Earthing Problems

[Onoff]

A bfo copper plate will go in in the next few days. The soil that comes out of the dug hole will be sieved and put back, probably with a scattering of bentonite cat litter as an experiment. Pics & test readings to follow as I do it.

I just like having a go even if I'm wrong!

 

[Onoff]

No offence to JW but I can't get on with watching him / his videos.

Photonic Induction is more my god.

 

[brightspark]

A bfo copper plate will go in in the next few days. The soil that comes out of the dug hole will be sieved and put back, probably with a scattering of bentonite cat litter as an experiment. Pics & test readings to follow as I do it.

I just like having a go even if I'm wrong!

no offence but your making a mountain out of a molehill . rods need to go in to solid ground

 

[mtt.tr]

To do a nice detail I think I'll go with this:

View attachment 389290

View attachment 389291

View attachment 389292

The bolted connection will corrode

 

[Onoff]

The bolted connection will corrode

It'll be copper plate, copper strap, copper nuts and bolts. Why?

 

[Onoff]

Interesting reading here suggesting my earth plate should go in vertical:

https://www.electrical-installation.org/enwiki/Installation_and_measurements_of_earth_electrodes

The original rod position was right in the corner where two concrete paths meet by the house. I do wonder if the soil there is too dry?

The rod is also about 5m from a damn great conifer of some type, trunk is over 2' diameter. I again wonder if that has a drying effect on the soil locally. I know if you remove a big tree, especially on clay, you get "heave" where the clay takes up the water that the tree would have.

(That's the SWA going to my garage above, a whole other story!)

 

[Onoff]

A bit of background:

A few years ago we were on holiday and the house sitter kept hearing "an air rifle" being fired near the house. Had a look but couldn't see anything. It transpired a tree branch was rubbing on our overhead mains cable and had worn through it! Blue is the phone wire, the black incoming mains comes from the pole far left in the neighbour's garden, across the boundary to the corner of our house:

https://flic.kr/p/2onpXMv

The house sitter called the DNO out who did a lovely bodge job under the eaves. They fitted a new bit of cable from the pole to the house where they did a taped up joint:

https://flic.kr/p/2onpX1q

They then stuck a sticker on the original, untouched, years old 100A head:

https://flic.kr/p/2onrbja

Thus I do have the option of going PME but want to play with the earth plate first. Plus I'd have to get them in unless Amelie paid a visit.....

 

[brightspark]

for a kick off i wouldn't bury an earth rod anywhere near that tree it will suck the water out goodstyle .sink a rod well away from it and take the reading

 

[Erie Fred]

I've read every post, and I'm cornfused (I cornfuse easily...)
So you run 230 vac one wire (hot) as opposed to the US, where we run "split phase".

But either way, you have a "Hot" and a return or "Neutral" correct ?

And ground, like we do, is just for safety ?
Or is current flowing thru the ground wire normally ?

 

[Guineafowl]

I've read every post, and I'm cornfused (I cornfuse easily...)

We find US domestic voltages confusing

Most commonly, distribution is 400V, 50 Hz three phase wye, with earthed/grounded star point. Each house gets one phase. The star point connection runs to each house as a combined earth and neutral. At the house, the earth and neutral are split. Everything is 230V, which is the voltage between a phase and star point (sqrt3x400).

OP doesn’t have the combined earth/neutral, just a neutral so has to supply his own earth stake.

Earth/ground is only for fault currents, yes.

 

[Erie Fred]

We find US domestic voltages confusing

Most commonly, distribution is 400V, 50 Hz three phase wye, with earthed/grounded star point. Each house gets one phase. The star point connection runs to each house as a combined earth and neutral. At the house, the earth and neutral are split. Everything is 230V, which is the voltage between a phase and star point (sqrt3x400).

OP doesn’t have the combined earth/neutral, just a neutral so has to supply his own earth stake.

Earth/ground is only for fault currents, yes.

O.k. that clears things up.
Thank you for taking the time to "splain it.

So if I read correctly, the OP has about 6 amps of current flowing in the ground wire ?
Would not this suggest a leaky appliance needing repair ?

 

[awemawson]

No that is the 'potential fault current' as his earth rod is too high a resistance. Needs to be higher to trip safety devices reliably as I understand it.

