NEC System Grounding
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- Опубликовано: 31 июл 2024
- A short video about the different system grounding configurations addressed in the National Electrical Code. I will try to create a Part 2 before long, explaining why we grounded systems and equipment, and why we bond equipment.
Always good to come back to this and refresh even if you’ve listened and watched this video before.
Awesome video Brother, you do your trade and the public a great service buy explaining not only the systems but most importantly the codes and when and how they work and how to apply several different views and approaches so anyone can understand how to work on their own system safely and efficiently and most importantly keeping it or in some cases getting it within code.. Thank You for Your Time You Are 1 of a Very Few Who Can Explain and Teach in a Very Easy to follow along way. Please Keep Up The Great Work, God Bless Brother And Have A Great Day...
Great video Mr. Ryan thanks a lot for your videos, l used to see you with Mr. MIKE HOLTZ in those seminars years ago, and now i am Happy because your doing the same like Mr. HOLTZ, one day he said, in one of his videos, " Mike Holtz, someday is gonna go away, it is not gonna be here anymore", but this is the future people that is gonna follow my legacy, and there you are, thanks a lot Sir, God bless you and thanks for you videos and the time you share. Greetings from Houston Texas.
Note that in the introductory slide I indicate that a three-phase, three-wire, wye-connected system could be ungrounded if the voltage is 277/480V. That should be just 480V, not 277/480V.
Boss I love your videos . Very knowledgeable and up to date . Can you please make a video about 300.3(c) there is a lot confusion about this article
Great video Ryan. I currently taking Grounding and Bonding class as part of Local 3 IBEW Apreticeship program in NYC, and this video is incredibly helpful. Thank you.
Another great video Mr.Jackson. I’ve wired up transformers but have never had one that was gonna be a corner grounded one. Learn something everyday.Love your videos.
Thanks!
Thank you very much! Very informative and clear. Will be looking forward to the next - why we ground video.
Thank you for the video. I will watch it again and someday when I start working on transformers, this video will give me an advantage.
Great great video! Very well explained and very informative. Much appreciation. 💯
Excellent video! Great job.
Best video I’ve seen on subject
They make a three phase 208 volt delta primary with a 480Y277 volt secondary thus providing you with a grounded secondary for just that purpose. I installed one for a Acme-ridley machine.
Great job! I can follow everything you say
Thank you for explaining this
Thank you for your data!
Excellent!!
Boss I love your videos . Very knowledgeable and up to date . Can you please make a video about 300.3(c) there is a lot confusion about this article
Good job Ryan
Thanks Ryan, very valuable info...one follow up question about the back fed transformer, if this transformer is used as a step up unit (208 to 480v) and connected to another delta wye transformer to step down from 480v to 208v) if I use corner grounded delta of the step up unit, 1) How the connection would be at the step down transformer primary? And 2) does this means that I don't use a fuse for the grounded phase at the primary protection of step down? transformer?
Great video!!!
Thanks Edgar!
Great video, on the 240-120 volt Delta, when you say connect to one of the windings I saw a transformer for this type of setup and the secondary was marked X1 thru X4. So would your X4 be like your Xo and get tied to earth along with your neutral and all the bonding. I know one of your X1-X2-X3 windings to ground would be your wild leg. Is this
Pretty much wired the same as a 208/120 Y transformer, just obviously a different voltage output Thanks!
In what situations would you want to say have a ungrounded delta on the secondary vs a corner grounded delta on the secondary... and with your explanation of not putting the grounded conductor on a circuit breaker do you mean not putting a overcurrent protection device from the neutral to the ground?
Would it be appropriate if i had a corner grounded delta on the secondary to put the grounded conductor on a 3 pole breaker to get 480 phase to phase?
Excellent video. But what about 2 wire 120v?
Connected to the Dirt, Love it!
