I don't usually do domestics but when I have (just to keep good customers happy), I'd say about a third of the time there is nan insufficient earth from the supplier side, despite being set up as a TN-S earthing system.
On a domestic property in a nice area of Jo'burg we have just rewired I started to test for the COC. Test between each phase and earth, yes there is 230 volts (+/-). When I do the loop test at the mains position the Ze is 4.4ohm and fault current of 56 amps.
Its a 3 phase TN-S earthing system. I do the same test between phase and Neutral (to get PSCC) and that comes back ok (0.38 ohms and fault current of 590 amps on a 80 amp Main MCB, its at the end of the road so I figure its quite away from the sub-station of the local feeder pillar).
Now I know the fault current has to be at least twice that of the main breaker.
Every time I get this, I get the customer to call the municipality to log a problem and they send a member of the city power bakkie brigade out with a battered multi meter who check between live and earth and they confirm there is voltage. I get the my loop tester out and explain that the problem is not the voltage but the lack of earth. I perform the test in front of them and then show the results and they look at me like I am speaking mandarin.
I have seen city power convert from what is supposed to be a TN-S to a TNC-S earthing arrangement. Is this the norm for SA sparks?
Sometimes they have added an earth spike as well. It depends on who rocks up.
Do you guys just link out Neutral and earth at the mains position? I kind of figured - its before the main switch - not my domain.
The UK system is clearly marked if it has PEN conductor for a TNC-S earthing system. How can you just assume its a PEN conductor?
How do you guys deal with this. Last time I had this I went back to site 5 times to meet with city power before I got someone who had a clue what I was talking about and they dug up a bit of the road and sorted it.
On this particular job I can see the incoming Earth, it is definitely set up as a TN-S earthing system. Yes, I could put and earth spike in and an earth leakage and have a TT system but they are a pain in the backside as far as I'm concerned because of the nuisance tripping. Not a good solution as far as I'm concerned
How do you guys resolve this?
Oh, by the way the neighbouring house to the left - perfect earth reading. The house to the right, same problem as me. No earth.
Surely the municipality must make this right. The mains incoming position is on the boundary wall so it is there problem - Right?
What do you guys usually do? Everytime this happens I just end up going back and forth? Or is that just part of the process?