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?

 

[westward10]

Impossible to say some dwellings have an electrode under the floorboards.

 

[brianmoooore]

Impossible to say some dwellings have an electrode under the floorboards.

Plenty will have it under six inches of concrete in the 'extension'.

 

[davesparks]

Yes it is possible to have an underground TT supply. Any supply can be made TT if required.

However it more than likely has an earth connection available that nobody has yet taken advantage of.

Contact the DNO to check the availability of an earth.

 

[Ajf100q]

Yes it is possible to have an underground TT supply. Any supply can be made TT if required.

However it more than likely has an earth connection available that nobody has yet taken advantage of.

Contact the DNO to check the availability of an earth.

Thanks, yes they are getting a survey from Dno to see what can be done.

 

[AngelLaHash]

I would be a bit shocked if it is a TT system in.
looking at the area it looks like NEW BUILDS there (within a few years)


"The new wording within Regulation 411.4.2 is the final paragraph, where it introduces a recommendation that an additional connection to Earth by means of an earth electrode to the main earthing terminal. ." Taking for Napit site
i did notice the Sticker 25/08/23 and i wonder how old the house is

(hope this is within this site rules)