Continuity between neutral and earth

[John Rumm]

Erroneous statement followed by a non sequitur... Mmmm useful ;-)

[Mike Humphrey]

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 working on.

Mike

[dr.s.lartius]

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).

[tabbypurr]

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 :)

NT

[John Rumm]

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[1] 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 customer's earth.

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).

[1] 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)

[Huge]

[48 lines snipped]

Precisely.

[David]

This looks to be another advantage of RCBOs.

I had them fitted because I kept knocking the main breaker out with earth/ neutral contact when changing stuff.

Isolating both live and neutral can have advantages when you want to keep most of the house powered up when you work on one circuit.

Cheers

Dave R

[Andy Burns]

Except most RCBOs only break the live pole, the neutral passes through them, but only for sensing, there are double pole RCBOs but you'd have to go hunting for them

[John Rumm]

Take care with that though since most RCBOs are only single pole switches (even if they are connected to neutral to allow for current imbalance sensing). Hence they can't provide isolation of the circuit.