Earthing improvement products and ideas

[AndyD]

If you suspect your earth impedance tester is giving suspect readings you can use a standard loop impedance tester to check it if you have one.

2 ohms sounds good as the target impedance, fingers crossed if you managed to get a much longer spike in the ground. I'd never normally give a rigid quote for installing earthing, it's way too unpredictable. Usually I offer a provisional costing based on experience of the area and an hourly labour rate but warn the customer it may be more or they could be lucky and it may be less.

[hartdev@hotmail.com]

I will research that and give it a bash, I have a Top Tronic T1825 loop/psc/load tester.

Hopefully I can use it.

Totally agree about the unpredictability of quoting for earthing, forgot to reply that the area is Scarborough, I have done a few new installations in the area (about 6) although most of my experience is in industrial control panel building for Oxygen generator cylinder filling plants and other types of gas mixing etc for companies like Afrox, so earthing is definitely not my best skill yet as I never really had to do it much.

Scarborough is never a great place to get good earth readings but I have found that usually if i do a thorough earth mat and knock in at least 2x 3/8th 1.8m spikes x 2, earth reading is good.
I'm not much of a business man and hate negotiating costs at a later stage, but I suppose I need to get over it haha

This property though, is almost solid rock everywhere, they are actually building onto the bed rock with bricks in some places and raising the whole foundation to be level with the rock. Don't know how legit that is but the engineer has been there quite often so I'm sure he deems it safe.
Anyhow thanks for the advice, much appreciated

[AndyD]

I'm interested to know how you got on. Did the drilling give you a low impedance reading?

[hartdev@hotmail.com]

Hi Andy
My apologies for the late reply.
Firstly I saw a small tree with lots of greenery at the base and started knocking in a spike there. Managed to get a 1.8m spike down and then another 1.5 piece (cut 300 off).
That got me down to about 15 ohms.
So I was still a bit unsure as the core drilling was a lot more than I originally was quoted so didn't go ahead with that.
However I got lucky when the plumbers had to put there septic tank in. They had to excavate lage pieces of rock and left a large Trench where I could play around the edges. Found a couple of spots and put down another 2(1.8m spikesx2). Brought all spikes to one central point.
Earthing now awesome bit of rain we had may have helped too. Don't know know.
Thanks for all the advice

[AndyD]

Thanks for the follow up info, great to hear it was a sucess story.

Earthing now awesome bit of rain we had may have helped too. Don't know know.
Thanks for all the advice

Some moisture would certainly have helped and also over time the ground around an earth spike settles and almost always the impedance reading (Ra value) improves considerably.

[mygoggie]

I have found that you can mix activated carbon and bentonite and this creates a viscous conductor with a large surface contact area in which you can place your grounding conducter (mat / rod). Once wetted, it will stay damp for very long periods. Just be aware that activate carbon can oxidise the copper so try and place some sacrificial copper plumbing pipe around your conductor, not touching it. Bentonite and activated carbon you can buy at at a chemical supplier using our national flower in it's logo.

@AndyD, with due respect I would suggest you refrain from the practice of:

On the tricky installations I usually connect to any structural steel in the building or even reference meshes in the slabs with a welded stud, just make sure you clearly mark any connections as being electrical earth. You'd be surprised how effective slabs and structural Ufer earths can be.

The reason is that you are effectively creating a 0.3V battery cell with the steel being the anode and any copper wiring electrically connected to it (and to intentional or unintentional ground somewhere) the cathode. The steel will therefore be eroded over time and the structural concrete member will be compromised. You most likely will be hold liable for any subsequent damage due this practice. Just some good and sound professional advice from my side. We all learn something new everyday!

A second (and quite interesting) reason is that you are effectively building a telluric current collector ....

[AndyD]

I have found that you can mix activated carbon and bentonite and this creates a viscous conductor with a large surface contact area in which you can place your grounding conducter (mat / rod). Once wetted, it will stay damp for very long periods. Just be aware that activate carbon can oxidise the copper so try and place some sacrificial copper plumbing pipe around your conductor, not touching it. Bentonite and activated carbon you can buy at at a chemical supplier using our national flower in it's logo.

@AndyD, with due respect I would suggest you refrain from the practice of:

The reason is that you are effectively creating a 0.3V battery cell with the steel being the anode and any copper wiring electrically connected to it (and to intentional or unintentional ground somewhere) the cathode. The steel will therefore be eroded over time and the structural concrete member will be compromised. You most likely will be hold liable for any subsequent damage due this practice. Just some good and sound professional advice from my side. We all learn something new everyday!

A second (and quite interesting) reason is that you are effectively building a telluric current collector ....

I've never seen any electrical regulations in any of the countries I've worked that state telluric currents should be a consideration in the design of any electrical earthing arrangements. If you can provide any reference to them in any regulations relevant to electrical installations then feel free to discuss them.

I'm not sure I understand your reasoning behind advocating the structural building steel is not connected to the MET.

The structural steel of any building would be a part of the equipotential earth zone of its electrical installation wherever it's exposed so a conductor between the steelwork and the MET would effectively be both an earthing conductor and bonding conductor.

Galvanic corrosion is caused by DC voltages and currents. Earth currents flowing through the earthing and bonding from the electrical installation, whether they be fault currents or functional earth currents, would be AC.

A joint between dissimilar metals can act like a small battery and be the cause of corrosion locally around the contact area of that joint but that wouldn't be a reason not to use a copper conductor with an approved crimp-on lug when making a connection to a steel item. As for the building steelwork integrity, I'd suggest it would be less susceptable to corrosion if it's electrically tied to earth than if it was allowed to float as extraneous conductive which would allow it to assume a voltage other than zero wrt earth. Using concrete encased building steelwork as earthing is an accepted and well documented practice, check out Ufer earthing for more info.

Why do you say earthing of structural steel could cause problematic galvanic corrosion to the fabric of a building?
Would you advocate that connecting structural building steel to the MET is bad practice? (I'd be very interested if you can cite regs to back this up)