Earthing systems, EV charging connection options and open PEN detection devices.

Earthing systems and what options are available when installing an electric vehicle charging unit.
Does TN-S really exist?
TN-C-S broken PEN conductor problems and the 5 possible solutions given in BS7671.
Do the various devices available to detect fault conditions actually work?
Problems when using TT at a location which has a TN-C-S installation.
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[@RubenKelly-whitby]

More cars should look like that! In all seriousness the simplified drawings are so helpful for understanding from the ground up.

[@2013Davey]

Hi John, Dave here... old, cold and retired quite a few years ago. Whilst everyone was bonding the heck out of every thing, I kept telling them that safety through isolation was the 'better' method... however my very simple suggestion for an option 6 would be, 'EV charging should be via a class II psu'.

[@jwflame]

That option is in BS7671 as 722.413 Electrical separation. Unlikely to be used due to the substantial cost and inconvenience of a large transformer for every charge point.

[@2013Davey]

@@jwflame I hear what you say, but 'substantial cost and inconvenience' vs for example the >substantial cost of digging up / earth works (pun intended) and reinstating driveways, the building trade have nice yellow ones that could serve as a great conversational piece in any home. Also for less money than it costs to get Bob the builder out of bed

[@IrrationalRecreation]

@@2013Davey , Bear in mind that fast EV chargers are roughly between 7 to 20 kVA. That's going to be a physically bulky and relatively expensive isolation transformer. Single-phase site transformers in the 10kVA continuous range are about £800 (and near 100kg) which buys you quite a bit of labour even in the leafier outer-London suburbs.

[@rsp6549]

Onlooker from the U.S. here. For some reason I'm fascinated by U.K. electrical and electrician videos (Thomas Nagy and David Savery are personal favorites). I'm amazed at how utterly paranoid you guys are about household electricity. OTOH, we use 120 and you guys use 230. Sure, if we get shocked it really hurts, but, mathematically, if you get shocked it really, really hurts. P.S. It would take an electrician here about an hour to fully install a Tesla charger here, and that includes the half-hour he takes padding the bill. If he even pulled out a Fluke to check his work, I'd be amazed.

[@marquisdemoo1792]

Welllll....you might want to watch this video explaining why the USA is not 120V: kzbin.info/www/bejne/oH7QhqKQnZh7p5Y Yes your ordinary outlets will be 120V....but car chargers will be 240V. That said it will still be safer as the potential to Earth is always 120V....but in 120V systems, compared to 240V, the likelihood of fires increases as you have to draw higher currents for the same power.

[@ismscsim]

So the safest solution is a TT earth mat and remove the supply(offgrid) and make water and gas cables non conductive. This video is exactly what I have been trying to get to grips with. Timely and fabulous resource. Many thanks John.

[@iansyme3535]

John Ward, for many years during my 43yrs of employment with BT (formerly GPO when I joined in 1972) earth testing was one of my duties as a Precision Testing Officer. In small telephone exchanges situated in the country earth testing was carried out every couple of years. I was involved also in testing what is termed "Earth Resistivity" testing to determine what size and type of earthing system was required. BT strived to get an 8ohm or better earth electrode system but this was very seldom achievable in rocky areas. Even with massive grid systems (we used solid copper bar) or multiple earth spikes bonded together or joined up and driven in the ground by a type of impact wrench it could prove impossible. Specialised Meggers and tables were used to determine the best earthing method. You are quite correct in stating that it is nigh on impossible to provide a low resistance earth with one or two spikes unless you are in very, very "good ground" with a low earth resistivity. Quite what the answer to this I am sure you have puzzled over. If some fancy (and probably very expensive!) bit of kit comes on the market to act as a safety cut out then I hope to hell it is a lot more effective than some of the new fangled "arc protection devices" you have tested over the last year!

[@nutgone100]

I would’ve thought the best thing is an isolation transformer. You’re basically starting again. Not cheap though, especially for high power applications.

[@keirstitt8277]

People often forget that the ground impedance is only as low as the impedance of the other end of the circuit through ground. Often due to space restrictions we test earth electrodes with a fault loop impedance tester which usually gives a value about 5-10 ohms higher than a three electrode test. Of course this is because the loop impedance includes the impedance of the DNOs earth. Where there's a PME system that actually has multiple earths - rare as the regular electrodes along the cable simply don't exist - this should be low. But you get a TT system fed from a post mounted transformer - which our local DNO aims for a 10 ohm earth electrode but in reality the geography makes that a pipe dream. And ultimately we should be less interested in a race to low earth impedance, and more interested in the fundamental safety objectives - limit touch voltage and ensure protection operates within limits. Back to the original topic. I'm sceptical about the importance of potential to local earth - I think extraneous conductive parts are far more an issue which on a drive limits us to next-doors car and maybe external plumbing. I'd therefore be more interested in ensuring that two neighbours have a low resistance between their respective earth terminals - which if they were both PME on the same supply cable then this would be very low. If this is inspected periodically - and frankly if you've got an electric car you possibly should get your EICR when recommended even if the extent is limited to the charger. I'm not convinced that at LV we get shocks capable of causing injury between a PME failure and the puddle on our concrete drive we're stood in with inappropriate footwear. I'd love to see evidence otherwise.

[@andreasbentz6106]

Hi John! I fully agree with you, that establishing a proper low resistance grounding is the only option to do it properly. Not only for EV-charging, but also for the general installation of the house. Thank you for giving me this insight into UK domestic installations. I am from Germany and I was asking myself halfway through the video, why on earth (pun intended) you consider a TN-C-S network to be a problem. OK PEN faults can happen, but hey, the ground-connection of the "potential alignment rail" would bond the PE and the neutral close to earth potential. This rail is the central point of the house where all the metal parts as well as the PE are connected to and which is also connected to a low resistance grounding. I was aware, that single phase supply is typical in domestic installations in many parts of Europe, but I am mildly shocked, that low resitance grounding does not seem to be required by UK regulations. In publicly accessible EV-Charging installations it is even required, that the foundation of the charger has a separate low resistance grounding in order to prevent potential differences that can occur between the far away grounding of the building (which is present on the PE) and the earth potential at the location of the charger (e.g. when a lightning strikes nearby). Sometimes (over-)regulation sucks, but in this case I'm glad we have it. Anyway - a good video. I learned something and I like your style of presentation. Subscription you have. Best Regards Andreas

[@IAmThe_RA]

Can you elaborate more about the standards there especially the "potential alignment rail" that is connected to a low resistance grounding?

[@andreasbentz6106]

@@IAmThe_RA Hi there! In Germany it is mandatory, that every building has a proper grounding with a low resistance to ground potential. This can be done in several ways (e.g. a ring of flat-iron around the foundation, a connection to the steel reinforcement of the concrete foundation, a pole that is driven deep into the ground). The gounding resistance has to be measured in a standardized way and documented. Now this grounding is connected inside the building to a terminal-rail called main-grounding-rail (formerly potential-alignment-rail), which is located close to the termination box of the electrical grid (the endpoint of the grid where the main fuses and the meter are located). All metal components of the structure, that can be touched (e.g. water- and gas-pipes, plumbing, handrails, roofing, rainwater-ducts, satellite dishes) must be connected to this main-grounding-rail. In larger structures you find additional grounding-rails, that are connected to the grounding to reduce the wiring effort. This ensures, that every conductive piece that can be touched have ground potential, even if they bring in a different potential from elsewhere (e.g. a lightning strikes 500m away from the building and the water-pipe runs close to the strike and has elevated potential. Now to the electrical installation: A three phase TN-C-S type grid comes with L1, L2, L3 and PEN (combined neutral and protective earth). The PEN is split at the termination point of the grid into neutral and PE of the installation. A fault of the PEN in the grid would mean absence of PE in the installation, with all negative consequences. Therefore in Germany the PE must be connected as well to the main-grounding-rail of the building. That is why you locate it close to the termination point of the grid. This ensures, that the security mechanisms work properly, even if the grid does not provide earth potential through the PEN. On the contrary - when the grounding of the building should fail for whatever reason, the PEN still ensures at least a "close to earth potential" because the PEN is also connected to the main-grounding-rail of all neighboring buildings. Hence the TN-C-S grid type is considered here superior to the TT grid type, where the earth potential of the electrical installation relies solely on the proper grounding of the building. I hope this is what you where asking? Best Regards Andreas

[@IAmThe_RA]

@@andreasbentz6106 Thanks for you detailed elaboration 👍

[@hgn6716]

Hi I was wondering what value is considered acceptable for the potential alignment rail? When tested what is the maximum value in your legislation?

