Acacia Road......Bananaman reference? God I loved that show as a child! 😊You're a legend and inspiration to us all John. Thanks for the much valued content! Mike.
I think it must be either a mistake or the Electrician may not be informed??? I am sure that they will have a diode connect to the earth so no voltage or current finds its way back, I am pretty sure that is the case, why would someone design something as bad as this?? If you were to connect a diode to it , it will not allow any current or voltage, thus it can flow into it but not the otherway around....And if there is a diod connected to it not to allow the reverse power etc, you can sitll be sure that all earth in a big building will have power as allot of it is flowing to it from leakage current etc, in building where it is no PEN SYSTEM ANYONE DARE TOUCH THOSE BIG EARTH WIRES, THUS THERE IS A PROBLEM IN THE EXPLANATION HERE... UNLESS some one was so stupid that he was totally blind to design a system like that, which I do not belive it is the case, inside that box somehwere there has to be a diode to make sure it does not allow revers power, but all other power on the earth in all system is commong it is leakage current and it is in all building not just for PEN system....
Superb video, thank you. I particularly like that you show there isn't a single, simple indicator, and one needs to follow the issue to it's furthest extent. Never assume, and never miss an element of safe working to save time.
Just when I thought I'm finally reaching a understanding of why and whats happening. You say "your only scratching the surface and 3 phase is more complex". Excellent demonstration, thank you for your time and effort that goes into making these videos. I've learnt so much from you. Your 1 of the greatest minds in our industry.
I spent over 10 years working on the distribution networks and dropped neutrals caused everything from all electrical appliances in the properties failing (spectacularly if on different phases) to dead livestock, electrocuted Koi carp and several house fires. Great clear and concise video.
Then why is he afraid to remove my comments??? Think about it the system of PEN was designed by who?? An electrician or a phd engineer? Of course it would have been someone with phd so why would he make such a big mistake???? The system does not allow revers power did you know that, there is diode on the end of it with other protective system not to allow reverse power and john ward and others are going around revearling themselves ha ha ha ha. I have worked in all big buildings like BBC , National Audit office ITV TV building all of them or not PEN system and do you know how much leakage current flows to the earth in those building?? Anyone touching those earth rode will end up dead.... and it is nothing to do with PEN... Now do not remove my comments neither praise me but be thankful for learning....
Hi John thanks for this video. I work in a quarry and one time after an electrical inspection , it was the next day in fact the asphalt plant operator called and said the plant was acting strange, various things weren’t working and some items had tripped. Anyhow I went up for a look and discovered very strange voltage levels at various points in the electrical panels. I eventually traced the problem which was in a three phase distribution board in the next building. The insurance inspector had disconnected the numeral conductor while testing and he never re-connected it. 🤦♂️ As you say the voltages across various circuits varied like crazy. It’s a wonder something didn’t get damaged.
Thanks for this, very informative. Something to point out, even if you don’t have any current on your bonding conductor when disconnected at the time of testing, that’s not to suggest it doesn’t suddenly become live when someone down the road comes back from holiday and switches stuff on! I treat ‘earthing’ conductors as if they are live at all times, easier to respect it than be a victim! Thanks again 👍👍
I remember the first time an engineer from our local supply company said "It's all PME now" and thinking do I trust a remote earth connection managed by the DNO? And here we are! Great work as always John. You are an asset to the trade. Thank you.
That’s a cracking test rig demonstrator John. Tip of the iceberg indeed, three phase brings new problems. Voltages with sizes and angles to add up vectorially, parallel paths, each affected by the magnitude of the current. Reminds me of HND electrical networks from nearly 30 years ago. Looking forward to more of it. All the best.
Greetings John, another great, clear and concise explanation Also very handy use of transformer ratios to lower the voltage , increase the current but safely show the principles,, Very well presented,,, I bet those lamps were getting hot! Thank you for this!
Hi John, From an old spark from the 60's. An excellent tutorial as usual, you definitely put some work in to that rig for the benefit to others, I applaud you. I often thought of this scenario and tried to visualise that having water and gas pipes buried would act as very effective earthing rods at the same time effectively parallel paths conducting current to the neighbours and also carrying current back to the substation at the same time thus would mitigate the need for a separate earth rod for safety to limit the touch voltage, please correct my if I'm wrong perhaps my 75 year old brain is defective also. I wait with exited anticipation for your next video, your and excellent communicator. Peter.
your right the water, gas, and lead sheath on the incoming supply gave you a good earth untill the suppliers changed everything to plastic IEE REGS says it all how many times have they not got it right....obviously everything doesent go back to earth so fit an RCD as close to the meter as you can this will keep john out of your house as he seems to be more interested in whats going on in the neighbours house, mabe they fitted their own meter, and mabe john is colluding with the cartel to take the rest of your rights.
This is normally true but large currents flowing down supply pipes are obviously not good news particularly with gas. I wouldn't be surprised if pipe joints could end up being a point of high resistance and so local heating. More generally, metal supply pipes are gradually being replaced with plastic. In an increasing number of houses the gas is being disconnected entirely and a heat pump is installed outside, these have metal cases, which are connected to the TNCS supply earth.
Very well explained and thought-out information. Thank you for these educational videos. Nobody does these videos like you do; the in depth explanations, are fantastic, and rare. Sooooo glad you are back JW!👏👏👏
Excellent video as ever JW, probably an issue that will happen more and more commonly as the network ages and not something electricians are necessarily going to be looking out for, can't wait for the horrifying 3 phase episode :)
Then again, in some dwelling/building situations, utilities are going more and more to plastic pipes all the way and so perhaps reducing the overall alternative return path impedance. But then some retrofitted plastic pipes are being fed up inside the existing metal ones (e.g. gas) so you probably still have bonded metal going into the ground. Perhaps even the water conductivity in plastic water pipes can become significant in neutral disconnect fault situations if everything is plastic? As a home-owner, I guess the lower the chance of other dwellings 'helping' with your circuit return in the fault case that just you have a disconnected neutral incomer, the more likely you are to get a shock situation but also the more likely you will find your appliances going 'crazy' or not working. It's a tricky bugger. Definitely worth checking the current on as many bond wires you can clamp around and measuring the potential between the two conductors of any 'earth' connection you disconnect before touching.
