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Posted By Topic: Main Earthing arrangement

Sparky3636
Oct 20 2019 17:44

Hi all I'm starting my electrical apprenticeship soon and i have been studing up on earthing arrangements, and im curious to know on my own house -please see photo where does the solid green wire go to, goes down brick cavity but would it go to an earth rod near the meter box location, for the life of me i cant see any pits or earth rood arrangement. it's bugging me, or does it go back to the pole somewhere. trying to work out what sort of arrangement this is. appreciate the help
   

Sparky3636
Oct 20 2019 17:46

sorry photo not great but bascally there is solid green wire that conrcts to a lug which connects to the MEC wire. trying to source where the solid green wire would be coming from
   

DougP
Oct 20 2019 18:30

The main earth conductor goes from the main switchboard to the main earth. The meter box is not the main switchboard.
The main earth could be the concrete slab. But the connection should be accessible.
However that might not be the main earth conductor. Until you find the earth electrode, it's hard to tell.
   

DougP
Oct 20 2019 18:40

Or that might just be a normal protective earthing conductor for the meter box which will go to the main switchboard.
   

Sparky3636
Oct 20 2019 19:05

It is labeled earthing conductor on the earth cable. I did think maybe it’s going down to the slab but like you mentioned I thought it would have to be accessible.
   

DougP
Oct 20 2019 20:42

The meter box earth can be connected to the main earth conductor, if it's on the cable route to the stake.
You would have to look in the main switchboard to work it out possibly.
Of course you shouldn't be opening up the switchboard as you aren't licensed.



   

AlecK
Oct 21 2019 10:02

The fact it's labeled as MEC is evidence, but not absolute proof.

The rules around this have changed over time, as well as there being local variations in different areas.

All of which makes it difficult to tell from a single photo exactly how this installation has been installed.

I'm struggling to think of any reason for having such a label on a conductor attached to the meterbox. These days, "MECDF" labels are only required at electrode. Used to be required at swbd end of MEC as well.
The meter enclosure isn't either of thos, so it's a non-mandated label - even if this is an installation where the MEC "detours" into and away from the meterbox (as used to be a common practice).

I can see 2 green wires.
One light green, with label, that appears to be a core of a TPS cable that also has a red core connected to a fuse.
I'd assume the red is a controlled tariff (water heating?)mains going to the main switchboard, and that therefore the light green wire goes there also. It almost certainly acts as PEC for the meterbox.

The other is a dark green unsheathed. My best guess is that this goes to an electrode somewhere.
Thus between them the two wires may act as the MEC.
Such an arrangement certainly would not comply with today's rules.