Earth Electrodes Part 1
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- Опубликовано: 4 июн 2024
- Earth electrodes - earth rods, couplers, covers, other types of electrodes, step potential, dangers with farm animals.
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In the event of a ground fault where you know or suspect the ground to be energised (downed power line etc) live earth, they actually teach you to shuffle your feet keeping them close together as to not create a high potential difference between one foot and the other
We're taught to jump out of the cabin of hooked up equipment (eg crane hitting overhead) with both feet together too, then shuffling away. I think this is only preferred if a fire breaks out and you need to get away. Luckily I'd never encounter this as I'd likely lose balance and place my hands on the ground too, defeating the purpose ;)
@@darkstar_448 lol
Presumably if you jump along the ground (but always keep both feet together) it would work the same as shuffling but allow you to move a bit quicker?
@@Berkeloid0I can see how your thinking and your right as in that jumping would be faster but the reason this is not a suggested method is I suspect that jumping would really increase the chance of falling, and if you were to fall then you would be in a much more dangerous situation.......
@@Berkeloid0
Top marks for the cow illustration :).
A baked bean on legs? They have feelings too ;)
You should start a new season on animals as conductors.
You mean "the creature"? :)
Had a nice example of the effect of current flowing through the ground many years ago during a thunderstorm. My BiL and I were sheltering from a thunderstorm sitting next to each other under an awning pitched on thin soil over chalk. We were both on metal chairs but he had is hand on another one and got a real jolt when lightning stuck the ground ten yards or so away. I felt nothing.
Graham Langley wow amazing story thanks for sharing
That may be,but that is a lot more voltage than the max we use.400 volt wont get to far through the ground.Ground at a certan depht has a big resistance.And what about the earthleakswitch??That would be tripped in a instant.So really, i find this a bit obsolete.Of course you gotta have a groundpin,but that whole story about the voltage a meter away today is obsolete.
Very interesting JW, looking forward to the next installment. 👍
Excellent subject thanks for posting!
Great stuff JW. Your lectures are very informative and much appreciated. Thank you!
It's useful to know that there are attachments available for SDS drills which can be used to drive earth rods into the ground and those can be more effective than using a hammer.
im glad you did this , there are a LOT of videos of electricians putting rods in but they dont seem to have calculated how many they need they seem to think one is enough when it may well not be
some older sparks will remember the problems we had with overlaping step potentials when rods were commonly used on properties in conjunction with voltage operated elcbs .one set of regs calls it sympathy tripping a house with a fault 3 doors down would trip the one 3 doors up but it was a step forward to electrical safety , interesting video john thanks
As always hats of to you my friend.
Being British, I prefer British terminology to Merkin terminology. Even so, I've just realized the Merkin terminology is future-proofed. When Muskie gets to Mars he just needs a grounding rod. When us Brits get to Mars we'll be unable to decide whether to rewrite all the books and re-label all the equipment so we have Mars rods or if we continue to call them earth rods on Mars, leading to great confusion.
Various online dictionaries define 'Ground' as the surface of the Earth.
If we decided to colonise Mars, should we run a bonding cable from the home planet to avoid this type of confusion?
Hi John work as an electrician in Ireland we use a galvanised earth box about 6" square with lid and 20 mm entery hole..Very robust. Thanks for all your knowledge.
It would be great if you could produce a video on installation of domestic underground mains cables to a shed or outdoor lighting - relevant, regulations, safety issues, etc. I am sure many would be interested.
A very good explanation. Thank you.
Interesting video John. I'd never thought about the potential danger of the energized earth around the electrode during fault conditions.
In Phoenix my house has an UFER where the slab of the garage is actually the grounding system. In my opinion it's just about useless from what I can tell. It's soo dry out here that I don't think the concrete has any moisture to be found. People say they work, however I had to add grounding robs in addition as I had way too much RFI on the ground, mostly from a local AM station.
Classic JW. Solid information. What your new Megger 1741 like for testing earth rods?
🙋♂️ Hi john, new to rods but will you be covering readings such as zs & how they effect disconnection times given in bs7671? Thanks 👍
Hi John. Great video not sure about your drawing of sheep/cow. Good speaking to you at this year's Elex 2019 show. Looking forward to next part video. Tim
Next episode... *Hammer time!*
Remembering a tom Nagy vid of installing a rod into the pavement outside a house. Do not recall if he put a little sticker with his name on it.
Hi John,
Thanks very much for the video.
Just to clarify,
If you installed a one metre long earth rod within say 300mm of another one metre earth rod in series both lugged together using a 16mm earthing conductor.
1) Would this not be of any benefit to the overall resistance value unless the conductor was as you said 2 meters apart?
2) Would this cause any problems?
Thanks
Never really give much thought to these until the grounding fails. Had that happen and also had the remaining ground wiring in the house become live with mains AC. Needless to say found out pretty quick there was an issue when metal knobs and enclosures would arc to your fingers when you touch them.
Lively topic and a relevant one as regards safety for everyone.