@@haldo691 No connection between the incoming main and the house earth, which is a staked rod. Water main is plastic and no gas supply, so no metallic connections to another property. Not sure what else to say.
Perhaps we should all start running on 12V🤔😁 Joking aside you’ve successfully highlighted a very serious problem that will only become more prevalent over time. To truly test for dangerous voltages on disconnected bonding conductors (on a compromised system) we need to reference/ test it to true earth, meaning we need to put a temporary test rod in the ground far enough away form any of the properties in the street!! Who said TNcS was the best earthing arrangement?😃
What a precise and accurate explanation supported by a superb demonstration, much appreciated. The test setup must have been a lot of work! Thank you John.
As a mature sparky, learning doesn’t come easily 🙈 I would like to both thank and congratulate you on your 2 videos on Diverted Neutral Videos 👏🏻👏🏻👏🏻👏🏻 It explained the subject so, even old “f” like can understand it. All Gas engineers, should be made to watch them! Then they may actually use the lead in their tool bag when they remove meters, instead of a jump lead for their cars! Many Thanks Thomas
Brilliant demonstration and rig, a lot of thought and time has went into building what is an excellent experiment. Can only imagine the calculations on a three phase system with say 20 houses, the variables and voltages would be infinite. Reminds me of college exam problems. All the best.
Very interesting and well presented. I think this has explained a problem with a friends boiler installation AND a problem with contactless voltage sensors. The boiler had been reinstalled in the loft space. When the gas service technician checked the boiler with his contactless voltage sensor, is flashed and bleeped, as did mine BUT when probed with a DMM NOTHING showed! Just goes to show that all these expensive ELCB's, RCCB's etc are absolutely useless in this fault situation!
This has been very informative. As a ham radio operator the one thing I struggled to understand the most when I took my test was grounding and bonding. I remember learning about the different earthing configurations such as TN-C-S and I remember a situation being explained to me where if you have a really good low impedance RF grounding system you can run into issues where your RF ground ends up sinking current for your neighbours which can lead to an unsafe situation either risk of electric shock or the high currents melting your cables and burning your house down. I believe this is pretty much the exact same scenario but explained much better. My old house was TT a system with it's own ground rod outside which I seem to recall as being much less risky however it was made dangerous by some metal thieves who decided to steal the 8 inches of cable from where it came through the wall to the top of the ground rod so I had to replace that at one point. I now live in a house with a TN-C-S system and after moving in it needed a lot of work on the plumbing and we replaced a section of metal water pipe just after the service entrance with plastic but that was before the bonding so we added a cable to bridge the plastic part but as someone doing a bit of DIY plumbing I had no idea how dangerous that could be.
Good video John. Been an electronic engineer most of my working life so spotting the effects of a broken return connection are second nature. I had considered the effect of a broken neutral here as it has a looped supply, but the water supply is in plastic and there's a galvanic isolator in the incoming gas main so no parallel paths.
Correction: Well there was a galvanic isolator on the incoming gas main but it's not there now. Can't find any pictures but you can clearly see where it was as I couldn't paint the wall behind it. Must have been removed when the regulator was changed in 2009 and I hadn't noticed. FWIW the gas supply is in plastic but changes to steel before emerging from the garage floor. They no longer allow joints like this to be underground and I wonder if this video's topic has something to do with it.
@@pjeaton58 Not enough of a conductor to be of any concern. Resistance of water in a plastic pipe over just a metre is so high that it won't conduct any appreciable current, let alone the distance to the next house.
@@blower1 Really ? Well I won`t be intentionally touching a metal tap on the end of a plastic pipe fed from a water heater where all ground integrity has failed. Perhaps JW would like to construct a demo of this scenario to prove that it`s OK this time using the full 230vac with 30ma RCD of course !
Hi John, the close where I live in the past the neutral of the 3 phase supply broke, each house depending on the balance of the phase loads either had high or low volts. Many appliances were damaged and repaired free of charge. I now have a earth rod in addition to the supplied neutral. I suppose if it happens again all houses will be earthed by my rod! What about the my house TNCS where the supply cable is lopped out to another house. The water and gas supply here are plastic. thanks for the demonstration.
Very interesting came across this recently when the gas board damaged a supply cable while digging. I have a lovely video sent to me by the gas fitter of the spark on the gas pipe lol
I love this demo. So easy to follow. If you can't know ahead of time whether there could be a voltage on everything bonded to earth in the house you're working on until after you disconnect the bonding wire, how can you do that most safely so random residents in the house don't get shocked from trying to wash the dishes? Is there another tool you could put across that bonding link that would alarm the moment the voltage appeared and preferably re-link that connection to prevent shocks?
I hope that all's well John. Having learned so much from your TH-cam content I have my fingers crossed that it won't be too long before we hear from you again - your clear explanations and dry humour are much missed! Best wishes from just down the road in Dorchester.
Great Video, made me realise that just checking for currents in bonding conductors isn't that informative and disconnecting a bonding conductor is more risky than I thought. So I have learnt something but now feel even more confused about the subject. But it does show that bonding to a pipe that isn't actually connected to real earth substantially increases risk in open pen conditions. Sounds like the only safe way of doing things is to make sure no one is going to touch anything, disconnect and measure voltage to real earth. Given there are about 400 instances of open pen a year, about 0.002% of houses I wonder how many will actually make these checks.
