Ground Resistance Measurement, NEC 2014 - [250.53(A)(2)], (26min:27sec)
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- Опубликовано: 23 фев 2014
- This real world test will be conducted by Nationally recognized Code Expert Mike Holt and electrical utility professional Joe Symmes using a 3 pole fault potential method, a clamp on meter to check the ground, an Amp meter to measure the current flow in the event of a ground fault and a volt meter and also test the test potential.
Mike is nationally recognized as one of America's most knowledgeable Code Experts and electrical trainers. His instruction has helped tens of thousands of electrical professionals ensure that the proper design and installation of electrical systems are in accordance with the NEC. His dynamic and animated teaching style is relaxed, direct and enjoyable. Mike's best quality is his ability to communicate technical topics in an easy-to-understand manner.
For information on Mike Holt products visit: www.mikeholt.com or call today 888.632.2633
Mike Holt is a true legend. I have learned so much from your videos. Thank you and god bless.
Thank you
This is the first Mike Holt video I've watched and I cannot express how happy I am to have stumbled upon it. I've been looking for videos on grounding electrodes testing, megger process etc. We've had over 20 instances of lightning damage on low voltage 2 wire irrigation systems. I've been watching your videos all week, the grounding and bonding video last few days. I cannot thank you enough for sharing your hard earned knowledge. You are saving lives.
Wow, thank you!
"if I was having someone install ground rods, I'd pay by the ohm" hahaha, love ya mike
@Mike Holt Mike is This Really You?
I love that I'll pay by the ohm lol damn funnylol
You pay him by the Ohm, he'll pour a little saltwater as he drives the rod, that will increase his wage ;)
Thanks for the great knowledge you are passing down, I have watched most of your videos and they are the best source out there!
I love your videos and have watched them all. Congratulations on your knowledge and ability to teach. I've learned an awful lot from you. As a radio amateur, I had many, many doubts about grounding. Now, after watching your videos, I have finally understood what I have to do to properly ground my station. Keep up with the good work. Thanks from Brazil.
"Still didn't trip a breaker- we'll see what the future holds"
GFCI breakers nowadays because of this man🤣
This is a really great video covering the The Grounding System (G.S.). G.S. is a science of it's own.
Many people (that's in reference to electricians) don't realize the importance of the ground. I am a retired electrician and came across many instances where the G.S.was shoddy as all get out. Don't get me wrong, I also saw many, many well installed G.S. too.
Any way, the G.S. is what helps make your electrical system safe. When a new trainee or a journeyman came along and would ask which wires were the most important, I explained the G.S. wire is THE important wire (system).
You can tell that Mike's not just book smart but has actually done some work in the field
I'm an electrician, that's my core...
Great instructional work, thank you.
Great video! Thanks to you guys for performing these tests. The reason I even stumbled upon this video is because I am trying to learn how the plastic moisture membrane between the poured on grade concrete slab will affect the use of a Ufer type ground system. I will continue my search.
I would love to see a follow-up video that incorporates the water line and how that plays into the grounding. Most homes in Mt area used the water line as the original grounding.
Excellent description and examples
Its interesting that 25 Ohms is allowed in the US. In Hungary the ground rod contact resistance must be under 10 Ohms even in the worst conditions(dry soil in summer, frozen soil in winter, rocky soil). The soil is usually good here and 2 pieces of 2 meter long ground rods at least 2 meters apart from each other is already inder 5 Ohms. Small houses have single phase 230 V 32 A serivces, larger houses have 230/400 V 3 phase 25 or 32 A. Higher services are possible but usually not needed because most houses use gas or wood stoves for heating. The gas pipes must be bonded to the ground in the panel.
In reality no one in the US is actually proving to their inspectors that they are under 25 ohms. They are just driving two, 5/8” 8ft grounding rods at least into the ground at least 6 ft apart and connecting them. That ends up being much less than 25 ohms.