Fantastic stuff JW, love it, I'm sure a lot of electricians need Earth rods/Electrodes de-mystifying. Thanks for your hard work explaining this stuff. I never took into account potential difference between livestock's front and rear feet..lol..opened my eyes for sure. :-) looking forward to EP:2
Yeah you've got to be super careful with earthing milking parlours - even if you don't flat out electrocute them, the cows can get a slight electric tingle through their feet (they don't have hard hooves or anything) they'll find it unpleasant which makes them reluctant to go and get milked.
hello John. can you do an earth rod installation video that would be used for an high end hifi system.i have a good set up,but cant find any vids on how to earth the system correctly. i have 2 x mono amps , pre amp ,dac , streamer, hiend dvd player ,11 channel receiver ,with a 11.4.2 speaker system. where and what do i earth,and where to on the back of the machines.i cant see any earth screws /clamps to wire to. thanks
Hmmm hat can I say?! “Brilliant video” once again. Thank you for sharing your knowledge: educating us new sparks! May I kindly request a video on selecting various devices and cables for a particular installation etc, using BS7671? Thank you
Lincoln
Hi, can you talk about temporary earthing with generators?
It would be interesting to discuss the advantage of installing an earth electrode on pme systems. Some supply authorities will not give a pme connection in a basement location unless an earthed mesh is installed under the floor.
Thats because the mesh will provide less resistance and a better earth. Covering their own arses.
muzikman2008 You’ve got that wrong. The reason for the mesh is not to improve the earthing: it is because a pme (combined neutral/earth) can float a few volts above true earth potential. Installing a mesh connected to the pme means there can be no potential difference between the basement floor and the pme neutral/earth. This is also the reason why pme earths are not permitted in buildings without equipotential bonding.
@@johnschlesinger2009 and how is that achieved? Through lower resistance by the mesh grounding the floating voltages from the pme?
@@muzikman2008 The mesh is connected to the pme terminal. Therefore the mesh will be at the same potential as the pme: equipotential bonding.
Thank you very much for a very good vlog.
Thanks John
Do I need one of these to my shed ? I have armored cable connected to the house earth and the sheds fuse box
The ground cable for my house appears to be bare galvanized steel, about 5mm in diameter, leading into the soil right next to my foundation directly below my meter.
Our earth rod (whatever it's made of) sticks up above ground a couple of inches. It seems to be for the telephone though - not connected to elec. supply !
Here, where I live, it is mandatory to connect the supply cable neutral conductor to PEN rail or to use a 5-wire supply cable and the PE and N conductors are both connected to transformers N connector. The grounding electrode is just a backup.
@@mikeZL3XD7029 Yes, we have 3-phase in every building.
Thank you
Hi John (and all who read this). I remember approx 4yrs ago that a dog in Greenock/Gourock that died after lifting it's leg at lit bollard to pee died (I was a wheel known Company that had been installing the earth rod, probably road navvi, not spark that carried out the wiring, hence the poor dog suffered
Oh my god, you remembered me the concept of step voltage, nice. Is there any tutorial book about these topics, I mean something that covers BS7671 chapters. As you know 7671 is good as a source but not tutorial like your videos. Someone recommended me " Safety of Electrical Installations Up to 1000 Volts " by Wilhelm Rudolph that I couldn't find. Is there any good book in the market?
Great looking creature.
i watched the power company install a pole transformer once. they power-hammered 3 9 foot lengths of ground rod in all joined together, i guess they REALLY wanted that thing grounded! lol
Getting down to the water table ?
@@mikeZL3XD7029 With a small image of JW waving what could easily be taken as a snooker cue, I've now only got Judd Trump in my mind ;)
Good video as usual - is it required by the regs to protect the Earthing cable connected to the rod with conduit or Coppex?
Depends on the size of the cable.
@@jwflame Thanks - maybe you could expand a little on this in part 2?
Earth electrodes cause more discussions at work than any other subject, street lighting by the way. Once you have completed all these parts I’m going to suggest my colleagues watch them so they understand why they are used and where they should be placed. Thank you for the insight. Have you any plans to make a video showing the 3 wire and 4 wire method of testing these please?
Hi John - Amateur radio operator here, much confusion about earthing radio gear - I have a PME/TN-CS system at my house, RF energy on mis-matched antennas can come back and haunt you with un-earther radio gear (mostly all antennas are a compromise and standing waves on the feed lines come back to the radio depending how good or bad the SWR at the antenna is), I can either earth to bonded pipes or use a ground rod - what is best? Closest ground rod would be 10 feet away, closest bonded pipe would be 5 feet away - I appreciate any faults in neighbours houses could potentially effect me with bonded pipes - and a cut or failed power cable in the street could effect me with a ground rod, and no earth at all can cause RF energy burns, never had one but plenty of Ham's have... Too long an earth wire could radiate RF energy and cause EMC problems on TV's n such, currently, only my power supply to the radio is earthed via the plug earth, which I assume is the same as earthing to bonded pipes? - what would you do?