[@andreasbentz6106]

@@hgn6716 Hi there! The answer is not as easy as providing a single valaue. The reason is, that the legislation requires "a proper function of the protective devices", hence the tripping value of the RCD in mA and the voltage of the measurement determine the required resistance value. Most measurements are taken at 50V and this means, that a 30mA RCD requires a maximum resistance of 1660 Ohm (which I consider a bad grounding), which is usually not a big problem. If you have a 300mA RCD at a construction site or an older building, this maximum drops to 166 Ohm which is sometimes hard to achieve, especially if the grounding is not properly done or has rotted away in older buildings. Also the hot summers with practically no water in the soil down to a level of 2-3m below ground were an issue. In addition to the absolute value, you also need to observe the requirements for the measurement. The required procedure is a differential measurement called 3-wire measurement. You need a main ground probe at 20m distance to the potential alignment rail and an additional support probe also in 20m distance of the main probe (a triangle is OK). For Installations in rural areas, this is doable, but in urban areas you often have no chance to reach a proper distance for the probes. In these situations, other procedures are accepted. If you want to see such a measurement, there is a video on youtube kzbin.info/www/bejne/hIGViJSenaeJlaM But be warned, the guy is Bavarian and talks the local accent, which is very hard to understand even for native German speakers. So the automatic subtitles do not work. At 14:00 the actual preparation and measurement starts. Cheers Andreas

[@TheEulerID]

The fundamental problem here is that TN-C-S is potentially dangerous anyway as a broken neutral can put near mains voltages on anything bonded to earth. So even if you don't have an EV, that garden tap can go to dangerous potentials compared to the ground you are standing on. That goes for any metalwork attached to the outside of a house which is bonded to the incoming earth. Of course, it's true for the inside of the property too, but presumably the regulators think it unlikely that there's an independent path to earth as, presumably, all internal metalwork ought to be bonded. The broken supplier neutral problem will also apply to anything operated outside the house via an extension lead. Really, if this is a significant systemic problem then it could only be "fixed" properly by electrical supply companies being required to install devices that cut off power and the point of entry to the property if dangerous voltages are detected on the neutral/earth supply. So this is not a new problem caused by EVs, it's just that, presumably, the latter are just rather larger and more accessible hunks of metal. In any event, I suspect we will see a lot of people just using 13A standard sockets and an extension lead to "top up" and EV on an ad-hoc basis.

[@grahamturner6119]

PME Supply was in my opinion a cheap and nasty way out for the Supply company a auful lot of electricians didn't like the idea when PME came out

[@AWellesley]

We’ve just moved house and plan to get a new driveway installed. So glad I watched this video before any work on it has started.

[@kalayaskitchen]

if you use rebar mat make sure its welded in the matrix X crosson pointd and not just "wired" get your welder to tag weld it all together and then have a couple of bits coming up at a suitable corner, remember tho it will rust externally so get an electrican to make a rust proof connection to the ground plane (which is what it is) Look up UFER GROUNDING SYSTEMS in wiki etc

[@thesolderman861]

Dear @John Ward Good explanation. I can see one security risk you might not have seen in the first glance. When looking at @35:42 and @13:33 with many houses on the same phase but with a broken combined N and PE wire for all those several houses, your house with a good ground connected Earth Mesh + Earth Rod might get a very big current on its PEN wire coming from the street. So from my point of view it would make sense to have a Fuse in this wire when it enters the house, to avoid to have a glowing wire in the basement in such a case of a broken PEN somewhere down the street. Regarding the amperage of the fuse I would suggest to have it 1.7 times the rating of the main phase fuses, in case you have a three phase installation in your house. The local earth mesh /rod must always be connected to all the PE wires of the house and water piping etc. in the house. The fuse should only break the incomming PEN against this fire risk. Addendum: I just discussed this idea with another experienced guy and he mentioned that this PEN Fuse could blow when you are not at home and notice the troubles in the powergrid, and the grid might be already repaired when you come back home. So the Fuse should have a supervision electronics. In case of a broken PEN Fuse you might not notice it, as the Earth Rod/Mesh would still allow a medium load to run properly, e.g. you might only notice a flickering in the light when the fridge motor starts. Furthermore he recommends to cut all the power to the house whenever the voltage of any of the 3 Phases and the Neutral is outside of a certain acceptable range. You might need an independent little earth rod to measure these voltages to a proven reference ground point.

[@simonschertler3034]

Beeing happy that here in Germany, Austria and Switzerland most houses have such massive earthing systems since the 1970th😏. Additionally all installations where you will install a EV charging point have a 3phase supply.

[@patdbean]

So 3 phase for EVs, thus giving charging in the 20kw+ range not 7kw range and charge speeds of 50mph+ and not 15-20mph

[@evzenhedvabny6259]

Not necessarily. My property has main breaker of 3x32A. So I would use 3x20A for the charger. It gives me cca 14kW.

[@patdbean]

So more than the 7kw we would get in the UK on a single phase? At that rate you would charge at about 30mph and I assume those 32A fuses could be upgraded if the cables are up to it?

[@simonschertler3034]

Here the normal type 2 charging point at home has 3x16A. The reason are the regulations of the power companies. Charging points >16A (single and three phase)need the agreement of the power company. In some cases you have to pay >2500euro for this. Max current for single phase applications is 20A@230V in all cases. Though single phase car chargers with 7kW are pretty useless here. Technically it is not a problem to change a car whith 32A@3x400V (22kW) because most houses have a supply of 4x35 or 4x50mm2 Aluminium and a 3x50A Fuse in the cutout box.

[@evzenhedvabny6259]

@@patdbean Depending on my agreement with my supplier. When my neighbours wanted electric heating they had to wait. There was not enough capacity in local transformer. Our rules are very different from UK. But yes we can have 16,25,32,64 Amp B type breaker if local conditions allow.

[@gbelectricks]

I can confirm the exact scenario you describe in your video (@ about 8 minute mark) happened to me today in work. I attended a property that was having a new service cable installed into the property by the dno. Originally the all the houses in the street had a tns pilc cable into each house. A new SNE (separated neutral earth) cable was run into the property. With a split concentric cable. But, at the joint in the street, the main service was a relatively newly installed “repair cable” it was a concentric tncs with a COMBINED neutral earth!!! The new service head has been labelled up sne (tns) even though it truly is tncs. The dno engineer suggested the way to check would be to perform a continuity test between neural and earth at the head to ascertain a true tns situation (with a suitably low, but not too low reading!) It certainly is food for thought!

[@effervescence5664]

Was thinking of putting a TT stake in for my own EV motorcycle point but it would have to be within 2m of the plastic gas main and TNC-S supply so hard luck there for me. What gets me though is the lovely metal kick stand on the bike reminds of the days when Cars had cables hanging down off the chassis to ground them out against air friction and static electricity. So why isn't that a valid option to just plug the car directly into the ground, surely if the mass of the car is already in direct contact via exposed metal to the ground the likelihood of a person being the favored path is diminished.

