EPS

[Marcus]

Luckily my spark is very on it.
I am waiting for the guidance note because at the moment it can read either way - are sparks now suddenly going to be putting earth rods in on almost any job(?!).

Lucky man! How do we find these people?

More to the point, why isn't/wasn't extra earthing always a desirable thing in any circumstances? Can anyone imagine a situation when it could cause a problem?
When we get such dramatic about-turns it makes me suspect that the experts always knew what was needed, but were stitched up by people on committees who were only there to represent vested interests. The changes in building regs or fire safety approvals which lead up to the awful fire in Grenfell Tower are a case in point.
A

An earth rod could, in theory, be an issue on TNCS / PME supplies if there's a bad connection on the combined neutral/earth conductor, as the neutral current would try to return to the substation via the earth rods and earth, potentially raising the earth /neutral voltage to a dangerous level, and creating dangerous voltage gradients on the ground around the rods.

Here in west Wales they went through a phase of using aluminium crimps on the copper cables on overhead supplies: every now and then i have to call WPD out when i find a dodgy neutral or earth - but so far this has always been on TNS supplies.

[AE-NMidlands]

An earth rod could, in theory, be an issue on TNCS / PME supplies if there's a bad connection on the combined neutral/earth conductor, as the neutral current would try to return to the substation via the earth rods and earth, potentially raising the earth /neutral voltage to a dangerous level, and creating dangerous voltage gradients on the ground around the rods.

Is this really plausible? How come no trips have reacted to it and prevented it continuing?

[Marcus]

An earth rod could, in theory, be an issue on TNCS / PME supplies if there's a bad connection on the combined neutral/earth conductor, as the neutral current would try to return to the substation via the earth rods and earth, potentially raising the earth /neutral voltage to a dangerous level, and creating dangerous voltage gradients on the ground around the rods.

Is this really plausible? How come no trips have reacted to it and prevented it continuing?

Yes. if the fault is in the dno's combined neutral/earth conductor, then there is no trip to react: any trips in the installation (house) would not 'see' the fault as it is effectively upstream of them; even an rcd with a 'functional earth' wire - which disconnect if the earth voltage >50v from neutral - wouldn't disconnect as the house earth is connected to neutral at the dno's header so is at the same high voltage relative to true earth; and as the transformer protection is a fuse - as long as the current is below the fuse rating, it doesn't care if the current return path is via the neutral/earth cable or the earth.

[Stinsy]

Luckily my spark is very on it.

I am waiting for the guidance note because at the moment it can read either way - are sparks now suddenly going to be putting earth rods in on almost any job(?!).

It is very unclear! As-written the regs say all installations must have their own earth rod.

Sparks hate installing earth rods! The risk of hitting something (power, water, gas, sewage, someone’s basement) is too high, often there isn’t a convenient flower bed so they end up breaking concrete or messing with block paving or whatever, and then there is no guarantee the rod will give an acceptable reading.

The “danger” with installing your own earth rod on a TN supply is that in the event of a PEN-fault your earth rod could become the return path for all electric used by you and everyone else downstream of the fault.

[AE-NMidlands]

Can a layman tell what sort of supply he has? In an ordinary Victorian semi in an ordinary street, with the original cabling... Looks like a new fuse holder though.
Here's mine, with the cable continuing through into next door.
A

[Stinsy]

Can a layman tell what sort of supply he has? In an ordinary Victorian semi in an ordinary street, with the original cabling... Looks like a new fuse holder though.
Here's mine, with the cable continuing through into next door.
A

That’ll be a looped TN-C-S.

[AE-NMidlands]

That’ll be a looped TN-C-S.

So if I have understood correctly, DON'T have a permanent supplementary earth, but make sure you do have one which is switched in (to the house circuits only) when running off batteries isolated from the mains?
A
p.s. except that our earth doesn't come off the neutral conductor in the fuse installation as shown in the training videos (e.g. but presumably is joined to the neutral via the cable shielding somewhere remote.

[cojmh]

The “danger” with installing your own earth rod on a TN supply is that in the event of a PEN-fault your earth rod could become the return path for all electric used by you and everyone else downstream of the fault.

So, can you get the DNO to change this and if so what do you need to get it changed to?

Whilst the risks are probably very low of this ever happening, I prefer the "it cannot possibly happen" way of thinking with electrical installations.

Thanks,

[marshman]

The “danger” with installing your own earth rod on a TN supply is that in the event of a PEN-fault your earth rod could become the return path for all electric used by you and everyone else downstream of the fault.

So, can you get the DNO to change this and if so what do you need to get it changed to?

Whilst the risks are probably very low of this ever happening, I prefer the "it cannot possibly happen" way of thinking with electrical installations.

Thanks,

There is no "one size fits all" answer to the earthing "problem/question". Which is why the regulations/recommendations/guidance keeps changing. S0 much depends on where you are (single isolated house in the middle of nowhere or a Victorian terrace in a town or a new build on a modern housing estate etc.) Earth faults can and do happen, can be and are dangerous and it is not as simple as just banging in your own earth rod - it might mitigate against some potential problems but others may still exist depending on your situation. AND just because you have an RCD or any other protection device does not mean it can work under all fault conditions.

There is a guy who posts "instructional" videos on Youtube, John Ward, they are a bit "dry" but the information and explanations are clear and easy to follow. Because it is a complicated subject there are several of them, but this one is a good place to start.

[Marcus]

Can a layman tell what sort of supply he has? In an ordinary Victorian semi in an ordinary street, with the original cabling... Looks like a new fuse holder though.
Here's mine, with the cable continuing through into next door.
A

That’ll be a looped TN-C-S.

I would have said that was TNS, but it's difficult to be certain without measurement.

At the moment, I'm operating on the principle of: if a local earth rod is required and the supply is TNC, then convert to TT - but yes, it's a pain here in Wales where you're lucky to find 6" of soil in places, and when you do get a rod in it sometimes reads 400 odd ohms so you need to fjnd a place some distance away for another rod; 240ohms, okay and another...

I'm still ploughing through amd 2 so i don't have an opinion on the new requirements yet...