310.15(E) Neutral Conductor

Explanation of when and why we count a neutral as a current carrying conductor for the purpose of derating (ampacity adjustment).

[@joeljahnke9000]

Dave, you are an exceptional teacher. I appreciate, so much, your organized and sequential manner in which you teach. You rock!

[@Calico5string1962]

Your video presentations are simply the BEST I have ever watched. So we'll explained and presented. As an industrial/commercial electrician for over 40 years, I really enjoy watching your stuff! It's always a great refresher for me. Thank you, Dave, for sharing your knowledge and insight!

[@JesseKlaus]

This is probably the most thorough explanation of shared neutrals I've seen - well done.

[@danielelise7348]

This guy actually makes learning this complex stuff enjoyable.🤔⚡

[@khanhho8471]

Thank you Dave. You make it very easy to understand.

[@bahbee5659]

“Oop, keep my thumb down.” A great educator & can bring a smile to my face👍

[@stephendavis6408]

Clear and concise explainations of both the theory and the NEC. Thank you.

[@pamdemonia]

That was great! Wish you had been my code teacher when I was an apprentice!

[@michaeldonnelly2977]

THANK YOU! I was looking for an explanation of exactly HOW current can possibly flow back to the source through the second hot leg on a multi wire circuit, from an electrical theory point of view. You explained it very simply and eloquently with your “trading post“ analogy. Thank you, sir! This was very, very helpful!

[@soundman2604]

Best teacher ever, and above all correct!

[@martf1061]

16:35 Thank you. Now i understand why, sometimes, the engineers asked for a double wired neutral in transformers. I learned more in 2h watching your explainations, than i did in 20 years . I suggest you do some videos about motors.

[@doctorgoodwrench]

Thanks for continuing to post, Dave. Your explanations are remarkable.

[@davegordon6819]

Thanks for your vote of confidence, and thanks for engaging with the other viewer. I put a link to my new "open neutral" video in the responses below if you're interested.

[@charlieperez6844]

Im so glad i subscribed to your channel. Your videos have helped me understand a bit more. Thank you!

[@johnnyelectric7572]

again....just a great Teacher. Thanks!

[@benfurnish9948]

Fantastic video. It makes total sense now. Plus a bonus for having the Soli Deo Gloria posted.

[@davegordon6819]

Thanks brother. I am thankful for God's mercy to me and may He help us both to use what He has given us for His glory.

[@user-xw5ve7nc9k]

Thank you very much.

[@DanielRamos-bq8py]

excellent job sir ! well explained and much appreciated !

[@michaelcostello6991]

Excellent lecture. So well explained. Cannot think of any questions after this

[@renediaz5162]

Thanks for the awesome and useful class!

[@mph5986]

Clearly and easy understand. 👍

[@Lazdinger]

Soli Deo Gloria for this man’s videos.

[@mcarroll598]

Excellent explanation!

[@user-or3rm9tt8l]

Thanks...I really enjoying

[@ryanjourneymanwireman4937]

One of the best electrical videos I've seen (hoping info is correct) but thanks

[@paulmullen573]

Great videos, Dave. A suggestion... a set of videos on Grounding and Bonding would be super helpful. I understand the concepts, but I don't understand how the grounding and bonding topics are organized in the NEC and I spend a lot of time flipping pages to be sure.

[@MrKandela10]

the best explanation!

[@ramonqo1]

You are the best.

[@ochoaelectric5175]

Nicely done

[@michaelarriaga08]

Excellent video thank you so much

[@xevierred6330]

Fascinating

[@abigalanderson7494]

I like how Dave puts the code section next to his pictures

[@Peace88Hi]

Thank you prof.

[@daveculbertson602]

Very informative video.

[@TheCompton1963]

Dave is the best! 🧑🏻‍🏫

[@justd3123]

so clear, tnx

[@tfun101]

At 6:40 I was like….”ohhhhh duh” and it all finally made sense. 🙃

[@safetythirdified]

Where have you been all my life!

[@brentcory8194]

Great video! So am I correct in saying in most commercial applications i.e. office buildings, schools, medical offices, etc. we should be counting the neutral due to 310.15(E)(3)?

[@RustyJeepHole]

Thank you sir

[@mariogregory4922]

I like Dave!

[@morelightpm457]

Excellent video. JW - LU #613

[@chadhardwick9214]

Dudes a correction factor ninja….😎

[@yusprogres5271]

Yessss

[@tommywatterson5276]

I remember something about neutral ampacity rating at 70% of phase voltage

[@brianskellenger9344]

🎯

[@faroutdesign]

Great video! I don’t get to work with a lot of wye systems. I have seen a 10 awg neutral on a shared system with non linear loads. Is this a code article requirement or just a good work practice?

[@alyssaisaackson6797]

I have a 3 phase solar inverter combiner panel the load is balanced on all 3 phases. I don’t even think the neutral Carry’s current would I have to count it ?

[@pakistanian2325]

May Allah bless u.❤

[@markchidester6239]

Is there a situation where the neutral wire needs to be larger gauge than the "hot" wires because it has the potential of carrying more amps than the "hot" wires?

[@ericthered9655]

Why doesn't the voltage increase if the waves are out of phase?

[@TheMinecraftACMan]

For the single phase drawing at the top, where you had two separate multi-wire circuits, would it introduce the potential for any weirdness if the two non-shared neutrals were accidentally swapped?