[@Cptnbond]

Hi John. I'm living in a country where all gas has been phased out, as well as metal water pipes. Nowadays, all water pipes in residential buildings use plastic pipes. I have a three-phase supply; thus, the O-PEN solution looks ideal. The TN-C-S code allowance for extra metal nets under the concrete floor comes in handy for the future if building a separate garage or extending the main building becomes a reality. Thanks for sharing your knowledge. I'm pleased you explained why with your use cases and not referring to code only. Cheers.

[@Halleck-yk9ep]

Another great video that brings the regs into the real world. Looks like this issue is going to be a real head scratcher for some time yet.

[@djb774]

Well done John! That is the most comprehensive overview of the subject I’ve seen and illustrates the rather dry regs surrounding this confusing issue. I think it raises more questions and concerns but it does highlight the complexity! Hope the IET watch it! 👍

[@redd605]

It's only a matter of when someone gets hurt from electric shock driving.these cars .

[@grahamwhiting6567]

Thanks for a thorough summary John and for pointing out that those chargers designed using a CT on the PEN, are not compliant with the principle of reg. 415.1.2. That is going to give many EV Charger installers a problem, so I'm not sure it'll be welcome news to them! Zappi device anyone? V2G is being quite widely seen as a way to give our future national supply more flexibility and reserve, as EV's take over in the next few years. The OVO V2G project with around 400 installations, has run into exactly the problems you describe and having discarded the Matt-e device, (DNO stability problems as well as single phase protection issues) they now insist on a separate earth electrode installation. They require this to be the regulation distance from incoming supplies but allow a test impedance up to 100 Ohms, which may be practical but obviously then reies on the CT/RCD style protection installed. I installed an 8 metre long 16mm diameter rod and 75Kg of conductive concrete (Furse/ABB product) to make my separate earth for this project, but it still tests at 30 Ohms in this rocky Peak district area.

[@tonyshorthouse8357]

People are left to self-assess an installation. Also a manual process to declare an EV installation to the DNO. Would the same issues apply to heat pumps? Are there many properties affected by looped supplies, or shared supply fuses? My business is establishing a cross industry group to identify risks for EV charging ahead of the mass market migration to EVs, heatpumps, PV and battery storage. Interesting to read issues related to V2G trials with WPD and OVO

[@jordeebrompton]

zappi doesn’t just rely on a CT. It has many inbuilt safety features. myenergi.com/zappi-2-bs7671-and-protection-features/

[@pdken3081]

@@jordeebrompton well it sounds convincing but it would be good to hear John's view.

[@TWOKDOK1]

@@jordeebrompton yes but it still relies on what is effectively an RCD device alone to protect against a fault current passing through the user. Has Myenergi confirmed compliance with 415.1.2? That is key.

[@ramin2011m]

Even my kids know you because I’m watching your video all the time.

[@Chris_In_Texas]

Here in the US we have the UFER grounds as well on newer construction. Our house was built in 2007 and has a concrete slab foundation that has about 1000 Sq M in size that is connection along with two ~3M ground rods. I have seen a loss of the neutral with our split phase here. Usually it will become evident that something is wrong as many 120V devices start to blow up and catch fire with the wild voltage swings. I had a UPS that caught fire and had flames out the side, and of course it kept powering along because the batteries took over as well. The car chargers that I have installed are two wire chargers with no neutral. The bring out 240V with a safety ground. Our new NEC code in 2020 requires all garage or outside outlets be protected by GFCI now for anything under 250 volts, which include now car charger outlets and RV type plugs. There is no current cap anymore (before it was only on 120V 15-20A circuits) on these so all outlets will have to be protected that are in a garage or on the outside of the house.

[@williammartinculleton7523]

Wow, sure that's food for thought, there must be a lot of unsatisfactory EV charging points around ⁉️. Thank you Mr JW.

[@Daniells1982]

Agreed mate. This is a total can of worm isn't it. So convoluted to achieve a compliant and safe installation. Times like this I wish I'd been a bricklayer. 😒

[@Mainly_Electrical]

Daniells1982 would of earned more money

[@andy530i]

@@Mainly_Electrical Even labourers are on more than most sparkies.

[@Mainly_Electrical]

andy530i disgusting mate most skilled trade paid peanuts really unless your the top dog

[@DanstheEngineer]

Massive can of worms. Another great video and explanation Sir John Ward

[@PJB71]

Thanks John Excellent video, I’ve watched this twice, I’ve put off doing the car charging point course for 3 years, due to constant changing regulations. I was doing a bit research prior to taking the course this year. I was planning to install the Zappi for TN installs, however after watching this, I don’t think I’ll bother with the course, until some sort of solution is found.👍🏼

[@jwflame]

The Zappi is about as good as it gets for equipment. The real solution is foundation earth electrodes, which are only practical for new construction.

[@PJB71]

John Ward as you say it’s only a solution on new builds & the chances of that happening are next to none in my opinion. So I think they need to come up with something else, PME has never been allowed with caravans, so why with cars? This video is excellent & so educational.

[@TWOKDOK1]

@@jwflame As the Government is ‘mandating’ EV’s in future, the potential risk will increase proportionately, surely it is then incumbent on the Government to declare a commensurate mandate to use 3 separate distribution conductors as the infrastructure is upgraded to cope with the required capacity. The PME 2-conductor system was clearly implemented driven by reduced costs. At the time the collective risk v benefit was probably acceptable. But with hot tubs, and EVs now increasing rapidly, this is no longer the case. I am astonished that DNOs are permitted to effect 2-conductor repairs on 3-cabled systems, thus knowingly degrading the safety of all affected consumers. This is then compounded by the fact that they don’t appear to be required to inform those consumers that, as a consequence of those repairs, not only has safety been compromised but it is actually being camouflaged because the potentially unsafe TN-C-S system is masquerading as a relatively safer TN-S system at the cutout. Is anything being done about this?

[@mathman0101]

As always sir a wonderfully crisp and clear presentation. On request would be at each point don’t assume people are following as exactly as you hoped and keep stating the obvious. I would also try to put links for people wanting to learn more not not links from standards and codes only but also reading elsewhere from a scientific electrical engineering perspective. That way people can learn at a much greater depth, hopefully pushing them to get more formal training.

[@peterobinson8908]

Thanks for the advice, major headache, lots to consider. Thanks once again. Pete

[@ombratth]

In Norway we have all three systems (TN, TT & IT). In regards of TN we get 3~ TN-C to the house, then we split the PEN to PE and N and get TN-S. We then have the following requirements: Surge protection, Earth lekage with Type B (Type A is not allowed with the exeption if the charger has its own dc lekage detection). I’m often pussled to see the difference in how different countrys do electrician work :P Like the one house you show about connecting to the PE from the supply line, but use a eart rod insted. Now allowed. We also have to drag a 25mm2 wire round the house and connect it to the PE bar. Acting as our earth rod. It’s not that common too only get 1 phase, but same principle with TN-C-S and earth wire in the ground. 1 phase systems is more common in old houses and often IT or TT systems and not TN. IT and TT we dont get neutral, we get 2 or 3 phases with 230v between them, and we do the same regarding the earth wire.

[@dd313car]

If you split PEN to PE an N this is not TN-S, it's TN-C-S . TN-S would be 5 cores incomming (L1, L2, L3, N and PE.

[@ombratth]

dd313car I know. I’ve never come across TN-S from the supply company. But we are not allowed to use tn-c from the main switch board in for example a big building and to the next. Here we nede to use tn-s.