Thank you
Thank you very much for explaining this so well. I have been a refrigeration service tech for 38 years and have never had it explained this well. I have a question . I was on a job within the last 2 weeks, where an electrician used a 2 pole disconnect and claimed the grounded phase did not need to be disconnected or switched or opened by a breaker. I did not like it but he has been in the field many years himself. I felt the need to follow the professionals advice. After seeing your video I see one definite problem. The wire is orange and needs to be white or gray. I have always seen a 3 pole disconnect regardless of type of 3 phase. We have it all here . Corner grounded delta , high (wild ) leg, standard wye etc. It looks like it would be a bit of trouble to mark and/or color code all the wires in a building to meet code. Is this why I have always seen the 3 phase disconnect/breaker everywhere ? Thanks again for explaining this so well. If it matters I am in the Midwest area. I am thinking of encouraging the store owner to have a standard 3 pole disconnect installed for ease of maintenance. Like you say it wont get you unless you get across a hot and grounded leg. However not everyone is familiar with this. They don't read voltage or a volt pen will not light up on the grounded phase and they think there is nothing there. The people that almost know something about electric is what bothers me the most. Another concern is if we have a major disaster and the transformers get changed to WYE....now our orange wire is hot. Possibly blow main breaker but then store will be down. All thoughts welcome. Sorry this got so long. I really want to understand this for the future.
Thanks for the compliment. For a corner-grounded system, a common method is to just install single phase panels like you have in your house and use 2-pole breakers. The grounded conductor (the grounded phase) in the panel is wired just like the neutral in your house's panel. So to answer your question, you can use 2-pole or 3-pole, either way.
In your scenario of reverse feeding a 480 volt transformer...would it be considered single phase 480 volt since you are grounding x3?
Hi Rory. It would still be three phase.
Hey Ryan, I have a question about corner ground delta, when wiring a disconnect switch is the corner ground conductor supposed to be a dummy fuse or uninterrupted circuit, we're can I find some information about the proper way to wire a corner ground disconnect switch? Thanks Steve.
Hi Steve. Yes, its a dummy fuse, unless the fuse is used fir overload protection of a motor. See 240.22 and the section in 430 that it points to. I want to say 430.36 but that doesn't seem right and I'm away from my book.
Ok, Ryan I will check it out .Thank you for getting back to me . ZAP! ZAP! FAST!
24:16
Hi Ryan
I have a high leg delta
3 phase 120/240 volt system
There is one single pole circuit thar feeds 4 wall pack metal halide fixtures which have multi tap ballasts
I fed them on the b phase, single pole 208 volt with nuetral splicing onto the ballast on the factory 208 tap.
Anything wrong with that?
It was 6 years ago and lights still operate flawlessly each night on 208 photo cells
Yes Eric, just make sure that the circuit breaker is straight rated (240 volt) not slash rated (120/240 volt) as per article 240.85 of the NEC. Pretty much all 3 pole and some 2 pole breakers are straight rated.
Thanks
So if i put my tick tester on the case or any metal parts of a corner grounded delta system it would ring?
Does a neutral tick?
You can run single phase 208 volt loads to the high leg. Just make sure you use a straight rated 240 volt breaker. All 3 pole and some 2 pole are straight rated as per NEC 240.85.
Agreed, you can if there are no other prohibitions (such as 110.3(B), obviously). Agreed, a straight-rated breaker would be required.
I installed 2 240 volt wall heaters to the high leg using the high leg of a 3 pole breaker.
I’m not going to waste time looking for a neg reply …..but who is down thumbing this?🙄. Thanks Ryan.
There are people who give a video a thumbs down seconds after it is posted.
Isn't bonding to the frame of a portable generator considered to be grounded?
Did I miss it, or did you skip why main panels are bonded but subpanels aren't (unless there's a separate UFER, unless I'm mistaken)? In my experience, this is one of the most commonly misunderstood concepts of bonding... If you cover this in another video, could you provide a link? Agree with the other commenter who praised you for taking over where Mike Holt will eventually be leaving off, just found your channel and am almost through the content. Thanks for sharing!
Mike Holt has some discussions on this. The short answer is the grounded conductor (neutral) must be connected to ground in only one place so as to prevent situations where there may be parallel paths to ground. I agree, this deserves a much deeper discussion.
Hello Ryan
I don't think you can have a corner grounded 240 volt delta because the midpoint of a phase you'd get 120 volt which would require it to be grounded there?
