System Bonding Jumpers for Different Types of Systems, NEC 2020 - [250.30(A)(1)], (8min:34sec)
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- Опубликовано: 15 апр 2021
- In this video, I’ll discuss the “System Bonding Jumper” (SBJ), its function, and its importance to ensure a safe electrical installation!
This video is an extract from Mike Holt’s Understanding the 2020 National Electrical Code Complete Training Library. For more information about this product visit www.MikeHolt.com/code or call 888.632.2633.
For over 40 years, Mike Holt Enterprises has been providing quality electrical code training to help electrical professionals learn the Code, prepare for exams, and improve their electrical knowledge. Visit www.MikeHolt.com for exam preparation tips and training, instructor and curriculum support, continuing education options, free videos and graphics, and so much more.
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Praying for continued recovery from your mishap recently. Blessings to you in the Lord, brother.
Much appreciated
Mike, you're very much appreciated. For years I've been recommending my students sign up for your forum and e-mail newsletter. Thank you for continuing to fight the good fight and for being a mentor to many across the skilled trades.
Oh, what a nice message. Have a wonderful day.
Mike is the man. Passed my Texas Journeyman test with a 97 first try with his material. Guys if you want to win spend the money to get his stuff you won't be disappointed.
Thanks, now get going with our Business program so that you'll be ready for the next level, then your masters, then the moon! MikeHolt.com/Business
You reiterated the exact question I was reviewing with my team. Thank you Mike. I just sent this clip to like 20 people.
Mike, I actually got called to do a service call for a 500kva transformer where the "electrician" did not properly bond at the transformer and caused a whole mess of issues! So yes! you are 100% correct when you say "electricians" do not know the concept, or even forget it all together!
Can't get easier than this!
I find it interesting that Electricians still have confusion about this. A seperately derived transformer system is the most straight forward system to bond and ground, in my opinion.
That’s why you’re watching this video? 😂
You should also consider that the majority of electricians are mainly installers that just work off blueprints. It is a very small percentage of people searching out this information.
God bless you mike. Please take good care..
Thank you and God Bless you and your family.
Honor God and thank him for that... love it
Thank you for clearing this up Mike.
Any time
thanks, I'm in your apprenticeship program great video 👍🏼
Yes, you are one of the new leaders in the industry! I'm so happy that I can be part of your life and the lives of your fellow classmates. Give a shout out to them for me! (yes this is Mike Holt).
First off, God bless you brother. I've seen an missing sbj. The tale tale voltage you will get on 208 panel for example is 77 volts on a to b phase and close to 277 on a to c. This has to do with the sine wave. The system tries to correct itself by a missing differential voltage. It doesn't read 208, if my memory is correct. Phantom voltages on the neutral to ground is also a tale tale sign from my troubleshooting memory.
Amen for God's blessings! Thanks Mike.
Thank you, God Bless
Thank you Mike.
You are welcome, have a great day.
Thanks Mike!
No worries!
Mike, thank you for all the great information.
In keeping with the objectionable neutral current line of of thinking, if the utility company providing the source bonds and grounds their transformer and then I bond the service disconnect as required, are we not creating the same neutral current problem?
Parallel earth/neutral current is not a problem.
Thanks as always
You are welcome.
love these videos. question regarding system bonding jumpers. in a corner grounded delta would it be a good idea to ground a phase at the meter socket enclosure? what if it was originally a 3 phase 3 wire delta with no neutral and you wanted to ground a phase, where should the main bonding jumper be at?
The NEC requires service grounding at the service equipment (service main), see 250.24(C). Excellent point.
Mike, thank you for all the great information
according to what i have seen in this video when SBJ is not installed then the voltage between the line and the ground is zero volt , so if sombody touch the hot wire he will not get an electricall chocked ?.
hope to answer my question
thanks again.
Correct!
Thank you, sir
You are most welcome.
One question , what about a residencial conection where the transformer ( with sbj installed) is not part of it, and the suply wires are only line and neutral?, must be installed the sbj?, if not, what is the path clearing a fault?
Grounding of service equipment must be in accordance with 250.24.
Can a weak neutral coming from the power companies service line cause an electrical fire? It is being held on by only 2 of its strands going to the weather head of a 100 amp service.
Please post your question on MikeHolt.com/Forum.
Do you have to use bond bushings on flexible metal conduit on primary and secondary flex seen it done multiple ways please advise and tell me where I can find in code thanks
Of course not unless 250.97 applies (which it doesn't). In addition, it serves no purpose to put bonding bushing and jumpers from a 'connector' that is connected to a raceway that does not qualify as an EGC. Why do people put them on? Who knows, probably it just makes them feel better.
Mike..let’s say I don’t drive a ground rod for my transformer. Everything is bonded correctly but the only thing missing is my GEC. I still clear faults and still get correct voltages correct?
You are 100% correct, I've submitted to have the grounding to the building grounding electrode system requirement removed.
quick question... if the transformer is wye bonded but there is no GEC(nor metal conduit) to the next disconnect, the neutral and a new grounding rod must be bonded at said disconnect?
See NEC 250.30 on SBJ, SSBJ, and GEC.
@@MikeHoltNEC thank you!
If there is a difference in potential between ground and line why don't you read it on an ungrounded system?
A ideal voltmeter (ideal as in perfect, not the brand name) would have infinite ohms of input impedance, and would read a difference in potential between line and ground on an ungrounded system.
However, a realistic voltmeter will have a finite number of ohms as the effective impedance of the input, typically on the order of magnitude of Megaohms. You can demonstrate this by constructing a voltage divider with two 1kOhm resistors, and measuring across one of the two resistors. As expected, with 1 kOhm resistors, you'll likely get half the supply voltage as your read-out. Now try it with 10 Megaohm resistors, and it likely will not measure exactly half the supply voltage. You will see the voltmeter becomes a resistance in parallel with the resistor you are measuring, which reduces the equivalent resistance of that section of the circuit. An ideal voltmeter would not do this, but a realistic voltmeter will. An experiment such as this, can allow you to infer the input impedance of your voltmeter.
If the effective impedance of the voltmeter is low enough that it has less impedance than the air/insulators between the other two phases and ground, then it will become a preferred path for current to flow, that will temporarily ground the system. It will settle on an equilibrium, where there is zero voltage difference between the phase under test and ground, and therefore draw no milliamps of current to register a voltage read-out on the voltmeter.
Thank you for answering the question!
@@carultch im going to re-read and chew on this reply. I am in electrician school and find new training info like this very interesting. Thank you.
@@elc2k385 I was surprised when I first did this experiment. With our equipment they had us measure the voltage divider with 1 kOhm resistors, and then with 1 Megaohm resistors. I thought for sure it would measure half the supply voltage, and didn't expect anything else. But sure enough, it measured significantly less than half the supply voltage.
@@carultch thank you for the detailed answer. It is not clear at all at first, you need to apply the right reasoning. Would be very nice if @Mike can make a short video explaining this mathematically 👍🏻
No/bad ground you will get different voltage readings.
The ground (earth connection) has nothing to do with the voltage of the phase conductor and the metal enclosures of the system (because of the system bonding jumper).
If you have no system bonding jumper this would make voltage to ground 0, wouldn't this be a lot safer? If someone is to touch a live wire in a system with no system bonding jumper, there is nowhere for the current to go to. Now I know there are benefits to having a system bonding jumper to clear faults and surges but still... why does this take priority over someone's life if someone was to touch a live wire?
Watch this video - studio.ruclips.net/user/videompgAVE4UwFw/comments