[@Basement-Science]

This whole thing seems so ridiculous. Somehow it was apparently perfectly fine to shock everyone in case of a broken Neutral before, whether they are touching metal parts in the kitchen, washroom or the outdoor tap, and any type of metal building materials that may or may not be earthed. And yet somehow, just because a car _may_ be outside, the exact same fault is supposed to be so much higher that NOW you need to improve things, *BUT only for the EV charger.* Getting shocked everywhere else is still perfectly acceptable. Personally, I typically wear shoes outdoors, whereas indoors, I am likely to touch metal parts while standing on a stone floor with bare feet. I always assumed all countries would be installing earthing rods *_at a minimum_* next to each building for *Decades.* Really, this regulation just seems to be designed to deter people from adopting EVs. They _could_ have mandated at any point that all buildings need to be upgraded to certain safety standards if improving safety was actually the goal.

[@TheEulerID]

As you say, it's an existing problem, which John fails to mention. A garden tap can go live in the event of a broken neutral. I suppose the regulators work on the basis that if the fault happens in the house, then all the metalwork will be bonded and there's no independent route to earth save whatever you are standing or sitting on. However, it won't help that garden tap issue (or anything else outdoors). I suspect the regulators thing that the biggest issue with EVs are that they are massive chunk of metal, that might be parked in a street or an easily accessible driveway. However, I'd note that even if a bullet-proof charger could be produced, there's nothing stopping somebody doing a "top-up" charge via a standard 13A socket. Really, the only way to protect against this is to have something on the incoming supply that cuts it completely if a break in the neutral is detected. That way the entire property is protected. Of course it still had issues with possibly requiring an independent earth reference (although I have by doubts it that's all it's used for that it's quite the placement issue that John lists for that sort of role). However, at a certain point, I wonder just how many improbable combinations of events have to happen to make this a real danger and just how many tens of billions of pounds have to be spent to save how many lives.

[@jwflame]

Until relatively recently, most homes in the UK had gas and water supplies in metal (usually steel) underground pipes, and as those were bonded to the main earth terminal of each building, that vast network of buried steel pipes acted as an earth electrode, so when the PEN conductor was broken, the voltage on exposed parts was kept low due to those connections via the gas and water services. What's changed is that virtually all new installations use plastic (MDPE) pipes for gas and water, and older gas and water networks are being upgraded by replacing the buried steel pipes with plastic ones. There was an attempt to get earth electrodes for TN systems into the wiring regulations (BS7671), however that only made it into a draft version and was removed from the final version. Earth electrodes are permitted for TN systems and have been for decades, but as they are optional, they are rarely installed.

[@TheEulerID]

@@jwflame Strange you should mention gas utility pipes as yesterday evening on of my RCBOs (the downstairs ring) tripped accompanied by what sounded like load fireworks outside. A look outside, and there was a spectacular firework show dancing up the side of a neighbour's garage about 30 metres away. It was merrily blazing away and setting light to overhead trees. It appears that a neighbour's carelessly disposed of barbecue coals had melted through a bin and then through the gas feed pipe. The crackles and bangs and sparks were, I suspect, due to fire affecting the incoming mains power. I reset the RCBO four times before it settled down when the fire was out. I was not the only one so affected as another neighbour had his RCD trip. The power got turned off at the substation for a couple of hourse to allows the gas supply to be made safe and, very likely, the mains power. So the question is, how could what appears to be an electrical problem on the supply side to another house cause RCBOs and RCDs to trip in a nearby properties? I even got quoted in a local newspaper (via text scraped off the local town web forum site). www.oxfordmail.co.uk/news/18516389.firefighters-tackle-blaze-chipping-norton-village/

[@sbusweb]

@@TheEulerID Some RCBOs will trip on overvoltage and some other states. I've seen Wylex WSES RCCBs that like tripping when there is a power-cut too. Certainly with 'spikes' of power on/off, the capacative coupling of filter-capacitors to earth can cause RCD trip. Also note the capacacive-filtering of line-(N or E) capacitances, inrush to reservior capacitors etc, can in any case trip the overcurrent protection in MCBs/RCBOs, if you have lots of loads connected and the mains voltage 'comes on' at a high voltage point all of a sudden...

[@TheEulerID]

@@sbusweb I was guessing that some unusual surges had happened. The RCBOs I have also include a functional earth and those contain logic to detect some neutral line failures. Perhaps the voltage between earth and neutral went too high and t tripped. Perhaps some stray currents were flowing through the ground. Whilst it's a TN-C-S system, earth is bonded to metal gas and water pipes. I have had an RCBO trip when the power came back on after a power cut once, and I put it down to some sort of capacitive load. Fortunately it's not the norm as I get at least half a dozen very short power cuts a year. Enough to put my computer and comms equipment on a UPS.

[@kevint3845]

Interesting video some very well made points 🤔. I wonder how many have been killed or injured due to issues, are the issues truly understood in the industry. Would be interesting to do a video on already installed systems to see how many comply.

[@michaellink3832]

As transportation is being increasingly electrified, surely all new builds connected to a TN-C-S supply should be required to have a local, distributed earthing system installed such as a grid or copper wire around and below the perimeter of the concrete slab. Buildings where I live in Norway (with both TN & the older IT supplies) have this sort of arrangement and earthing arrangements for charging have been unproblematic, though many have dug up their driveways to install higher capacity cabling to their garage or carport.

[@nua1234]

In Ireland nearly all houses have TNCS and always have had a local earth electrode.

[@patdbean]

17:15 why didn't they just go the "whole hog" and put the tap on the 'top' and the outlet on the bottom, So it could drip on to the live connection ? 😁

[@PersonGamma]

That design is insane.

[@dav01kar]

Thanks JW, very interesting topic.

[@jimreece7615]

The Tesla Gen 3 Wall Connector Manual has a link to this video. congratulations JW on your endorsement by Tesla.

[@mihdogg]

Excellent Explaination Wow you have helped me to understand a subject that baffled me for ages . You are Very honest and really want people to be safe amazing ! you took the time out to create this video the calm way you explain and the drawings you use done it for me totally enjoyed and learned something new in this vid , much appreciated . Thank you Very much Richard Alexander

[@dropdatabase8224]

Just use an NVR, problem solved.

[@bobrose7900]

Fascinating video John. Boats tend to have an isolation transformer at the point of entry, the supply is then used for socket outlets and charging onboard. Would this be an option here for the supply to the charging point?

[@richardlang2185]

Dear John. I do appreciate your knowledge and videos. You are very good and Thank you for doing that. One comment about this video. On the last section (ii). You forgot about metal water and gas connection when you created metal mesh in the drive way. If you have several houses connected to the same PEN and broke somewhere before all those houses, you transferred all load from other houses threw metal water and gas connection to your metal mesh. You'll overload all your earth connections due your house acting as main PEN connection for neighbour houses. I would not recommend to use that option as well unless replacing metal water and gas for plastic. But than you created TT. Also you cannot have TT and others system of Earthing mixed together. You can have one or another. I would like to have your comment on this please. Kind Regards Richard

[@mastergx1]

A great explanation as always John, thanks. Just a quick heads up - after scouring the internet for car charger designs - I have come across the EVO EV charger which has built in PEN fault protection for single phase supplies. How it achieves this is beyond me and according to the blurb, its some kind of proprietary system the company has developed. Might be a neat solution.

[@rogertorressabate1804]

Hi John, thanks for such good explanation, really helpful. In case of an outdoor 3-phase EV chargepoint (say a supermarket parking), would option (i) imply no further protection method should be used? Or that would only be the case if no other loads were connected to the same supply? Thanks!

