Is it a tt supply

[Ajf100q]

Might be a silly question, but can a tt supply come into a property via underground .
This property in question, has no overhead cables supplying it but looks like it might have an earth electrode somewhere.
Thanks.

 

[westward10]

Possibly have you done a test to it?

 

[Ajf100q]

Possibly have you done a test to it?

Not yet, just seen some pictures.
I've never come across a tt supply that wasent supplied via overhead cable, that's why I thought I would ask if it was a thing.

 

[pc1966]

Have you any photos?

While I have never worked on them, I have seen terraced houses in London that were TT supplies fed from what looked like normal underground cables.

 

[Ajf100q]

 

[Ajf100q]

The earth cable on the left of met, just dissappears into the ground with the service cable apparently.

 

[pc1966]

The earth cable on the right of met, just dissappears into the ground with the service cable apparently.

I can't be sure, but that looks smaller than 16mm, maybe as small as 6mm? That would be consistent with it being a TT rod and not a supply TN earth.

You might find Zs is very low like TN if bonded services are large and/or linked to TN supplies in other houses, but if you can identify the conductor that is the means of earthing then a Ze test would confirm it is likely TT if somewhere in the, say 5 ohm to 200 ohm region.

Can you see if it has an incomer delay RCD, or if all boards are all RCD/RCBO?

 

[Ajf100q]

I belive that it is a dual rcd plastic cu.
I think the Lh earth looks to be 16 or maybe 10 mm, if compared to the size of the incomer.

 

[westward10]

There is nothing from the service head?

 

[westward10]

I can't be sure, but that looks smaller than 16mm, maybe as small as 6mm? That would be consistent with it being a TT rod and not a supply TN earth.

You might find Zs is very low like TN if bonded services are large and/or linked to TN supplies in other houses, but if you can identify the conductor that is the means of earthing then a Ze test would confirm it is likely TT if somewhere in the, say 5 ohm to 200 ohm region.

Can you see if it has an incomer delay RCD, or if all boards are all RCD/RCBO?

I can't seem to view the pic but if it is 6.0 this doesn't mean too much.

 

[Ajf100q]

There is nothing from the service head?

Not that I can see.
And the homeowner says there's nothing visible outside in terms of an earth electrode.

 

[pc1966]

I can't seem to view the pic but if it is 6.0 this doesn't mean too much.

Indeed, not a reliable indicator!

But given the new-ish overall look it would make it unlikely as a DNO-offered earth connection.

 

[nicebutdim]

Can't help wondering what the separate RCCB is supplying.

Has all the hallmarks of an electric shower with no overcurrent protection, although the round cable suggests I could be wrong.

 

[James]

If I was to guess I might say car charger.

 

[Ajf100q]

So , isn't possible to have tt supply come into property from underground?