@@Braindead154 And if one needs to prove one can pour a few barrels of water on the ground rod before they come to test.
It is the voltage. On single phase 230 V the voltage is on the neutral is 230 V if broken. In the US it is at most 120 V but can be much lower. On well balanced system it is close to 0 V. High loads in the US do not even use neutral so they do not contribute to the current on the neutral.
Three phase offers similar befits as the US system but the phase voltage is still 230 V
I would be most interested in the resistance of 50 ft of #4 solid bare copper in an 18” deep trench vs your 50 ft straight down deep ground rod in the same location. We have achieved better lightning protection and lower resistance with long trench bare copper . It seems particularly good for suppression of building to building transients from nearby lightning. So much so - that now it is our standard practice to add bare copper to any excavation trenching and to underground concrete (Ufer Ground) all tied to the main service entrance ground rod(s).
the idea behind deep rod, is that you get closer to underwater moisture and it becomes more conductive, it all depends on geology and climate
What OHMS did you get down to ?
Great demonstration video on grounding and measurement techniques! (One an advanced electrician, from Hungary)
Excellent demonstration. Thank you.
i just did yesterday the dangerous method mentionned by mike, this video was really enlightning, bc we have 230v i got like 1-2amp range for a 4 feet deep rod
i guess i understand why TT is popular around here, only utility grid people who use TN-C actually dig a deep rod for their transformers
I fail to see your point. TT is typically used where the ground resistance is low.
Thank you for the information. The 25 ohms the NEC requires and two ground rods 8 Ft. apart I never seen how it worked. Up here in Alaska we have a lot of ground water and you can in wet years meet that but now that we have not had good rains never happens. I once worked on an explosive storage bunker and the government (ARMY CORPS) required 50ft. Rods like you installed and every 25ft. around the bunker. This took a long time for two of us and 500 MCM ground loop cad welded to the rods.Kent
Excellent topic.Well presented too. Seems though there is a good case to offer gfi at the mains input though.Standard in Europe nowadays. Many thanks.Learned a lot.
I LOVE this video and would like to thank Mike Holt for producing it. As always, here comes the "but". i have two comments that i'd like to make on this video. I recently asked the inspector in our local area about the exact method that you're using it this video, if simply using Ohm's law and applying the 120v to an isolated grounding electrode would be permissible. I specifically requested using a 5A non-time delay fuse and seeing if it would blow that fuse, and he said that he couldn't understand why not. So i've been doing a little research into this. My two comments/questions on this GREAT video would be: 1) We are not actually testing for resistance to the Earth as static and lighting would think of finding it's way "to the Earth", but we are actually testing resistance from our grounding electrode to the utility company's grounding electrode system THROUGH the earth. that applied voltage of 120v is simply trying to find its way back to it's source, the transformer from which it is derived. so technically speaking , we could improve our resistance to this test by improving the grounding electrode at the transformer just as well as the one on our system. but then again, we're not really testing our resistance "to the earth," we're improving our resistance between 2 grounding electrodes THROUGH the earth. 2) if this testing method is acceptable (as i really don't know a practical point to measure "the earth" from), why would we buy the expensive testers if a simple 120v application and a simple R = E/I calculation can be done? or much less, a 50-cent 5A glass fuse could be used? I think the point made in the video of 120v being too dangerous to handle is a moot point, as we are professionals and should be able to safely manipulate 120v. Thank you in advance for your thoughts.
There are not two grounding electrodes, there is one (that we are measuring the contact to the earth resistance) and the millions of others once interconnected to the utility multipoint grounded neutral.
Yes your return to neutral is also going to be effected by your neighbours grounding rods. If you have many other grounding rods in your immediate area then the return to neutral will have a less resistive path than if your house was out in the boonies. But IMO the ground is mostly for equipment and health protection in case of surges such as lightning or to keep the RCD working in case of a main Neutral failure.
