Neutral Woes


D

Doctor D.

Wotcha,

Could someone tell me whether it has it EVER been permissible to borrow a
neutral on a landing light please?

Last weekend I replaced a consumer unit for a friend, and on
pre-commissioning
tests I realised that something was amiss. Investigation revealed that that
the landing light was running from the downstairs lighting circuit (despite
the fact that both switches are one gang) with a neutral borrowed from the
upstairs circuit.

The property was built in the mid 1960's and cabling is plastic. Supplying
lighting cable is earthed, whilst switch drops are not. Would the borrowed
neutral date from the original installation on the property, as it does not
appear much has been done to the wiring in that part of the house.

Due to the time of day we discovered this "characteristic" I left it
with both lighting circuits connected via the RCD, to be sorted when I have
to lift the floorboards on the landing to carry out some more rewiring in
the next few weeks. The friend is aware of the problem with his wiring.

I am fully aware of the dangers associated with borrowing neutrals, and
would just appreciate knowing it was ever commonplace or acceptable?

Thanks.
 
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H

Harry Bloomfield

I am fully aware of the dangers associated with borrowing neutrals, and
would just appreciate knowing it was ever commonplace or acceptable?
It was never acceptable, but is commonplace. It was once common to have
just one single lighting circuit for the entire house, the installation
of some earths suggests that some rewiring has been done which might
have been the time when it was split into two circuits.
 
B

Bob Mannix

Doctor D. said:
Wotcha,

Could someone tell me whether it has it EVER been permissible to borrow a
neutral on a landing light please?

Last weekend I replaced a consumer unit for a friend, and on
pre-commissioning
tests I realised that something was amiss. Investigation revealed that that
the landing light was running from the downstairs lighting circuit (despite
the fact that both switches are one gang) with a neutral borrowed from the
upstairs circuit.
You should worry! I discovered my landing light was fed from the downstairs
live circuit and the upstairs live circuit (one in each switch). Merrily I
went along, having removed the upstairs circuit fuse, dismantling another
upstairs light fitting. SWMBO turns on the landing light from downstairs. By
this time I had broken the upstairs neutral circuit and had the wires in my
mitt. Landing light glows dimly, due to the fact that I am the neutral
circuit, after the neutral has risen in voltage enough to be very
noticeable. WTF! Some time later I realise the person who did it obviously
wasn't aware of the existence of 3core+E and got a bit stuck having laid in
the 2core+E to a 3 gang switch downstairs already operating downstairs
lights. "Never mind, there's a live here, that'll do". Grrrrr.
[/QUOTE]
 
L

Lurch

You should worry! I discovered my landing light was fed from the downstairs
live circuit and the upstairs live circuit (one in each switch). Merrily I
went along, having removed the upstairs circuit fuse, dismantling another
upstairs light fitting. SWMBO turns on the landing light from downstairs. By
this time I had broken the upstairs neutral circuit and had the wires in my
mitt. Landing light glows dimly, due to the fact that I am the neutral
circuit, after the neutral has risen in voltage enough to be very
noticeable. WTF! Some time later I realise the person who did it obviously
wasn't aware of the existence of 3core+E and got a bit stuck having laid in
the 2core+E to a 3 gang switch downstairs already operating downstairs
lights. "Never mind, there's a live here, that'll do". Grrrrr.
How do you manage to get two lives in one circuit? Surely you had it
that the live was from downstairs and the neutral from upstairs.
When some of these installation were, well, installed there would more
than likely have only been one lighting circuit so the neutral wasn't
borrowed. At some time over the years thick people change the CU's and
split the lighting circuit thing "ooh, more convenience etc...", not
very often do they think "ooh better check those circuits for
electrical safety before altering it". I generally leave lighting as
it is when changing CU's for this very reason.


SJW
A.C.S. Ltd.
 
