If the electricity company's neutral gets disconnected at the meter or somewhere outside the house

[JohnW2]

My supply is from overhead and is polyphase.

So is mine.

TP for my workshop and 1ph for my domestic via the star pointed pole mounted tranny, then underground. My domestic loading is negligible so everything is reasonably well balanced.

Roughly speaking, each floor of my house is fed by one of the three phases. The load across the three phases is usually very unbalanced (far greater on the ground floor than the other two floors) - but 'so what'?

If I lost a phase in my workshop, it would be instantly noticed.

If I lost a phase (which has occasionally happened) I would notice fairly quickly - extremely quickly if it were the phase which serves mainly the ground floor.

 

[JohnW2]

Yes exactly. The supplier's N gets disconnected away from the house. The house's N and E are intact and shorted together inside the meter's housing. The house's own E, in my case a rod in the ground, obviously has some resistance, which has not been noticed, not until the supply's N got disconnected. Now, all current consumed in the house goes through the house's E rather than the supply's N ....

True, except that, if the earth rod were the only connection to earth, 'all current consumed in the house'would be a tiny fraction of what it would be with the N connected - probably to the extent that little, if anything, in the house would 'work'- because of the relative high impedance of the path to earth (hence back to the transformer's neutral) afforded by the rod. If there were extraneous-conductive parts (like metal water and gas supply pipes) bonded to your house's 'earth', then the impedance to earth they provided might be low enough to result in the excessive currents (possibly over-heating etc.) in bonding conductors.

There are things in and outside the house that can have a much better E than the dedicated earthing rod, or the dodgy connector that bonds N + E + N together.

There should not be anything inside your house which has a path to true earth which is not bonded to your house's earthing system. All bets are obviously off once gets outside the (hopefully 'equipotential zone' of) house - but that is always going to introduce some potential hazards (e.g. with outside lighting and sockets etc.)

You can have a very bad E, and never know, not until your supplier's N gets disconnected.

That's certainly one way in which one can become aware of a 'very bad earth', but there are other ways - e.g. if a fuse/MCB in a TN installation fails to operate when there is a 'L-E' fault in something within the house.

In my house in the UK (this is another house) I do not have a special earthing rod, would it not be a good idea to install one? I am thinking, if the supply's N gets disconnected, then I will also lose the house's E completely, save for random copper water pipes.

Despite what some people might try to say,adding an earth rod would do no harm, but nor would it necessarily make much difference in scenarios such as you are contemplating (because of the high impedance of the rod's connection to earth). The most important thing is that anything within the house which might provide a path to true earth (like metal supply pipes) should be bonded to your house's earthing system.

 

[endecotp]

The house's N and E are intact and shorted together inside the meter's housing.

Please post a photo showing this.

Experts, is this normal? I was under the impression that when you have an earth rod, you should not have N and E joined together. Am I wrong?

(Is the house you’re describing outside the UK?)

In my house in the UK (this is another house) I do not have a special earthing rod, would it not be a good idea to install one? I am thinking, if the supply's N gets disconnected, then I will also lose the house's E completely, save for random copper water pipes.

No. You have RCDs, right?

 

[flameport]

Experts, is this normal? I was under the impression that when you have an earth rod, you should not have N and E joined together. Am I wrong?

N&E connected is a TN system, and those in the UK have typically NOT had earth electrodes.
However electrodes for those have been allowed for ever and are now recommended.
Most other countries have been installing them for decades.

TT systems in the UK and everywhere else do have earth electrodes and on those, N&E are not connected anywhere.

The lack of earth electrodes on UK TN installations until very recently has resulted in many people incorrectly believing that the presence of an earth electrode automatically means a TT installation, and that adding an electrode to a TN installation will somehow cause massive problems.

 

[JohnW2]

Experts, is this normal? I was under the impression that when you have an earth rod, you should not have N and E joined together. Am I wrong?

Sort-of (wrong). If the house's E is derived from (hence 'joined to') the incoming N, then it's being used as a TN-C-S supply, which hopefully means that the distribution cable has been PMEd.

However, thereis no reason why one cannot add a local earth rod to a TN-C-S installation (which is no different from bonding an incoming water/gas pipe). Indeed, you may recall that it was only at the eleventh hour that a requirement for all installations (including TN-C-S ones) to also have local earth rods was removed from the draft of the current edition of BS767.

 

[akist]

Sort-of (wrong). If the house's E is derived from (hence 'joined to') the incoming N, then it's being used as a TN-C-S supply, which hopefully means that the distribution cable has been PMEd.

However, thereis no reason why one cannot add a local earth rod to a TN-C-S installation (which is no different from bonding an incoming water/gas pipe). Indeed, you may recall that it was only at the eleventh hour that a requirement for all installations (including TN-C-S ones) to also have local earth rods was removed from the draft of the current edition of BS767.

In the UK, incoming water and gas have been plastic for decades, since at least the 80s. Then it was black and yellow, now it is blue and yellow, but plastic all the same.

In the TN-C-S supply, which I assume is what I have in the UK, the E only exists as long as the supply's N is intact. If incoming N gets disconnected, then the house has no E - EXCEPT random, undetermined paths, some of which could be someone taking a shower.

I think the addition of one or more earthing rods would provide an extra layer of safety.