[@davegordon6819]

Good question. If the two neutrals were swapped on the right side of the top diagram it could create a big problem. You would then have the lower black wire sharing a neutral with the upper black wire. The result would be that that neutral would carry the addition of the two black wires - meaning that if each was carrying 20 amps, the neutral would be carrying 40 amps. They would not cancel each other out. It would be like sharing a neutral between two wires from the same leg (bus) in a residential panel. This is why when we are working with 120/240 V single-phase panels we need to make sure that if we share neutrals, we share them between one wire from one bus and one wire from the other bus. Likewise, in other facilities where we run more than one multiwire branch circuit within the same conduit, we must identify which neutrals go with which phase conductors [see NEC 200.4(B)]. Alternately, if you tied the two neutrals together, you could entertain similar issues depending on how much current is flowing on each hot conductor... I plan, at some point, to make videos that focus on current flow with the various systems and point out these sorts of problems.

[@warrenjtaylor8714]

The first system is slightly wrong i thought because the coils are wound in opposite direction, so line to line is 180 out of phase. Hence the 'split'. Also tell them it's a voltage source not current source if any load asks...

[@mikebavoso26]

Very good. Does anyone know if Dave is a professor at a nationally recognized University?

[@patricksmith2414]

Would the neutral count if it were a 4-wire, 3 phase wye connected system with only 1 phase conductor and the neutral?

[@BG-eng]

Every time you have a single phase a neutral Carry the current back so that group is counted as 2 wires

[@TM-cm4gb]

Quite interesting, as european i wasnt sure how US 120/240V thing works but logical ofc. Fault with open neutral would cause all kinds of shenanigans in the the system then whereas in EU system it would fully turn off the circuit. I wonder if it is a problem with devices getting destroyed etc with that kind of fault.

[@okaro6595]

Three phase is common in Europe and in it the results are similar to what in the US split phase. On the other hand in the UK style single phase broken neutral puts full 240 V to equipment cases. In split phase and three phase it can be smaller than the full mains.

[@NeoN-PeoN]

Is it not the case that basically all home setups are unbalanced? I mean, no one is going through their homes and adding the amps up on each circuit to ensure they're balanced. So in the neutral is probably always carrying current, right?

[@pld8993]

In individual circuits (1 hot paired with 1 neutral) the neutral carries the same amperage as the hot and is always counted as a current carrying conductor.

[@jeanv4871]

Hi Dave, my husband has some questions and wanted to know if you do one on one video calls plz let me know! Thank you!!

[@Waffel-eb2gf]

whta does it mean when you say "add heat" ?

[@GailsonPvPwtf]

*raises hand* If you take 2 of the hots in a 3 phase service to power a 1 phase device, wouldn't the voltage be irregular since the waves and troughs of the AC current aren't oppsite and balanced? Apprentice here.

[@WorBlux]

Assuming a wye configuration - peak to peak Voltage across 2 phases is 2(cos(30)) of p2p-V on and single phase. So 208 on a 120 Wye. But it's still a regular sine wine. (Any addition of sine waves at the same frequency is another sine wave on that frequency.

[@etherealrose2139]

Power goes in and out both conductors. It's a perfect sine wave at whatever voltage the two are at line to line.

[@stevebrule6172]

I have a tricky multiple choice question, hopefully someone with more knowledge can help me out A White/grey wire in a feeder circuit ________: A)Be bonded or have a circuit breaker B)Is the largest wire in that circuit C)Should not have a voltage to ground My notes: On the main panel, neutral is connected to the bar that is bonded with the panel, the green grounding wire is also connected to the same bar. (so does that mean the answer is A?) In the sub panel, the neutral wire is connected to the neutral bar which is isolated from the metal box with plastic between them, the Green grounding wire is separated and is connected to its own bar that is bonded to the sub panel box. In the circuit that this question applies to, --------- “The neutral wire is going to be sized larger than the Green grounding wire” (But that doesn’t mean it’s the LARGEST in the circuit right? Because the two hot wire could be the same size) --------"The neutral should have no potential difference(voltage) to the ground" (does that mean the answer is C?) (But that doesn’t mean it’s the LARGEST in the circuit right? Because the two hot wire could be the same size)

[@muradzeynal]

hey brother, did you find the answer? I want to know as well

[@dlp7130]

Hello mrs Dav.. so if the main neutral wire loose what is going to happen to the system?

[@davegordon6819]

If the neutral is still connected but loose, it could create a high-resistance point in the circuit that would not only get hotter than it should, but could create voltage drop due to the high-resistance point being in series with rest of the circuit. However, if you are asking what happens if it gets disconnected, then I'll refer you to a video I just made that addresses that exact issue of an "open neutral": kzbin.info/www/bejne/gnvZqpWVjNqdkMk

[@dlp7130]

Thk you very much mrs Dave

[@P8ntmagnit]

What song is this?

[@Victorkorchemniy]

“Counting the individual neutral, with one hot.” I get the electrical theory, but it’s not in writing in the code book. How come ? They should add a #4 to clarify that even though is common sense, it’s not mandated in code in specific writing

[@TrevorSachko]

Balanced load, don't use a neutral. Unbalanced load, use a neutral.

[@grabir01]

Remove the earth ground. Then what you say is true.

[@timault8209]

Dave... Why do you call power carried by a conductor "heat". I 'think' I know why. But can you explain your use of that word in the context of this lecture, please? (Notice, fellow viewers, that I ask DAVE... and not YOU... for Dave's explanation.)

[@JAYDELROSARIQ]

There are no harmonic you need flux

[@abdelghanich7804]

hello, Dave i have a question and if you have a time answer me please , first of all thanks for every efforts that you give us so , In a single-phase transformer input, one wire getting entry as live, another as neutral. But what would be in case of its output? In output, which-wire would be phase, and which-one would be neutral? pasteboard.co/dlGFszYF6Iai.png

[@BG-eng]

The system is AC, any one can be hot or neutral. but usually ground/bond is connected to one of the wire which is than identified as neutral. Let’s wait for Dave to comment further