B

Bob Mannix

Lurch said:
How do you manage to get two lives in one circuit? Surely you had it
that the live was from downstairs and the neutral from upstairs.
When some of these installation were, well, installed there would more
than likely have only been one lighting circuit so the neutral wasn't
borrowed. At some time over the years thick people change the CU's and
split the lighting circuit thing "ooh, more convenience etc...", not
very often do they think "ooh better check those circuits for
electrical safety before altering it". I generally leave lighting as
it is when changing CU's for this very reason.

I did not say there were two lives in one circuit, I said there were two
circuits and the two way switch arrangement for one light (the landing
light) used both of them. In a normal two way switch arrangement, the live
from one circuit and its local switch is fed (via the 3core+E cable) to the
remote switch. In my case the remote switch was on the end of a 2 core +E.
The live for the remote switch was then borrowed from another switch in the
same box, that was on the downstairs circuit. This made the lights worked
but also sometimes connected the two lives together and electrified me!

Hope the ASCII art comes out OK

Correct:

L---------------------------------------------------------------------------
----------------

/o----------------------------------------------o |
N--------[LIGHT]-------------/ 3-core (and
earth) /o-----

o----------------------------------------------o/


SW1
SW2
Incorrect:

L----------------------------------
|

/o----------------------------------------------o
N--------[LIGHT]-------------/ 2-core (and
earth) /o------------ A different live

o----------------------------------------------o/

The 3-gang switch downstairs was new, so probably postdated the installation
of two lighting citcuits, which I believe was done in the 60's.

I suppose that, had it originally been one circuit, such an arrangement
would have been OK, but no-one should have ever replaced the switches and
left it like that. I believe there did not use to be a landing light switch
downstairs. Someone ran a cable down and fitted an extra switch to the box
(badly).

Bob
 
L

Lurch

Lurch said:
How do you manage to get two lives in one circuit? Surely you had it
that the live was from downstairs and the neutral from upstairs.
When some of these installation were, well, installed there would more
than likely have only been one lighting circuit so the neutral wasn't
borrowed. At some time over the years thick people change the CU's and
split the lighting circuit thing "ooh, more convenience etc...", not
very often do they think "ooh better check those circuits for
electrical safety before altering it". I generally leave lighting as
it is when changing CU's for this very reason.

I did not say there were two lives in one circuit, I said there were two
circuits and the two way switch arrangement for one light (the landing
light) used both of them. In a normal two way switch arrangement, the live
from one circuit and its local switch is fed (via the 3core+E cable) to the
remote switch. In my case the remote switch was on the end of a 2 core +E.
The live for the remote switch was then borrowed from another switch in the
same box, that was on the downstairs circuit. This made the lights worked
but also sometimes connected the two lives together and electrified me!

Hope the ASCII art comes out OK

Correct:

L---------------------------------------------------------------------------
----------------

/o----------------------------------------------o |
N--------[LIGHT]-------------/ 3-core (and
earth) /o-----

o----------------------------------------------o/


SW1
SW2
Incorrect:

L----------------------------------
|

/o----------------------------------------------o
N--------[LIGHT]-------------/ 2-core (and earth) /o------------ A different live

o----------------------------------------------o/

The 3-gang switch downstairs was new, so probably postdated the installation
of two lighting citcuits, which I believe was done in the 60's.

I suppose that, had it originally been one circuit, such an arrangement
would have been OK, but no-one should have ever replaced the switches and
left it like that. I believe there did not use to be a landing light switch
downstairs. Someone ran a cable down and fitted an extra switch to the box
(badly).

Bob
I think you misunderstand. You did say there were two lives in one
circuit, whether you meant to say this or not is a different matter.
But, there are not 2 lives, the live is taken from the downstairs
lighting, sent upstairs via the 2c+e through the switch on the landing
and onto the landing light fitting. There are no other lives in this
light, only one, not 2. there might be a red cable coming from the
landing light to the landing switch but it's taking power to the
light, not from it. So that's one live, not two.
The ASCII art didn't survive as you may have noticed. So I'm going on
what I managed to reconstruct out of the schrapnel!


