Broken earth wire into ground: looking for ideas how to approach

Calahonda52

just happened to spot this this morning in a house when cleaning out a corner for some other work.

The cable from pole is sleeved above the concrete in the GB as in the picture

The house was built in 1968 so just wonder how far down the head of the earth rod might be.
Thanks as always.

2011

What is the earth cable for?
Is it on the customer side?
Do you suspect that it is going to an earth electrode that is burried under concrete?

You could consider kangoing out the concrete and using a submarine (scotch) connector.

Calahonda52

2011 wrote: »

What is the earth cable for?
Is it on the customer side?
Do you suspect that it is going to an earth electrode that is burried under concrete?

You could consider kangoing out the concrete and using a submarine (scotch) connector.

The other end goes into the consumer unit in the house.

Yes I believe it is going to an earth rod

meercat

Without seeing the installation , I wonder is it simpler and possibly better to sink a new earth rod and new wire to consumer unit. You would possibly do this in the same time. you should get a rec to do it.

Calahonda52

meercat wrote: »

Without seeing the installation , I wonder is it simpler and possibly better to sink a new earth rod and new wire to consumer unit. You would possibly do this in the same time. you should get a rec to do it.

Maybe, except the route of the gas main and water main to house is unclear so I think the first shot will be to dig a little to see how far down it is.
Thanks

meercat

Calahonda52 wrote: »

Maybe, except the route of the gas main and water main to house is unclear so I think the first shot will be to dig a little to see how far down it is.
Thanks

It looks like the cement has eaten into cable

Wouldn't be too confident about earthing in such an old house tbh. Can't imagine earth rod is up to regulations. You also would need to join earth cable.

Best practice would be replacement cable and rod

Still think new one would be quicker and cheaper

Bruthal

Yes a new rod, earth wire and inspection box would likely be easier and tidier than fixing that existing setup.

2011

Bruthal wrote: »

Yes a new rod, earth wire and inspection box would likely be easier and tidier than fixing that existing setup.

Agree 100%

An earth electrode burried under concrete is pretty useless anyway.

Kevin McCloud

2011 wrote: »

An earth electrode burried under concrete is pretty useless anyway.

Nearly every housing estate in the country would have their earth bar driven under the foot path which is concrete. Are you suggesting all these are useless?

Bruthal

Kevin McCloud wrote: »

Nearly every housing estate in the country would have their earth bar driven under the foot path which is concrete. Are you suggesting all these are useless?

Well they are if the earth cable is broken off them, and the end of the earth rod is also buried.

2011

Kevin McCloud wrote: »

Nearly every housing estate in the country would have their earth bar driven under the foot path which is concrete. Are you suggesting all these are useless?

I am suggesting that electricity follows the path of least resistance. When multiple parallel paths present themselves the current divides proportionally as per Ohm's Law.

Typically the resistance values between an earth electrode to the general mass of earth would be in the region of 100 to 200Ω when the soil is damp / wet. Soil under concrete is far less moist and therefore the resistance to the general mass of earth is far higher. So yes a single earth electrode completely buried under concrete is pretty useless. Under fault conditions the vast majority a fault current to earth will return to the star point of the transformer star point via the neutralising point and from there down the neutral, not via an earth electrode that is buried under concrete.

Bruthal

On a neutralized system, the single earth rod at a House is more a passive item during normal workings. And even during the one fault that it does come into play, a failed neutral, the earth rod is now isolated from the rest of the earth rods on the system from the transformer, and so does little to help the problem.

During normal functioning of the system, the house earth rod does form a part of the multiple earth points on the neutral.

Any fault current that would go the earth rod path in normal operation, would also take that path just from normal neutral current. It would be minimal.

Kevin McCloud

2011 wrote: »

Soil under concrete is far less moist and therefore the resistance to the general mass of earth is far higher. So yes a single earth electrode completely buried under concrete is pretty useless. Under fault conditions the vast majority a fault current to earth will return to the star point of the transformer star point via the neutralising point and from there down the neutral, not via an earth electrode that is buried under concrete.

Soil under concrete being far less moist is debatable, why bother with dpm in the foundation when building a house if this is the case?

2011

Kevin McCloud wrote: »

Soil under concrete being far less moist is debatable

No it is not.
It is a known fact that it is harder for rain to penetrate a concrete path than soil.

why bother with dpm in the foundation when building a house if this is the case?

Because concrete is porous enough to allow some moisture through.

Kevin McCloud

The thinking of a footpath as a roof over the soil is incorrect, be interesting to do an experiment and drill a core sample in the path and one just outside the path and measure the soil dampness on the two.
Im fairly confident there will be no difference worth talking about.

2011

Kevin McCloud wrote: »

The thinking of a footpath as a roof over the soil is incorrect

Nobody suggested this.
In fact in my last post concrete was described as "porous".
Concrete will block a substantial amount of rain but it is far from waterproof.
A footpath will cause a reduction in moisture content of the soil underneath resulting in increased soil resistivity.

be interesting to do an experiment and drill a core sample in the path and one just outside the path and measure the soil dampness on the two.
Im fairly confident there will be no difference worth talking about.

I have witnessed this type of test has being carried out many times on large installations. I can say with confidence that you are incorrect.

Bruthal

Kevin McCloud wrote: »

Soil under concrete being far less moist is debatable, why bother with dpm in the foundation when building a house if this is the case?

The dpm example is not ideal really.

If the moisture level under concrete was 25 percent what it is in the open, do you now think that means no dpm is needed?

Bruthal

A single earth rod on it's own is not much use regardless of what the soil is like. If one rod has impedance of 50 ohms surface area connection to earth, and another 100 ohms, there will be no noticable difference in a neutralized system.

Neutral failure outside the house and it can make a difference to the voltage on the earthing in the house for any given load that happens to be on in the house. But not a lot in the overall scheme of things. Good bonding is more important.

Calahonda52

Thanks guys.
Will get a new rod and an inspection box as suggested

Calahonda52

Neighbour has offered this as an earth rod, its 4 feet long.
If so how does earth wire get attached?
I will fit the rod in ground and get a sparks to do the rest.
Thanks

Risteard81

Calahonda52 wrote: »

Neighbour has offered this as an earth rod, its 4 feet long.
If so how does earth wire get attached?
I will fit the rod in ground and get a sparks to do the rest.
Thanks

Just leave it to the Electrician.

2011

Calahonda52 wrote: »

Neighbour has offered this as an earth rod, its 4 feet long.
If so how does earth wire get attached?
I will fit the rod in ground and get a sparks to do the rest.
Thanks

The 10mm sq. earth cable goes between the U bolt and the rod.
It is best to double the connected part of the cable over when terminating. Tighten it up well and finish by covering the joint with Denso tape.

This should junction be installed in an inspection box and finished flush with the ground.

Calahonda52

Risteard81 wrote: »

Just leave it to the Electrician.

If I do and he/she drives it through the gas pipe or the water main or the sewer pipe who carries the can?

2011

Calahonda52 wrote: »

If I do and he/she drives it through the gas pipe or the water main or the sewer pipe who carries the can?

The electrician.
That is what thier insurance is for.