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Yes a neutral Carries the unbalanced current of the system it is 100%-2000% a current carrying conductor

This is not correct. It may carry current but it is not looked on as a current carrying conductor in most cases because of what I described earlier. I also posted the yes and no of neutral as a current carrying conductor.

Read article 310.15 (B)(5). The bold is exactly opposite from what you said

(5) Neutral Conductor.
(a) A neutral conductor that carries only the unbalanced
current from other conductors of the same circuit shall not be
required to be counted when applying the provisions of
310.15(B)(3)(a).

(b) In a 3-wire circuit consisting of two phase conductors
and the neutral conductor of a 4-wire, 3-phase, wye-connected
system, a common conductor carries approximately the same
current as the line-to-neutral load currents of the other
conductors and shall be counted when applying the provisions
of 310.15(B)(3)(a).
(c) On a 4-wire, 3-phase wye circuit where the major
portion of the load consists of nonlinear loads, harmonic
currents are present in the neutral conductor; the neutral
conductor shall therefore be considered a current-carrying
conductor.
 

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Once again... because the neutral only carries the imbalance, the heat generated by the full set of conductors (including the neutral) is similar to a circuit fed by hot conductors alone (no neutral) that's why code doesn't count it in the de-rate calcs for a raceway.
Read this over for as many times as it takes for it to sink in.
 

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Don't let semantics get the better of you or you'll be running in circles chasing your tail.

"Current Carrying Conductor" is an odd term. "Conduct" means carry current. If a conductor doesn't carry current, why would it even be there?

Not counting the equipment grounding conductor / green wire in ampacity calculations is easy to understand - the equipment grounding conductor only carries current in fault conditions.

In multiwire circuits, there is a cancellation effect so the neutral may carry less current than the hots. If all the hots are fully loaded and perfectly balanced, the neutral carries zero. However also note that under other circumstances the neutral carries more than some of the hots. For example in a four wire multiwire branch circuit on a wye system you could have

load on A = 20A
load on B = 20A
load on C = 0A
load on N = 20A

The neutral is carrying current (full load in fact) and is carrying more than C hot.

Or you could have

load on A = 20A
load on B = 5A
load on C = 5A
load on N = 15A

The neutral is carrying current, and is carrying more than B or C hots.

(BTW, these examples are everyday occurrences. If you have a bank of cubicles in an office fed with a four wire 208/120 multiwire branch circuit, the receptacles in the cube base will be on one of the three phases. If one person plugs in a space heater to an A receptacle, and another plugs a space heater in a B receptacle, you'll have that loading above.)

You can play the values for A, B, and C on this graph

20A three phase MWBC neutral current (desmos.com)

and notice that no matter what you do, the biggest perimeter you could draw is the perimeter of an equilateral triangle with the side equal to the full capacity of the circuit. The perimeter of the triangle is the combined load on the four wires. So the maximum TOTAL load on the four wires is THREE times the full load of the circuit. So it makes sense to count these four wires as THREE for derating purposes, which are based on the combined load on the wires.

So they tell you that you don't have to count the neutral in your derating calculation, but it's not because the neutral doesn't carry current, it just works for making the calculations.
Worth pointing out that your equation only works for linear circuits (i.e. resistive loads.) When capacitance and/or inductance shift the wave form in time, the loads can add rather than subtract. Harmonics were especially bad because so much of harmonics are triplens, and triplens ALWAYS add. So if 50% of all three circuits' loads are in triplen frequencies, the neutral conductor carries 150% of the phase circuits. It's my understanding that a bunch of fires were attributed to this phenomenon which is why the NFPA went a bit crazy over neutral sharing and under-sizing. It's also my understanding that the initial hysteria was later determined to be way overhyped. But all that is only my understanding from things I've been haphazardly told by various people - your mileage may vary.
 

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I'd suspect that MWBC's in residential due to the Arc fault regs as well as the current crop of freshly minted dunces they're more trouble than they're worth?

On many contracts sharing neutrals is prohibited now by the specs, probably due to the high harmonics problem which you say is now under better control?
Probably. Three possible issues with shared neutrals - load due to triplens, arc fault hijinks, and possible damage or injury from a short circuit backfeeding into one circuit via a shared neutral with the other circuit. On single phase systems, personally I'm not convinced that harmonics (or phantom power) can be severe enough to cause conductor damage or fire. That is, I have been shown the math showing that it's possible to dangerously overload a circuit with a shared neutral of the same size, but I remain unconvinced that a real world system could generate that level of neutral current. I've certainly seen devices whose power factor is at or even below 0.50, but I'd have to be shown that even this can generate more than 50% each without having some offset when combined. (Neutral current I mean - obviously a 0.50 power factor will double the phase current compared to a resistive load.)

That said, I never allow shared neutrals except for circuits whose breakers I intend to tie together, even though I'm unconvinced that it's the problem it was once considered to be.
 

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All of this is a moot point for me. We build to plans and specs, which always says no shared neutrals. The handle tie rule for shared neutrals killed it. Before that it was hit or miss in the specs.

The last time I’ve seen an oversized neutral on a job, was probably late 90s. For some reason isolated grounds seam to be making a comeback. What’s the point of an IG when they plug in a touch screen Point of sale with a two prong wall wort? The job I’m on now has a dedicated panel for point of sale. It’s just a 100A panel fed through a 208 to 208 transformer, no I.G. But why bother just to plug in an iPad. It’s probably just to make the engineering company more money?
 

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All of this is a moot point for me. We build to plans and specs, which always says no shared neutrals. The handle tie rule for shared neutrals killed it. Before that it was hit or miss in the specs.