Will you be covering electrodes for generators? , cheers
@@mikeZL3XD7029 mainly the ones used on work site offices and and canteens, seems to be a lot of confusion on how to earth them.
Where do you get your earth rods from? I like the parts you have got much better quality than what my wholesaler gives me.
Screwfix £11
Get the 5/8 inch ones - the 3/8 are thinner, unthreaded and generally useless.
John Ward thanks 😊
Most electricians use conduit boxes to cover/protect earth rods.
£30 for an upside down bucket seems extreme ;-) lol
This is the one i use ,looks fantastic www.ebay.co.uk/itm/Lightweight-Earth-Inspection-Pit-Furse-Electrical-Plastic-Inspection-Pit-And-Lid/123901088205?hash=item1cd91491cd:g:hE8AAOSwB2hddSbj
in Australia they dont :) slam them into the ground leaving typically 8 or so inches exposed, typically hard up agaisnt the brickwork tho right below teh board
Great video about electrical earthing. Is a good idea to put dielectric grease on the threads to prevent wear with screw / unscrew manouvers ? waiting to see the install
Threads in general? Dielectric grease wont prevent thread galling and wear. You need to use anti-seize grease for that, or a specialized conductive anti-seize grease if the connection has to pass current directly. Dielectric grease is mainly used to electrically insulate and seal connections. As for the ground rod, once its in there you wont mess with it again until its rotted away and you have to sink a new one from my experience, so I doubt it would be an issue.
@@mysock351C Thanks for the very good reply. I meant conductive threads to prevent wear of the copper layer , but since you've clarified on the rod this now goes to general use in conductive threads. There are some multimeters that have grease on the rotary switch contacts , eg fluke 17b+, is also dieletric grease, since it was the original source of the initial idea
Hello John,
Which one is the best earth rod to buy please.
Please advise me.
Thank you.
Best wishes from Leicester ENGLAND
Depends on the soil conditions, and rods may not be suitable in all locations.
However if rods are to be used, they should be the type with threaded ends and connectors so that they can be driven deeper, and a large diameter, as the surface area is the main thing which affects the resistance.
The unthreaded small diameter ones should be avoided.
Reg 542.2.8. Are the screw connectors sufficient when joining electrodes or that has changed now in the 18th?
'other suitable mechanical connectors' will cover screwed joints.
if you install multiple rods, the copper wire connecting the main supply and all rods needs to be continuous? or can we lug each end of the cables (16mm of course)?
The rods need to be connected together, but no requirement for that to be a single continuous wire.
The cheaper rods do not have threads so you cannot join rods together, are these any good?
Well, actually you can, there are non threaded, pressure fit brass sleeves for those ones. Although not every warehouse may have them or even know about them...
I do wonder about the efficacy of the ground rod at my home in Australia... House slab on rock and the ground rod sticking out 350-mm and exposed. Should like to test it given your explanations on grounding rods John. Your previous video on testing ground earthing systems has helped my amateur needs for understanding too. Thanks for the info mate! Interesting too about the potential difference over the length of a cow. :-) Shouldn't worry the narrow gaited kangaroos then too much. They are commonly hanging around the house at night feeding on the grass.
When a fault occurs the current wants to take the path of least resistance back to the source (substation) to complete the circuit. In Australia, your earth rod will be directly connected back out to the substation via the low voltage neutral which is a very low resistance path. The substation itself will have an earth grid connected to the LV neutral as well. The rod at the meter board is really only a fail safe that will assist if the neutral connection between the substation and your house is damaged or broken-it helps make sure there is always a path back that can be used instead of just through your body. However in an urban area with many houses, all the house electrodes are interconnected and make a very low resistance path back to the substation. The multiple paths here help reduce the current flow through one particular electrode.
@@darkstar_448 z
So, presumably, if you had a yard or a caravan site, it would be best to use multiple earth rods and not just rely on the CPC earth wire in the armoured feeds to hook up boxes from the source.?
What if my neighbour's earth rod goes live and mine is 40V dissipation away, will the metal housing of my kettle and toaster go live?
I assume it's probably the same in the UK, but in the US, when installing a grounding system, you're supposed to do a soil resistance test to determine how many ground electrodes are needed. I don't know the specifics, as I'm a general maintenance person as opposed to an electrician, and things like ground electrodes are way out of my scope, so if I find or suspect there's a problem with the grounding system, I'll call out an electrician to sort it out (unless it's something obvious like a disconnected ground wire between the circuit breaker box and the ground electrode(s) but I do know that this sort of testing is supposed to be done. Also, at least with regards to residential and light commercial buildings, we don't put any sort of cover over the ground rod. It gets driven into the ground several inches below the surface, and the ground wire is run underground to it and clamped to the rod. Usually, in the case of a house with a block foundation that extends a couple feet above grade, the ground wire will come out of the house, run straight down the exposed portion of the foundation (secured to it by clamps screwed into the masonry) until it's underground as far down as the top of the ground electrode, then it runs straight to the electrode. That exposed section of ground wire is typically then used by telephone and cable television companies to attach their equipment grounds, as well. Sometimes by idiot installers (cable installers are notorious for this, usually the telephone company people have functioning brains) who remove one or more of the clamps to pull the wire away from the foundation so they can attach their ground lead easier. But I digress...
