Branch Circuit, Multiwire, NEC 2020 - [210.4], (19min:38sec)

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Multiwire branch circuits are a cost-saving wiring technique that shares one common neutral conductor between multiple branch circuits. This technique saves wiring costs but introduces a handful of dangerous side effects, including potential confusion, safety, and equipment damage risks. Multiwire branch circuits require each phase conductor to be on different phases. Doing this guarantees their shared neutral will never need to carry a higher current than any of the phase conductors, which is why it is possible to use the same ampacity for all the current-carrying conductors of the multiwire branch circuit. Preventing the need to use a larger neutral conductor, is where the cost savings happen, so this is only permitted by the code when the phase conductors are on different phases.
This video is extracted from Mike Holt's Understanding the National Electrical Code Complete Library, to learn more visit www.MikeHolt.com/code or call 888.632.2633.
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Опубликовано:

16 авг 2020

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Комментарии : 314

@OwensandCompany 3 года назад

I was working at a hospital, a maintenance electrician was working nearby. He opened a junction box and unbundled the neutrals while the circuit was energized. There was a nice POP ....... A few minutes later the Director of the Laboratory walked out into the hallway and asked why the power to a section of his lab just went out. At the end of the day, there was $120,000 worth of damaged equipment...It was a multi-wire branch circuit.

@josephsteffen2378 Год назад

WOW! Disconnect the Neutral and you just made a 240V circuit. "Let's be practical, not perfect." Hey, just trying to earn a living...not make a killing.

@superalpha

If the plans specify NO multiwire branch curcuits, then bud accordingly.

@surfride101

I have wired a dozen or so homes ages ago for my father a gc. I messed up several jobs by overloading the neutral with breaker/leg misplacement. It was eventually caught, no damage done and corrected. Neutrals are anything but neutral, it should be called something else, like return, neutral minimizes the danger, much like interchangeably using grounding and bonding; that too is a deadly mistake. Just ask the families of the dead burned alive in the enclosed metallic bus stops with metallic grated benches... On a three phase panel, the 220 leg is orange and labeled stinger; a novice should head the messages; dont F with this. I digress; too many improperly trained, improper supervised and lazy inspectors create deadly hazards; like I did. Appreciate you!

@hippo-potamus Год назад

And all that DANGER just to save a neutral wire run.

@jeffsmith8737 2 года назад

I’m sure the guy with his manager buddy appreciates the shout out for their insurance fraud at the Best Buy lightning incident!

@NunyaDamBusiness69

To dumb the phrasing down, also known as a shared neutral 😮

@timrxn5414

NOW I understand why I got zapped after killing a breaker and going into a box. Multi branch circuit but no handle-tie. I’m a diy’er but trying to learn what is ACTUALLY going on and not be just a hold-my-beer hack. Thanks for your excellent videos

@larryroyovitz7829 Год назад

I came here because I have a critical loads, 120v sub panel, where I want to bring just ONE more circuit over to the subpanel, but it's part of a multiwire branch circuit. And the second circuit, I don't want to bring to the sub panel - nor could I anyway, as it's a 120v panel, thus on a single phase. I'm dead in the water over this last circuit unfortunately.

@garbo8962 3 года назад

Do not get creative. Thanks for that quote.Have homeowners to so called engineers get creative. Best one was on a Friday afternoon and project engineer said o yea you guys have to hurry up and get a 50 amp line ran for a tech coming in Monday morning to start up a new machine. Told him that would require triple time to have it done on Sunday. He said just grab power from the 3 hanging 20 amp cords hanging from ceiling. Say what. He said 20 + 20 + 20= 60 amps. Broke his heart when we told him you can not parallel #12 wire. 3 of us made 3 days pay for working that Sunday. Told him if you have the money we always have the time.

@crowlsyong 2 года назад

Mike Holt gets me excited about electricity. Man I just love his vibe. Have a good day!

@rafaelcastro6466 2 года назад

Thank you Mike for all the technical support, information-Advice that you share! 👏

@TRYtoHELPyou 3 года назад

The Murphy's law thing made me lol, thanks for that.

@visiblepulse 2 года назад

Last year I opened a ceiling gang box to tap in for a doorbell transformer. When I removed the wire nut from the neutral, the home run white lifted. In a nearby study, a 6-outlet adapter with surge protection started sparking and smoking. I could not pull it out of the outlet as it was screwed in. I reconnected the neutral and was then able to remove the adapter and drop it outside while it continued to melt. The shared neutral condition had presented the surge protect circuit with over 120v.

@krakenwoodfloorservicemcma5975 Год назад

Thank you for the great instruction and positive outlook on health and life! They are equally important in my opinion!

@mohameddoumbouya7367 2 года назад

This helped thank you Mr.Holt!!!

@nyinfamous2k2 2 года назад

This guy is awesome, I would have paid much more attention if all my teachers were these good.

@NipkowDisk 3 года назад

My house (built in 1978) has two MW circuits. Neither of them had handle ties for the breakers (they weren't even next to each other although they were on separate legs) AND the circuit to the laundry room used the device yoke for dividing it up!!. Needless to say, I fixed that very quickly.

@neilbrookins8428 3 года назад

Great video. Very helpful. One thing that may cause people to connect multi wire branch circuits wrong is the use of tandem breakers. If you connect the two hots to two tandem breakers you will over load the neutral because tandem breakers are same leg. But many people assume that any adjacent breakers are always opposite leg. Tandem is an exception to that.