[geoffers]

Originally Posted by rwh202

If you were your neighbour, then you'd be none the wiser and not know if looped..

I guess in our case the supply cable went through the party wall, as my neighbour's meter cupboard (in a back to back terrace) was the mirror image of mine. So the supply was clearly coming from my side of the wall.

So this possibly might have been more of a clue than the normal case, where the person on the end of the loop just has a single cable coming up from below ground into their head unit in the same way as a non looped supply

[meldrewreborn]

@geoffers

I watched the video. The concerns seem to be if the supply cable were damaged at some point away from the home so that the home only received a live supply but no neutral and/or no earth.

It seemed to me that this was likely to be an very uncommon happening, but if it did, wouldn't most of us be concerned within the home rather than an EV outside? And wouldn't all the homes affected have no functioning electricity as no circuit would be possible? I'm only asking to understand this potential risk over which the occupier has no control at all.

Perhaps @retrotecchie would like to comment.

[geoffers]

@meldrewreborn - that video was purely relating to EV charging, requiring T-T earthing which is NOT connected to household TN-C-S earth.

There's some other extremely good videos by J.W going into the whole issue of earthing, and electrics in general.

I hadn't realised how complex it all was, but now think I understand a bit more about the requirements. Particularly for extraneous metalwork (pipework) to be earth bonded in TN-C-S earthing senarios (now the majority of household). It's not just so you won't get a shock if you touch your pipework - it's so that there's a separate path to earth if your combined neutral/earth is damaged somewhere down the line.

However now, although your property could be safe this has the potential for your neighbour's property to become "live" if somebody happens to be tinkering with the protective earthing in that property. If their protective earth was broken, the path to earth could be from your property pipework via their pipework and through your neighbour! ⚡💀

These are all worst case scenarios but they have to insure against these - hence the complexity of BS 7671

[meldrewreborn]

@geoffers

My gas was in a metal pipe but is now in yellow plastic running inside the metal most but not all of way, and my water was originally in lead but 37 years has been in blue plastic laid independently - so again no metallic connection to the street.. While the old pipes are still there there is no continuity to the street mains.

I fully appreciate the video was concerning itself with EV's and their charger, but similar considerations inside the home would apply in the unlikely events considered.

[retrotecchie]

Originally Posted by meldrewreborn

Perhaps @retrotecchie would like to comment.

Anything other than PME (which is now a no-no) is fine

I'm a big fan of T-T and used in conjunction with any external wiring is mandatory in my book.

But T-T has to be done properly and I've never trusted some installations I've seen!

My shed has T-T for my solar as the 30 foot run to the house would need a 6mm earth cable which is a bit overkill with 2.5mm L and N 🤣🤣🤣

On a slight tangent, if you have a gas boiler now, it has to be directly earthed back to the consumer unit rather than relying on a water or gas pipe. The earth wire in the power cable feeding it is not good enough. Gas Safe engineers are now condemning gas installations for substandard electrical earthing.

[geoffers]

Originally Posted by retrotecchie

Anything other than PME (which is now a no-no) is fine....

@retrotecchie ...You've got me confused 😵‍💫

National grid say

Protective Multiple Earthing (PME) is the most common type of low voltage earthing provided at new installations.

Is their advice now out of date or something? 😲

https://connections.nationalgrid.co.uk/make-a-change/replace-equipment/earthing-pme-service/

<edit>Ahhh ... I guess you mean for EV earthing 🤓</edit>

[rwh202]

Originally Posted by meldrewreborn

@geoffers

My gas was in a metal pipe but is now in yellow plastic running inside the metal most but not all of way, and my water was originally in lead but 37 years has been in blue plastic laid independently - so again no metallic connection to the street.. While the old pipes are still there there is no continuity to the street mains.

I fully appreciate the video was concerning itself with EV's and their charger, but similar considerations inside the home would apply in the unlikely events considered.

In the home, you aren’t likely to be able to touch a true ground at the same time, so no shock. It’s the potential difference that’s the problem. A bird can sit on a 100kV line with no issue!
A car floating at 240v that you brush against whilst in contact with true ground is the risk.

[geoffers]

Originally Posted by rwh202

In the home, you aren’t likely to be able to touch a true ground at the same time, so no shock. It’s the potential difference that’s the problem. A bird can sit on a 100kV line with no issue!
A car floating at 240v that you brush against whilst in contact with true ground is the risk.

...and the car can't be a route to earth either, since it's sitting on rubber wheels😎

[geoffers]

Originally Posted by meldrewreborn

@geoffers While the old pipes are still there there is no continuity to the street mains.

Ahhh - but the metal pipes don't need to connect to anything : the fact that they are in the ground is providing a good T-T earth, in the same way as an earthing rod. (though "good" is questionable, since it all depends on the Ω resistance)

My (1946) terrace didn't originally have any "continuity to the street mains" (ie TN-C-S with the household earth taken off the incoming combined earth/neutral) - it was originally wired as T-T, with loads of (bare) wire connected to every pipe in sight under the floorboards, then ultimately connected to the incoming lead mains water supply.

[retrotecchie]

@geoffers

NO! Water pipes may not be used for earthing since the 14th Edition went obsolete back in the 60s.

The Energy Networks Association rules say:

The use of the supply water pipe as an earth terminal ceased to be permitted in the 14th Edition of the wiring regulations in 1966. There may however be properties where this practice continues, where such conditions are discovered a letter to the customer as outlined in Appendix A shall be issued requiring them to take remedial action to ensure that their installation has suitable earthing. Where network conditions permit a DNO will provide a dedicated earth terminal compatible with network construction.