Testing the ground with dedicated test equipment is by the book but for some electricians it's a case of driving as many as needed till the earth fault loop impedance is low enough that touch voltage is lower than 50v during a fault. But I'm not an expert in it
there we go: in australia they are quite happy letting the earth rod sticking out over the surface.
It was the same here, years ago. Nobody had heard of Health & Safety regulations.
@@RWBHere
we have health and safety regulations. no worries about that.
How does the resistance of the earth connection vary depending on moisture content of the surrounding soil? For example during drought conditions when there is no rain for several months.
It's pretty subjective, but depending on the soil and rock anything from a few ohms to a few hundred ohms per meter.
You're right. Dry soil will conduct more poorly. You can improve ground conductance by pouring epson salt mixed in water into a hole around the rod. One power company study found that improved the conductivity three fold.
That’s a lot better quality rod than I have ever been supplied from the wholesalers
£6 from Screwfix.
The voltage differences around the rod is called the voltage gradient.
On one of our sites the electrical engineers deemed that the site location for the earth grounding spike needed to have a special "earthing pit" dug. I was not there when they did the work and I did not get a chance to see what it entailed. Perhaps you could go through this at some point? It has intrigued me ever since.
Probably done to fill the area around the electrode with a conductive material such as marconite or a conductive concrete.
@@jwflame Interesting, thanks for the reply.
With a TT system when the rod goes in the ground and takes a fault how does it get back around to the transformer if the rod ends in the ground is it absorbed by the mud ?
Current flows through the ground back to the transformer.
@@jwflame Thanks John makes sense just passed my 18th wiring regulations, I wanna learn lots and your videos helped me, when I did my AM2 the s plan boiler video was great help great understanding
Wow I bet they are hard work to hammer into the ground. Id hate to get the rod 3/4 of the way in to the ground and then hit an impasible rock.
I can't wait to see it installed though :) Something we don't get to do in college.
Planet Conker .... hack saw 🙈
A few tips, check for underground pipes (gas, water), pre drill the hole with a 450mm long 10mm bit. If the thing gets stuck find a bigger hammer!
Can MS steel rod be used as electrode?
Yes, but it's likely to corrode fairly quickly, so won't last long.
Fancy! We don’t have any threads! We also don’t cover them here in the US
why is TT still used? surely the supply could be configured to TN-C-S. is there a reason this isnt done?
TN-C-S isn't suitable for use in all situations.
@@jwflame Wow the man himself. Thanks for the reply.
When wouldn't it be suitable? I'm still learning, not qualified just yet.
Situations such as swimming pools, hot tubs, caravan sites, and some other outside installations like electric vehicle chargers. May not be desirable in others such as remote buildings which have metal framing, or metal water pipes.
Why cant we put the 2 rods near one another. arent we trying to increase the surface area to make the connection to earth better? Why should we care about the voltage shells overlaping?
I like to use a Thor copper-headed hammer to drive the rods into the ground. You can hit it as hard as you like with no risk of burring up the thread on the rod.
can aluminum be used?
It would work, although it's very likely to corrode away to nothing in a short time.
Hello, I'm not sure your definition of "step potential" is quite on the money: I understand it to mean the electric potential possible between two limbs - feet! - whilst taking a step on the ground affected by the potential gradient.
Read the regs, his definition is spot on.
@@daverhodes382 oh, that's reassuring! Can you help me with a reference?
@@daverhodes382 IEEE std 80 defines it as, "The difference in surface potential experienced by a person bridging a distance of 1 m
with the feet without contacting any grounded object." Do you have an alternative reference for "the regs"?
@@obd6HsN I agree with you here too, but similar concept to what was explained. It's generally step and touch potential that is assessed which is based on the current flow between two feet (step potential) or hand and foot (touch potential). The reason for these two is that they are most likely scenarios for a human to become part of a faulted circuit. I think it's in IEC 60479 where the resistance of a human body is defined based on the way they are hooked up which is then factored into the equivalent faulted circuit to determine current through them and hence chance of fibrillation. The assessment for touch potential is generally more strict as current flow through hand and foot has a much higher chance of flowing directly through the heart.
Not an electrician but when you say the top of the electrode should not be accessible... if there is a fault resulting in current to earth then everything grounded in the house would potentially be at 230V in which case an animal sniffing the top of an earth electrode would be the least of my worries. Am I missing something?
Great video from a remote house on a TT system ;-)
If you are inside, everything connected to the electrical installation should be at the same voltage, which is why protective bonding is installed. If standing on the ground outside there will be a substantial voltage difference between the electrode and everything else.
I've only heard about farm animals getting shocked in this way from lightening strikes to the ground.
It’s not like the electrical faults occur daily
There was an incident in 2011 where two racehorses were electrocuted in the parade ring at Newbury due to an underground cable fault under it.
