On 07/12/2017 13:11, firstname.lastname@example.org wrote:
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).
If you turn off the main switch (which is double pole) the continuity
between earth and neutral should go away. If it doesn't there is
probably a fault on a circuit - but not necessarily the one you were
On Wednesday, 6 December 2017 20:31:35 UTC, email@example.com wrote:
cutting the return from one socket and then connecting each side of the ext
ended ring to one of the cut ends.
corresponding pairs of wire). I have just connected it to the main ring an
d 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 a
ppear 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 connect
ed together in at least one place is a person who is not qualified to do su
ch work and the resulting installation is at risk of being in breach of the
Building Regulations. See http://www.gutenberg.org/files/27182/27182-h/27
On Thursday, 7 December 2017 13:35:22 UTC, John Rumm wrote:
The OP reported that connectivity had, to his surprise, been found
between his neutral and earth wires. It is a requirement that the local ne
utral wires must, somehow, be electrically connected to the terrestrial Ear
th, and it is a requirement that the local earth wires must, somehow, be el
ectrically connected to the terrestrial Earth. Therefore the reported conn
ectivity is required to exist, and so should be expected; it occurs due to
at least one connection, somewhere; such a connection may be man-made metal
lic or by way of the terrestrial Earth (or by any other reliable means, if
any is possible).
On Saturday, 9 December 2017 12:46:05 UTC, firstname.lastname@example.org wrote:
neutral wires must, somehow, be electrically connected to the terrestrial E
arth, and it is a requirement that the local earth wires must, somehow, be
electrically connected to the terrestrial Earth. Therefore the reported co
nnectivity is required to exist, and so should be expected; it occurs due t
o at least one connection, somewhere; such a connection may be man-made met
allic or by way of the terrestrial Earth (or by any other reliable means, i
f any is possible).
In fairness I did once see an installation that must have been relying on a
n extraterrestrial earth :)
On 09/12/2017 12:46, email@example.com wrote:
That is a somewhat different statement from "neutral and earth MUST
be connected together in at least one place". Even then its still
questionable. With a TT supply its fair to assume the neutral will be
connected to earth at the transformer. However that may be the only
place, and there may be no direct connection to the neutral to the
Their earth should be independently connected to earth locally, however
that may show hundreds of ohms resistance to the earth point on the
supply and hence to the neutral at entry to the premises. (and that
obviously ignores things like IT setups with gensets etc).
 Yes, I know the OP does not have one of these, but you made a
blanket statement without qualification.
Low impedance connectivity as described by the OP is not *required* to
exist (since it may not be possible), and on TT installs may not.
Indeed, and that is different from what you said previously.
I also took issue with the assertion that someone not intimately
familiar with earthing systems would not be "qualified" to work on an
electrical system. I have met a number of professionally qualified
electricians that only have a tenuous grasp on such things, but they can
still produce good quality work by applying the rules as specified.
I would assert that its perfectly possible to do a safe and compliant
extension to a socket circuit, and know nothing at all about earthing
systems beyond the need to connect the wires to the socket and test the
continuity when done (as I did many times when I was 12, and would not
have known my earth loop impedance from my elbow!)
The final "at risk of being in breach of the Building Regulations" was a
rather mealy mouthed straw man IMHO. One could argue that everyone is
"at risk" of being in breach of one building regulation or another, but
there was nothing in the OPs post to suggest that was likely here - the
fact that he was asking questions about his observations that obviously
resulted from testing his installation should offer reassurance that
improper work would be much less likely rather than more.
(here endeth the rant about people offering unhelpful criticism in place
of useful advice)
Yes, but when breaking into a ring to add something, he doesn’t need
to know about the required connection between earth and neutral to
do that safely. In spades when it happens back in the sub station.
On Thursday, 7 December 2017 22:21:49 UTC, Rod Speed wrote:
You should, before responding, read carefully what has previously been writ
ten, and think about it. When neutral and earth are connected together at
the sub-station, they are connected together at that place. I did NOT put
anything about "connected together within the premises".
Yes. A person who does not know that the voltage and the resistance betwee
n neutral and earth should each be small is a person who is likely not to k
now all of the proper safe wiring practices that the Regulations require.
(c) John Stockton, near London, UK. Using Google, no spell-check. |
Mail: J.R.""""""""@physics.org - or as Reply-To |
Stop bickering. I mean, its supposed to be earthed, where its earthed only
affects the wiring between that earth and the one that should be down the
line toward the substation, so who really cares?
This newsgroup posting comes to you directly from...
It's not that simple. If you short local earth to neutral here, it will
trip the RCD.
Neutral and earth should only be connected together where they are
designed to be. Which will vary according to your type of mains supply.
With my older installation it isn't done in my house. Presumably at the
local sub station.
*(on a baby-size shirt) "Party -- my crib -- two a.m
Dave Plowman firstname.lastname@example.org London SW
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