[@tinytonymaloney7832]

Just a thought JW, from experience of new house bashing in the 90's adjacent house are put on a different phase, so for example 3 new adjacent houses would be spread over 3 different phases. Therefore if a nutrual was lost according to your sketch then there could be a potential of 400v. BTW good vid.

[@djb774]

Hi Tony, out of interest did they keep Semi’s on the same Ph?

[@totherarf]

Not quite ..... If the 3 houses each had the same lode the "neutral" cable between them would find its own resting point at 0 volts! It is only when the loads are not balanced the neutral would be at a corresponding voltage, up to (if two houses have no load) 360V! Sill not good! If you want to visulise it imagine it, picture a triangle measuring 415 units to a side. The center point of the triangle is the neutral /earth and each point is one phase. If you measure from point to center it is 240 units and if you extend the line from one point untill it intersects the side of the triangle you will get just over 360 units ;0)

[@tinytonymaloney7832]

@@djb774 I have seen in the past some old council houses, semi's, that shared the same over head cable, looped into one and out to next door. Back in the 80's, a hideous black twisted cable tacked along the underside of the eves. Very much doubt that sort of thing is down now.

[@iansanderson4664]

@@djb774 Not necessarily. About 50 years ago my next-door neighbour was dying and had electrical equipment powering his bed. His company's fuse blew, so they called the Electricity Board and I supplied the bed from my house. The first things that the man from the electricity board did was to check how I had connected the bed in case replacing the company's fuse would connect two phases together.

[@iansanderson4664]

I should have said this was the then neighbour in the same pair of semis.

[@kalayaskitchen]

Im in Thailand and responsible for my own and a neighbours installations, so for my house I use an UFER GROUNDING system as used by the military and raised (but not named) in the last but one systems. As I oversaw the construction here I used welding of all the rebar, and copper linking cables with brass connectors loaded with a coating of copperease, (old sea dog trick) then set into the concrete, connecting electically all foundations, risers and beams, floors, and also the roof trusses which are all steel tag-welded onto the columns. I then made multiple earth points at 4 corners of the buildings and on the eaves tied back to the installation frames/box. I used lightning rods. So in all with EMP style mains protectors for the computer equipment I have a bonded together system well into the ground which is slightly salty sand mostly damp all year around. No one does this here and most Thai installations are totally dangerous with numerous local stories of people killed or vegetated by shocks in the rainy seasons. It's a form of "TT" and that is what I selected after agonising about it. Anyone self-building in Thailand or anywhere tropical for that matter should regard UFER grounding (the concete having a lot of free ions) as essential. I thought of buying (I was drunk) a large 1-1 isolation transformer too - but opted for my own TT system. I've not made measurements w.r.t impedance but I feel 99% confident it's better than any other reliance on using the company neutral. (two wires only overhead). All premises water pipes are plastic.

[@evzenhedvabny6259]

After seeing this video i can say that i now understand some other countries regulations. Some countries using TN - CS incorporated in their regulations an article saying that property has to have own earthing system which is connected to the point where PEN becomes split into PE and N.

[@raymaone]

You are on the right track. My particular interest is in removing the 'Burden ot the Law' where old, inappropriate or just dangerous regulations stand in the way of a happy life! My proposed solution is to dig up the garage floor and turn it into a super earth - then rewire according to best practice ignoring current regulations. If the solution is indeed correct it will become the de facto standard. Regulations follow 5yrs later. What would you add to my 'super earth' to complete the system and what mesh or conductive concrete would you recommend? Thanks David from Wales!

[@hotrex7779]

Hi John thanks for the vid very well put . I have one thing that you did not touch on that I feel could be something that needs to be considered . Where you are adding an additional earth mat to the property that will help with the problem for Ev charging it also has an additional problem. In the event of a open pen conductor in the street your earth mat being of low resistance could actually be carrying a large amount of current from the whole street to earth so depending on the size of your earthing conductor to your earth bar and from it to the mat it could prove to be a fire risk . As has been found in the past . This in no way meant to detract from a excellent vid . Regards bill

[@nickbengtsson6518]

Thank you John, most helpful as always

[@Sculptoroid]

Interesting topic. Good video. In case of a PEN damage all internal appliances get high voltage on their chases - that can be very dangerous. Water heater, stove, laundry machine, to name a few.

[@millomweb]

Water heater will be fine - earthed via water feed :)

[@Sculptoroid]

@@millomweb You'd be surprised. Water is not a good conductor of AC. Metal pipes are. Plastic pipes aren't.

[@millomweb]

@@Sculptoroid I know it's not a good conductor but it's better that steel threaded conduit that's gone rusty ! (A friend asked me to connect his cooker in his new (old) flat I wired the cooker in ok but the best earth I could find was his hot water cylinder - that was the best source of Earth for the flat. I told him to get the place rewired.

[@Tom55data]

Very useful video, thank you The issue you highlight for PME supply and car charging is founded on the problem on N supply line becoming broken to the house. Although this is serious - it is unlikely (but must be considered). The question I would like to ask is the problem that, depending on the effectiveness of the bonding of the supply neutral, and the current draw on the mains - there will be a voltage rise on PME earth (ie neutral) of between zero volts and 20 volts compared to true earth at your car which is not connected to ground via the tires. It a person now plugs their car in in the rain while wearing flip-flops etc, you could get a potential difference of 10-20V between true-earth (the wet ground) and the car (connected to PME earth) once the charge is started. Surely this is a issue as 10-20 volts in a wet environment could be conductive. What is your opinion of this likely scenario. (I have a PME house wiring with separate TT earth for my isolated earthed garage using 3 earth spikes - with plastic gas and plastic water piping and the mains incomer 30m away for my car charger earth rods.). Maybe borderline. Next problem , many people use "granny-chargers" from a house supply which of course certain to be PME earthed. Could you do a video on the standard safety equipment in a car charger supply - DC detect, earth/line/neutral solenoids, asymmetric signal detect on the pilot pin for earth failure and so on. Many thanks.

[@pramodgavit7666]

Extremely Great full for such informative VDO

[@daverdaceng]

Brilliant video and explanation- nice one!

[@yevgeniyshawyer2767]

this video is most of the useful video I ever watched!!! Thank you/!!!!

[@MichaelPickles]

Great video! I've learnt some good information here. I'm looking to put in Victron inverters 8kV x3 and batteries 57kWh. This will make the house a off grid system using the main grid as a backup generator only. So TT. All the pipes to the house are plastic. I'm looking to upgrade to three phase And can reconfigure the Victron inverters to that spec.

[@eyjaheimaproject4563]

JW, what's your opinion on earth grids embedded in concrete foundations and any resistance caused by the concrete to (true) earth/ground? Thanks for your educational videos.

[@badbanano]

Now that you’ve made a proper ground, you have a proper way for lightening to sneak in and fry your electronics. ⚡️

[@adam-user]

This was a GREAT video, thanks!

[@SeanBZA]

I know the supply for me is TNS, because the cabling was stolen at the substation, so I got to see them put it back in. The cable they installed to replace the stolen cable was still a 4 wire SWA cable, replacing the original paper insulated steel tape armoured cable that was cut out. However in areas with overhead supplies the cabling is TNCS, as the cabling to the poles has mostly been replaced with ABC over the years, replacing the original 4 conductor with aluminium 4 conductor, with the supply always being TNCS with the drop to the houses, only still overhead bare wire for properties that have not been transferred to non related owners for the last 30 years, otherwise it becomes a buried cable and external to property meter, being a TNS supply from pole to meter, and then a grounding rod by the meter. Old properties grandfathered in, as some have grounding to water pipes, or a ground rod, or nothing, depending on the age.

[@gasgas2689]

Did they remove the bodies before replacing the cable, or just dig them into the ground along with the new cable?