The last time I’ve seen an oversized neutral on a job, was probably late 90s. For some reason isolated grounds seam to be making a comeback. What’s the point of an IG when they plug in a touch screen Point of sale with a two prong wall wort? The job I’m on now has a dedicated panel for point of sale. It’s just a 100A panel fed through a 208 to 208 transformer, no I.G. But why bother just to plug in an iPad. It’s probably just to make the engineering company more money?
Actually it usually costs us money, although if it's a percentage job (most contracts are fixed fee) we'd make more money. Handle tie rule was when I stopped using shared neutrals - before that I'd always shared neutrals, and only oversized when it was shared circuits feeding computers 'cause switching power supplies used to be really nasty. And I completely agree that I.G. is almost always a waste of money. It's nice to keep such things on dedicated panels if there are twenty or thirty circuits of them, especially if they'd otherwise be sharing a panel with something really nasty like welders, but generally speaking that too is a waste. All electronics work at low voltage DC, and a properly designed power supply should be able to handle pretty much any normal level of distortion. We used to have a theater client (since bought by the Chinese) who insisted on I.G. for all the P.O.S. and computers. Then you go to an old theater and see the exact same equipment running just as well on non-I.G. panels - and as you say, all running through ungrounded wall warts. The only real exception might be medical equipment, where maybe a tiny ripple might induce a tiny but significant disturbance in output and safety requires a ground plug. But even then, unless it's running through an isolation transformer, how much benefit will one ever see at an outlet?
 

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All of this is a moot point for me. We build to plans and specs, which always says no shared neutrals. The handle tie rule for shared neutrals killed it. Before that it was hit or miss in the specs.

The last time I’ve seen an oversized neutral on a job, was probably late 90s. For some reason isolated grounds seam to be making a comeback. What’s the point of an IG when they plug in a touch screen Point of sale with a two prong wall wort? The job I’m on now has a dedicated panel for point of sale. It’s just a 100A panel fed through a 208 to 208 transformer, no I.G. But why bother just to plug in an iPad. It’s probably just to make the engineering company more money?
I think the two main reasons for isolated grounds is to 1. show an orange outlet for electronics only. 2. Have an excuse for the electronics / computer guy when their equipment tanks. "You needed an IG receptacle" is what they can claim.
 

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Once again... because the neutral only carries the imbalance, the heat generated by the full set of conductors (including the neutral) is similar to a circuit fed by hot conductors alone (no neutral) that's why code doesn't count it in the de-rate calcs for a raceway.

It costs an engineer practically nothing to make a specification for dedicated neutrals, larger wire, or a larger conduit. The contractors and customers can fight over the price. :p
1. I agree with the statement that it basically costs almost nothing in most cases to pull a full size neutral just as it does with an “isolated” ground.

2. I agree with the statement that harmonics don’t matter but for other reasons. There are two consequences to excessive harmonics. When I say excessive I meant to the point where voltage THD is over 5%. The first is it impacts transformer capacity. If you are close to loaded it pushes you into voltage drops, which is just another way of saying you have a THDv problem. The second is the downstream devices are eating the surges and sags that the transformer puts out, with all the consequences of that. A bigger neutral isn’t going to cure this.

3. There are REAL common mode currents that are sometimes an issue. In medium voltage especially current capacitively couples onto the neutral or ground which is part of why utilities run a neutral on pole lines. It is worse as voltage increases. At 480 it might be 1 A. On a 23 kV system I’ve seen 50 A (600 A circuit). It also shows up with VFDs by nature and I’ve seen 90 A on the ground. This happens on all circuits, even “3 wire” ones. It is just often very small. It is much worse on closely coupled circuits like concentric wound neutral cables.
 

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When the Shlt hits the fan...
blames something no one really could possibly understand, ... that way...
Nobody gets hurt...
And physics, being non cooperative to any specific desdirable outcome... can't be punished...

Just accepted...

"Because ya canna blam the laws of physics captain!!!"

Amirite?
 

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I am starting to use the simple terms like white wire, green wire, or bare wire. Some people get confused with grounded, grounding, bonding, so it makes things simpler to explain things. For instance, do we ground the pool or do we bond the pool? Do we run a grounding conductor or a grounded conductor?
Six words and each have a different definition…

Ground Grounded, Grounding,
Bond, Bonded, Bonding…

Explaining these terms to a customer or someone unfamiliar with the terms helps to define what’s going on with what you want to talk about.
 

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Six words and each have a different definition…

Ground Grounded, Grounding,
Bond, Bonded, Bonding…

Explaining these terms to a customer or someone unfamiliar with the terms helps to define what’s going on with what you want to talk about.
Try explaining them to a homeowner. Many electricians including myself use them interchangeable. That is why I like colors.
 

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Try explaining them to a homeowner. Many electricians including myself use them interchangeable. That is why I like colors.
Why would you use them interchangeably when they mean different things? You should probably stop doing that you will instantly sound more intelligent
 

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Why would you use them interchangeably when they mean different things? You should probably stop doing that you will instantly sound more intelligent
How many people say " ground the pool" or "ground the panel"? Does one attach the grounded conductor or a grounding conductor. If you never did that then I guess you are perfect. There are many people who sound intelligent with their ornamental words but their intelligence ends there. Besides try explaining this to a homeowner.
 

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How many people say " ground the pool" or "ground the panel"? Does one attach the grounded conductor or a grounding conductor. If you never did that then I guess you are perfect. There are many people who sound intelligent with their ornamental words but their intelligence ends there. Besides try explaining this to a homeowner.
John V is saying he's getting better and letting **** slide. You should too. ;)
 
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