 

[Guineafowl]

O.k. that clears things up.
Thank you for taking the time to "splain it.

So if I read correctly, the OP has about 6 amps of current flowing in the ground wire ?
Would not this suggest a leaky appliance needing repair ?

No, he’s used a multifunction tester to effectively measure the impedance of the earth/ground path, and use the voltage to calculate what fault current would flow in the event of a phase to ground fault. Ie, the prospective earth fault current.

Since even a good earth stake won’t reliably pop an mcb, everything on his type of earthing needs to be protected by an RCD (GFCI).

An impedance of over 200 ohms is considered unreliable as a fault path, even though it would easily pass enough current to trip a 30 mA RCD. Hence the drama.

 

[Onoff]

@Erie Fred in the UK we have primarily 3 earthing systems domestically.

TT which is mine, an overhead supply, on poles, where the customer supplies his own earth. There's a vulnerability to any overhead earth being taken out by say falling trees.

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Where I am they have "upgraded" the TT system to include intermediate earth spikes on the poles and turn in into a TN-C-S system. New properties get connected TN-C-S. The problem is that low lifes periodically reach as high as they can get with a petrol saw and steal the earth spikes from the poles! It's one of the reasons I'm happy to have a working earth of my own.

TN-S is the other common system here.

 

[Erie Fred]

Where I am they have "upgraded" the TT system to include intermediate earth spikes on the poles and turn in into a TN-C-S system. New properties get connected TN-C-S. The problem is that low lifes periodically reach as high as they can get with a petrol saw and steal the earth spikes from the poles! It's one of the reasons I'm happy to have a working earth of my own.

That's the same problem we have over here...Methheads snip off the ground coming down the pole (they usually reach about 8'), no-one knows that their ground is gone.

In our system, another problem boils down to loss of neutral (corrosion at the pole connection usually), and it creates a floating situation.
Heavy 120 vac loads (fridge) get's pulled down to 70-90 volts and burn up, lights on "other side" get 150-170 volts and pop.

 

[Onoff]

That's the same problem we have over here...Methheads snip off the ground coming down the pole (they usually reach about 8'), no-one knows that their ground is gone.

Our poles have galvanised steel covers over them but.....

A lot of the poles aren't in the best condition here. Some even have danger notices on but just get left. With the UK supplies and distribution having been privatised many years ago it's often a profit first attitude so infrastructure upgrades don't get done as perhaps promptly as they should.

 

[Matrixx]

just to clarify the type of install.

 

[brightspark]

View attachment 389671just to clarify the type of install.

its a tt system fitted with 30 ma rcd and an earth rod or rods depending on ground -soil conditions

 

[Hotstuff]

The only time I have ever found it necessary to get creative with earth electrodes was when the client had an indoor swimming pool and to avoid issues with the supply neutral, we had to employ a TT earthing system to protect the whole house installation.
To ensure the earth touch voltage could not exceed 50 Volt we had to provide a earth electrode that didn’t exceed 20 Ohm.

To the OP, if you are committed to creating a TT installation with sufficiently low Ze to enable your MCBs to operate within 0.4 seconds in the event of your RCD failing to operate; are you aware of the maximum permissible impedance needed to ensure that your MCBs will operate?

The impedance of your electrodes will vary and may also depend upon the reliability of the earth conductor termination to the electrode or any other metal to metal joints.

If your 30 mA RCD is in good working order your main earth conductor only needs to flow 0.03 Amp to operate.

Good luck with your project.

 

[Onoff]

To the OP, if you are committed to creating a TT installation with sufficiently low Ze to enable your MCBs to operate within 0.4 seconds in the event of your RCD failing to operate; are you aware of the maximum permissible impedance needed to ensure that your MCBs will operate?

Just back from the pub so aware of very little!

I'm not sure if I have the tables showing the current curve characteristics of these Type 1 & 2 C50 breakers!

BS 3871?

Vaguely recall the yellow / white writing on them dictated something too? Interrupt rating?

Pit should be dug this weekend and maybe I'll get the plate buried. Not sure if I'll have the brass nuts and bolts to bolt the "strap" to it.