I've seen grounding rods at the store, but never needed to install one. The ones I've seen here in the US are 8 or 10 feet long, so you don't screw them together. My house is grounded by the wires being attached to the incoming copper water supply pipe.
Using water pipes for the earth hasn't been permitted in the UK since 1966.
@@jwflame Interesting. My house was built in 1998, properly inspected and all. Seems like the UK and Europe have better safety standards than us generally though.
@@Cadwaladr I would doubt a house since 1980 has a significant amount of buried water piping that is metal. On the other any metal piping (water or otherwise) that could become energized by an electrical fault has to be bonded to the safety ground system, the low impedance wiring that will trip the breaker if it becomes live via a fault.
Is there a problem if a TN&C system also has an earth electrode?
No, it's probably beneficial if there is one (or some).
@@jwflame but what happens, say, if the incoming neutral supply, (overhead in my case) should somehow be cut. Wouldn't this mean that the return would go through the earth wire to ground?
Do typical TV antennas found on house roofs need an earth?
I have heard of TVs “leaking” AC into coax connections. The TV antenna sockets in our home sometimes give a nasty sting.
Not for a single dwelling. Communal systems that supply multiple dwellings usually do.
@@jwflame The CAI recommends bonding aerial distribution system if the number of items connected to it is seven or above, due to the cumulative permitted leakage currents, AKA touch currents, of double insulated devices likely to be connected to it. Here's a link to an article on this: www.aerialsandtv.com/earthbonding.pdf
@@Graham_Langley Thanks for that. I live in a block of flats with a distributed aerial system and have had a bit of a zing off the aerial socket in the past. Now I know why... Someone's in for a Bo**ocking!
Graham Langley This could explain a lot
@@CoolJosh3k I've got a TV distribution system here using an 8-way Global Loftbox, which has a chunky earthing post on it. ATM it's bonded to the adjacent mains socket which is probably good enough as the wiring is in good order, but it's on the list to run a bond down to the main earth block before I close up access to the wiring run.
5:45 why would a person get electrocuted in this scenario when we understand that at any moment in time the electrical potential of the surrounding ground and the electric potential of the earth electrode are essentially the same?
As an aside I could; not think of who Mr. Ward's speech pattern reminded me of. then it came Angus Deacon
...standard Earth rod resistance < 5 ohm..safest Earth system is probably a TT totally isolating Neutral & Live in residentials ..
also used as lightning rod end point ?
Really the purpose of a lightning rod is to drain the building electric field above and prevent a strike, so they're usually pretty specialized. You don't want to actually attract the lightning, but help prevent it. The sharp point on a lightning rod initiates corona discharge, and theoretically prevents a strike by lowering the electric field in the sky above, so you do need to tie into a robust earth ground to ensure the charge can safely drain away. If the rod does get hit, its kind of iffy as to whether the lighting rod and earth grounding will actually provide protection. The local church had its steeple hit by lightning and even with something like 000 AWG copper braiding to ground the rod it still blew the steeple to smithereens (made one helluva bang, too). Right afterwards all I could see was just fiberglass, wood, and bits of copper wire everywhere. Same thing with my old mans office. Nuked the lighting rod and all the ground wiring, and took out a bunch of computers and the clock tower. Theres so much voltage and current its difficult to actually conduct it away.
@@kirkhamandy Sharp points do allow charge to be dissipated. This can be demonstrated in the lab, and airplanes use this quite effectively to drain charge away from the airframe. Have a look next time you fly and you will see lots of sharp needle-shaped electrodes coming off the trailing edge of the winglets and wings of most planes. The actual mechanism I described is not a myth. Its efficacity is hard to demonstrate, however, since its hard to say how changing the local e-field would impact the path of a stepped leader as its on its way down. Some have made specialized installations that have shown that they can drain sizable amounts of current during a storm with an array of sharp electrodes.
@@kirkhamandy Now as for their effectiveness, I can say from experience from seeing strikes and the aftermath on various buildings that unless its a skyscraper with a metal girder construction they are not that effective. The lightning simply blows apart the ground strapping, even if its 3/O or 4/O gauge. A single wire just doesn't seem to cut it. Even seen it blow apart a copper water main at my office. Youd think a big copper pipe would handle it, but a bolt cruising past my window proves otherwise. Blew a giant hole in it. The installations that do seem to work are ones for towers with multiple leads to conduct the strike away. Obviously having one is better than nothing, but its not a guaranteed solution. Maybe the NEC, NFPA, and local regulations today are better, but back then it did not seem adequate to contain a strike.