Excellent demonstration. With all the rocks in Tennessee, it would be virtually impossible to drive a rod 50’ deep.
Thanks for the video. There have been some wild electrical issues in my area. Got some UPS's installed for all the sensitive equipment, but realize the ground is bonded to the water pipe in the house... and not only that, but it's super corroded. Definitely going to be getting a clean ground installed to two 8 ft grounding rods. I live in a kind of half collapsed area economically so no tradespeople are available.. have to do it myself. Thanks for the video, it makes it easier to conceptualize and to install everything properly. I think this will actually help my neighbors as well, since there is just a lot of weird grounding going on that is causing power surges... or something. We got hit with one so bad It fried half the LCOS on my car dash... scared the shit out of me. Thought it was EMP or something, but.. who knows. Weird area. Just hope these new rods will fix some of the issues.
Great experiment.! Thank you, guys.
Our pleasure!
Thank you so much, that was so helpful I wonder how long the ground would be for land with so close surface water. about 9 feet and how many ground rods I need to neutralize 1. 30 A of 230V , 2. 40KV of 1mA.
Thanks Mike !
Truly outstanding information. Thank you!
Mike first time in 30 years I've seen you in work boots, go scuff em up a little!! Enjoyed the video, Your Indy Instructor Mike Fox.
I really appreciate the videos Mike, also appreciate the jokes in this particular video hahaha good way to keep it fun 😄
With the clamp on method you can reduce the safety issue if you put a 3/4" pc. of pvc sleeve over the exposed rod then bond the wire to the rod followed by a piece of say 2" pvc that extends beyond the top of the electrode. Next. Put your clamp around the 3/4" pvc. Now this the part I get a kick out of, stick that piece of wire into the receptacle...classic..Now turn on the power...classic..thanks!
Great job Mike.....you are a rockstar in the electrical world.....I will use this vid to teach the linesmen at work....... thumbs up man!!!!!
so your linesmen go into panel w/o PP and avoidance of NFPA 70E where is this?
Thanks ,it was helpful
Amazing video!! Thank you for this explanation!
Excelente video
I am curious what the depth to ground water is at the site. Perhaps it would greatly influence resistance.
Nice informative and effort full video :)
I was taught to install multiple rods minimum 6' apart to achieve 25 ohms or less. I have never seen rod extensions. I am generally in California clay.
There is no need to get 25 ohms or less, and the NEC requires ground rods to be separated at least 6 feet.
Thank you very much for sharing this valuable information.
"Looks like there is a relation between the resistance and this current flow" - uses ohms *law* to calculate... :)
It's a great video, just busting some chops.
Howdy.
Absolutely wonderful clip.
As I see it. A low soil resistance facilitates shock protection by increasing the fault current and thus speeding up the breaker triggering.
Another approach would be Encirclement of the Environment of Utilization (house). This would facilitate shock protection by Potential Equilization in the fault environment.
High regards.
That is NOT what this video shows, and your suggestion is also not going to provide any shock protection. Watch studio.ruclips.net/user/videompgAVE4UwFw/comments?Fcomments
Great seeing Mike estimate that math on the fly. The more you do that the better you get at a general math estimate. Obviously Mike does this multiple times a day for the last couple decades. But that is just an estimate of course.
apparently mike don't even need an instrument, he's using them just for show
Is the fluke meter set to milli amps
Great video.
I've heard that current can travel with almost no resistance through the earth, that is, once you get it past the resistance of getting it into the earth.
It would take men like you to prove or disprove such a thing please do
Thanks a lot for this educative lesson, but what is the formulas for calculating both EARTH and GROUND resistances ?
Damn Mike looking young
I was younger than! but I'm not too bad now for a 70 year old guy! Watch some videos of me on my Mountain Bike at MikeHolt.com/Mike.
