Should You Install an Earth Rod?

Joe Robinson digs into the new recommendation for installing earth rods on TN-C-S earthing systems. What sparked this change in BS7671 and how will it affect electricians?

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00:00 What is Joe doing with an earth rod?
00:48 Earth electrode now recommended in BS7671
01:38 What can be used as an earth electrode?
01:50 Why the change?
02:58 TN-C-S earthing system voltages
03:33 Electrode size and resistance
03:56 Fault protection and ADS
04:25 Is foundation earthing the future?
05:20 Checkout guidance note 8
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[andyhodchild]

A very brave man 'putting' an earth rod so close to other services!

[idrismartin]

The worst shock I ever had in my 55 years in the trade was on an army camp housing contract I was tasked with a 2 hour response loss of supply to a married quarter I checked the supply no voltage from live to earth and neutral I opened the grp meter box on the outside wall to inspect the meter and cut out there didn't seem to be any obvious problem there I grabbed hold of the gas pipe exiting the gas meter enclosure to pull myself up from squatting and got the shock of life I was standing on wet grass and gripping hold of the pipe. I managed to let go of the gas pipe breaking the circuit with me as the main conductor. On closer examination the pen conductor had become disconnected inside the joint in the road with the live conductor still attached every earthed appliance and bonded metal was live so if it was my property with a tncs pme supply yes I would install an earth electrode just in case.

[nua]

I always wondered why UK didn’t require earth rods. As in Ireland which also uses TN-C-S, has had earth rods on all domestic installations for decades.

[andrewrussack]

Australia predominantly uses a TN-C-S system. All LV installations have their own earth rod. A neutral-earth connection is made at every installation, referred to as the MEN (multiple earthed neutral) connection. In some states, notably South Australia due to the use of steel and concrete composite Stobie poles, a CMEN (common MEN) system is used, where the earth conductor is effectively continuous from generator step up transformer to LV installation, that is a common grounded neutral is used for all voltages. The steel joists of all Stobie poles are connected to the neutral carried by the pole, if LV is installed on that pole. In most residential areas, all poles carry a neutral/earth, bonded to the pole joists, even if no LV is present.

[charpantidiskonstantinos]

Here in Greece, the construction of foundation earthing is mandatory since 2010 in all new building constructions. It is controlled by urban planning and if it is not there, the building is not connected to the electricity grid.

[sergiofernandez]

I think the DNO/DSO should provide the Earth and it should be free from defect. However in all things that cost money, they are making the the Sparky and customer foot the bill. To be honest I would say that BS7671 reg 411.4.2 could be split into new build and retro fit existing instalations. It is far easier to fit/install Earth rod/spike/plate/grid during construction than it is to retro fit a rod/spike/plate/grid at a mid terrace house in your average town.

To add the cat amongst the pigeons what if your house is on a looped supply?

[ashleyrowe]

On some recentish DNO works i found/saw that they installed a rod (although it was horizontal) when they back filled the hole.
I honestly think that the supply companies should provide the earth rather then pass the buck to us installers. They know the true nature of the cables/networks they adapt to add or alter services so they should provide a reliable connection
On many supplier faults i have come across over the years on their networks, when i ring to report a higher then required reading, the first thing they try to do is ask whether the system was ever an over head supply etc etc to try a get away from sorting out the failed joint etc etc
If they dont want to provide a safe electrical supply service then why should all the existing maintenance charges they add to everyone bills be chargeable per month

[DANWALKER]

Very good to see the first part of the video making you aware of the dangers in driving metal rod into the ground with no Rubber Gauntlets on and not to do so near to services….

[MrBubbles.-]

What's your thoughts on regulation 542.1.1 that says earthing arrangements may be used jointly or seperately, but regulation 542.1.201 that says the MET shall be connected to earth by one of the methods. (Ive not typed the complete quote out). It's a bit contradictory that In 542.1.1 we can mix earthing systems but 542.1.201 clearly states ONE.. What's your thoughts on this?