@@kirkhamandy The spikes on the airframe are also to dissipate static that inevitably builds up from flight since the plane is moving through very dry air combined with particles of ice, dust, etc. Most of the lightning protection is in the copper around the wire looms and mesh in the composite wings as you probably know, but that's an aside. I have seen ones that work. These had multiple guy wires (i.e. towers) that provide a more effective means to conduct the strike without incident, but the strikes that I did see or the aftermath of in buildings Ive worked in did damage to the lighting rod installation and burned out some electronics and so forth. The church was the most extreme, with the ground strapping blown to pieces, and what was left was quite blued, indicating it got quite hot. This was also during a period of exceptional activity so there were more strikes to see, so it could be down to odds. Although oddly enough the AM tower behind me outside my window that's owned by CBS never gets struck (or at least very rarely). I've tried during storms to capture or at least witness it, but whatever they have, the lightning just doesn't seem to hit it, which is surprising given its the tallest thing in town and its made entirely of steel. But that aside the one take home is if I ever have a need to install one, I would go considerably over code to make sure it works as intended and can convey a strike if it does get hit.
@@kirkhamandy Also I think there is some merit to the possibility that dissipating the fields above might have a beneficial effect, and in documentation they freely admit that sharp points are not as effective at capturing a lightning strike (i.e. lower average number of strikes). Also seeing as how the tower behind me seemingly goes without being struck (I've seen the field around it be hit, but not the tower). Since local charge is being dissipated, there is some potential for an effect, but I have not seen any real good studies showing it does or doesn't work. Only that opinions change. My suspicion is that it probably does locally have an effect on the path of the streamer/stepped leader, but could potentially cause the lightning stroke to bypass the rod installation and hit the structure below. Obviously the lightning propagates by the initial breakdown of the air, which is driven by the field gradients as well as the charged particles that are accelerated once the air ionizes. Impacting the fields around a structure would (or at least should) have an impact on how and where the lightning ultimately ends up striking. I can say that lightning LOVES utility poles and wires, since I've seen multiple strikes, even outside of my grandparents house that had lightning rods. Skipped the rod, and chose the service entrance below. So the properties of structures do impact how it behaves locally. I think static dissipative arrays and the like do have an effect, but so far all there really is is anecdotal evidence of "we installed it on a high risk structure, but it still got struck afterwards" sort of thing. It would be nice to know that if it doesn't work despite being able to move large amounts of charge locally, why it doesn't work. E.g. the effect is too local to impact the final ionization path before the stroke sort of thing.
Local rules dominate this topic. In my jurisdiction, 2 - 8' rods spaced 10' apart are mandatory. The tops cannot be concealed in any way and must be above grade by 2". Only clamps with bolts penetrating the cladding are permitted. No threads or extensions are allowed. Check your local rules. I've never seen the methods of this video used in the states.
👍👍👍
Hi John, great vid as usual. But £20-£30 for a square, plastic bucket ?!?!?
About right - just google "earth inspection pit"
@@mra813 or search 'square plastic buckets' on ebay. I know, it wont be up to some BS standard. LOL.
Why wouldn’t the RCD trip?
This video doesn't mention RCDs - is your question about another one?
The RCD would trip, that’s why it’s essential that they are installed on TT systems as the mechanical MCB would not have enough fault current to trip, whereas the RCD can have a maximum of 1667 ohms to trip under earth fault conditions
I didn't get the point of it all - so what is the clue here?
Like the video as normal
I'm not convinced by your reason for installing electrodes some distance apart. The purpose of the electrode(s) is produce a relatively low-resistance path to earth, and that's mostly about contact area with the ground particles. Two rods close together gives you the same contact area as two widely-spaced rods. So it should give you the same earth resistance. Yes you'll change the shape of the surrounding voltage field, but not the potential, nor the distance-decay value, so I don't see what you gain. It doesn't matter that they are in each other's fields - they just amount to a more complicated-shaped electrode (like the mesh you mentioned). If each element of an electrode had to be widely spaced for electrical reasons then it would make sense to separate the components of a mesh and spread them out.
Perhaps I am missing something here, but I don't think so.
If the argument that “you don’t want the rods close together because they’ll be ineffective” why then would a mesh be used? Seems to me that a mesh is functionally identical to several earth rods in close proximity.
Hi Jw they used to use solid copper rods
Where corrosion from stray current is potentially present (such as installation near an electrified railway), they will still use them. Does cost a lot more though.
@@darkstar_448 yeah should imagine stray current and moist soil would remove the plating then make short work of eating a steel bar lol I would imagine it would be even worse on DC (electrolysis oxidation wise)
You can bang them thru the ground and other services with an sds adapter.
This is what I do - the SDS drill is of course on the "hammer only" setting.
Bosch do an adapter, £17 well spent!
Interesting. I have never seen a threaded ground rod. The ones here in the US are smooth and our clamps are crap. That threaded clamp would actually stay on the rod. Ours are a two piece clamp on arrangement which are prone to coming apart when a weedeater whacks the wire and yanks it out. I have never heard of or seen a box for a ground rod either. They don't exist here. Here a ufer ground is the preferred method but when a ground rod is used it is 8' long and driven below ground surface then the wire is clamped on and buried. Unfortunately many rods were not driven deep enough and left above grade and the clamp falls apart from damage. There are also requirements for two rods in some cases as well. Our rods are copper clad like yours or galvanized is also available. There was a time when houses had solid copper rods but that is rare window between when houses were not grounded (earthed) and when copper prices started to rise. Ufer is preferred as pounding an 8' rod into rock and clay is not easy even with a ground rod driver attachment.
