Ground rod test Ground Rod Testing Measurement: Grounding methods, John Shook
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- Опубликовано: 17 окт 2024
- Testing, Ground Rod, Measurement, two resistor method, Calculations, Easy Method, NEC 250.53,A2 Electricians Need to Know: Resistor I Use: 225 Watt 25 Ohm Resister, or for 240 V use a 225 watt 50 ohm Resister Page 584 MC14681, 28K6295, ((Book) Newark Elements14), is $15.89, JS.
Respect . You have once again proved that you are never to young to learn old tricks. Respect
This is one of the most concise explanations of measuring ground resistance I have seen. Thank you.
Thank you for the video. When testing a ground rod in an existing home, is it necessary to first disconnect the ground cable running between the ground rod and the breaker box?
Great video, a real good simple no nonsense straight forward method of "performance testing". Well done.
John I love it! Great way to do this without the fall of potential method and a costly equipment.
Just a question. One end of the 225W 25ohm resistor is connected to grounding rod (via the clamp) and the other end of the resistor is connected to the hot wire on the extension cord?
Correct, JS.
I was also confused. He mentioned the neutral, but I think no neutral wire is needed to do this test. Is that correct?
John, thank you so much! Was wondering how to do this, didn't seem like you could use an ohmmeter, one probe stuck in the ground and the other on the ground rod and expect any accuracy. Followed your method, simple Ohm's law to the rescue. Result was eight ohms. Thanks buddy.
John, thanks for this old school lesson. You are plugging into an extension cord. Which wire is connected to the 25 Ohm resistor, the neutral or the hot? Watched video again, it's the hot wire - the neutral is just for double checking the resistance of the resistor. I am guessing we better make sure when we plug into the extension cord we don't get those reversed! What gauge wire is connected to the ground clamp?
12, The Hot, the Ground is in the Ground back to the Pannel. JS
Hi John. Nice video. Do you want to disconnect the GEC from the ground rod when testing? I did a service change and wanted to test the ground rod.
Thank you, again, John.
Straight to the point explanation! Thank you.
This is great. Really got me thinking. One question: 250.53(A)(2)Exc. specifically says: "If...electrode has a resistance TO EARTH of 25 ohms or less..." Is that what this test is actually measuring? Assuming the service is not otherwise grounded in any way, wouldn't this be measuring the resistance THROUGH the earth from the rod to the street transformer? Or maybe it's the same thing? Forgive my ignorance. I'm just trying to wrap my head around this.
Yes. To Ground where ever the ground is.
Finally tested the setup using the 225W 25 ohm resistor. Testing, I get 4.8 amp as expected. Installed a new 8-foot ground rod and tested - read 0 amp. Installed another new 8-foot ground rod bonded to other new rod and still get 0 amp. If I clamp to old, original ground rod I get 4.8 amp. Doesn't seem to be working for the new rods. I measured resistance between old ground rod and neutral (grounded conductor) of the extension cord and got 1 to 2 ohm.
Thanks for the excellent explanation... I'm working on setting up a test setup. You mention using smaller resistors, but is there risk of these burning up? If my calc is correct, this test across a 25 ohm resistor (120V) produces 576 Watts of heat. 50W 25 ohm power resistors are readily available and cheap.
yes 25 is best. JS
@@JohnShook I tried two of the 50W 25 ohm power resistors I bought off Amazon. During test of first one to verify 4.8 ohms (probably took 15-30 seconds) the resistor was very hot and fried to open circuit. Hooked up the second one and it fried the same way in a 2-second test. I'm thinking none of the low-wattage-rating resistors are going to work. I'm going to spend a little more and the the 225 W wire-wound resistor... and try again.
I was wondering the exact same thing. Is there a reason we can't use 100 ohm resistor because that would be 1.25 amps and still need to dissipate about 150 watts? You also could get the current without an amp meter by measuring the voltage across the resistor (V = IR)
thank you so much sir, coz' some inspector are requiring additional rod instead if only one. they dont know the installation is very hard running underneath the old house.
Hi there, excellent video on testing earth ground resistance.
Got a question though. What if the supply voltage is 240V what value of the ohmite that should be used. I would greatly appreciate your precious answer.😊😊😊
120 V
@@patshook1088
I don't really understand your kind response. My country's incoming voltage supply is 240V. So what value of the ohmite should I use since the one used in this video is for a 120V incoming supply.😊😊😊
@@firdausravindar977I’m not 100% certain but I would think use the same value.
