I have bought a new ceiling light for my wifes latest project, an Art Deco living room ! On removing the existing fitting I found that there are only two cables both of which are coloured red!
As the new fitting has a step down transformer I assume it will be necessary to wire it correctly i.e. Live to live and neutral to neutral and somehow fit an earth (the two red cables are contained in an iron tube conduit).
How do I find out which is live and which is neutral without any test equipment??

On Fri, 18 Jan 2008 17:50:44 +0000, Unclebill
wrote:

How do I find out which is live and which is neutral without any test
equipment??
I have used a couple of ways of doing this but neither are suitable for a public
newsgroup since they could both be dangerous.
Suggest buying a neon srewdriver.

Geo

The message
from Geo contains these words:

On Fri, 18 Jan 2008 17:50:44 +0000, Unclebill

wrote:

How do I find out which is live and which is neutral without any test
equipment??
I have used a couple of ways of doing this but neither are suitable
for a public
newsgroup since they could both be dangerous.
Suggest buying a neon srewdriver.

If so, make sure it's the old-fashioned sort, not one of those that
lights up anywhere near a live supply and make sure you don't have
rubber shoes and aren't standing on an insulated stepladder.

However, since Maplin do perfectly serviceable multimeters in a neoprene
hoster for prices which vary from £2.95 to £5, everyone can have a
meter.

"Geo" wrote in message
...
On Fri, 18 Jan 2008 17:50:44 +0000, Unclebill

wrote:

How do I find out which is live and which is neutral without any test
equipment??
I have used a couple of ways of doing this but neither are suitable for a
public
newsgroup since they could both be dangerous.
Suggest buying a neon srewdriver.

Geo
I have learned to remove my neon screwdriver from my top
pocket and hide it when working with real electricians.
They are not excatly regarded as de rigueur.
--
Graham

%Profound_observation%

On 18 Jan, 17:50, Unclebill wrote:
I have bought a new ceiling light for my wifes latest project, an Art
Deco living room ! On removing the existing fitting I found that there
are only two cables both of which are coloured red!
As the new fitting has a step down transformer I assume it will be
necessary to wire it correctly i.e. Live to live and neutral to neutral
and somehow fit an earth (the two red cables are contained in an iron
tube conduit).
How do I find out which is live and which is neutral without any test
equipment??

--
Unclebill

Come on guys - not very intelligent answers. Try thinking first.

The answer is that a transformer is totally insensitive to which way
it is connected - it is after all just a floating coil, (or strictly a
pair of coils - primary and secondary). So it doesn't matter which
way it is wired.

As far as the earthing is concerned, if there is no earth tag on the
fitting, then it is safe to assume that any metal parts are isolated
from the fitting and that a double fault would be required to make the
fitting live.

If on the other hand there is an expectation that the fitting should
be earthed, then the OP does have a problem as it is not acceptable to
consider the conduit as a an earth as it will have mechanical joints
in it that may have suffered corrosion over the years The solution
is I'm afraid to pull the two cables back through, pulling in new
cables plus an earth cable.

I would suggest that the OP gets professional advise as his original
question does suggest that his knowledge of electrics is beyond such a
rewiring activity.

Rob

In article ,
Unclebill wrote:
I have bought a new ceiling light for my wifes latest project, an Art
Deco living room ! On removing the existing fitting I found that there
are only two cables both of which are coloured red!
As the new fitting has a step down transformer I assume it will be
necessary to wire it correctly i.e. Live to live and neutral to neutral
and somehow fit an earth (the two red cables are contained in an iron
tube conduit).
How do I find out which is live and which is neutral without any test
equipment??

I'd say you should get a book on basic theory and read it before
attempting any electrical work.

--
*Everyone has a photographic memory. Some don't have film *

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

In message , Graham.
writes


"Geo" wrote in message
.. .
On Fri, 18 Jan 2008 17:50:44 +0000, Unclebill

wrote:

How do I find out which is live and which is neutral without any test
equipment??
I have used a couple of ways of doing this but neither are suitable for a
public
newsgroup since they could both be dangerous.
Suggest buying a neon srewdriver.

Geo
I have learned to remove my neon screwdriver from my top
pocket and hide it when working with real electricians.
They are not excatly regarded as de rigueur.

so why not chuck it away ?

--
geoff

Unclebill wrote:

How do I find out which is live and which is neutral without any test
equipment??

By buying some...