No. You can absolutely have a 240V corner-grounded delta.
Ok
Then can you have an ungrounded 240 volt delta?
@@Gazebomanfla Yes.
A 240 volt delta system can be center tapped grounded and obtain 120 volt as per 250.20, so doesn't that mean it must be grounded even if corner grounded?
@eric fox No. You can not ground a 240V delta and limit the voltage to ground to 150V. When you ground the midpoint of one phase, you get 120, 120, and 208 to ground.
Ryan, I checked your channel and you have not come back and explained how grounding works as you suggested you would in this video. I have a question for you about EGC function. Situation: 480-208/120 Y 75Kva transformer connected to the 480V main panel primary, and feeding a 225 amp MCB panelboard. 3 pole 30 ampere breaker feeds an electric unit heater. Service is properly grounded with GEC. Transformer connected to intentionally grounded steel. Correct EGC's as required from trans to panel and panel to unit heater. Question: If phase A shorts to the unit heater body(assume first half of the sine wave for direction(breaker toward heater case)), what path does the energy follow from that point? Or where does it go to or through. Respectfully, Kevin
Hi Kevin. Sorry, I haven't had the time to do another grounding and bonding video, although I still plan on doing it one of these days.
As far as your question goes, you didn't specify which (voltage) system the heater is installed on, but current always returns to it's source via every path that is available.
Ryan Jackson heater is 208volt 3 ph. Please bear with me. Saying to the source is what is always stated. How does it get there is important.
@@KevinCoop1 From the transformer to the panel, the green wire is a supply side bonding jumper sized out of table 250.102(C)1, and not an EGC sized out of 250.122. The correct size SSBJ should be a #2 where 250.122 table will give you a #4 for 225A. There is no OCPD at the point where the transformer secondary conductors receive their supply from which to properly size an EGC, so table 250.102 is based on the size of the ungrounded conductors, 4/0, for a 225A panel.
rynocop I agree with your findings. But I still have not heard an answer to my original question. From the heater short circuit to the case, what is the travel path of the fault current? 99% of people I ask this question get it wrong. You can try if you would like. Many can tell what the NEC says, but many can not tell "why" it says what it does. Respectfully, Kevin
I am very confused by the sine wave direction statement. Forgive my ignorance, but I'll do my best to answer as I understand it. From the point of the ground fault on the enclosure of the heater, fault current would flow through the enclosure of the heater to the point at where the EGC is connected to the enclosure, through the EGC to the ground bar in the 225A panel, through the ground bar to where the supply side bonding jumper from the transformer is connected, through the SSBJ to the ground bar in the transformer, across the system bonding jumper to the neutral (XO) bar, through the windings of the transformer, back out on A phase through the OCPD. Hopefully the amount of fault current is sufficient enough to trip the breaker within 1 cycle (20-40 times the rating of the breaker). Notice the fact that the service and separately derived system are properly grounded (connected to earth) has no affect on facilitating the operation of the OCPD. Current does not try to find a path to ground, contrary to the understanding of most electricians. It will find the path of least resistance (which is all paths in parallel) back to the source, then back through the breaker to trip the breaker and open the circuit to eliminate the fault condition.
I have seen a lot of wye ungrounded system in petro chemical plant in the Philippines
I'm not an electrician, just an interested layman. It's hard to find good, solid info like this on RUclips if you're an American. (Most youtube videos I've seen on grounding use IEC/European terminology). If I understood you correctly, our residential installs strictly use what the IEC calls TN-C-S earthing. Is this the law or is it just "best practice" on the utility side?
I'm not familiar with the term TN-C-S, sorry.
Good
Hello Ryan
If you didn't ground the 208/120 system Wouldn't you still have 208/1.73=120 by wye transformer rules?
Sure, they have nothing to so with grounding.
120 volt across a phase to neutral point < 150
With less than 3 loads I normally use ungrounded system for reliability
However you lose a phase because you are grounding it? So you would have 2 phases 480 volt between them and 277 volt between either one and your now grounded phases? And 0 volts between your now grounded phase and grounding conductor? Sorry just trying to understand I am a little confused.