You do a good job
Many Thanks, what if I want to ground a high voltage power supply of 20 and 40 KV of 300w and 120V respectively ? can I use many rods of lower depth instead of just one like yours
his point of the video is measuring your ground resistance... because using a single ground rod isnt always enough if your grounding material is high resist. a single 6ft is enough typically enough for residential code here I was surprized to see him having to go 50ft... high sand content maybe?
You said that the better grounding reduces the touch potential which is true but even with 2 at 50' it does not really protect you because the hair dryer is a tiny load. If you were running a space heater and a fridge on the same line (L1 vs L2) your touch potential would probably be close to 100volts as this circuit is basically a voltage divider. Another way to look at it is if you have an unbalanced load over 13 amps then the entire voltage drop will result from the ground rod resistance so 120V at the ground rod. Also, I wonder how deep the ground rod at the poll has been driven because it contributes to your resistance.
True. That's why a Diferential switch is necessary.
Looks like you guys got alot of sand in florida.
Where does the current go?
If it takes that much depth to get your proper resistance, then how in the world can the nec say you're automatically good by having 2 of them driven 8 feet deep 6 feet apart?
excellent guys .... most informative video ...
came here searching for lightening system ground resistance n found out this ...
Mike - what was the coupling method between rods when you added extension rods? No CADWELD?
www.zoro.com/erico-ground-rod-coupler-rod-dia-58-in-cc58/i/G0953102/?gclid=CJ6S266qpNICFQcGhgodup4DcQ&gclsrc=aw.ds
What if one uses the Uffer ground (concrete-encased electrode, the foundation rebar network). You can break a little concrete, find the rebar, grind the rust, install a #4 CU solid with approved clamp, use a little fast concrete to patch the foundation hole. Does the foundation rebar have lower resistance to the ground compared to the 50' and 30' ground rods? If so, it would trip the breaker.
Nope, a Uffer ground will NOT trip even a 20A breaker; which is okay, since grounding is not for the purpose of tripping a breaker. See studio.ruclips.net/user/videompgAVE4UwFw/comments?Fcomments to better understand the purpose of Grounding verus Bonding.
Sir,
In the last experiment of touch potential if we reduce the earth resistance (in case of Loss Neutral) the touch potential rise .
Than if touch potential rise than it is not safe ...
Best explanation
Glad you think so!
i have used assoc research three point method for
( we have four units like this and two clamp ons ) thirty plkus years and the results are good. we cant use the clamp on for isolated ground rods etc . resusts are eroneus .
The clamp on meter is only good for specific applications, so I understand.
Does reducing earths resistance, increase or decrease the touch potential? "As we reduced the earth resistance and you lose a neutral, the touch potential increases"So we really want to have a good ground, a very low resistance ground, because it does provide a reduction in touch potential"
I just watched your youtube video "Grounding-Ground Resistance Measurement" 26min:27 sec published 2/24/14. I found it very educational but one thing left me confused.
At 13:26 into the video where you were reading the resistance meter with it's dial at "1" and the scale multipier at "1000" you said it was 100 ohms. Whatam I missing? That would be 1000 ohms wouldn't it?
it is actually 0.1
I have a feeling that the ground rod went into the ground in an angle (not vertically), reaching a lesser depth elevation than the sum of the electrodes' height. The depth elevation -- measured vertically -- makes a bigger difference than the combined length of the grounding electrode.
This is not the case, it's Florida. It would not have made any difference in 'contact' resistanc'' since resitance doesn't change with depth, it changes with 'surface area.'
@@MikeHoltNEC This AEMC grounding video states that 'doubling the grounding electrode (GC) *DIAMETER* reduces resistance to ground 10% BUT doubling the GE *DEPTH* lowers resistance up to 40%'. Watch 9:06 - 9:34.
ruclips.net/video/NP9Jbdi_k6s/видео.html
Here in Houston We use a light bulb if the light lights up the ground rod is good.
Hopefully you now realize that this is not a suitable method...
