TT or PME

[aliensbrains]

Just been to look at a job and found this. It's an overhead supply so could be pme at the post but no earth back to the cutout and (although admittedly i didn't have much time to have a proper look) I didn't spot a rod.

I'm thinking advise the customer to get the dno to come and have a look and fit an isolator while they're at it.

Any thoughts?

Thanks!

 

[aliensbrains]

Confirm the arrangment as there can be several variations even with PNB.
From that sure would be nice to know if the DNO have offered / provided an Earth terminal

And where it is!

 

[Teddy Lop]

Is "main supply earth" an assumption or confirmed? could it not be another bond?

Low reading could be a parallel path of connected metalwork, eg earthing of boiler/gas pipe (by both bonding and/or cpc's) going to a neighbour's TNC-S connection? Did you do a proper Ze ie disconnecting the "main supply earth" to test it?

If unsure about a TNC-S connection, a low resistance check N-E is a first thought...

 

[aliensbrains]

Yes, I disconnected the (assumed) main earth and measured 0.27ohms.

 

[aliensbrains]

Update from customer: National grid have been round, removed the PME sticker and informed the customer they'll need an an earth rod installing.

 

[HappyHippyDad]

Update from customer: National grid have been round, removed the PME sticker and informed the customer they'll need an an earth rod installing.

One small sticker causing so many problems!
I know we can't guess but, if I had to guess, I bet there's an earth rod somewhere, probably beneath a new porch or conservatory!
If you really want to @aliensbrains you could let us know what Ra you get on your new rod, as we like things like that

 

[aliensbrains]

One small sticker causing so many problems!
I know we can't guess but, if I had to guess, I bet there's an earth rod somewhere, probably beneath a new porch or conservatory!
If you really want to @aliensbrains you could let us know what Ra you get on your new rod, as we like things like that

Interestingly, national grid also recorded 0.27ohm L-N, the exact same reading I got when I measured Ze from the 10mm 'main earth' in the consumer unit.

So now I'm thinking, what is the best thing to do with that 'main earth' once I've installed a rod...