It is still three phases, with no way to get 277V. You get 480V between any two phases, including the grounded one. You would get zero volts between your grounded phase and the metal parts/equipment grounding conductors. No need to apologize, this is a confusing concept for most people (that's why I wanted to make the video, I get a lot of questions on this).
While you don't lose a phase, you don't fuse the grounded phase. You can use a single phase panel, but it's still 3phase.
Rory Barnard Did you get a response that answers your question so that you understand? The diagram for your question is at 32:50 in the video.
Let me ask ya a question, cause I’m not an electrician and not smart enough to learn this code. Now our local high school I was on the grounds and saw what I believe to be a mark on rocks around a small brass statue. They looked like black burns two like snake eyes, smaller and then larger sets of marks. To me it looked like the electrical behavior in a jacobs ladder type device. This is a wet location where students walk. Covered with Pine needles so it looks dry. The school has electrical transformers on the surface of earth. They are buzzing loudly, like they are overloaded. These two things combined looked to me like there is an electric arc seeking a ground. But I’m a science teacher and not an electric engineer so I can not explain this problem to the school sufficiently. There was one student in a straight line with these marks that was found dead early one morning under the bleachers(metal) on concrete. That was brushed off as a drug overdose even though it took a separate county coroner over five months to come to the drug conclusion. I don’t believe an autopsy was done. I believe the child was electrocuted. Now, consider another child has a heart attack incident. That a difibrulator brought back. To me this sounds like the child’s electrical heart rythyms we’re disrupted by that electric arc seeking ground again. I don’t want another person to die on this campus as a result of bad wiring. The school was built in the 60’s but recently before these incidents installed an access control system. I am not sure what that was because it doesn’t close doors or block entry in anyway. Our county is notorious for hiring contractors with questionable ability and not having any one to follow up to see if what they paid for was done correctly. This part of the school is outside with the hallways being Davenports covering walkways. I try to explain this to the school officials and since they think the only safety issue a school can have is criminal and they see anyone that explains contrary data must be a criminal. So they change the focus and the real issue is never addressed. Any thoughts Ryan?!
At minute 32:00 you mentioned if you did not ground the system you will not get 120 from line to neutral or XO. That is false, you will still get 120v , you simply will not have a path to clear a ground fault.
Yep,I misspoke. I should have said that you would not get 120V to the metal parts.
God bless you such a great videos
I am just asking about article 100 npfa 70 2017 if you can explain it it will be great thank you
That delta high leg will design its own ground on the premises. The fused ungrounded primary feed will be grounded underground(service lateral) and will be protected by 21st century ground detecting methods. If you live in a flood plain the service equipment will be located on the upper floors. Not in the basement!
I'm not sure what you are saying.
Maybe it isn't correct but I also my SBJ in a transformer with a few spots of white tape very much like the photo. Always have and I can't remember a single complaint. Nice to know there is another weirdo out there like me!
Im kind of old school and the code has only a few color marking requirements
Equipment grounding is green
Ungrounded conductor is white or grey
Main( unless green screw)/ system bonding jumpers or G.E.C do not require identification.
*grounded phase*
Please post exact definition of grounded in the code
Connected to earth 🌎
@@RyanJacksonElectrical
Complete the definition. What about the ground in an airplane and ships?
@@bobcocampo The NEC does not apply to aircraft or watercraft. See 90.2. The reason the definition no longer discusses a "body that takes the place of earth" is because of 90.2. That language was removed in 2008. I'm guessing that is what you're fishing for.
NEC is my bible.
Hmmmm. If an ungrounded system.... has a measurable capacitance between the phases and Earth (and it WILL.... because PHYSICS...) doesn't that make it a grounded system...? (capacitance... is "an impeedence,".....) or does the NEC use a nuanced definition... of impeedence? (Not being snarky here... I'm a failed EE student.... who dropped out of college in favor of my concurrent Electrical Apprenticeship.... because my wife and I had a lot of kids already.... and I needed to devote more time to making money in the here and now (then...) than in the future (now.)
No.
How come the electricians get shit on in Jackson? That delta high leg will accomodate any piece of equipment you may bring home from your best first job!