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Old 01-27-2012, 02:59 PM   #1
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Difference between neutral and ground for 120V


I came across this statement while surfing around.

This explains why you want to connect the N and G only at the main panel and not at any sub-panel.

"Why not connect the neutral and ground at other points in the system?
Because if a neutral wire became disconnected (I've seen it happen), the return path for electric current could be along a ground wire. While that itself may not be a big hazard, if that ground wire also became disconnected somewhere, parts of the ground system could be energized. That's not EVER supposed to happen."

Do you agree with what is said here?

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Old 01-27-2012, 05:29 PM   #2
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Difference between neutral and ground for 120V


The main reason is that the neutral wire is a current-carrying conductor, and the ground wire is not.

You don't want your regular circuit's current flowing over the outside of your equipment/apparatus, etc.

The neutral wire does not need to become detached in order for shock hazards to exist.

When the current level gets high with a large load, there will be resistance in the electrical path. If you touch the outside of the appliance, and are standing on a grounded surface (or touching another grounded surface like a sink for example), some of that current can jump through you instead. Shock hazard at the least, and lethal at its worst.

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Old 01-27-2012, 05:39 PM   #3
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Difference between neutral and ground for 120V


I am sure there will be plenty of other view points !
But the statement is correct !
You want to avoid the earth system becoming an
currant carrying conductor,
Or exposed earthed metal surfaces can become live !
(washing machines / clothes dryers).

That point is clear !
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Old 01-27-2012, 06:49 PM   #4
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Difference between neutral and ground for 120V


Yes I agree with the statement.
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Old 01-27-2012, 07:12 PM   #5
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Difference between neutral and ground for 120V


Quote:
Originally Posted by highdeserthome View Post
Do you agree with what is said here?
Don't know yet.

I get at least 9 combinations of neutrals and grounds being broken or having continuity back to the panel, then neutrals and grounds being fastened together [let's say only at the midpoint of the run] and then being broken upstream or downstream of the midpoint connection.
Some of these cases may prove to be trivial but I'd have to see each diagram and do its numbers.

Assume 100' of #14 copper back to the panel and a 10A current that is supposed to be flowing in the neutral and that N & G are grounded at the panel.

The present recommendation may have been judged to be the lesser of several evils, depending on what is likely to fail first and how many of what kind of failures are expected or have been found to happen from experience. It's Failure Analysis 101.

Last edited by Yoyizit; 01-27-2012 at 07:16 PM.
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Old 01-27-2012, 07:43 PM   #6
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Difference between neutral and ground for 120V


I would say it is partially true. KB gives a good explanation.

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