Sounds like a pretty good method to me :D but better if you had something that could draw 5A minimum a light bulb would only draw 500ma if your lucky. These days They are all energy saving of one type or another and a modern lamp might only draw a few milliamps. 6W LED / 240V = 0.025A
Can not comprehend without a schematic drawing!
Watch it again, it's just Ohm's Law.
hi can you help me i have a fluke 1625 ground tester and we don't know if we are doing the things rigth
let me know when ready to sell the tester, Thanks.
this stuff amazes me. i wish i would have stayed in school
Let's not worry about the past, let's start working today for the future. Watch all of my videos online, attend some of my seminars, order some of my books and DVDs, become more educated and make more money!
Wish you could explain bit more detail in relationship to stray tingle voltage on farms.....four legged creatures standing on the ground getting say 4v shock from water in a plugged in heated water bucket even with main power switch off.
update..watched your Nev video....farm is quite a way from substation so NEV of 4v probably normal....so how does a person allow horses standing on bare ground drink from heated water buckets. Other than tingle voltage filters with 300:1 tranformers between neutral and ground that are probably no longer made...Equil potential grid for horses to stand on outside probably not affordable.
When use clamp-on in TT system how can the device transmit the signal? Because there's no connection between neutral and ground in the load side.
The three-point fall of potential method. Do an Internet search.
Very informative videos Mike.
Just a query, i noticed at 19:25, current draw from the induced voltage on the rod was 5.75mA and not Amps. Can you verify that value please. Am interested to know why such high current draw without a known load and what work is being done by the power evidently present in the circuit.
The earth is part of the circuit path, and the current was not in mA, but in Ampers. Watch it again please.
so basically every house that house a single or double grounding rod system that is 8ft down does nothing because if the resistance was checked, all of them would be way over 25 ohms. That's encouraging to know.
It depends entirely on the soil in the area, both soil type and moisture content.
the purpose of that electrode is not to replace a neutral conductor. that is not the purpose of grounding, bonding has the purpose to clear a fault. the purpose of that electrode is to dissipate a 3,000,000V bolt of lighting or other static electricity to the earth. the idea on the bolt of lighting is, that the lower the resistance is, the smaller the voltage gradient around the bolt will be (and the less damage it will cause to the surrounding area).
The purpose of that electrode at the service entrance is to place a ground reference local to the structure for the life safety of utility personnel who might service that entrance panel while a neutral is not connected. Should a fault occur in a meter pan there is no fault interrupting device between the service entrance and the feeder transformer bank, so bonding the enclosure of the service entrance to earth potential is important.
Electrodes installed by code at the service entrance have no purpose in lightning protection as they don't present a low enough impedance path to earth to dissipate high frequency impulse energy from a strike. Most single phase service entrance installs are earthed with #6 AWG solid which is just not a low impedance conductor at 5khz-5mhz.
If you want to add supplemental protection to your dwelling for lightning suppression you should install a three pronged approach of 1. aerials surrounding the roof of the dwelling and the peak of the roof bonded to a supplemental electrode network around the perimeter of the building. 2. This network should be bonded to your service entrance at a single point outside the home. 3. A transient voltage surge suppressor should be mounted to the service entrance and bonded to the unified ground/neutral connection.
Then you have a low impedance static dissipation system that prevents lightning strikes and clamps surge energy.
Also putting two rods in parallel does a lot if they are 100 ohms each thats 50 ohms total
James Johnson I would keep adding more or or deeper rods to my ground anode field till my impedance was under 5 ohm even if that meant my soil requires bentonite clay or some other enhancements to make the necessary grade.
Wouldn't the current showing on the meter depend on the distance from the Ground r\Rod?
No, the current is only a function of the applied voltage and the 'contact' resistance of the rod to the earth resistivity. Once past 25' there is no longer any resistance to the current, since there are so many parallel paths for the return current to flow on.
Were wrong saying "elec. current will always take the path of least resistance to ground" Actually it takes the path of least resistance to its source.
