a pendant fitting. Double-checked with a neon 'driver - not live,
is says. Unscrewed one of the neutrals. As I do so it sparks quite
impressively. Why?

(I chickened out and turned off the whole house supply in the end. Wife
really enjoyed that on a Sunday evening...)

It was a pretty common pendant arrangement - four cables - incoming
L/N/E feed. Outgoing feed. Cable to switch. Cable for pendant fitting.


A spark must means there's current flowing - but where from? I did
wonder whether the 12v transformers for the halogens might have caused
it?


There is current returning through that neutral block from one of the
other lights upstream of that fitting. Disconnect the neutrals, and one
will be at 0v (near enough), and the other will be live, as there's no
voltage drop across the 'on' light, because no current flows. I learned
very early on that you can get quite a belt from a neutral that way!


Ah, didn't notice the first bit that you had turned off the MCB for that
circuit. Forget what I wrote above!

AJB wrote:

Tweaking some lighting, I turned off the mcb for the LX circuit and
opened a pendant fitting. Double-checked with a neon 'driver - not live,
is says. Unscrewed one of the neutrals. As I do so it sparks quite
impressively. Why?

A couple of possibilities...

As others have said there may be a crossed circuit of some description.

A spark must means there's current flowing - but where from? I did
wonder whether the 12v transformers for the halogens might have caused
it?

You did not say where you got the spark from (i.e. if it was to the
neutral connector itself, or to earth). If it was to earth you need to
remember that a neutral ought to be regarded as a live conductor. It may
have a voltage on it that is some way away from earth potential. How far
will depend on how "stiff" the supply to your property is and how many
other properties share "your" neutral. The result is that it can be a
few volts above ground - certainly enough to pass a reasonble current to
earth.

--
Cheers,

John.

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

"John Rumm" wrote in message
news:4377cad5$0$82650$ed2619ec@ptn-nntp-
You did not say where you got the spark from (i.e. if it was to the
neutral connector itself, or to earth). If it was to earth you need to
remember that a neutral ought to be regarded as a live conductor. It may
have a voltage on it that is some way away from earth potential. How far
will depend on how "stiff" the supply to your property is and how many
other properties share "your" neutral. The result is that it can be a few
volts above ground - certainly enough to pass a reasonble current to
earth.

--
Cheers,

John.

Yup it was certainly enough to throw my glasshouse breaker when earth was
touching neutral on an otherwise disconnected circuit.

Pete
www.thecanalshop.com

"AJB" wrote in message
...
Tweaking some lighting, I turned off the mcb for the LX circuit and
opened a pendant fitting. Double-checked with a neon 'driver - not
live,
is says. Unscrewed one of the neutrals. As I do so it sparks quite
impressively. Why?
snip

You're a frecking good example why we now have Part Pi(iss)...

In article ews.net,
LID says...


You're a frecking good example why we now have Part Pi(iss)...


So, using an 'authorised' company would have prevented that, eh? Just
like the last poster's story....