We lost neutral on an expensive piece of equipment running on 3 phase 415V, the smaller loads, i.e. all of the control electronics, were wired between a phase and neutral and some of the medium loads like motors, pumps and fans were running from a different phase to neutral. When the equipment was switched on, the electrical cabinet emitted a great deal of smoke!
Great effort John. Great demo. Very difficult to calculate this stuff. So many different scenarios to deal with. Safe working Procedures will be easier to create than trying to calculate whether it's correct or not based on measured values at properties.
Fantastic video John. Would a smart meter pick up on the broken neutral or not? What about a buried phone cable into the property, could that carry Amps to another property? Also with some coms cable, Could that be connected to a differnce power source (transformer) in the next town along thus using different Supply&Earthing characteristics? I am looking forward to the next episode
Meter won't detect anything, as it's just connected to the L&N conductors after the CNE cable is split. Even with the CNE totally broken, current in the L&N will be the same, which is also why RCDs won't trip either. On top of that, meters only measure current in the line conductor, the neutral is a solid link internally.
Hi. I just watched one of your other videos that shows exactly how a 3 port valve works. The one with the lights showing the flow. Nice video which clarifies something for me. The reason I found your video is because I am in the process (tomorrow) of replacing a Switchmaster 400 with a Tado Wireless receiver. I did this before in another house so have some familiarity. Although that system uses 2 separate vales for the hot water and heating. The system I am installing the receiver to tomorrow, has a hot water cylinder in the airing cupboard, small tank in the loft for the radiators while the cylinder is fed from the large cold water tank in the loft. I think this what you call a gravity fed system (I'm not a plumber). The thing about this system however, is that the controller only offers the following configurations: Hot Water only or Heating and Hot water. But, NOT Heating only. The switches on the controller literally says this so I know it's not an issue with the valve. Which by the way is a Drayton Mid Position (it says MA1 on the unit). This controller I think was installed in 1970 and I have no idea why it could not have been installed with a controller that gives all valve position (Hot Water or Heating. Or both). Ok so here is the issue. According to Tado, once I have followed their instructions, the function of the water flow valve will not change. Basically keeping me in the same situation as before. Can you advise me what I need to do in order to get all valve options on the Tado. As in, should I get a plumber/electrician to just re-wire this ? Surely this should be very straightforward. What do you think ?
Very useful demonstration and brilliantly made test rig . It shows is a very strong reason and argument for TT arrangements being preferred for metal services such as gas or water. Makes me wonder if it should be considered as a regulation requirement for all metal service properties to be only TT or TN -S perhaps.
Very nicely done. I love the rig with ELV AC. I've never liked the idea of PME because of this possibiliy (what was wrong with TN-S!?). I've never had a broken PEN conductor before but I have had a broken phase on a 3-phase supply (L3 I think). Just making a point that they can and do fail - even though it is rare.
TN-S is expensive. Also it has a problem with possibility of broken PE. This in itself does not cause any harm which is the bad thing as it goes undetected. Then if you get an equipment failure you get shocked.
I have always had a concern with TNCS. The guidance should be to fit a separate earth electrode.. especially given new homes use plastic incoming water or gas.
Many thanks for another very insightful video. I like many others learn so much from your videos and your in depth knowledge. Just one question: would it be at all possible/ feasible to fit a PEN- fault detection/protection device at the origin of an installation, similar to that of many modern car chargers like the Zappi, that would safely isolate the complete electrical installation in the event of damage to the pen conductor in a tncs system. I am just very intrigued to know if this could help prevent this dangerous situation from occuring and if there is any reasons that this could not be done. Apologies if this is a stupid question it is just something that has been on my mind so I thought i would ask the expert! Many thanks again
Hi All i My Self have fitted O-pen fault Detection as Matt:e after DNO service for out Ev chargers & Outdoor Commercial industrial Supply’s feeding Market Stalls & funfair Rides as of Respect to BS7671 pen conductor TNC-S / PME As Stated Guidance Note NO7 My Situation Was Payed Area Or Rd . Remember the Dangers off Of Extraneous Conduct Parts if Converting to TT touch potential. Street furniture !
The devices sold as 'pen fault' detection and similar are not suitable for a whole property for various reasons. They are sold as a partial solution to EVSE installations outside, and that is all they are intended for. Will cover these in a future video.
Hi John Ward just wanted to say thank for your Demonstration of Diverted Neutral Current 10 / 10 As Commented already 3 phase & Neutral Worse Going back to me O-pen Device unfortunately there’s no place to Go cause ist thing it says BS7671 / Guidance note 7 plus escqr BS7909 the earthing of Pme TN-C-S not to be used to Supply Equipment out doors due touch potential plus likely hood of Open Pen Conductor especially where it is impossible to convert too TT System on hard standing Grd ( it’s not a park soil or Green ) installation has full earth leakage protection including time delay type A plus 30MA front end Rcbos . My only concern would be to Derate the o-Pen Device for touch Voltage 70 Volts to Dry location 50 Volts to 25 volts for wett location . Although as you Quote note Designed for whole installations . As per wonderful escQr plus 1989 electricity at work Regs BS7671 it’s an Engineering Judgement 🤔 Can’t See me using an Safely isolating transformer Not Practical
@@jwflame Thank you very much @jwflame for the reply, I thought that there must be a reason that this would not be suitable, I look forward to the video covering this issue. You really are teaching many people how things work and showing why we need to do the things we do. It is all very well knowing the correct way to do things but the reasons why is the really interesting bit. The subject of touch voltages is the area I find most interesting but also the most difficult to wrap my head around. How touch voltages are limited to less than 50V and if this is always feasible in most installations. How touch voltages are calculated in the event of a fault, etc really is an area that I believe many electricians would struggle with (or perhaps just me)! I would be hugely grateful if in the future maybe this a subject that you could touch upon, but then again I am sure you have a long list of future videos that you have planned. Many thanks again, it is much appreciated.