--
Cheers,

John.

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

On Fri, 18 Jan 2008 17:50:44 +0000 someone who may be Unclebill
wrote this:-

As the new fitting has a step down transformer I assume it will be
necessary to wire it correctly i.e. Live to live and neutral to neutral
and somehow fit an earth (the two red cables are contained in an iron
tube conduit).

If the fitting is double insulated then there is no need for an
earth. If you don't know what the symbol for double insulation is
then you don't have the necessary skills to do the work.


--
David Hansen, Edinburgh
I will *always* explain revoked encryption keys, unless RIP prevents me
http://www.opsi.gov.uk/acts/acts2000/00023--e.htm#54

On Fri, 18 Jan 2008 14:02:20 -0800 (PST) someone who may be
robgraham wrote this:-

If on the other hand there is an expectation that the fitting should
be earthed, then the OP does have a problem as it is not acceptable to
consider the conduit as a an earth as it will have mechanical joints
in it that may have suffered corrosion over the years The solution
is I'm afraid to pull the two cables back through, pulling in new
cables plus an earth cable.

Pull them back to where? All the way to the consumer unit? That
might be difficult in many conduit systems, as there is unlikely to
be a wire going all the way even if there is space in the conduit.

An alternative is to measure the impedance of the conduit. Despite
the statements of some, conduit can make a perfectly good protective
conductor provided it was installed and maintained properly. A short
flying lead connected to a bolt tapped into the box is then all that
is needed. However, it is vital to measure the PSC at the box and
check that a small copper conductor can cope with this. It may be
necessary to use a larger size than would be standard in a T&E
cable.


--
David Hansen, Edinburgh
I will *always* explain revoked encryption keys, unless RIP prevents me
http://www.opsi.gov.uk/acts/acts2000/00023--e.htm#54

In message , David Hansen
writes
However, it is vital to measure the PSC at the box and check that a
small copper conductor can cope with this. It may be necessary to use a
larger size than would be standard in a T&E cable.

I know what T&E is but PSC?

--
Si

On Sat, 19 Jan 2008 09:14:51 +0000 someone who may be Si
$3o&m wrote this:-

I know what T&E is but PSC?

Prospective short-circuit current. The hundreds or thousands of amps
that will flow at that point if there is a short-circuit.

It should only flow for a short period before the protective device
operates, but the wiring has to be able to take this current while
it flows if there is not to be further damage to the wiring.


--
David Hansen, Edinburgh
I will *always* explain revoked encryption keys, unless RIP prevents me
http://www.opsi.gov.uk/acts/acts2000/00023--e.htm#54

In message , David Hansen
writes
On Sat, 19 Jan 2008 09:14:51 +0000 someone who may be Si
$3o&m wrote this:-

I know what T&E is but PSC?

Prospective short-circuit current. The hundreds or thousands of amps
that will flow at that point if there is a short-circuit.

It should only flow for a short period before the protective device
operates, but the wiring has to be able to take this current while
it flows if there is not to be further damage to the wiring.

ta

--
Si

"John Rumm" wrote in message
...
Unclebill wrote:

How do I find out which is live and which is neutral without any test
equipment??

By buying some...


Impovise, wet your finger and touch the wires in turn. You will soon find
the live cable.

It will save you a few quid.

Adam

Si wrote:
In message , David Hansen
writes
On Sat, 19 Jan 2008 09:14:51 +0000 someone who may be Si
$3o&m wrote this:-

I know what T&E is but PSC?

Prospective short-circuit current. The hundreds or thousands of amps
that will flow at that point if there is a short-circuit.

It should only flow for a short period before the protective device
operates, but the wiring has to be able to take this current while
it flows if there is not to be further damage to the wiring.

ta

It would actually be more appropriate to measure the Earth Fault Loop
impedance since it is the integrity of the earth that is in question.



--
Cheers,

John.

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

John Rumm wrote:

It would actually be more appropriate to measure the Earth Fault Loop
impedance since it is the integrity of the earth that is in question.

Quite so. Short circuit compliance can be taken as read if the rating
of the cable exceeds that of the fuse or circuit breaker protecting it.

--
Andy

On Sat, 19 Jan 2008 16:01:24 +0000 someone who may be John Rumm
wrote this:-

It would actually be more appropriate to measure the Earth Fault Loop
impedance since it is the integrity of the earth that is in question.

Quite right. My mistake.


