Re: shore power contection

[HighTechRedneck]

The intent of continuous special identification for the ground is simply to prevent mistakes.

That's the thing that seems odd to me about this section.  It just seems so much more important to me to know a hot wire and which phase it is at all points along its path than to know the ground wire at all points.   A mistake with a hot wire is usually much worse than a mistake with a ground wire.

Oh well, like I said, it is the code and my puzzlement with this point makes no difference.

[Sean]

...
Then I assume it is OK to run a short section of the SO wire from this connector to a junction box?

The SO is only allowed if the connector hangs loose, as a "pendant."  Now I see your connector does have a mounting flange, and I am assuming you intend to mount it somehow on the side of the coach or in a panel.  In that case, you are correct:  SO can not be used.

Understand that the connector you have there is really a marine item, and the rules are very different on boats (which are not covered under the NEC, but, rather, a whole separate litany of codes and guidelines such as those promulgated by the ABYC).  So it likely has that shroud on the back for connection with marine cable.

For your application, you will want to mount it in an enclosed junction box of some sort.  In which case, you can simply discard the plastic shroud.  Tie your #6 THHN wires directly to the connector -- the connections are compression-fit with set screws.

HTH,

-Sean
http://ourodyssey.blogspot.com

[Sean]

...   A mistake with a hot wire is usually much worse than a mistake with a ground wire.

Actually, this is a common misconception.

The reality is that the ground system is there precisely to ensure that "mistakes" (or failures) in any of the other wires result in the fault current being carried safely away immediately.

"Mistakes" in hot wires, such as open circuits, are easy to detect, because the device or receptacle usually will not work.  So the installer and/or end user will know something is wrong.  By contrast, a mistake, such as an open, in the ground is completely undetectable in normal use, and only shows up when problems with the other wires arise, possibly with deadly consequence.

As such, the code considers the safety ground to be the single most important conductor.  With it, shorts to frame and the like result in immediate grounding of the fault current and resulting circuit interruption (from fuse or breaker).  Without it, fault current is likely to find its way to ground through the next human to touch the appliance.

HTH,

-Sean
http://ourodyssey.blogspot.com

[Dallas]

The intent of continuous special identification for the ground is simply to prevent mistakes.

That's the thing that seems odd to me about this section.  It just seems so much more important to me to know a hot wire and which phase it is at all points along its path than to know the ground wire at all points.   A mistake with a hot wire is usually much worse than a mistake with a ground wire.

Oh well, like I said, it is the code and my puzzlement with this point makes no difference.

Mike,

The ground is actually called a "Safety" ground. It is there to CYA if something goes wrong in the other 3 wires. It is suppose to carry the current back to the main box and then to ground. That's why you do not want the ground or the neutral to be connected to the bus body in any way. If it was, then when you, as the conductor touched the body, you would be the best circuit completion to earth.. probably not a good thing.

Humans make a much better circuit than copper.

Dallas

[HighTechRedneck]

Yes, I understand and agree with the importance of the safety ground.  I agree that open grounds are stealthier than open hot wires.  I even agree that it is the most important wire in the lot.  But my curiousity is merely over why the NEC considers the identification of hot wires mid run to be less important than identification of the safety ground midrun.  To me this would be analagous to only requiring flamabile liquid tanker trucks to have a small warning sign near the inlet/outlet pipes, but requiring water tanks to be labeled "water" all over the tank so that somebody needing water could easily find it.

In my perfect world , all wire runs would use the proper color wire for each conductor on the whole run.  But I know that in real practice, especially on the heavy wires this isn't always possible.  I'm just amazed that the NEC mandates continous identification of the safety ground but not the hot wires.

[Sean]

...  But my curiousity is merely over why the NEC considers the identification of hot wires mid run to be less important than identification of the safety ground midrun.

It doesn't -- the safety ground must be green, and all hot wires must be some other color.  So you can easily tell which wires are "hot" -- all the ones that are not green or bare.  The only issue is telling the hot wires apart from each other, which, from a code/safety standpoint, is irrelevant -- they are all considered to be equally dangerous.

Note that the "neutral" wire is considered hot for code and safety purposes.  That's because it carries current.  If one end of the neutral is grounded (as is required by code), and you cut the neutral someplace, you now have two ends, one of which is at ground potential, but the other of which is at the exact same potential as any other hot wire in the circuit.  Also note that "neutral" is an oddity -- most power circuits don't have one.  Household and small appliance power is the exception.  FWIW, the code also requires the "neutral" be identified for the full length whenever possible, but it does allow for termination-only marking.

In my perfect world , all wire runs would use the proper color wire for each conductor on the whole run.

That's the NFPA's "perfect world" too.  But they do recognize that there are circumstances in the "real world" that makes this sort of perfection impractical.  For example, often a circuit will be run for 240-volts, using two "hots" (usually red and black) and a safety ground.  Some later time, when the circuit gets re-purposed for a 120-volt load, either the red or the black now needs to be re-tasked as "neutral."  Without the code exemption, the electrician would have to rip out one or the other of those wires and replace it with a white one.  In practice, anyone who has tried can tell you that, often, you can't simply remove and replace a single wire, and you end up having to yank the whole circuit and start over.  So the code allows for this kind of re-purposing by using termination marking.  Since the safety ground, however, is mandatory in all circuits, there is no need to allow for re-tasking of this wire.

And, as we have already discussed, in the real world wire is not available in all colors, especially above #6.  But even in smaller gauges, wire is commonly available in black, red, blue, green, and white, whereas colors for three-phase, such as brown, orange, and yellow, while available, are much harder to come by.

-Sean
http://ourodyssey.blogspot.com

[Bob Gil]

Thanks Sean.

I guess I am back to the drawing board.

I will see if I can get a flange mount that will go to and box some where.

They sure do make it hard on a little man trying to get that kind of stuff.  I have not found any thing other than the marine stuff that is like that.  I guess I will keep looking and stop trying to buy any thing (like that $30.00 inlet) that I might not be able to use in the long run.

[HighTechRedneck]

For example, often a circuit will be run for 240-volts, using two "hots" (usually red and black) and a safety ground.  Some later time, when the circuit gets re-purposed for a 120-volt load, either the red or the black now needs to be re-tasked as "neutral."  Without the code exemption, the electrician would have to rip out one or the other of those wires and replace it with a white one.  In practice, anyone who has tried can tell you that, often, you can't simply remove and replace a single wire, and you end up having to yank the whole circuit and start over.  So the code allows for this kind of re-purposing by using termination marking.  Since the safety ground, however, is mandatory in all circuits, there is no need to allow for re-tasking of this wire.

Thanks Sean.  That makes sense and is what I was looking for, the common sense behind it.