SJW
A.C.S. Ltd.
 
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D

Doctor D.

Harry Bloomfield said:
It was never acceptable, but is commonplace. It was once common to have
just one single lighting circuit for the entire house, the installation
of some earths suggests that some rewiring has been done which might
have been the time when it was split into two circuits.
Sadly I'm 99% sure that this is all original.

The cable is stranded with shiny plastic insulation, none of the earth wires
are sleeved.

The CU was the original (8 way I believe) Wylex unit and appears to have
been designed with two lighting circuits as it's quite a big place.
 
B

Bob Mannix

Lurch said:
On Fri, 23 Jan 2004 11:54:39 -0000, "Bob Mannix"

I think you misunderstand. You did say there were two lives in one
circuit, whether you meant to say this or not is a different matter.
But, there are not 2 lives, the live is taken from the downstairs
lighting, sent upstairs via the 2c+e through the switch on the landing
and onto the landing light fitting. There are no other lives in this
light, only one, not 2. there might be a red cable coming from the
landing light to the landing switch but it's taking power to the
light, not from it. So that's one live, not two.
The ASCII art didn't survive as you may have noticed. So I'm going on
what I managed to reconstruct out of the schrapnel!
Sorry the ASCII art confused the issue. There was also mutual
misunderstanding (and, as you point out a mistake on my part).

a) By circuit I meant upstairs or downstairs lighting "circuit" not the
local circuit for the light (I could have been clearer, sorry) - clearly
there is only one live in each of these.

b) Yes, you are right, of course, the two lives were never connected at the
same time to the light, my mistake- the ASCII art was correct, I think, I
misread it when describing the arrangement in words. The arrangement was as
you describe.

Still very wrong as the live supply for the light should come from it to the
switch(es) and back not from another lighting circuit, but not quite as bad
as I described. The fundamentals that I suspect whoever it was laid in 2
core+e and then started scratching their heads and bodged it, causing me
pain, still remains. (I pulled it all out and installed it properly).

Bob
 
H

Harry Bloomfield

Doctor D. wrote on Friday (23/01/2004) :
Sadly I'm 99% sure that this is all original.

The cable is stranded with shiny plastic insulation, none of the earth wires
are sleeved.

The CU was the original (8 way I believe) Wylex unit and appears to have
been designed with two lighting circuits as it's quite a big place.
Stranded would be pre metrication. No earth wire would mean pre 1965 at
a guess. The sleaving came in round about the time of metrication.

The earth back then, was only required if there was a metal fitting to
be earthed, otherwise there was no need. That might explain why the
switches lack an earth wire.

You might consider rewiring it to bring it up to current standards.
 
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L

Lurch

[..]
Sorry the ASCII art confused the issue. There was also mutual
misunderstanding (and, as you point out a mistake on my part).

a) By circuit I meant upstairs or downstairs lighting "circuit" not the
local circuit for the light (I could have been clearer, sorry) - clearly
there is only one live in each of these.

b) Yes, you are right, of course, the two lives were never connected at the
same time to the light, my mistake- the ASCII art was correct, I think, I
misread it when describing the arrangement in words. The arrangement was as
you describe.

Still very wrong as the live supply for the light should come from it to the
switch(es) and back not from another lighting circuit, but not quite as bad
as I described. The fundamentals that I suspect whoever it was laid in 2
core+e and then started scratching their heads and bodged it, causing me
pain, still remains. (I pulled it all out and installed it properly).
Good idea rewiring, although it wasn't classed as a bodge when it was
done, if you did have 2 lighting circuits from day 1 it was probably a
sparky not quite being up to date with current practices, i.e.
borrowing the neutral when splitting the lighting in 2.
Then again it was the 60's, apparently hazey for all involved anyway!!


SJW
A.C.S. Ltd.
 

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