Lovely John. The issue is serious, I think personally all new homes should have the earth electrode being connected with the MET of the TN-C-S as stated a recommendation in BS7671 to help this cause. So many electrical contractors are unaware of the above.
It has to be said JW that is a very very impressive test rig you have constructed there!! Hopefully that is a copper water pipe cut off there not a Gas pipe though?
@mikenco Yes, I'm rather concerned about John too. But I must say, that his method of teaching is a bit arrogant and humourless, it would be nice if he could crack his stone face with a smile. But that's sadly, just John. That being said, we do all hope that he is well, and getting on well with life. Concerned for John...... 😐😐😐😐😐😐😐
Still have my main earth rod from TT days. Left connected as I don't trust the PME I have now. Plastic incoming gas and water. Question: Can disconnecting a main bond in my property where next door has a broken PEN lead to them getting shocks? (assuming metallic services) Seems so. Even with non metallic services they may get a tingle ( and kit not working). Seen the 3 phase scenario( overhead supply and storm damage). Seen the mixture of TNC-S and TN-S in a steel frame building as well. ( not permitted). Even if you think you have TN-S, it may be TN-C-S- up the street somewhere. !!! Great video.
Another brilliant eye opening video explaining a pretty complicated and possibly lethal situation, which will in fact be common throughout the UK. I would suggest most electricians will not know too much about. This video should be shown to anybody who works on domestic electrics, and crucially Gas and Water pipes. There must be several fatalities stemming from this diverted current situation. The most worrying thing its dangerous almost by design. TNCS is a pretty poor arrangement really considering the parallel paths through connected and bonded pipework in the streets. Should we reconsider the our Bonding practices or install plastic pipework as it enters the property as standard?
Great video John. Surely this just goes to show that PME systems are shit and supplied because its cheaper. Also reason why its not allowed i believe to supply petrol stations.
Lovely setup for teaching. I was wondering if todays smart meters do any current imbalance tests between the live and neutral cables coming in (ie, more current in the neural than live) ?
We could say that electrical testing should now take place each year to confirm a healthy PME system, similar to a gas boiler check. A basic check on the integrity of the DNO supply that should be mandatory.
Great video, and I can only imagine how complex it gets. Two questions though...1) If Property A looses it's combined earth and neutral, and also has the power off at the main breaker, wouldn't the whole CPC in Property A now be live? 2) Given those copper pipes go through the ground, wouldn't some or all the current flow naturally to earth rather than feeding back to the property with faulty neutral?
Acacia Road......Bananaman reference? God I loved that show as a child! 😊You're a legend and inspiration to us all John. Thanks for the much valued content! Mike.
I think it must be either a mistake or the Electrician may not be informed??? I am sure that they will have a diode connect to the earth so no voltage or current finds its way back, I am pretty sure that is the case, why would someone design something as bad as this?? If you were to connect a diode to it , it will not allow any current or voltage, thus it can flow into it but not the otherway around....And if there is a diod connected to it not to allow the reverse power etc, you can sitll be sure that all earth in a big building will have power as allot of it is flowing to it from leakage current etc, in building where it is no PEN SYSTEM ANYONE DARE TOUCH THOSE BIG EARTH WIRES, THUS THERE IS A PROBLEM IN THE EXPLANATION HERE... UNLESS some one was so stupid that he was totally blind to design a system like that, which I do not belive it is the case, inside that box somehwere there has to be a diode to make sure it does not allow revers power, but all other power on the earth in all system is commong it is leakage current and it is in all building not just for PEN system....
Lots of time and effort gone into that rig John. Well done.
Everyone else better step it up 😂
I have now watched many of your videos over the last few years and must say that you, sir, are a truly excellent communicator
This is the best explanation of the topic that I have ever seen. Many thanks for the time and effort making your videos.
Superb video, thank you. I particularly like that you show there isn't a single, simple indicator, and one needs to follow the issue to it's furthest extent. Never assume, and never miss an element of safe working to save time.
Just when I thought I'm finally reaching a understanding of why and whats happening. You say "your only scratching the surface and 3 phase is more complex". Excellent demonstration, thank you for your time and effort that goes into making these videos. I've learnt so much from you. Your 1 of the greatest minds in our industry.
I spent over 10 years working on the distribution networks and dropped neutrals caused everything from all electrical appliances in the properties failing (spectacularly if on different phases) to dead livestock, electrocuted Koi carp and several house fires. Great clear and concise video.
Then why is he afraid to remove my comments??? Think about it the system of PEN was designed by who?? An electrician or a phd engineer? Of course it would have been someone with phd so why would he make such a big mistake???? The system does not allow revers power did you know that, there is diode on the end of it with other protective system not to allow reverse power and john ward and others are going around revearling themselves ha ha ha ha. I have worked in all big buildings like BBC , National Audit office ITV TV building all of them or not PEN system and do you know how much leakage current flows to the earth in those building?? Anyone touching those earth rode will end up dead.... and it is nothing to do with PEN... Now do not remove my comments neither praise me but be thankful for learning....
I’ve been guilty of disconnecting main bonding clamps from pipes in the past, and not giving it a second thought.
This has opened my eyes!
People ask me "is there any TH-cam videos I can watch to help me learn about electrical theory?" I say watch John Ward.
Very well explained 👏
Hi John thanks for this video.