[@dorin2212]

Thank you for those infos, verry usefull!

[@Tom-Lahaye]

Very helpful explanation of different earthing systems and their hidden cans of worms as you call it. It actually means that having a TT system and all plastic water and gas mains coming into the house is the safest option where no neighbour can make my plumbing and car live unless they willingly connect a wire to it? With all plastic mains pipes under the sidewalk and to my house, does the minimum distance of 5 m between my earth electrode and mains still apply?

[@jonnosmith5501]

Excellent video John, like always very informative and I'm always learning. Check out the EV charger "Zappi" a product made by myenergi. Detects PEN conductor faults within the charging unit. No earth rod required. Had one installed at my property, its a brilliant device.

[@Marcel_Germann]

I use a 22 kW wall charger, three-phase (3x32A), but had to limit it due to the service provider. They were afraid the whole grid will black-out because I charge my car. The unit is adjustable. It monitors the fault current, it switches off if there's a fault current of 6mA (AC or DC). In addition the circuit is protected by a three-phase 30mA type A RCD in the fuse box. If you don't have a wall charger with a DC protection integrated, you require a type B RCD or type A+EV. The wall charger also monitors the voltages between all conductors, and if all three phases are live. If one is missing, it goes into error mode. It's not only mains voltage that could become dangerous, there's a high voltage battery in the car. In the most sold electric car in Europe, the Renault Zoe, the battery voltage is 400V. That's enough to spoil your day. The Zoe also measures the earth resistance, if it's too high it won't charge. So owners nickname it as a charging diva. The system here is TN-C-S and all have an additional earthing electrode. In newer houses it's integrated into the base plate of the house, in older installations it's mostly a retrofitted earthing electrode. Back until 1990 they simply used the incoming water pipe made of thick cast iron as an earthing electrode. So, I didn't rely on just one method. I installed it the way I got several layers of protection.

[@richardwinter6141]

Marcel Germann but that’s not enough to comply with the Regulation in the UK

[@merlinfizz]

Very informative John. If an A393 matrix is laid out 6m x 4m x 1.8m below ground within a concrete slab with a connection to the property with 10mm earth cable connecting to the main fuse box which is about 8meters away. Would it be safe to then have a swimming pool built so the pool is 365mm distance higher than the concrete slab?

[@peterengland6153]

In NZ I we have a TN-C-S (MEN Multiple Earth Neutral), with grounding rod, in most of NZ the soil is clay loam (extremally wet clay loam lately), with a resistance well below 10ohm.

[@antjohn5383]

I think the Zappi 2 overcomes all these challenges mate David in Australia

[@eviain]

Great video, as some one who has a charge point installed prior to these and the previous regulations, so is reliant on the house hold earthing it’s also somewhat concerning as to what the best way forward is, although I do need a new drive way at some point! Is there also a potential here to alter electric vehicle charge port specifications to allow the car to reference earth directly avoiding the tyre issue, obviously not much help for the current generation of EVs. Also be interested in how seriously this issue is being taken, as the number of options seems to suggest there’s a degree of casting about going on.

[@alunroberts1439]

I have to ask if service pipes are metallic and under ground therefore grounded just like a earth electrode are they a form of a earth electrode in them self's

[@liberatodelgreco4430]

Just wondering, if an earthing mesh is layed under a tarmac drive would that work as well .

[@allansmith8925]

Hi John, finding your video looks to have been fortuitous for me and wonder if I could ask for a little bit of advice. We have moved into a house which has a workshop some 20m down the garden with a 60Amp supplied via 3 core SWA. House is TN-C-S (Via overhead lines) and in the near future we having a double carport built next to the workshop. Whilst we don't have an EV at present I am guessing that in the next decade it is likely we will so I wanted to be prepared for anything needed whilst building it. From your video I am guessing it will be worth installing some metal under the floor which will be block paving. The carport will be 6m x 5m and my thoughts are to run either 25m roll of 10mm copper pipe or 6/7 lengths of 15mm copper pipe soldered in the subsoil in bands across the floor area (which is heavy clay) leaving the pipes exposed in one corner to attach an earth clamp. The questions are:- 1) Do you think this plan of using copper pipe is sensible and will that be enough (I don't want to use steel as it will have a decade to start rusting before we are likely to use it so may not work)? I recognise it is dependent on a lot of external factors to get the ohm reading low enough and nothing is guaranteed so just want some guidance on the density of copper to be used per M.As a fallback we can probably supplement with earth rods as there are no other services near the workshop. 2) Does the grid have to be connected all the way back to the earthing point in the house or will the electrician be able to connect it to the CU in the Workshop? Your video mentions connecting it to the MET. Final anecdote for the Part P cert when the SWA was installed it seems they went to the trouble of bonding the water pipe which clearly comes in as blue plastic before switching to copper and a festoon of bonding cables/clamps under the kitchen sink, downstairs toilet sink and central heating pipes in various places but they failed to bond the Oil pipe or LPG pipes which both come in as copper from underground :( Guess this will need to be rectified!). Thanks Allan

[@stuartgilbertson]

Would one of the options be to splice plastic PVC into your incoming gas and water mains (1-2m worth, to isolate your house from the "grid's" earth), and then simply drive your own earth rod?

[@RWATraineeElectrician]

Interesting video 👍

[@madhavdivya]

John, we do use the TN-S System in India. Not obsoleted.

[@Wilkkid1]

A lot of new builds and mainly high rise flats in London that my company I work for I believe is tns systems, cable from the substation is split consentric ( sne) and a separate neutral and earth all the way to the hdco or msdb and separate all the way to the cut out

[@ursulanield9767]

Does a standard three-pin socket mounted externally used for EV charging require its own separate TT or a open pen fault detection device?

[@MrCrouchback]

What about a contactor with the coil fed from the supply, fused etc before the meter tails. If there is a fault or breakage the contactor drops out.

[@BHFJohnny]

The version with the mesh grid under property. PEN broken. Doesn't this mean that the vehicle charger works normally, RCD won't trip because it has no reason, everything works and I have no way of knowing something is wrong? I presume only way is to measure loop impedance which will be significantly higher than normal 0.35 ohms or less in TN-C-S, am I right?

[@davidandlouise8238]

Thanks John!

[@ericthekingthekingtheking4842]

John Wouldnt the metal mesh scenario be the same under fault conditions as the others where the metalwork makes your bonding and whatever in your house live,

[@jwflame]

The mesh is still connected to the live parts, but would have a much lower resistance and provide a path for the current, so the voltage at the mesh (and anything connected to it) will be significantly reduced.

[@alan2804]

John Ward Wouldnt that imply that a long run of metal water/gas pipes between a row of houses have an equally low resistance and then not be a problem? Secondly as many house supplies of water and gas are in plastic pipes is there a need for such a distance separation from earth electrodes?

[@jwflame]

@@alan2804 Yes, if the pipes are metal it will act in the same way as an earth mat or grid, and that's why broken PEN conductors were not such a problem in the past, as most houses had metal gas and water pipes. For the last couple of decades, all new gas and water pipes underground have been plastic, and huge numbers of older metal ones are being replaced with plastic as areas are upgraded, so without installing an earth grid or mat there is nothing to provide a supplementary earth for most properties. For a TT system there is no need to separate the electrode from plastic pipes, but it must still be well away from underground cables.

[@giz177]

@John Ward Why are outside socket not thought about the same I could be holding a piece of equipment that's at a different potential to the ground I'm standing and with a open PEN would the RCD still operate??

[@giz177]

One more question is If you were to TT your EV charger and put the rod 10m away in the back garden and the EV charger is on your driveway and the water , gas, and electrical supply run directly under could there be a potential difference in the charger and the ground your standing on?

