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Old December 7th 17, 10:55 AM posted to uk.d-i-y
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Default Continuity between neutral and earth

On 07/12/2017 09:44, harry wrote:
On Wednesday, 6 December 2017 20:31:35 UTC, wrote:
Hi All

I have broken into a ring main to extend it to another room. Essentially cutting the return from one socket and then connecting each side of the extended ring to one of the cut ends.

I test the extended ring and it was sound (ie only continuity between the corresponding pairs of wire). I have just connected it to the main ring and did a quick continuity check. Live is ok but it seems that neutral (blue) and earth now have continuity. Given I tested the extended ring it would appear that the original ring suffered this problem. However if this was the case wouldn't the RCd at the MCU have tripped before.

Any ideas?

Thanks

Lee


Neutral and earth are bonded together back at the substation.


That is true.

It's important that this is the only place they are bonded.


That is certainly not true for TN-C-S (PME) supplies which are the
default "standard" for installs these days.

(the clue is in the "M"!)


--
Cheers,

John.

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Old December 7th 17, 11:02 AM posted to uk.d-i-y
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Default Continuity between neutral and earth

On 2017-12-07, John Rumm wrote:
On 07/12/2017 09:44, harry wrote:
On Wednesday, 6 December 2017 20:31:35 UTC, wrote:
Hi All

I have broken into a ring main to extend it to another room. Essentially cutting the return from one socket and then connecting each side of the extended ring to one of the cut ends.

I test the extended ring and it was sound (ie only continuity between the corresponding pairs of wire). I have just connected it to the main ring and did a quick continuity check. Live is ok but it seems that neutral (blue) and earth now have continuity. Given I tested the extended ring it would appear that the original ring suffered this problem. However if this was the case wouldn't the RCd at the MCU have tripped before.

Any ideas?

Thanks

Lee


Neutral and earth are bonded together back at the substation.


That is true.

It's important that this is the only place they are bonded.


That is certainly not true for TN-C-S (PME) supplies which are the
default "standard" for installs these days.

(the clue is in the "M"!)


In our last house, there was an earth at every pole on the overhead supply.


--
Today is Sweetmorn, the 49th day of The Aftermath in the YOLD 3183
Ph'nglui mglw'nafh Cthulhu R'lyeh wgah'nagl fhtagn.
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Old December 7th 17, 11:09 AM posted to uk.d-i-y
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Default Continuity between neutral and earth

In article ,
Brian Gaff wrote:
I was always told that Neutral was supposed to be earth, or almost so.
Otherwise we would have two lives.
Brian


It's earth at the substaion, but its volage wrt earth at your home will
depend on how evenly the phases are loaded. 10v wrt earth isn't uncommon.

--
from KT24 in Surrey, England
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Old December 7th 17, 11:31 AM posted to uk.d-i-y
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Default Continuity between neutral and earth

In article ,
wrote:
I test the extended ring and it was sound (ie only continuity between
the corresponding pairs of wire). I have just connected it to the main
ring and did a quick continuity check. Live is ok but it seems that
neutral (blue) and earth now have continuity. Given I tested the
extended ring it would appear that the original ring suffered this
problem. However if this was the case wouldn't the RCd at the MCU have
tripped before.



Assuming you are testing with the main switch off (double pole) you have a
fault. If testing with only the MCB etc (single pole) off, normal.

--
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Old December 7th 17, 12:10 PM posted to uk.d-i-y
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Default Continuity between neutral and earth

On Thu, 7 Dec 2017 09:23:40 -0000, "Brian Gaff"
wrote:

I was always told that Neutral was supposed to be earth, or almost so.
Otherwise we would have two lives.
Brian


One of which would then be a negative wouldn't it?

In the past I think some people referred to the black , later blue
wire in domestic wiring as the negative which was wrong but possibly
influenced with tinkering with cars where batteries have a positive
and negative pole, or maybe for old timers it was a hangover from the
days of DC mains.

The yellow 110 volt plugs intended for use with transformers in the UK
to give a 55-0-55 volt supply usaully have both pins identified with a
moulded L rather than an L and an N but I reckon few people using
or even wiring one have noticed.

G.Harman


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Old December 7th 17, 12:20 PM posted to uk.d-i-y
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Default Continuity between neutral and earth

On Wednesday, 6 December 2017 20:31:35 UTC, wrote:

I have broken into a ring main to extend it to another room. Essentially cutting the return from one socket and then connecting each side of the extended ring to one of the cut ends.

I test the extended ring and it was sound (ie only continuity between the corresponding pairs of wire). I have just connected it to the main ring and did a quick continuity check. Live is ok but it seems that neutral (blue) and earth now have continuity. Given I tested the extended ring it would appear that the original ring suffered this problem. However if this was the case wouldn't the RCd at the MCU have tripped before.


ISTM that a person who does not know that neutral and earth MUST be connected together in at least one place is a person who is not qualified to do such work and the resulting installation is at risk of being in breach of the Building Regulations. See http://www.gutenberg.org/files/27182...-h/27182-h.htm, VI.

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Old December 7th 17, 01:46 PM posted to uk.d-i-y
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Default Continuity between neutral and earth

On Thursday, 7 December 2017 11:10:34 UTC, wrote:
On Thu, 7 Dec 2017 09:23:40 -0000, "Brian Gaff"
wrote:

I was always told that Neutral was supposed to be earth, or almost so.
Otherwise we would have two lives.
Brian


One of which would then be a negative wouldn't it?

In the past I think some people referred to the black , later blue
wire in domestic wiring as the negative which was wrong but possibly
influenced with tinkering with cars where batteries have a positive
and negative pole, or maybe for old timers it was a hangover from the
days of DC mains.

The yellow 110 volt plugs intended for use with transformers in the UK
to give a 55-0-55 volt supply usaully have both pins identified with a
moulded L rather than an L and an N but I reckon few people using
or even wiring one have noticed.

G.Harman


Dc mains used the 2 phase 3 wire system, so half of end users got + and half got -ve dc supplied.


NT
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Old December 7th 17, 01:52 PM posted to uk.d-i-y
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Default Continuity between neutral and earth

On 2017-12-07, charles wrote:
In article ,
Brian Gaff wrote:
I was always told that Neutral was supposed to be earth, or almost so.
Otherwise we would have two lives.
Brian


It's earth at the substaion,


And in a PME installation, at lots of other places.


--
Today is Sweetmorn, the 49th day of The Aftermath in the YOLD 3183
Ph'nglui mglw'nafh Cthulhu R'lyeh wgah'nagl fhtagn.
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Old December 7th 17, 02:11 PM posted to uk.d-i-y
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Default Continuity between neutral and earth

Yes only the MCB was switched off. Rest of the CU was on
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Old December 7th 17, 02:24 PM posted to uk.d-i-y
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Default Continuity between neutral and earth

On 07/12/2017 13:11, wrote:

Yes only the MCB was switched off. Rest of the CU was on


Yup, that only isolates the live. N is still connected to the neutral
bus bar and hence the supply neutral via the main switch. E would be
connected to the supply neutral either at the PME head end (and multiple
other places) or at the transformer if your supply was TN-S. (it will
also be connected to an independent earth in the case of TT or any
installation with main equipotential bonds to incoming metallic services).


--
Cheers,

John.

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


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