I work in a quarry and one time after an electrical inspection , it was the next day in fact the asphalt plant operator called and said the plant was acting strange, various things weren’t working and some items had tripped. Anyhow I went up for a look and discovered very strange voltage levels at various points in the electrical panels. I eventually traced the problem which was in a three phase distribution board in the next building. The insurance inspector had disconnected the numeral conductor while testing and he never re-connected it. 🤦♂️
As you say the voltages across various circuits varied like crazy. It’s a wonder something didn’t get damaged.
Thanks for this, very informative. Something to point out, even if you don’t have any current on your bonding conductor when disconnected at the time of testing, that’s not to suggest it doesn’t suddenly become live when someone down the road comes back from holiday and switches stuff on! I treat ‘earthing’ conductors as if they are live at all times, easier to respect it than be a victim! Thanks again 👍👍
I remember the first time an engineer from our local supply company said "It's all PME now" and thinking do I trust a remote earth connection managed by the DNO? And here we are! Great work as always John. You are an asset to the trade. Thank you.
That’s a cracking test rig demonstrator John. Tip of the iceberg indeed, three phase brings new problems. Voltages with sizes and angles to add up vectorially, parallel paths, each affected by the magnitude of the current. Reminds me of HND electrical networks from nearly 30 years ago. Looking forward to more of it. All the best.
Greetings John, another great, clear and concise explanation
Also very handy use of transformer ratios to lower the voltage , increase the current but safely show the principles,,
Very well presented,,, I bet those lamps were getting hot!
Thank you for this!
Brilliant the way you describe things clearly and in a understandable way , love you videos 👍
Hi John, From an old spark from the 60's. An excellent tutorial as usual, you definitely put some work in to that rig for the benefit to others, I applaud you. I often thought of this scenario and tried to visualise that having water and gas pipes buried would act as very effective earthing rods at the same time effectively parallel paths conducting current to the neighbours and also carrying current back to the substation at the same time thus would mitigate the need for a separate earth rod for safety to limit the touch voltage, please correct my if I'm wrong perhaps my 75 year old brain is defective also. I wait with exited anticipation for your next video, your and excellent communicator.
Peter.
your right the water, gas, and lead sheath on the incoming supply gave you a good earth untill the suppliers changed everything to plastic IEE REGS says it all how many times have they not got it right....obviously everything doesent go back to earth so fit an RCD as close to the meter as you can this will keep john out of your house as he seems to be more interested in whats going on in the neighbours house, mabe they fitted their own meter, and mabe john is colluding with the cartel to take the rest of your rights.
This is normally true but large currents flowing down supply pipes are obviously not good news particularly with gas. I wouldn't be surprised if pipe joints could end up being a point of high resistance and so local heating. More generally, metal supply pipes are gradually being replaced with plastic. In an increasing number of houses the gas is being disconnected entirely and a heat pump is installed outside, these have metal cases, which are connected to the TNCS supply earth.
Hello Mr John, thank you very much
A very informative demonstration as usual. I only vaguely knew this. Seeing this practical explanation was fist class.
Excellent tutorial as always John
Fantastic video John. I knew the theory, but actually seeing it in a realistic installation, it now all makes perfect sense. Thank you.
That's very true there's only so much you can visually see in your brain,,, but when it's presented in that fashion it really does make sense
Very well explained and thought-out information.
Thank you for these educational videos.
Nobody does these videos like you do; the in depth explanations, are fantastic, and rare.
Sooooo glad you are back JW!👏👏👏
Excellent video as ever JW, probably an issue that will happen more and more commonly as the network ages and not something electricians are necessarily going to be looking out for, can't wait for the horrifying 3 phase episode :)
Give the man a day off he's already done the rig for the single phase,,lol
Then again, in some dwelling/building situations, utilities are going more and more to plastic pipes all the way and so perhaps reducing the overall alternative return path impedance. But then some retrofitted plastic pipes are being fed up inside the existing metal ones (e.g. gas) so you probably still have bonded metal going into the ground. Perhaps even the water conductivity in plastic water pipes can become significant in neutral disconnect fault situations if everything is plastic? As a home-owner, I guess the lower the chance of other dwellings 'helping' with your circuit return in the fault case that just you have a disconnected neutral incomer, the more likely you are to get a shock situation but also the more likely you will find your appliances going 'crazy' or not working. It's a tricky bugger. Definitely worth checking the current on as many bond wires you can clamp around and measuring the potential between the two conductors of any 'earth' connection you disconnect before touching.
Had our gas meter removed. The meter guy had a big red "jump lead" to put across the meter during removal!
Very informative. Makes my TT installation feel like a good thing!
How do you know its TT all the way?
@@haldo691 No connection between the incoming main and the house earth, which is a staked rod. Water main is plastic and no gas supply, so no metallic connections to another property. Not sure what else to say.
@@tubaman66 And is the water in a plastic pipe a conductor ????
@@pjeaton58 it'll be a pretty rubbish conductor over anything but a very short distance.
Amazing video. I would never have even considered this. you turned the principles in to a clear concise demonstration.
Perhaps we should all start running on 12V🤔😁
Joking aside you’ve successfully highlighted a very serious problem that will only become more prevalent over time. To truly test for dangerous voltages on disconnected bonding conductors (on a compromised system) we need to reference/ test it to true earth, meaning we need to put a temporary test rod in the ground far enough away form any of the properties in the street!!
Who said TNcS was the best earthing arrangement?😃
What a precise and accurate explanation supported by a superb demonstration, much appreciated. The test setup must have been a lot of work! Thank you John.
thanks john this was very helpful and informative. i'm a gas man, electricity is weird. i struggle to get my head around it.
Excellent demo, as someone else mentioned obviously you have gone to a lot of trouble in order to create a great explanation, many thanks JW!
Another good down-to-earth explanation. Thanks, John.