It seems to me..the resistance of grounding electrodes isn't low enough to trip the breaker..why do we use them??Why don't we use only the neutral and branch circuit grounding conductors for the return path back to the source.
Watch ruclips.net/video/mpgAVE4UwFw/видео.html
Can you please explain what the dangers are in this experiment with respect to the amperage. I'm new to electricity.
Sorry, you would not understand. Just assume all of this is dangerous and you should NOT attempt this experiment.
Flint rock hard to get rod very deep. Thanks
I bet...
Excellent video. Suppose got I enough grounding rod in the ground to get to 20 OHMS of resistance, Would this much improved ground have an effect on flickering LED bulbs when my mini split is running ? 48K ACIQ 48Z-HH-M5 (220 volt Inverter) Meaning eliminate the flickering ? Appreciate your help here.
Please watch the video to understand the purpose of grounding. Grounding had anything to do with lights flickering. Please watch bates-electric.com/lights-flickering-in-house/.
read entire article carefully. Swapped out smart LED bulbs for Phillips, Still flickers. Incandescent bulbs in rest of house do not flicker. screwed down all bulbs tight. Turned off all breakers except for kitchen, two bedrooms, Laundry room. (only location for LED bulbs) so no overloaded breakers. Voltage fluctuation of approximately under
one volt over 15 minutes. Mostly stays around 122.1 volts. New wiring 7-2000. two inspection stickers from 2000 and 2001. Grand Traverse County. Loose wiring: none. tightened all connections in breaker box 1/8th turn tighter. Mini split runs wall and provides plenty of heat. 4 head units. (can power 5 head units) Have a power line that comes down a hill and provides power for the house and a neighbor on each side. One house is closed down for the winter. (residents in Florida) The other house is a 77 year old widow. The power line coming down the hill is a potential lightning target. (2006 lightning strike. BLEW UP TRANSFORMER) This is why I was interested in the earth ground, I feel I need to improve the earth ground. One 8 foot ground rod in very,very sandy soil. What I am trying to understand is whether the improved ground of 10-20 OHMS of resistance would have any effect on the flickering LED lights. Did order a Ditek surge protector for installation at the outside disconnect box. (lightning insurance) What are your thought on the flickering lights ?
Short answer - no grounding has nothing to do with lights flicker. Please see www.mikeholt.com/mojonewsarchive/All-HTML/HTML/Lights-Flicker-(Dim)-When-AC-Starts~19991007.php
Good video but never neglect safety watches rings and shinny things
What electrical standards this earth clamp-on test procedure belongs to?
IEEE 81?
would the diameter size of the rod to the next diameter make a difference and also the type of material , can you try a galvanized or stainless steel . yes the price is a factor when driving 50 feet of rod
The key is 'contact resistance area.' A lager diameter ground rod adds 'some' area, but not enough to make much difference. Material doesn't matter, other than it's life. Longer ground rods add more 'area,' so this lowers the contact resistance (the same with five - ten foot ground rods.
Question: Can a person who has ZERO ground in a house, ground just ONE power outlet in the house by running a ground wire from the ground terminal out into a grounded stake in the ground? My house has old screw in fuses, and absolutely no ground wire anywhere. There's no plumbing or anything in the house to use for a ground either. I run a compost toilet/outhouse, and haul water there. I want to avoid the risk of frying my electronics but I cannot afford a full electrical update. It's 10,000-12,000 to do this (almost as much as I PAID for the house!!)... I won't be able to afford it for YEARS best case. SO what I want to do, is somehow protect my electronics by at least grounding ONE outlet cheaply. Is this possible? AND NO, I DO NOT HAVE INSURANCE, so I don't care if things are certified insurable, just so long as my gear is safe.
What did u end up doing, Like Mike said don't run the wire as u explained. While you could properly ground plumbing via proper rod in the earth, you can't use the plumbing as the ground it's not good enough.