[@patdbean]

29:10 are car tyres insulating these days? Are they not now conductive rubber, to dissipate static build up on the car.

[@raptorpome2577]

Static voltage is high voltage and the mains voltage coming into your house is only low voltage

[@seanpassant3174]

You can sometimes get very low readings from a single rod but it is so dependent on the underlying soil conditions, in lightning protection applications I've seen 6-9 ohms at a 3.6m x 16mm copper rod. In parts of London you might hit clay and you're laughing but 50-60 miles down the road in E Sussex you'll be into chalk and you've no chance. Foundation earthing is coming in an amendment soon that's fine for new houses but can it really be applied retrospectively to existing properties?

[@Basement-Science]

You could also "just" dig a trench around the house and add in a metal mesh band around the building. This also gives a pretty low resistance.

[@fickdich9918]

For TN-S systems that have been upgraded, why can't the remaining lead covered cable close to/entering the property be used as an electrode as it is always in contact with ground along its length?

[@muzikman2008]

And...that's why i'm sticking with my diesel van lol :-D Great explanation as always JW... enjoyed that.

[@DavidPlayfair]

Great video John. With many people needing EV Charge Points installed over the next years, and not all installers being as aware of the potential problems as yourself, this could become a major issue nationwide. Re the earth mesh idea, wouldn't multiple earth rods, or a very long earth rod, (away from pipes, etc., of course) be an option? I have seen copper pipes used as earth rods drilled into the ground by forcing mains pressure water through them, many years ago. Not suitable for all types of substrates but where this works several pipes can be soldered together to go down very deep indeed. Would that work?

[@tonyfot0]

Thanks JW

[@tomcrosbie6564]

Hi, Great video's BTW. Would installing a TT grid not be just as expensive as a £700 isolation transformer once you've taken into account the labour for groundwork etc?

[@jwflame]

On it's own yes - a more realistic situation would be to have that installed at the same time a property was being constructed or a new driveway installed, where the additional cost would be minimal.

[@philcross6037]

When you say you cannot use a TN-C-S for hottubs, How are people getting them installed? do you have to make a TT but then you are solely reliant on your RCD.

[@bonginkosicindi6138]

Hi JW i got a problem on my DB everytime the is a lighting storm my RCD trips i dont know if the problem is my RCD or my CPC PLEASE ADVISE

[@ratscabies8458]

Question. I have a garage concrete slab of approximately 70M2 that’s full of mesh reinforcement however like most concrete floors it’s laid on a plastic visqueen sheet for a damp proof course. Would using the mesh to connect the earth as John suggested still work in that situation ? Thanks

[@jwflame]

Depends on the construction - concrete would usually have 2 layers, the structural layer with the metal in it, then a DPC, with a screed over the top to form the finished surface. If the metal is accessible, easiest option is to just test that as if it is an earth electrode and see what results you get.

[@blankblank4459]

I have seen a document from a DNO saying customers' buried TT earth systems must be segregated from DNO's earth by 3.6m (unbalanced single phase install). Would this apply the the 'earth mat under the driveway' option given that it is connected to the TNCS MET? Thanks. Always appreciate your considerded opinions!

[@jwflame]

That applies if the mat is a separate TT earth, not connected to the DNO earth at all. Some specify even larger distances, up to 8 or 10m. If it's connected to the TNCS earth as an additional electrode, distance doesn't matter because all of the items are already connected together.

[@TheClashen]

Hi John, As usual really enjoyed your look at this subject. As I am installing electrics in a new Garage next to the house with potential work ensuing on the house after the garage so I forwarded your video to the architect. Do we need to think about the specifications to add to any foundations to improve the earth for a particular situation? Even found this article as looked for articles in carbon Fiber concrete reinforcing (See details below). After all do not want to carryout foundation work and wish we had considered earthing, as we didn't consider it for the garage floor and foundations, the focus here at the time was insulation cold bridging and a Radon membrane. Now to consider earthing. I am old enough to remember the Tefal heads adverts, think I need that extension to look into the subject further. Especially after watching the "Fully Charged" Tesla Power wall installation. Where is it all going to end up? How much up front work do we need to put into work now to save much more expense later. Was going to put a single phase feed into the new big garage but should I put 3 phase in and even ask the "Hydro" to reroute my supply for the house from the 3 phase in the garage. Then need to consider a balanced 3 phase usage. Yep the Tefal head extension is required I reckon and just as well I have just retired to have the time to look into all this!!!! Here is some bedtime reading for you. Electrically Conductive Cement-Based Materials January 2004 Advances in Cement Research 16(4):167-176 DOI: 10.1680/adcr.16.4.167.46658 Deborah ChungDeborah Chung

[@jwflame]

Foundation earthing isn't required yet, but is likely to be in the future. In terms of installing, if the concrete foundation will have metal reinforcement in it, then all that's required is to leave a small section of it accessible, so it can be connected to later. For the cables, the most practical option is to install them in a duct, so the cables can be replaced later if required.

[@ronanpoint6856]

Hi John, Another highly informative video. At 12:00 you said “You can’t put an electrode near to any of these items [cables, gas or water]…in many cases you’re looking at distances of around 5 metres…”. I can’t find this in the regs but would like to read more about it. Please could you tell us where it comes from? Thanks.

[@jwflame]

Most of it is in 'BS7430 Code of practice for protective earthing of electrical installations', some in Guidance Note 8, and distances from DNO cables can be found in various documents from the DNOs themselves such as Western Power, SP Energy Networks, a lot of which is partially of fully from the Energy Networks Association. Some useful things here: www.spenergynetworks.co.uk/pages/documents.aspx and here: www.westernpower.co.uk/documents/tech-info/design-standards/low-voltage

[@djb774]

btw... I need to look at the Zappi v2 again which we are advised complies, there’s a great demo on here with efixx but it must fit into one of the scenarios you gave?

[@jwflame]

The Zappi complies with what's written in section 722 of BS7671, however those regulations are not good enough as the protection will only be effective in some circumstances.

[@chrishorne3609]

Hi @@jwflame An excellent video which clearly explains the complexities (and pitfalls) of different earthing systems - something that a lot of people struggle to understand. As you say, the myenergi zappi complies fully with BS7671, ensuring that if a PEN fault is detected the output is fully isolated (including a fully rated disconnection of the earth on the output - worth checking some other EVSE to see if that's the case!). This protection operates in ALL circumstances to ensure that anyone who may be touching exposed metalwork at an elevated voltage to True Earth is protected from a dangerous electric shock. The hierarchy of protection is as follows: 1. The primary earth connection - PEN conductor, which is what the video is looking at 2. Measurement of voltage between Line and Neutral - which in most (but not all) cases will go outside the range 207V to 253V specified in BS7671. 3. A trip if there is any indication of current flowing in earth conductor (as explained in the video). This will trip in just a few milliseconds if a current of mA is flowing (similar to an RCD characteristic) - yes, a person touching the exposed metalwork will experience an unpleasant jolt (I know - I've tried it!) but they are fully protected from a dangerous electric shock. Really pleased that someone else is highlighting the shortcomings in a voltage only protection feature - we've published a number of papers to explain our concerns and there's a video on the e-fixx channel that shows what could happen when the PEN conductor is damaged kzbin.info/www/bejne/kJbHhaCiibF7aNk John - if you would like to spend some time with us looking at the zappi and discussing safety of EVSE then we'd love to host a visit at our offices in Lincolnshire (once we're allowed to travel again)

[@ashokpatel2700]

Thank you for the very informative video. Do you have any pointers on the design of the mesh please: 1) The size. 2) The material - I am thinking it will corrode and how best to connect a copper wire to it as two different metals will be involved and the joint buried. 3) A strange question to ask but could one use copper tubing that's been soldered as now connections would be copper to copper? I was thinking of using scarp 15/22mm tubing? Thank you.