 

[JohnW2]

In the UK, incoming water and gas have been plastic for decades, since at least the 80s.

In a good few cases. My water supply (in UK) still comes via metal pipes in 2025, as does that to everyone else in my village (but we have no piped gas supply)

In the TN-C-S supply, which I assume is what I have in the UK...

By no means everyone in the UK has TN-C-S. Indeed, it was only a few decades ago that no-one in the UK had it. However, from what you describe, your supply is being used as TN-C-S - so, as I said, let's hope that the incoming distribution cable has been PMEd!

, the E only exists as long as the supply's N is intact.

Yep - although there may also be additional paths to earth via bonded metal supply pipes,like the ones that you imply you do not have (although many people do).

If incoming N gets disconnected, then the house has no E - EXCEPT random, undetermined paths, some of which could be someone taking a shower.

There should NOT be any 'undetermined paths to earth', and if there were then the installation would not be compliant with regulations - all possible extraneous paths to earth ("extraneous-conductive-parts") should be identified and bonded the the house's 'earth'.

Ironically, if your person in the shower somehow touched a live conductor, they would NOT receive a shock (and no current would flow through them) if nothing in the house was connected to earth!

I think the addition of one or more earthing rods would provide an extra layer of safety.

As I said,it will do no harm, but nor will it do a lot of good. As above, and as I said before, the most important thing is that all extraneous-c-ps are bonded to the house's 'earth', so that there can be no significant potential differences (which could cause electric shocks) between any two simultaneously-touchable metal things within the house.

What you you feel that an earth rod would protect you against, and how?

 

[ebee]

I don't think you've ever quantified your view of what 'slightly conductive' may be. If you believe that it is such as to be a genuine concern, then the building should probably be condemned as not safe for habitation (unless the electricity supply were removed) unless/until extensive work were undertaken to either eliminate the damp walls or else somehow 'bond' them?

Around where I live a lot of the housing stock was built around 1900 +/- a few years, in fact some is 200 years old or more, not uncommon.
Sandstone, no damp course when built.
Some have now been injected but plenty have not.
How conductive? I`ve never actually tested.
Usually double skinned outer walls and the inside section could be brick or sandstone.
Before the advent of wire wall ties a lot had "thru-stones" again often sandstone.
I suppose the wally could be "fairly Earthy" especially in damp/rainy conditions but what readings one might expect? I have never considered it - I will out it down on my list of things to do.

In the past there was a lot of conductive metal pipework connecting thousands of terraced houses multiple times criss crossing each house in lead or later copper and once electric was supplied (TNS usually in the towns) then everybody`s Earth was held down by everybody else`s Earth so like a super giant Earth Rod/Mat in effect.
Only the change to plastic pipes started to lose that super earth interconnections.
I have found a few household supply incoming Electrics where the E was not there but being picked up big style by Main Bonding (How many "Electricians" just do a Ze with all bonding connected? Alarmingly many more than you`d think. Add a new circuit or do a rewire a proper Ze with all bonds disconnected is a must do but often not done.

Nowadays if everyone had at least one decent Earth Rod attached to the incomer it might help keep the voltage down?

 

[bernardgreen]

I don't think you've ever quantified your view of what 'slightly conductive' may be

My view is that any conductivity that allows a person to notice a tingle or greater should be investigated.

 

[ebee]

Yup, the safe thing about the UK Bathroom shaver socket is that the only shock path is Line to Line, There is no E to L shock risk, No N so no N to E or L to N shock risk, and only one item being used on that transformer anyway.

If one of those Lines becomes Earthy whether deliberate or by accident then the risks start to increase

 

[JohnW2]

My view is that any conductivity that allows a person to notice a tingle or greater should be investigated.

As I see it, the only situation in which one would get a tingle from a damp wall would be one in which touchable exposed- and extraneous-c-ps within the building were at a potential significantly different from earth potential (and one touched one of those and the wall simultaneously).

Without 'scraping the barrel', that should never be the case with TN-S or TT. With TN-C-S, there will always be some such PD (maybe enough to result in tingles in some cases), with the prospect of very large PDs in the case of supply-side faults.

However, the question is (as I implied), what you believe one should do (or should be required to do) if one 'investigates' and those investigations confirm that the tingles are due to 'damp walls' - evacuate the building unless/until something fairly major is done to the walls, or what?

 

[JohnW2]

Yup, the safe thing about the UK Bathroom shaver socket is that the only shock path is Line to Line, There is no E to L shock risk, No N so no N to E or L to N shock risk.....

I think that statement may confuse some people. With the isolated output of the transformer, the only shock risk is to someone who simultaneously touches both outputs of the transformer ('L' & 'N') - but no such risk if they simultaneously touch E and either of those outputs. The potential confusion arises at least partially because you are (presumably) using 'L' and 'N' to refer to the outputs of the transformer, neither which is any 'different' from the other.

, and only one item being used on that transformer anyway.

Yes, if an isolating transformer feeds two or more items, then there is a theoretical risk that a pair of faults could result in one simultaneously coming in contact with both sides of the transformer output, hence a shock.

If one of those Lines becomes Earthy whether deliberate or by accident then the risks start to increase

Sure, because of those floating outputs of the transformer then becomes analogous with a true 'N'.

Kind Regards, John