I’m not either but guessing is all I have since the video author will not respond and nobody else is willing either.
Thank you. This was very helpful.
I will probably need to put in on or two more ground rods, and a friend has no ground rod on his home electrical system at all!
would be interested in the differences between phases where you place the end of the extension chord. what about the voltage drop from the extension cord?
40-25=15, great job, thanks a lot.
Hey, John thanks for the great video. Could you tell me what type of resistor is that you're using? How many ohms and how much power dissipation? Thanks. I'd like to put a test system together like yours. I have a grounding rod on a new installation to test. Thanks again.
John Shook
225 Watt 25 Ohm Resister, Page 584 MC14681, 28K6295, (Book) Newark, Elements 14, is $15.89 JS
This was excellent. Thank you.
So John, where can I get a 25 ohm resistor like that. It would have to be at least 500 watts. Can't find one online.
Newark in element 14: Page 584 part # MC14681 225 watt 25 ohm 28k6295 stock #. $15.89 each. JS.
@@JohnShook Thank you John. Just this morning to inpector told me to drive another ground rod 6' from the other I installed. If I could prove less than 25 ohms I would have been fine. I will use your method. Funny, when I was a kid I used to collect earthworms for fishing by tying 120 volts directly to a ground rod. They do come up!
Me too, JS.
There are many unanswered questions in this comment section, can someone lead us to a destination where these or similar questions are answered in layman’s terms?
Great demonstration; I just bought a 225 watt 25 ohm resistor and can't wait to try your method. I am a little confused about the fact you started out talking about a much smaller 70 ohm resistor and did not understand how that fit in. You never demonstrated it being used in the measurements. For a second I thought you might be using the two resistors in series. If so, the small one was too small to see in the video, in use.
Ken the 70 is if you don't have a 25 ohm, just use the 250 watt 25 ohm for your 1st resister and the ground rod is your second.
Thanks for the video. I couldn't find a description of this video on your website. Is it no longer there or did I just miss it?
It's no longer there. TKS JS.
John, great show and tell video. One question I have: Is the connection from the 25 ohm Ohmite resister to the 120V extension cord only connected to the "hot" wire? The neutral and ground is abandoned?
Yes the ground rod will complete the circuit back to the panel.
What state are you in? Either I’m doing something extremely wrong or I have terrible soil. I sunk one 8’ rod in completely and got 150 ohms, In red clay soil in Georgia.
Clay can be an insulator. Ever hear of ceramics? If the soil is extremely dry can make a big difference too.
We get good information.Thanks.
I make the same tester it’s important here in Mexico it’s sandy and lots of ground rod are bad thanks
Is it Alternating Voltage(AC) (or) a Direct current (DC ) voltage is required? for the testing
It's AC, 105 to 125 V, 60 Cycle
@@JohnShook Can I use in 220V, 60 Hz for the same test?
I have followed all you steps but my breaker trip 😔, i have disconnected ground connection from my extension cord. I am using 4 x 10 ohm power resistor in series. Anyone have any advice on this? My voltage is 240v by the way and my specification require below 10 ohms.
240 / 40 = 6 amps ?.
Yup, i got that in calculation but it trips on the breaker. So i cannot measure my current flowing. My extension cord is not connected to ground. What have i done wrong?
Is it a GFCI? Those will trip with the slightest ground connection.
Why not just go straight from the extension cord hot to the ground rod and measure amps with out the 25 ohms resister. And does it have to be. A 225 watt on the resister
A 25 Ohms 50 Watt will work, Going from hot to ground is a dead short. JS
I am gonna second that, because i did just that this morning and the main switch tripped
@@JohnShook It is not a dead short. The ground rod has resistance back to the panel which is what we are trying to measure. The only purpose of the extra resister, in my opinion, is to limit total current which makes the whole measurement process safer and reliable. As an example, if your ground rod resistance was 5 ohms, then it would pull 24 amps which would flip a 20 amp breaker. By putting a 25 ohm resister in series, total current would be limited to 4 amps making for a safer test. Of course if your ground rod resistance was 60 ohms, it would only pull 2 amps which would be okay to measure without a second resister. We do not know the ground rod resistance ahead of time though, so putting a 25 ohm resister in series limits total current to no greater than 5 amps. I enjoyed watching this video. Thank you for the information.