[@jwflame]

Steel wire, welded into a 200x200mm grid. Some examples: www.specialistconstructionsupplies.co.uk/our-products/steel-reinforcement-mesh--rebar-for-concrete-slabs Corrosion isn't an issue as it's completely encased in the concrete.

[@Daniells1982]

I suppose we'd have to consider whether the manufacturer of the mesh sees their product as suitable for use as a means of earthing and are there specific terminations (no doubt meeting various standards/approvals) from mesh to earthing conductors on this type of set up?

[@hans.vbaalen]

@@jwflame isn't the problem with having a steel mesh in the drive, that in many cases the electrical supply follows a similar path to the house (certainly the case in our semi)? The mesh will likely be laying about 50cm on top of the supply cable/gas supply. Certainly less than 5m away from it as you suggest would be safe?

[@crazygeorgelincoln]

Wrap the mesh around the gas and water pipe when digging up the drive, then stuff the earth rod through the bonnet of the car. As far as I understood when a supply conductor is "broken" both or all three conductors covering a significant length go in the back of the people carrier.

[@Hairclone]

Thanks John! I don't understand why anyone would downvote this excellent video. I have one question regarding regulation (iv) however. If I understand this correctly, it is impossible to verify that (PE - actual earth) is below 70V rms even if we are measuring the (L-N) voltage in a single phase installation? Then why do Matt:e market O-PEN devices for single phase infrastructures, claiming that they conform with (iv) regulation without driving earth rods into the ground? Do they mean that it has to be connected to a earth mesh or metal structure so that simultaneously monitors the voltage between the incoming earth and real earth (metal grid)?

[@jwflame]

The single phase device just measures voltage between L&N, and disconnects when outside of the normal range, either too high or too low.. Their device complies with (iv), but whoever wrote (iv) assumed that it would cover all situations of broken PEN, which it does not.

[@williamredfern5504]

Just a question- if my place has an neutral combined earth input from the supplier could I have other earth points coming direct from the property to earth I Dont have or require an EV system ,also no gas supply plastic water pipes and no nearby properties ,is it safe Can someone answer this please,,

[@Richardincancale]

15:15 In most situations adjacent houses in the UK are connected to different phases to balance the load, so could the voltage between two cars could be 415v?

[@jwflame]

The car metalwork is connected to the neutral point, so it's unlikely you would get 400+ volts between them as that would require at least one of the vehicles to also have a fault between line and what was previously the neutral. The combined neutral/earth to both houses would normally be the same conductor, so it depends on where the break is relative to the supply to each house. Also depends on whether the 2 houses are using the same earthing system or not.

[@millomweb]

@@jwflame I see no reason to connect car chassis to AC neutral.

[@speedmytube]

​@@millomweb The car chassis probably isn't connected to AC neutral but it is connected to the CPC/earth which, in turn, is connected to neutral either at the cutout in a TNCS installation or, likely, somewhere in the street in a TNS installation.

[@marcaxe]

@@speedmytube Do you know if the body is still used as the return path for the general 12V system in an EV? Seems odd to earth reference it if that's the case, connecting the output to the supply side of an otherwise isolated SMPS.

[@speedmytube]

@@marcaxe yes it is

[@rossmurdoch7870]

Hi John Excellent video as ever. EV isn't a solution for all our transport needs in my view for many reasons. The cheap supply methods shoved in are the main issue, and the DNO should be forced to contribute to whatever solution is decided on. Too many times Electrical Installers have to work hard to overcome the DNO fails or the Manufacturers inadequate provisions for safety. This issue and AFDDs are two recent examples

[@gap9992]

I love watching your videos John - not in the profession but I just like to understand how things work - or try to at least! I am in the process of having an EV charger installed (by BT Chargemaster) and have never been asked so many questions ahead of an installation visit! The latest questions include "send us photos of your water and gas bonding" which got me watching your videos on that subject which then led me to this one! I have TN-C-S Given what you say should I cancel my installation for fear of being burned to a crisp, or just plan to wear thick rubber gloves and boots whenever plugging / unplugging my car to the charger? As a layman I assumed that if the main supply was damaged to cut the neutral / earth then the supply would be automatically cut off by the utility company? If that didn't work then one of the devices in my CU would do the job. If this is such a big risk why aren't houses in general protected? Why is charging a car such a special risk over and above something like a good old outside socket? Anyway, someone better get all this sorted because we are all supposed to be driving electric vehicles asap !

[@johnburns4017]

So, the best method is to forget the DNOs earthing. Run an earthing cable to the back garden ramming in a number of earth rods, cast in concrete if possible, all connected to each other. Then forget the suppliers earth connections. A TT. In the Middle East, because of hard rock we could only get 1 foot deep, so laid earth rods connected up horizontally in a star around an equipment building. The dry sand did not help to get a decent earth.

[@ats89117]

Being a US based electrical engineer not associated with the power industry, this was extremely informative but left me with a lot of questions. Over here, I think we are all required to have the neutral bonded to an earth connection at the main panel, but I think the earth is generally the water inlet pipe, so not a separate electrode in most cases. One question is how much better it would be if the current on the earth connection is continuously monitored? Would high current on the earth connection provide an indication of many of the fault scenarios that you discuss?

[@PeterDWard-wm2nz]

Can you suggest an earthing arrangement for a (Large) domestic property which has a 2 phase supply as the owner would like to install a standby generator. He has been told he does not have a PME system. Can he install an earth mat of low impedance (2ohms) to make the property a TT arrangement. But then what about the generator earthing, its giving me a headache.

[@B1cam]

Hi can we presume that the earth pad will be at a safe distance from any incoming domestic gas or electrical services as a pose to a earth spike? Thanks.

[@jwflame]

For an earth grid connected to the PME / TN-C-S earth, it doesn't matter if it's close to other services, because it's all linked together anyway. It would matter for a TT system, as that needs to be entirely separate.

[@B1cam]

Thanks John.

[@buekliev]

Thanks!

[@gino2465]

Good evening John another excellent video. Just to let you know Viridian EV make a unit which covers your item 5. Just purchased one for my EV charger. A question I would like to ask is can I use it for a caravan hook up as I want to fit one at home. I Realise before anyone makes a comment that it's not covered in the caravan regs, but it's the same situation I am in with earth Rods. Just your thoughts would be grateful. G

[@cooljim313131]

Does the Myenergi Zappi sort the problem as I believe it has PEN fault detection and so disconnects all L, N & E connections?

[@chrishorne3609]

Yes - the myenergi zappi was developed to solve the problems with (safely and effectively) installing earth rods even before Amendment 1 was written. It uses a combination of L-N voltage measurement (Indent 4) to capture those cases where the L-N voltage does go out of the range + a sensor to to detect any leakage current going to earth via exposed metalwork (ident 5). This trips if a few mA flows and in miliseconds so although someone touching the exposed metalwork may experience an unpleasant jolt (I've tested it myself - it wasn't pleasant) it makes sure that you don't experience a dangerous electric shock. It must be emphasised that this is a secondary protection measure - the primary protection is the combined PEN conductor, but it does ensure that the zappi EVSE installation is safe in all circumstances. This is an excellent video from John explaining in detail the complexities of earthing systems which are often misunderstood. For a demonstration of what a damaged PEN conductor can do to the combine N-E conductor in the property have a look at this video from e-fixx kzbin.info/www/bejne/kJbHhaCiibF7aNk

[@eviain]

Chris Horne excellent demonstration in the video, very much adding to the theory in johns video. Certainly considering the merits of replacing my Zappi 1 with a Zappi 2 or my drive way 🤔