How are you connecting the ground rods together so you have a solid connection?
6 AWG wire with ground clamps.
@@MikeHoltNEC thank you.
@@MikeHoltNEC I think he meant the couplings that allowed you to go 50 feet deep by connecting several ground rods end-to-end.
What a stud!
Sir ,during touch potential experiment ,the following is the sequence shown:
1) 1st with two ground
2) 2nd test with single ground rod.
Am i correct...
There is no sequence. I'm making a video as I'm learning...
Question sir,
During drilling rod is getting hot right? is there any effect in the ohms reading while hot?
No the rod is not getting hot, it's actually cooling off since the earth is cooler than the hot Florida air.
@@MikeHoltNEC I see.thanks sir Mike.
Try coming over Hawaii (Hawaii island) and trying that test on the Kona side. I guarantee you every technique, method, depth, distance, measurements and etc. will be entirely different. Bring your WHEATIES! The reason I’m interested in your results would be because of the earths composition. Our land is basically lava rock, high in iron content. Diving a ground rod 8’ is nearly impossible w/o predrilling a hole first. My point is that 50’ or six inch’s. The 8’ code is a myth.
What precautions did you guys take to safely short-circuit the neutral to the premises grounding electrode? The danger would have been if you made contact with the neutral lead while standing on the ground it would have made a circuit between you and the grounding electrode at the system transformer, correct?
We understood that if we touched the neutral and the hot we would have been shocked. We only used one wire from the extension cord.
@@MikeHoltNEC My understanding was that you attached the neutral to the grounding electrode which made a circuit that ran from the utility transformer, along the neutral, to the service panel, to the receptacle, along the extension cord plugged into that receptacle, to your wire, to the premises grounding electrode, through the earth, to the system grounding electrode and back to the transformer. So I thought the danger was that if you were standing on the ground and touched the lead of the wire coming out of the neutral socket of the extension cord, that your body may have completed the circuit to earth instead of the grounding electrode.
Great video btw, you're a great teacher.
@@rasputozen Nope, I attached the 'hot' to the ground rod. Please watch this video MikeHolt.com/Fundamentals before your respond back
@@MikeHoltNEC I see, the lead was plugged into the hot slot of the extension cord, not the neutral slot. My mistake. So to update what I wrote... The danger was if you made contact with the energized grounding electrode (or the hot lead directly) you would complete a parallel path to the earth (or a direct path if touching the hot lead directly), that would then go to the grounding electrode at the system transformer, then to the transformer, to the hot line, to the service panel, to the receptacle, to the extension cord, to the hot lead plugged into it, and back to your body. Is this correct now?
@@rasputozen Correct, watch this video MikeHolt.com/Fundamentals
I fail to understand which exactly, is the resistance their trying to measure.
is it the close loop resistance from the grounding? as in, the grounding metal mass in a grounding system is technically open and the only thing connecting it is the ground. is it that?
Watch this video studio.ruclips.net/user/videompgAVE4UwFw/comments
@@MikeHoltNEC thanks for the reply
So the neutral is being partially replaced by Earth via the ground rods and back to the utility pole ground. Hair dryer wouldn't run otherwise with the neutral removed. Earth being just another conductor even if it's not all that good.
Utility neutral.
@@illestofdemall13 I'll re-watch this video, good chance I was half asleep while doing so. My education is in electronics and try to keep myself educated on the electrical side as well.
@@jeffm2787 Also watch the newer videos on bonding and grounding. Mike Holt is the best.
Yes, but it works less than ideally. If it is 1800 W / 15 A / 8 Ω then with a 21 Ω ground resistance the current will be 4.13 A and the power 136 W.
I wonder how they got only 30 V voltage though as it should be about 85 V.
How does this relate to a ufer
It follows the same math, but a typical ufer can have a lower resistance than a ground rod, but not much.
