Dangers of a broken PEN Conductor

Spoiler alert: It’s not your problem to fix it, but you might be the one in danger.

For more information, do a general search for “PEN fault”.

An authoritative reference is Broken PEN

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Hmmm. So my EVSE is 8 years old and doesn’t have PEN fault detection.
And those fires weren’t from EVSE’s.
So how do I detect if I have a PEN fault at home?

Try reading the second reference.

From the IET article linked to in Robert’s post:

BS 7671:2018+A1:2020 generally requires a resistance value of less than 200 ohms,

Does this standard require that the installation be checked over a period of time to ensure the resistance does not increase above this threshold? I’m thinking about a scenario where the ground is very wet when the earthing electrode is installed.

My old (15th Ed, 1981) copy says the type and depth of earth electrodes shall be such that soil drying and freezing will not increase the resistance…

The earth rod should be installed wherever possible where it’s likely to remain damp, or if it can dry out, the resistance must remain below the required value. It should be checked at the interval recommended on the report form, along with the rest of the installation. It would be prudent to check again after an unusually dry spell.


@Robert.Wall ah, the joy of reading a massive web page on a phone, while being jostled.
If only I’d scrolled down far enough, before giving up. Or just read it on the laptop.

Clamp meter at the ready for 9:30pm when Go Faster kicks in and plenty of current hopefully won’t be on the Earth cable… :grinning: wish me luck!

Just keep your fingers out - else shockedshocked

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OK, so I’ve got some odd readings from the clamp meter, but are they “bad”?

Due evolution of my electrical install, I have an earth block, that everything connects to, like the house, the EVSE, the battery, the solar panels etc. Last night during Go Faster the house was pulling about 42amps/10kW, as the car, battery and hot water where all charging.
The house’s earth connection has approx. 150mA on it, the EVSE was a bit higher at 300mA-ish, the battery was around 150mA-ish. However, and it was difficult to get a solid result as it’s a bit packed around there, the main earth cable disappearing back into the 100A fuse unit, had up to 1.1A on it, which seems,err, a little high.
There are a number of CT’s and other cables very near to it that could be interfering, but should I panic?

You thoughts please Robert? :confused:

Is the 42 A you mention the grid import current? It does seem higher than I might expect.

Another measurement you could make is put down an earth rod well away from any buried steelwork, cables, water and gas pipes or other potentially current-carrying metalwork, and measure the voltage between that and your earth bar. It’s that voltage that drives shock current.

If you think there is a problem, then you need to involve your DNO, it’s their responsibility.

Interesting topic. Reminds me of railways stations. If you have an electric train and there is a fault in the train or track you can get 1000s of amps flowing (as their circuit breakers are set at at least 100s) and raising the potential of the “earthed” track due to its resistance back to the substation. That means anyone standing on a station and touching the train could get a shock, as their feet are possibly earthed to station potential (nearly at real earth) and their hands to train earth, with up to 100s of volts difference between them. Thus station platforms should be carefully constructed and the reinforcing rods in them carefully connected so the platform surface is neither at train nor station earth.

If some passengers all joined hands on the platform and touched continuously from the platform wall to the train it’s a shock risk if the train faults. The operators just hope no-one ever does this! But it was something I had to consider as a risk when analysing super crowded Far Eastern platforms. Note to Extinction Rebellion: don’t glue yourselves in a chain between the wall and a train!

Can also get some nasty corrosion going on in the station’s reinforcing rods due to these unequal voltages.