AC cord polarity?? Does it matter???????

Metro, the answer to:

"In most homes, aren't the neutral and "ground" combined within the breaker box?"

Is no. And this is very important to understanding the "leakage" problem oulined in the article you cite above.
The neutral is zero relative to the 120V on each side of it. But it is not zero relative to earth ground.

So depending how the power supply in a component is laid out, connecting one of the two AC plug blades to neutral will result in less ground current leakage through the "neutral" leg of the power supply circuit. As a matter of fact, that is why, as someone described above how to measure for the best plug orientation, they specifically mentioned not to connect the ground pin of the AC plug when doing the measurement. To which I'll add two more rules: turn off the component, and disconnect all other connections to the component (ICs, spkr cables, coax cable or digital feeds, etc) because they may be connected to ground somewhere on their other ends, and you don't want that.

The idea behind this testing procedure is to "force" current that would,in grounded components, ordinarily drain to ground, instead to "leak" through the neutral so it can be measured. And then minimized by choosing the proper plug orientation.

So why is doing this a good thing? Because when everything is hooked back up, some current will drain to ground through the ground leg, and every one of these conditions in your system represents a ground loop which increases the baseline level of hum (and sometimes noise) in the system.

Nsgarch,

Thank you for the informative response, and will look into it further. I did find some interesting articles after posting my last response, but still have inquiries pertaining to non-ferrous chassis having the same effect. Lots of veteran electronic engineers at my work, so I'll get to the bottom of this, yet.

Thanks again...

First, there is no such thing as "zero volts," we just agree to call something zero (the earth) and measure everything relative to it. It is completely arbitrary.

Second, neutral and ground are bonded in the sevice panel and only there. Go to Home Depot and look at a panel. The neutral bar and the ground are bonded. Another term for neutral is grounded conductor.

Third, in a house, circuits are taken off each "hot" conductor, and the currents in the grounded conductors (which are all tied together) cancel each other out. In other words, if, by chance, the currents on each hot leg were exactly equal, the grounded conductor could be disconected from the service neutral (and the ground) and every thing would work. All the current would flow through the hot legs.

Fourth, the reason the grounded conductor measures hot relative to ground is because the conductor has resistance, and there is current flowing through it. Since there should be no current flowing in the ground, and the two are tied only at the panel, there will be a voltage difference at the outlet (but not at the panel).

Fifth, Mr. Holt does not mention, although I am sure he knows, that all power is generated and transmitted as three phase, each 120 degrees apart in time. When each phase has equal current, they sum to zero and there is no net current to flow through the ground. Any current is due to the three phases being unequal and will be small relative to the total current draw. If any significant power is disipated in the Earth, the power company loses money.

The Earth naturally has absolutely enormous currents flowing in it, making the Earth into a giant magnet.

Polarity is a safety issue.

>>"Fifth, Mr. Holt does not mention, although I am sure he knows, that all power is generated and transmitted as three phase, each 120 degrees apart in time. When each phase has equal current, they sum to zero and there is no net current to flow through the ground. Any current is due to the three phases being unequal and will be small relative to the total current draw. If any significant power is disipated in the Earth, the power company loses money."<<
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>>"Mr. Holt does not mention"<<
>>>>>>>>>

The article was not written by Mr. Holt.
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>>"When each phase has equal current, they sum to zero and there is no net current to flow through the ground."<<
>>>>

In my neighborhood there is only one 7200V HV line on top of the power pole, feeding many pole mounted transformers. Lets say for argument, (A) phase of the 3PH 4W 7200/13200V wye feeder leaving the substation. No balance here....Just one ungrounded 7200V conductor and the grounded conductor, the neutral (single phase).... No balance in the (B) phase neighborhood or even the (C) phase neighborhood. I will grant you at the point where the 3PH 4W HV feeder branched out going their separate ways, from that point where the neutrals were joined to the main feeder neutral, back to the subtation the HV neutral only carries back the unbalanced load plus*....
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http://www.ibiblio.org/obp/electricCircuits/AC/AC_10.html#xtocid269101