A farm yard with multiple buildings, multiple DB boxes distributed all over the show, I’m still trying to make sense of it all, 3 phase feed.
There is quite a lot of electrical work, previous owners paying a portion and we are paying a portion. The sparkie said in his testing he noticed very little is correctly earthed, earthing is almost non existent in places. He mentioned to me he doesn’t like earth spikes all over the show I didn’t quite get his exact reasoning, he said he prefers running nice and thick earth cable back to the Eskom pole and use Eskom’s earth to earth everything.
Somehow this doesn’t make sense to me, won’t it make more sense to put a earth spike or 2 as needed at each DB and then bond them all together and also to the earth at the Eskom pole?
I’m thinking with his way if you lose one connection or that cable breaks in a single place then you lose the earth on all buildings. Where if you have a spike at each DB, then you only lose the earth on that DB if a cable breaks, while the rest of the buildings will still be fine until you can get the fault repared.
What does the experts say?
I just like to arm myself with enough info so I can ask the right questions and that it’s not so easy for someone to BS me with fancy talk.
With multiple discrete earth spikes on a single property what goes into the ground on one spike can come out of the ground on another. Then through your expensive equipment (destroying it) and back down another spike.
Then there is also a step potential safety hazard.
Your electrician is right, if the buildings’ earths are connected by a conductor to a single decent earthing point it is safer for humans and better for your equipment.
One thing to remember, the supplied earth may not always be there. If that cable or earth is broken, you will be floating. Don’t ask, but I had that, bad all round…
Best way is likely a single earthing point, and all earths tie down there, but that depends.
Adding to what @Phil.g00 said about multiple spikes. The earth itself is a resistor that becomes a “divider chain” when a large current flows through it, and if you have multiple spikes attached, a potential difference will actually arise between the two spikes.
Therefore you want one and only one place with a good earth. That is generally at the “Eskom pole”. At this point you generally have your medium voltage delta configuration converted to a 3-phase low-voltage star configuration. The medium voltage side (up on the pole) is not earthed, but on the low-voltage side the center tap of the transformer (neutral) is earthed as close as possible to the pole. And then from that point onward you treat it the same as a TN-S connection in the city. The earth always comes on a cable. After the bonding point, you are not allowed to treat N as if it can also be a T…