Lol ground rod driver attachment...an apprentice in American
Any clamp coming off from weed whacker wasn't right in the first place but I hear you on the not driven or installed correctly. Hacks everywhere
@@Bereft777 Here in the US we have a tool that slides on the end of the ground rod and has an SDS plus end so you can drive it in with a hammer drill. I do commercial and we always have ufer grounds. The only ground rods driven today are for trailers and for remodel work on older houses and out buildings. Very few used in new construction now.
@@Bereft777 The clamps we have here in the US are garbage. Even the expensive bronze ones are very chinsy compared to that threaded one. I wish we used those here.
Great to know the differences between how things are done in other countries thanks for sharing
John, Please let me know if I'm correct. Connecting an electrical system to a ground rod in your country is connecting 240 volts to the earth ALL of the time, not just in fault situation. Another comment, this step voltage is exactly why metal light poles should have earth ground conductor from the consumer unit and not a ground rod connected to it. I hope I got your terminology correct being from across the pond. Respectfully, Kevin
Hi Kevin
I the UK we have a three wire system no that dissimilar to your arrangement in the US apart from the fact that we normally have larger but fewer substations and the neutral is bonded to a very good earth mesh / rod at that point. We also use the cable armour or metallic sheath (on older cables) bonded to the earth and we also have what we call an equipotential bond that must be connected to any other services such as gas or water. If the building has metal sidings or is steel framed that is also bonded.
The primary difference between a UK and US install (aside from the split 110v lines with a centre tapped neutral) is that in a UK installation the neutral is treated as if it were a live or (hot) conductor. Unlike in the US the neutral and earth conductor are not bonded together at the consumer unit. They are separate until they reach the substation. We do have several kinds of earthing arrangements in the UK.
The only time an earth rod would be live is when it is conducting fault current away, this would only be for a very short period as all installations that meet code will have the circuits protected by an RCD device (GFCI in the US) and fault current flowing to earth would also be interrupted by the devices fuse if it was a faulty appliance, the circuits breaker or fuse and in the worst case scenario the (final / company / DNO) fuse that is before the meter. I may be biased but I personally think we have the best electrical distribution and wiring system in the world.... :)
I recommend you watch the series that John made regarding earth operation as it will give you far more information on earthing types ect.
I hope that is of some help to you.
Stuartbe Thanks for your comment! In US neutral and earth are bonded at the consumer unit(panelboard) same as there. I do not believe that your electrical systems are better or worse than here. As long as they are safe, I'm usually happy. I do consider your "IEC" standards as inferior to NEMA standards. Another thing, the mesh and rod used for earthing have nothing to do with 240 volt line conductor to earth(equipment ground) faults. These faults go through the bond to neutral at Consumer Unit and out to the transformer then come back and trip the RCD. Respectfully, Kevin
@@KevinCoop1 Thanks Kevin
I think we got some (wires crossed) Excuse the pun. I meant to say that the earth and neutral are not bonded at the consumer unit. With a standard earthing system the neutral has nothing to do with the earth until the bonding point at the substation. It is at that substation that a very low impedance ground is installed. Only very old installations have a seperate earth rod, not only are they rare but they are subject to very strict testing.
The neutral only caries fault current (with the live) in a live to neutral fault event. The earth will only ever carry fault current if an appliance fails or a live wire makes contact with an earthed back box, cable damage is done or a device is badly wired ect.
Rather than having an 11KV to single split wound transformers one large oil cooled transformer is normally used that has 3 separate phases 120 degrees apart. It was the case before the lovely EU (NOT) stuck there nose in that we used the phase colours Red, Yellow and Blue. When wiring a street the idea was that the Red phase and a neutral fed the first home. The next home would be on yellow and the third blue. Each supply is a 2 conductor cable and sometimes earth on its own conductor (or outside sheath) . So 2 conductors, phase and neutral fed each house. The idea was to balance the phases over a street. It is very rare for a domestic premises to have more than a single phase feed.
You stated in your first post the following "Connecting an electrical system to a ground rod in your country is connecting 240 volts to the earth ALL of the time, not just in fault situation." and this is not how it is done. If I am not mistaken (unless it has changed) your earth and neutral conductors are connected together at the distribution board. On a UK distribution or consumer unit as we call them there are normally two separate neutral bars to serve the two sets of breakers that each have an RCD. The earth conductor bar has no contact with neutral at all until the feed reaches the substation.
The reason I believe the UK system is better is that all circuits no matter what they feed are protected by a group RCD or GFCI. From what I have seen it appears that only outside plugs and garage sockets have GFCI outputs. The UK system has global RCD / GFCI protection. We also have safety covers that stop anything being pushed into the live or neutral, It is impossible to keep your fingers around the plug and make contact with the pins. The earth is also the first one to make a connection so there is very little chance of a chassis becoming live if there is a wiring fault.