As a mature sparky, learning doesn’t come easily 🙈
I would like to both thank and congratulate you on your 2 videos on Diverted Neutral Videos 👏🏻👏🏻👏🏻👏🏻
It explained the subject so, even old “f” like can understand it.
All Gas engineers, should be made to watch them! Then they may actually use the lead in their tool bag when they remove meters, instead of a jump lead for their cars!
Many Thanks
Thomas
Thanks for taking the time to produce this very educational video . Every day is a school day !
As always JW excellent explanation with the fault paths and great effort on the rig, looking forward to the three phase horror show!
Another fantastic explanation John on a subject a lot of us don't know enough about. Brilliant work on the demo rig!
I watch all your stuff John. Top bannana. Ill be able to self certify soon and truth is these videos are a valuable resource for life long learning.
Excellent tutorial, impressive setup John.
Thanks for sharing
It was a very interesting and educational lecture for us all, so thank you very much for setting it all up in such a brilliant way. 🙏
Great presentation John and thanks for all the hard work you put into it
Incredible opens your eyes to what dangerous situations can arise due to a lost neutral or broken connection
Brilliant demonstration and rig, a lot of thought and time has went into building what is an excellent experiment. Can only imagine the calculations on a three phase system with say 20 houses, the variables and voltages would be infinite. Reminds me of college exam problems. All the best.
Very interesting and well presented. I think this has explained a problem with a friends boiler installation AND a problem with contactless voltage sensors. The boiler had been reinstalled in the loft space. When the gas service technician checked the boiler with his contactless voltage sensor, is flashed and bleeped, as did mine BUT when probed with a DMM NOTHING showed! Just goes to show that all these expensive ELCB's, RCCB's etc are absolutely useless in this fault situation!
Brilliant explanation John, very good rig a lot of time and effort put in, well done * * * * *
This has been very informative. As a ham radio operator the one thing I struggled to understand the most when I took my test was grounding and bonding. I remember learning about the different earthing configurations such as TN-C-S and I remember a situation being explained to me where if you have a really good low impedance RF grounding system you can run into issues where your RF ground ends up sinking current for your neighbours which can lead to an unsafe situation either risk of electric shock or the high currents melting your cables and burning your house down. I believe this is pretty much the exact same scenario but explained much better. My old house was TT a system with it's own ground rod outside which I seem to recall as being much less risky however it was made dangerous by some metal thieves who decided to steal the 8 inches of cable from where it came through the wall to the top of the ground rod so I had to replace that at one point. I now live in a house with a TN-C-S system and after moving in it needed a lot of work on the plumbing and we replaced a section of metal water pipe just after the service entrance with plastic but that was before the bonding so we added a cable to bridge the plastic part but as someone doing a bit of DIY plumbing I had no idea how dangerous that could be.
Great Video clear visual representation of what can happen
Good video John. Been an electronic engineer most of my working life so spotting the effects of a broken return connection are second nature. I had considered the effect of a broken neutral here as it has a looped supply, but the water supply is in plastic and there's a galvanic isolator in the incoming gas main so no parallel paths.
Correction: Well there was a galvanic isolator on the incoming gas main but it's not there now. Can't find any pictures but you can clearly see where it was as I couldn't paint the wall behind it. Must have been removed when the regulator was changed in 2009 and I hadn't noticed.
FWIW the gas supply is in plastic but changes to steel before emerging from the garage floor. They no longer allow joints like this to be underground and I wonder if this video's topic has something to do with it.
And is the water in a plastic pipe a conductor ????
@@pjeaton58 Not enough of a conductor to be of any concern. Resistance of water in a plastic pipe over just a metre is so high that it won't conduct any appreciable current, let alone the distance to the next house.
@@pjeaton58 John's done this in a previous video. The answer was no.
@@blower1 Really ? Well I won`t be intentionally touching a metal tap on the end of a plastic pipe fed from a water heater where all ground integrity has failed.
Perhaps JW would like to construct a demo of this scenario to prove that it`s OK
this time using the full 230vac with 30ma RCD of course !
Superb teaching 'manner' and speed. TH-cam needs people like you, JW. Thank you.
Thanks again. I've watched this several times, hopefully I will remember it when I need to. I've also sent it to friends. You educate us all
That was a very interesting and informative video John. Thank you.
Thanks
The presentation and explanations on this video are Golden
Hi John, the close where I live in the past the neutral of the 3 phase supply broke, each house depending on the balance of the phase loads either had high or low volts. Many appliances were damaged and repaired free of charge. I now have a earth rod in addition to the supplied neutral. I suppose if it happens again all houses will be earthed by my rod!
What about the my house TNCS where the supply cable is lopped out to another house. The water and gas supply here are plastic. thanks for the demonstration.
Fitted my own earth rod when we were un looped by national grid. Water on plastic so should be good now gas removed.....
Excellent! I look forward to the 3-phase one!
Very interesting came across this recently when the gas board damaged a supply cable while digging. I have a lovely video sent to me by the gas fitter of the spark on the gas pipe lol
I love this demo. So easy to follow.
If you can't know ahead of time whether there could be a voltage on everything bonded to earth in the house you're working on until after you disconnect the bonding wire, how can you do that most safely so random residents in the house don't get shocked from trying to wash the dishes? Is there another tool you could put across that bonding link that would alarm the moment the voltage appeared and preferably re-link that connection to prevent shocks?
@mainly electrical , youtube, to learn my friend
Excellent video, helps alot trying to get your head around this. Real world scenario is going to be alot more complex, quite daunting.
I hope that all's well John. Having learned so much from your TH-cam content I have my fingers crossed that it won't be too long before we hear from you again - your clear explanations and dry humour are much missed! Best wishes from just down the road in Dorchester.