I would think a typical 4 slice toaster would be pretty great at testing ground rods. One side would be between 25-50 ohms for a typical 900-1100W toaster. Those Ohmites are a bit more expensive than they maybe used to be, toasters are cheaper.
225 Watt 25 Ohm Resister, Page 584 MC14681, 28K6295, (Book) Newark Elements 14, is $15.89 JS
you can go with a hot directly to an unconnected ground rod and find your resistance without all the extra resistors also they make a meter that is clamp on that uses radio frequency to measure ground resistance without using anything else or even having to disconnect anything
Problem is if your rod is low ohms, there will be too much current going. With 25ohm resistor cap it max for 5amps on 120v
@@rm6857 which is why more than one rod is used in a system as per code 😎 25 ohm min
you didnt understand, with low ohm rod(s) and without extra resistor you would make dead short, and fliped the breaker, thats why there is that resistor used.@@mattman8685
factual is always helpful.... thanks for the video
another simpler way you can test is using a multimeter . just flip the thing to ohms and one lead goes to the ground rod and the other lead to the service panel ground bus.
i have a house that was built in 1961 it doesnt have a ground can i drive a ground rod 8 feet deep and ground the new central air and heat straight to the ground rod
Yes, If you can ground the panel also, Some old services have grounds at the service pole at or 1 to 2 blocks Away, Power and light Grounds there Neutrals at the transformers, JS
@@JohnShook An old 1956 house with no ground rod, overhead power lines, the power pole with transformer is 30ft from the house electric panel. Is the house actually grounded at the pole?? Is that what you're saying?
Power and Light Grounds the Neutral usually at each transformer. Phase 1 and phase 2 and a grounded Neutral are brought to each house. JS.
@@JohnShook Ok thx. But does that mean the house doesn't actually need a ground rod near the elec panel? Or should one be installed?
It's good to run a ground near your panel and use a ground fault detector, for protecting Electronic TV's and Computers. JS
Thank you, sir.
Why not just hook up the hot wire to the ground and measure how many amps straight to ground? I don’t understand the need for the resistor.
That's a great way to collect Worms for fishing. If the ground rod is shorted to the panel the arc may surprise you. JS.
@@JohnShook I did it yesterday to a new ground rod I installed and it was pulling 7.69 amps, so I guess I have the necessary less than 25 ohms.
@@R900DZ 15.6 Ohms at120 V.JS
I love ❤ you, your brother Kristand, rest your neck
I was stunned working in canada how most electricians don't even have proper testing gear like megger or robin and they install two rods and don't even test them.
keen
Looking at some of your videos I figure you are or were an electrician. not many people know the word wiggy.
I would like to test the impedance of my ground rod on my ham radio antenna system to determine if the impedance is acceptable so that my surge protector that is installed in the antenna coax line is shunting transient voltages adequately to ground. Here is a link depicting the surge protection device:
www.alphadeltaradio.com/pdf/TT3G50_instruction_sheets-6.pdf
The ground rod is at the base of the antenna, driven 7' deep. I have a 3' run of #6 stranded, insulated wire from the lug on the surge protection device, which is then clamped to the ground rod at the base of the antenna with a bronze clamp.
I also have a 100' run of #6 stranded, insulated wire connected to the ground rod clamp at the base of the antenna. That 100' run of #6 wire is from the ground rod at the base of the antenna to the bonding electrode on the other side of the house to equalize the voltage on the circuit, so as to avoid a ground loop condition on the grounding circuit.
Can you advise how to test for impedance on my grounding circuit so I can know that my ground for the antenna system is working adequately to shunt transient voltages to ground, and what the impedance should be on that grounding circuit?
I will send this to an expert on Ham's antennas. JS
@@JohnShook Thanks John!
Holy shit. I wouldn't listen to anything this guy says.
Which guy, and why?
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Great video! My only question is what is the purpose of using a resistor? Couldn't you take the same measurements using just straight 120 and take a current reading?
Running the risk of short circuiting, The resistor is $15.00. JS
@@JohnShook thank you for sharing your gifts and knowledge. You've made a lifetime of keeping people safe. It's certainly something to be proud of.
With 25ohm resistor you cap maximum current for 5Amps on 120V network
How much heat will the resistor put off when testing?
It may get warm if used for an hour or so. I wrap it in electrical tape. JS.