So why was the ammeter reading in milliamps? Look at 14:50. It is clearly 5.6mA on the meter, yet he is saying it is 5.6A. Since the math works out (Ohm's Law), I can only assume a 1000:1 current transformer has been added off-screen?
+Munga Dey Yeah! what's up with that? He keeps saying "Amps Amps" all over , yet the meter keeps showing the readings in mA.
Yes, it's because they're using an external clamp ammeter (Fluke Y8101?) that outputs 1 mA for every 1 amp through the clamp. You can see it early in the video.
Thanks a lot, TechnicalLee, that explains the readings that they show on the video.
Has anyone ever seen this type of testing on a concrete encased electrode?
Doesn't matter why type of electrode you are testing.
Mike did you say that wrong at 23:07 ... Shouldn't it be, as you lose the earth conductance the touch potential goes up. Less resistance = better conductance to ground = less touch potential...
You are correct, thank you for pointing it out!
Awesome. Mike how come you have time to answer comments, write books, give semminars, study and teach the code, answer emails, and the other millións of thing you do.
The industry is important to me, so I just find the time.
My God all this to test rods omg
How deep is the water table?
I don't know maybe fifty feet or more?
Just wondering what happens when penetrated, lower ohms maybe or possible water contamination?
@@stevenlawhon3695 What happens if you get lower resistance, then you get lower resistance. But the resistance value is unimportant.
@@MikeHoltNEC Then why are they looking for lower ohms? unimportant?...mmmmmm oh well.
@@stevenlawhon3695 I don't know 'who is looking for lower ohms,' but who every they have no clue why. Understand my videos and my comments are related to the National Electrical Code, now what someone thinks. Find the person that's 'looking for lower ohms' and ask them to give you a rule for such a requirement.
soft ground but a HARD HAT
Dont you mean 120 volts A.C.???
Yep, what else could I mean?
@@MikeHoltNEC my bad ...120VAC 60Hz..I understand Sir.
“I would only pay him by the ohm.” Haha
I love that statement also. It just came out...
👍👍
Ohm Ohm on the Range
It's so funny to see Mike trying to help, very curious mind but kinda careless haha. 12:50 for example, messes with the instrument thinking he's got it but the other guy corrects it, they've been at 1000 multiplayer the while time.
12:31 keeps saying amperage but he means ohms lol. You can hear him pause and then say, "ohms" haha
@@mchipitt I know, my mind is alway on the move, and I'm just a 'real' guy. I'm okay with that...
@@mikeholt3717 I can see that! I just hope to find an eager journeyman or master electrician like you to teach me, as I'm about to step foot in the industry. I love your content though. I will try to test the grounding electrode's resistance at a ranch we purchased because the electrical work is botched and this video is very helpful.
Mike where’s your safety glasses!
Please answer these questions: What standard requires safety glasses and under what condition? When in the video do you feel I should have worn safety glasses per the standard and rule you quote?
spoiler: Mike Holt cut off that last 2' of that last section of rod he drove. That's why the camera cut away. ;)
I don't think my friend...
@@MikeHoltNEC I know, I was joking. We've all hit that wall and wanted to. I appreciate your knowledge and expertise. You were typically the goto reference from my apprenticeship.
Oh help me Jesus I'm lost and I'm the head expert in my field in my government agency
The problem is (happened to me) is that we were taught crap, and now we are trying to undo it in our head... watch the video again, and then watch ruclips.net/video/mpgAVE4UwFw/видео.html
Sorry but if Joe is using the clamp on method with just one ground electrode instead of multiple electrodes/grounding points, it is incorrect use of the clamp. You can't use the clamp on method on a single ground point. This is because there is no return path (close loop) for the current on that electrode.
Please watch the video again; the method shown is correct.
@@MikeHoltNEC Thanks Mike, the problem is the video does not show enough of the setup. Perhaps you can elaborate exactly how the reading is taken. Thx.
Y'all hit the water table at 30 feet.