JW at his best, thanks for your time, effort & expertise in producing this excellent presentation ☘️🇮🇪☘️
Bloody excellent
Clear and concise as usual, thanks.
Brilliant rig John! Such a useful and well thought out training aid
Thanks for the great video and the amount of effort you've put in to build up such a great demo
Thanks for the effort to build all that, and for explaining it all and putting the videos together. Very informative!
Great subject explained as simply as possible
Thanks John, excellent part1 but your marvelous demo jig shows how complicated diverted neutral currents can be.
This is an eye opener for sure
Great Video, made me realise that just checking for currents in bonding conductors isn't that informative and disconnecting a bonding conductor is more risky than I thought. So I have learnt something but now feel even more confused about the subject. But it does show that bonding to a pipe that isn't actually connected to real earth substantially increases risk in open pen conditions.
Sounds like the only safe way of doing things is to make sure no one is going to touch anything, disconnect and measure voltage to real earth. Given there are about 400 instances of open pen a year, about 0.002% of houses I wonder how many will actually make these checks.
We lost neutral on an expensive piece of equipment running on 3 phase 415V, the smaller loads, i.e. all of the control electronics, were wired between a phase and neutral and some of the medium loads like motors, pumps and fans were running from a different phase to neutral. When the equipment was switched on, the electrical cabinet emitted a great deal of smoke!
thanks for all the hard work you put into that jig. much appreciated as always.
Step by step, methodically explained. It's an excellent training video. Love the shirt too 😊
Wow that’s actually quite scary! Thanks for making this video, definitely something to be aware of 😱
Great effort John. Great demo. Very difficult to calculate this stuff. So many different scenarios to deal with. Safe working Procedures will be easier to create than trying to calculate whether it's correct or not based on measured values at properties.
Fantastic video John. Would a smart meter pick up on the broken neutral or not?
What about a buried phone cable into the property, could that carry Amps to another property? Also with some coms cable, Could that be connected to a differnce power source (transformer) in the next town along thus using different Supply&Earthing characteristics?
I am looking forward to the next episode
Meter won't detect anything, as it's just connected to the L&N conductors after the CNE cable is split. Even with the CNE totally broken, current in the L&N will be the same, which is also why RCDs won't trip either.
On top of that, meters only measure current in the line conductor, the neutral is a solid link internally.
Thank you John. Your videos are brilliant. All the best.
Cheers JW great insight into this new electric blind danger - many thanks again 👍
Brilliant video John!!
Excellent video John I could show this to my students. Your rig is superb
Hi. I just watched one of your other videos that shows exactly how a 3 port valve works. The one with the lights showing the flow. Nice video which clarifies something for me. The reason I found your video is because I am in the process (tomorrow) of replacing a Switchmaster 400 with a Tado Wireless receiver. I did this before in another house so have some familiarity. Although that system uses 2 separate vales for the hot water and heating. The system I am installing the receiver to tomorrow, has a hot water cylinder in the airing cupboard, small tank in the loft for the radiators while the cylinder is fed from the large cold water tank in the loft. I think this what you call a gravity fed system (I'm not a plumber). The thing about this system however, is that the controller only offers the following configurations: Hot Water only or Heating and Hot water. But, NOT Heating only. The switches on the controller literally says this so I know it's not an issue with the valve. Which by the way is a Drayton Mid Position (it says MA1 on the unit). This controller I think was installed in 1970 and I have no idea why it could not have been installed with a controller that gives all valve position (Hot Water or Heating. Or both). Ok so here is the issue. According to Tado, once I have followed their instructions, the function of the water flow valve will not change. Basically keeping me in the same situation as before. Can you advise me what I need to do in order to get all valve options on the Tado. As in, should I get a plumber/electrician to just re-wire this ? Surely this should be very straightforward. What do you think ?
Quite eye opening, great demonstration.
Brilliant content as always. Love the funky shirt. Keep up the great work John!
Very useful demonstration and brilliantly made test rig . It shows is a very strong reason and argument for TT arrangements being preferred for metal services such as gas or water. Makes me wonder if it should be considered as a regulation requirement for all metal service properties to be only TT or TN -S perhaps.
Well done john ,
Regards antony,Warrington Cheshire..
Very nicely done. I love the rig with ELV AC. I've never liked the idea of PME because of this possibiliy (what was wrong with TN-S!?). I've never had a broken PEN conductor before but I have had a broken phase on a 3-phase supply (L3 I think). Just making a point that they can and do fail - even though it is rare.
TN-S is expensive. Also it has a problem with possibility of broken PE. This in itself does not cause any harm which is the bad thing as it goes undetected. Then if you get an equipment failure you get shocked.
I have always had a concern with TNCS. The guidance should be to fit a separate earth electrode.. especially given new homes use plastic incoming water or gas.
Thank you J.W., excellent video, certainly an eye opener.
Many thanks for another very insightful video. I like many others learn so much from your videos and your in depth knowledge.
Just one question: would it be at all possible/ feasible to fit a PEN- fault detection/protection device at the origin of an installation, similar to that of many modern car chargers like the Zappi, that would safely isolate the complete electrical installation in the event of damage to the pen conductor in a tncs system. I am just very intrigued to know if this could help prevent this dangerous situation from occuring and if there is any reasons that this could not be done.
Apologies if this is a stupid question it is just something that has been on my mind so I thought i would ask the expert!
Many thanks again
Hi All i My Self have fitted O-pen fault Detection as Matt:e after DNO service for out Ev chargers & Outdoor Commercial industrial Supply’s feeding Market Stalls & funfair Rides as of Respect to BS7671 pen conductor TNC-S / PME As Stated Guidance Note NO7 My Situation Was Payed Area Or Rd . Remember the Dangers off Of Extraneous Conduct Parts if Converting to TT touch potential. Street furniture !
