What type of earthing system is this?

[davphi338]

Hi,

Can someone tell me what earthing system this is?
My daughter is in the process of purchasing this property. She is going to have to get a full rewire done but will she need to get the UK power networks in to look at the earthing or is it something the electrician will sort out.

 

[RF Lighting]

Looks like a TT supply. Any good electrician will be able to sort this. It certainly needs attention sooner rather than later as the VOELCB (the black box with the yellow button) will likely not work and you effectively have no protection against an earth fault at all.

 

[JohnD]

oh dear

it looks like a voltage-operated earth leakage device.

The answer to your question is "unsatisfactory"

Does the supply come via overhead cables, for example in a rural location?

There is a good chance that the electricity company will be able to provide a company earth, especially if the supply is underground.

If not it will need an earth spike driven into the ground

And a modern RCD or RCBOs. But that would be included anyway while installing a new consumer unit, to reach modern requirements.

 

[davphi338]

Looks like a TT supply. Any good electrician will be able to sort this. It certainly needs attention sooner rather than later as the VOELCB (the black box with the yellow button) will likely not work and you effectively have no protection against an earth fault at all.

So effectively an earth rod? Will there be much additional work for the electrician along with replacing the consumer unit and internal rewire. I haven't looked at the gas meter and water pipes so presume he may have to update the main earth bonding as well.

 

[davphi338]

oh dear

it looks like a voltage-operated earth leakage device.

The answer to your question is "unsatisfactory"

Does the supply come via overhead cables, for example in a rural location?

There is a good chance that the electricity company will be able to provide a company earth, especially if the supply is underground.

If not it will need an earth spike driven into the ground

And a modern RCD or RCBOs. But that would be included anyway while installing a new consumer unit, to reach modern requirements.

Hi, Yes. The supply is via over head line directly into the property via the x2 brown cables on left of first picture. Do you think its worth contacting the electricity company to do a site visit as soon as she has compleetd on the property to check if they can supply an earth or is it unlikely if overhead cable feed.

 

[JohnD]

it's possible with overhead cables. I recommend writing to them, rather than phoning. A phone call can be fobbed off, but a letter will be logged and passed along until it reaches someone who knows what to do. Their initial response will be based on their records. If they say yes, take it if it is free or costs less than £100. If they say no, try to get them to do a site visit in case the records are wrong. They can be up to a hundred years old.

You need to write to the DNO who owns the cables. The supplier who sends the bill doesn't. They are supposed to pass your request along...

https://www.ofgem.gov.uk/key-term-explained/map-who-operates-electricity-distribution-network

If you have sight of an electricity bill, it will show the Meterpoint reference number, unique to that property, but they can probably work it out from the address. Obsessives like me put it on a durable label next to the meter. Your gas supply also has a Meterpoint. In a previous life I was a Meterpoint Test Manager.

It looks like:

Your electricity supply
number is:
S 01 234 567

01 2345 6789 123​

 

[FrodoOne]

While being accustomed to the "normal" TN-C-S system used in Australia and having some understanding of other systems, I would appreciate some discussion of the above topic.
For example, how can "RF Lighting" tell (from the photos concerned) that it "Looks like a TT supply."

Please explain.

 

[RF Lighting]

Generally in the uk if the supply is a TN type, the suppliers earth will originate from within the cutout or from the cable directly adjacent to it.

In the op’s supply you can see it is supplied by two single conductors only. This rules out a TN-S supply as there would be an additional earth wire run in with the line and neutral. It is possible that the earth takes a different route but that would be unusual.
As you can see the neutral block is a straight through joint with no extra wires coming from it so it can not be TN-C-S

This leaves TT, which this supply has all the hallmarks of. It is supplied by single core cables, the cutout is made up of a separate fuse and neutral block, and there is a VOELCB in the consumers tails.

 

[Taylortwocities]

It is a TT system. It is the responsibility of you to provide the earth. The DNO will not be interested in that aspect. They also have NO interest in the condition of anything after the supply head and its fuse.

However

As you are looking at a new consumer unit and a rewire, you need to find a registered electrician. He/she can investigate if the DNO can provide the better supply type called TNC-S.

That will remove the need for an earth electrode and an up front Earth Fault device.

 

[AndyPRK]

no one has been near that for a long time!

 

[Taylortwocities]

how can "RF Lighting" tell (from the photos concerned) that it "Looks like a TT supply."

Experience, cobber.

 

[AndyPRK]

It wouldn't have a VOELCB fitted, unless it was TT

 

[crystal ball]

I came across a cottage with a VOELCB which had been converted to PME, so it is not a given

 

[RF Lighting]

Yes is not unknown to come across former TT supplies which have been changed to TN but the VOELCB left in situ as an isolator

 

[aptsys]

It is a TT system. It is the responsibility of you to provide the earth. The DNO will not be interested in that aspect. They also have NO interest in the condition of anything after the supply head and its fuse.

However

As you are looking at a new consumer unit and a rewire, you need to find a registered electrician. He/she can investigate if the DNO can provide the better supply type called TNC-S.

That will remove the need for an earth electrode and an up front Earth Fault device.

Why is TN-C-S a "better" supply type? I can think of many reasons why it isn't, and given every circuit is likely to be protected by some form of RCD there isn't really any additional burden to keeping the system with a TT earth.

I came across a cottage with a VOELCB which had been converted to PME, so it is not a given

PME is surely relating to the network and not the earthing system presented at the service head.