--
David Hansen, Edinburgh
I will *always* explain revoked encryption keys, unless RIP prevents me
http://www.opsi.gov.uk/acts/acts2000/00023--e.htm#54

OK everyone settle down !
I bought a multimeter, checked that the conduit really is a good earth and found out which cable was which. The new light fitting is up and running.
Thanks to all who made practical suggestions.
Bill

On Sun, 27 Jan 2008 21:30:06 +0000, Unclebill wrote:

I bought a multimeter, checked that the conduit really is a good earth

You can't do that properly with a multimeter. It doesn't take many ohms to
stop high enough fault currents from flowing and thus any overload/fault
protection from operating within the time it should.


--
Cheers
Dave. pam is missing e-mail

In article ,
Unclebill wrote:
I bought a multimeter, checked that the conduit really is a good earth
and found out which cable was which.

How did you do this with a multi-meter?

--
*Experience is something you don't get until just after you need it *

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

I followed the advice received from another well known forum :-

"Not much can be done without a meter. For a simple voltage test like this, one of the 10 quid argos digital multimeters would be sufficient.

You could also use a test lamp, but this would not give an accurate result of whether or not the steel conduit was properly earthed"

Also, from the same source :-

"it is likely that the metal conduit is being used as the earth, this is standard practice with metal conduit or trunking

Assuming you have a test meter, and assuming that one of the reds is an unsleeved neutral, then measring between both reds will show 230V, measuring between one of the reds and the conduit will show 230V, this is your phase conductor (and also proves the conduit is earth), then measure the other conductor to conduit should show 0V, this is your neutral and should be sleeved black.

Obviously working safely, etc etc

On Mon, 28 Jan 2008 23:07:41 UTC, Unclebill
wrote:


Dave Plowman (News);1815186 Wrote:
In article ,
Unclebill wrote:-
I bought a multimeter, checked that the conduit really is a good
earth
and found out which cable was which.-

How did you do this with a multi-meter?

I followed the advice received from another well known forum :-

Which forum would that be?

"Not much can be done without a meter. For a simple voltage test like
this, one of the 10 quid argos digital multimeters would be
sufficient.

This isn't a voltage test, it's a resistance test. And you are measuring
very low resistances - which a multimeter like that won't do.

--
The information contained in this post is copyright the
poster, and specifically may not be published in, or used by
http://www.diybanter.com

In article ,
Unclebill wrote:

Dave Plowman (News);1815186 Wrote:
In article ,
Unclebill wrote:-
I bought a multimeter, checked that the conduit really is a good
earth
and found out which cable was which.-

How did you do this with a multi-meter?

I followed the advice received from another well known forum :-

"Not much can be done without a meter. For a simple voltage test like
this, one of the 10 quid argos digital multimeters would be
sufficient.

Then it's poor advice for checking an earth. Digital multimeters draw very
little current and a poor earth with a high resistance - and this is
exactly what can happen with conduit - will show up as 'normal' with one.

You could also use a test lamp, but this would not give an accurate
result of whether or not the steel conduit was properly earthed"

In actual fact the reverse. A test lamp will draw some current and is
better than a simple volt meter. But the correct tester will draw a very
high current for an instant thus checking the earth is doing its job
correctly - ie capable of drawing enough current in event of a fault to
trip the circuit protector within the design time.

--
*What am I? Flypaper for freaks!?

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

In an earlier contribution to this discussion,
Unclebill wrote:

Dave Plowman (News);1815186 Wrote:
In article ,
Unclebill wrote:-
I bought a multimeter, checked that the conduit really is a good
earth
and found out which cable was which.-

How did you do this with a multi-meter?


I followed the advice received from another well known forum :-


That says it all!
--
Cheers,
Roger
______
Email address maintained for newsgroup use only, and not regularly
monitored.. Messages sent to it may not be read for several weeks.
PLEASE REPLY TO NEWSGROUP!

Dave Plowman (News) wrote:

better than a simple volt meter. But the correct tester will draw a very
high current for an instant thus checking the earth is doing its job
correctly - ie capable of drawing enough current in event of a fault to
trip the circuit protector within the design time.

Which raises an interesting point; many modern loop testers have a "no
trip" test facility that enables measurements to be made without
tripping any RCD on the circuit. With the increasing use of RCDs this
will become the typical way a test like this is done.

How many of them I wonder are still able to do a high current test
without tripping the RCD?



--
Cheers,

John.

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