The devices sold as 'pen fault' detection and similar are not suitable for a whole property for various reasons. They are sold as a partial solution to EVSE installations outside, and that is all they are intended for.
Will cover these in a future video.
Hi John Ward just wanted to say thank for your Demonstration of Diverted Neutral Current 10 / 10 As Commented already 3 phase & Neutral Worse Going back to me O-pen Device unfortunately there’s no place to Go cause ist thing it says BS7671 / Guidance note 7 plus escqr BS7909 the earthing of Pme TN-C-S not to be used to Supply Equipment out doors due touch potential plus likely hood of Open Pen Conductor especially where it is impossible to convert too TT System on hard standing Grd ( it’s not a park soil or Green ) installation has full earth leakage protection including time delay type A plus 30MA front end Rcbos . My only concern would be to Derate the o-Pen Device for touch Voltage 70 Volts to Dry location 50 Volts to 25 volts for wett location .
Although as you Quote note Designed for whole installations .
As per wonderful escQr plus 1989 electricity at work Regs BS7671 it’s an Engineering Judgement 🤔 Can’t See me using an Safely isolating transformer Not Practical
@@jwflame Thank you very much @jwflame for the reply, I thought that there must be a reason that this would not be suitable, I look forward to the video covering this issue.
You really are teaching many people how things work and showing why we need to do the things we do. It is all very well knowing the correct way to do things but the reasons why is the really interesting bit.
The subject of touch voltages is the area I find most interesting but also the most difficult to wrap my head around. How touch voltages are limited to less than 50V and if this is always feasible in most installations. How touch voltages are calculated in the event of a fault, etc really is an area that I believe many electricians would struggle with (or perhaps just me)! I would be hugely grateful if in the future maybe this a subject that you could touch upon, but then again I am sure you have a long list of future videos that you have planned.
Many thanks again, it is much appreciated.
Excellent demo. Did you install resistors into the water/gas path pipework to create those different currents?
No, that's purely due to the different lengths of wire and the difference in resistance between the wires and the copper pipes.
Lovely John. The issue is serious, I think personally all new homes should have the earth electrode being connected with the MET of the TN-C-S as stated a recommendation in BS7671 to help this cause. So many electrical contractors are unaware of the above.
An earth electrode is like taking aspirin on toothache. It does not to that much,
It has to be said JW that is a very very impressive test rig you have constructed there!! Hopefully that is a copper water pipe cut off there not a Gas pipe though?
Fantastic demonstration, love your videos.
Thank you very much for an interesting demonstration! Great explanation.
Is John alright? No content for 6 months.
@mikenco
Yes, I'm rather concerned about John too. But I must say, that his method of teaching is a bit arrogant and humourless, it would be nice if he could crack his stone face with a smile. But that's sadly, just John.
That being said, we do all hope that he is well, and getting on well with life.
Concerned for John......
😐😐😐😐😐😐😐
10 months now since last upload.
@@ninaevans4501 I love his dry style and miss his dulcet tones. I do hope he's alright.
@@2Sorts He's posted on Twitter in the last couple of months. My guess is he's just changed tack and gone off to do other things.
@@ninaevans4501 I emailed John. Rest assured, he's simply busy with paying projects! He says he'll be creating new vids soon.
Very well explained thank-you. So my question is why not have your own earth rod and bond that to your earth/neutral for extra safety?
That is what most countries do. In the UK no one bothers because such things were optional and not required.
@@jwflamethanks John for excellent demonstration...
Does Rcbo which is required by code force you to solve broken neutral?
@@RajiveeeRCBOs / RCDs do not detect a broken neutral.
Still have my main earth rod from TT days. Left connected as I don't trust the PME I have now. Plastic incoming gas and water. Question: Can disconnecting a main bond in my property where next door has a broken PEN lead to them getting shocks? (assuming metallic services) Seems so. Even with non metallic services they may get a tingle ( and kit not working). Seen the 3 phase scenario( overhead supply and storm damage). Seen the mixture of TNC-S and TN-S in a steel frame building as well. ( not permitted). Even if you think you have TN-S, it may be TN-C-S- up the street somewhere. !!! Great video.
Excellent presentation, my “I’ve learned something” for today. Thank you for your time and considerable effort into putting this together.
Another brilliant eye opening video explaining a pretty complicated and possibly lethal situation, which will in fact be common throughout the UK. I would suggest most electricians will not know too much about.
This video should be shown to anybody who works on domestic electrics, and crucially Gas and Water pipes. There must be several fatalities stemming from this diverted current situation.
The most worrying thing its dangerous almost by design. TNCS is a pretty poor arrangement really considering the parallel paths through connected and bonded pipework in the streets.
Should we reconsider the our Bonding practices or install plastic pipework as it enters the property as standard?
Great video John. Surely this just goes to show that PME systems are shit and supplied because its cheaper. Also reason why its not allowed i believe to supply petrol stations.
Lovely setup for teaching. I was wondering if todays smart meters do any current imbalance tests between the live and neutral cables coming in (ie, more current in the neural than live) ?
They do not, and that wouldn't detect a broken CNE conductor even if they did.
We could say that electrical testing should now take place each year to confirm a healthy PME system, similar to a gas boiler check. A basic check on the integrity of the DNO supply that should be mandatory.
Round of applause! Much appreciated
Brilliant video as always, cheers John
Great video, and I can only imagine how complex it gets. Two questions though...1) If Property A looses it's combined earth and neutral, and also has the power off at the main breaker, wouldn't the whole CPC in Property A now be live? 2) Given those copper pipes go through the ground, wouldn't some or all the current flow naturally to earth rather than feeding back to the property with faulty neutral?