With regards to NEMA and IEC I don't think the US military agree. I am ex Royal Navy submariner and I have worked on some engineering tasks in collaboration with some of the US navy engineers and the American electrical engineers designed the electrical systems using our standards. I do however happily admit that the NEMA standard external electrical external sockets are far better than the UK appropriately rated IP sockets.
It may well be unfounded but I just cannot bring myself to trust the US screw on wire nuts. Something about them makes me feel uncomfortable.
I hope we have sorted that out and please do not launch any ICBM's in my direction...... Don't forget we gave you all those trident's ;-)
Stuartbe Thank you so much. Speaking from this side of the pond, your electrical system, short hot to neutral will trip the circuit breaker. Short hot to ground will trip the GFCI because earth will cause enough current to trip the GFCI. We on the other hand have high fault values through equipment grounds to trip the breaker. It now makes sense. Awesome! Now an example. NEMATODE contractors are rated 100,000 operations. IEC contractors are rated 10,000 operations. In a dwelling, in the new codes, everything is GFCI, orAFCI or both now. Also receptacles are tamper proof as well. Most electrical videos on RUclips are by people wanting to make money and not knowledgeable. Respectfully, Kevin
Stuartbe Also, I recently learned why we have 120 volt systems in US. Tesla wanted 240 volts as standard, but Thomas Edison who invented and sold massive amounts of incandescent lights that run on 120 volts was powerful enough to get his way. Edison lost the AC vs DC battle.
Dam.... the copper Rod is made out of steel...... they fooled me 😂🤣👍
Me too!..i thought they were cheap for the CSA of copper..pmsl :-D
I thought of weighing them in 😂😂😂
@@zjzozn me too...pmsl :-)
How’s your brother Donald ? 😀
Trump...... 😂
i may be being thick but surely if the earth rod was at 240 volts when in fault so would the equipment it was earthing ! making it useless! so if a person touched the faulty equipment they would get a shock ! making the earth rod useless
Creamy Pasta If it was a very heavy current fault maybe but neutral is the same as earth in the uk and in most homes with old wiring and just fuses you could wire plugs with neutral and earth swopped and they would work happily till you either had the house rewired or moved rcbo,s look at whats coming in on live and coming back on negative any imbalance eg earth leakage triggers them but earth should be able to sink all the voltage as neutral does in most houses they are bonded to the incoming feed!
What if the cow had 2 legs?
Risk of shock would be much lower, but not entirely eliminated.
If you're paying £20-£30 for a polymer inspection pit, please feel free to call me. Ours are half that much and they have a locking mechanism.
That's one scary-ass headless sheep...
delicious arent they?
Good topic! You should check it Mike Holt's grounding videos. He has one where he measures the potential around an energized grounding rod.
FWIW, you will have far worse problems than a cow getting a shock from the grounding rod if it has line voltage on it and the breakers haven't tripped. That would indicate that the neutral hasn't been properly bonded to the ground. As a result, every grounded appliance in the house is now going to be at line voltage.
As far as I know the real reason for the protective enclosure is to prevent gardeners from cutting the wire with a string trimmer, etc. That is a real hassle, especially in the US where we usually don't have a protective enclosure over the ground rod.
What, exactly, is every appliance in the house going to be at line voltage in reference to? They're all still at the same potential relative to each other.
FYI we don't bond the neutral and ground at customer premises in the UK (TN-C-S systems aside - and that's handled by the supplier, not you, and does not involve a rod on the customer side).
Also, if your cables can be cut by a piece of nylon, you have other problems.
@@Monkeh616 if you have line voltage on the grounding conductor (which was the proposed circumstance), and the breaker didn't blow, then those appliance housings will all be at line voltage. Say the breaker is a 32A job: at 240V the ground resistance would have to be under 7.5Ω to trip the breaker. However, there's plenty of current there to injure or kill someone.
I'm not quite sure what you mean when you say the neutral and earth aren't bonded at the service entrance in the UK. Do you mean the utility is feeding a ground from the local transformer as well as line+neutral?
As far as weed whackers go, the effect isn't immediate, but cumulative abuse will work-harden the wire and cause it to snap. Feet, shovels, lawn mowers, weed whackers, etc, will all damage an exposed wire over time. Those ground enclosure boxes are a really good idea.
It will never be at mains voltage as its earth and is therefore connected to the neutral point of the transformer so it will always be at 0 volts. All the fault current will travel through it but as long as the earth lead isn't disconnected it will always be at zero volts
Only true if the mass of earth between the rod and the transformer had an impedance of zero ohms - which it never does.
Nice one Rodney 🙈
As a non-electrician, it surprises me that you are required to cover these for safety reasons when overhead powerlines often have their unshielded earth cables tied down directly beside pedestrian areas on the side of the road in the UK. I've always assumed they were ground wires anyway...
Are you talking about tension wires. Typically coming down at an angle from the pole into a strong foundation nearby. Often used at the last pole in a route, or where a route changes direction.