Or any more than you have to supply a Square D I line at 600 volts just because it is able to handle that voltage.
True, but isn't there a Code requirement that states that panels shall be clearly marked
to indicate the supply voltage?
The OP's situation, omitting the neutral when the loadcenter's labeling indicates that it is a 208y/120 tells me that unless you change the labeling to clearly indicate that it is being used as a "straight" 208y loadcenter, you will have a Code violation.
(Side note - I'll dig thru my '99 NEC to get a reference, if I locate what I had in mind I'll edit this post.)Numbers in following quote added by me.
(1)Actually you share neutrals with every circuit on the supply side of the source.
(2)Electrons do not know or care which side of a panel they are, they act the same either way.
(3)You can deny it to be true if you want but I challenge you to show how it differers electrically from one side of a panel to the another.
LOL Bob, I love how we can agree to disagree.
(1) Absolutely. But at that point you have larger conductors, lower impedance to the neutral point of the transformer and/or ground, and the benefit of load diversity and the effects of motors and resistive loads to help "even out the bumps" so to speak.
With branch circuits, you don't have those same conditions. I think we can both agree that differences in conductor size, length, ampacity, even wiring method (conduit, open air, romex, even routing) can have some effect on circuit performance, however slight.
(2) Uh... maybe, maybe not. I don't fully understand the physics of electricity and I'm sure there are many EE's who can tell stories of things that should never happen but do. So I take the middle ground on that one.
(3) I deny nothing, but I also challenge anyone to explain why, in my line of work, that shared neutrals cause trouble in audio and microprocessor control systems, and the use of dedicated neutrals solves/prevents those issues.
Because candidly, like any other person in business, if I can save costs while providing the performance standards my clients demand, I'm all for it. But in over 20 years of cinema and professional audio, no one has ever come up with the explanation that will allow me to share neutrals on the branch circuits without any issues. And I will not compromise my standards for system performance to save even a few hundred in wire cost.
Now the "isolated" vs. "non-isolated" grounding thing is a whole different ballgame. I have, so far anyway, found NO benefit to the use of isolated grounds. Proper audio wiring techniques take care of any grounding issues.
The LED screens in your example I would have supplied the same way with no quibbles. For one, all the reasons you point out are valid, and the savings significant. And you weren't dealing with audio signals and the high gain involved.
However, I challenge you to supply a few racks full of high-powered audio amplifiers that way and see what happens.
Bear in mind that in my challenge I realize that the potential increase in hum or other noise issues that can result won't matter in a large venue, but try to get away with that in the media room of a multi-million dolar home!
So we're working in different areas, and what works best for me is too costly (and understandibly so) in someone else's area. But as long as the client's happy when we're done, that's what really matters, right?