[banananaa]

In Finland we use a minimum of 25 meters of 16mm2 cu to be buried into the ground around the house plus the possible casting irons be grounded as well. It's not unusual to have an L-PE short circuit current over 1kA. The usual connection is tn-c-s and even tn-s requires the separate grounding

[DoctorElectricYouTube]

I've just built my summerhouse which is separate from my property by around 15 metres, now what do I do?
1 - Export the main earth from the property only.
2 - Export the main earth from the property and install an electrode to the MET of the summerhouse consumer unit.
3 - Export the main earth for the external cable protection and then not connect this main earth to the MET for the summerhouse consumer unit but install an earth electrode as a means of a main earthing conductor for the summerhouse consumer unit. - This is how you used to do it.
I have my annual NAPIT inspection this week so I'll be interested in what they say!

[robertburrows]

How many sparks test the voltage between TN earth and true earth ? . Not many . I've installed and earth rid when I get a high Ze impedance, simply because the DNO won't come out if it slightly over

[allsearpw]

Hi, yes back in 1983, when building my own bungalow and installed a 32mill amp trip on a pme system on the main switch the Electrical meter fixer suggested this and sent me a letter of advise from the then SEB, Whilst having this discussion on site, I said it was about time ever circuit breaker had a 32 mill amp trip built in, HOW thoughts catch up on one, years later, even after many years of IEE regs courses and asking lectures about this, no one had ever heard of this, when others had for though .?🤔👍

[notpoliticallycorrect]

The actual soil at the installation will have an effect on the efficacy of any grounding system, soil types and water content etc.will alter the resistivity and effectiveness of a rod, Chalk for instance is a very good insulator. Our local church is situated on a cut out of rock, plateau on the hill. The lightning conductor is cleated across and down the face of the rock, a journey of about 150 ft to a steel post in the soil below, but some of the land round here is below the water table and soggy wet all year round.When I walk my dogs in the stream you can see across to the back of the farm buildings on the other side, and for years the old barn and all the outbuildings, milking shed etc.that were there were being protected by the earths simply being bolted to one of a huge, probably 200+ ton pile of rusting RSJs just laying in a sodden ditch behind the sheds, it looked like a proper protected joint too not just an exposed nut and bolt! I never heard of any incidents, no one being fried etc.when I mentioned it to the guy who tested my house he joked that some areas around the village were so wet you could just chuck the rod on your lawn😊

[Hunty]

I believed the earth electrode was to help make sure the Neutral wasn't "floating" and was 0 volts and created a separate ground path to ensure water pipes, gas pipes and appliances that used earthing. But having earth electrodes too close together with another house has been known to cause electric shock issues if there is a Neutral disconnection fault in one house, the return current will run to the 2nd house to use that Neutral path, energising any earthed items.

[andrewpeabody]

So why does the regulation 411.4.2 say it doesn't apply to outbuildings? I nearly added one in my garage when I laid the SWA to it in case it got damaged. Then I saw a John Ward video saying it was a waste of time as the impedance was too high to trip the rcbos.

[kaylengowen]

Question; during an eicr on a tn system there’s a board going to a pig shed which is class as a permanent installation and one going a staff tea room which is a container made from wood which I wouldn’t class as a permanent installation. Would these need to have earth rods to keep the same equal potential?

[andyhodchild]

What happens when battery systems operate in island mode, if loss if supply includes loss of earth? Even with local earth rod?

[GZQCArtwork]

The lower the resistance (Impedance) is to true Earth the better. As long as it does not pull a fault Voltage from a nearby installation.
Being a qualified Radio Amateur, multiple Earth bonding is essential on the lower frequencies, as it reduced the noise floor on receive, and encourages a better efficiency on the transmitter.
Electricians would benefit from learning the Syllabus for the Radio Amateur's Exam, as it clarifies Earth resistance over Capacitance between wires in the air over the ground.
Multiple Earthing increases capacitance by a huge factor. It also protects against Lightning strike damage.

[paulaustin]

There is now so little metal work in contact with the ground on the distribution system since the late 70s early 1980s all Pvc served cables. That every bit of extra earthing is needed. It might ge worth foing done videos on the ENA guidance for earthing and what current practice is especially with regards to step and touch potential.