SUBPANEL

[ActionDave]

EARTH connection will NOT help you from getting a shock '

Wrong. Earth connection will not help you in clearing a fault.

 

[electrofelon]

Wrong. Earth connection will not help you in clearing a fault.

Earth connection will not help you from getting a shock either, unless one of the electrodes is a very low impedence path back to the source like a metal water pipe connected to another service. In that case, the lost neutral may not be noticed for years. But dirt will not lower the potential between the service with the lost neutral and ground any significant amount unless you are standing right on the electrode.

 

[ActionDave]

Earth connection will not help you from getting a shock either, unless one of the electrodes is a very low impedence path back to the source like a metal water pipe connected to another service. In that case, the lost neutral may not be noticed for years. But dirt will not lower the potential between the service with the lost neutral and ground any significant amount unless you are standing right on the electrode.

Agree in the context of all of the electrical world, at least the North American part of it.

Disagree in the context of the discussion at hand.

 

[electrofelon]

The post that winnie made holds true again in your question here. There is no direct yes or no answers, but the short answer is you are less likely to get shock at the service panel no matter what the condition of the neutral because the connection to earth is right there and you have the requirements for all the metal raceways to be connected with more than a simple lock nut.

Agree in the context of all of the electrical world, at least the North American part of it.

Disagree in the context of the discussion at hand.

Can you explain what you mean by " context of the discussion at hand", I'm a little confused, maybe we are talking about different things?

 

[ActionDave]

Can you explain what you mean by " context of the discussion at hand", I'm a little confused, maybe we are talking about different things?

I am seeing the discussion having to do with why we don't re-bond the neutral at sub panels.

That naturally leads into questions about the service, where we have code mandated neutral current on metal parts. That's why we have rules about service raceways needing a bonding lock nut and the GEC being at the service.

 

[electrofelon]

I am seeing the discussion having to do with why we don't re-bond the neutral at sub panels.

That naturally leads into questions about the service, where we have code mandated neutral current on metal parts. That's why we have rules about service raceways needing a bonding lock nut and the GEC being at the service.

I am just a bit confused on your disagreement with domnic's statement , and your statement that I bolded in the quote.

 

[jstjohnz]

If you re-bond at the sub panel then you also have a parallel conductor violation. I think the main danger would be if the neutral were to open, then you have the ground wire carrying the neutral current with no obvious sign that there is a fault.

 

[jstjohnz]

OK, probably disregard my last post. I was thinking of a scenario where you ran separate ground and neutral to the sub and re-bonded. But most likely if you were going to re-bond at the sub you would only run one conductor from the ground/neutral bus of the main panel to the ground/neutral bus of the sub, so my previous comments wouldn't apply.

 

[junkhound]

Another aspect if the home or building is connected to a metal cased well.

Any continuous leakage current thru the conduit or grounding conductor can result in severe and rapid electrolysis of the well casing, leaving holes in it and potential well failure over time.

 

[Terrier]

Common Cause of Stray Voltage

Common Cause of Stray Voltage

If both the main and sub are bonded to neutral, their cabinets will be at different potential because of the voltage drop on the neutral conductor. Of course this will be very small and imperceptible during normal operation but in some rare circumstances could be a shock hazard, for example during a fault (high current flowing=how voltage drop).

The improper wiring of sub-panels is one of the common items found to contribute to Stray Voltage (small voltages, typically less than a few volts, that may not be harmful, but can stop dairy cattle, dogs, pigs from drinking or cause other adverse behavior). You will note from the list of commonly impacted animals, this is often a problem on farms, where the farmer/owner had performed much of the wiring themselves, not understating the need to keep the ground and neutral conductors separated after the main panel.

 

[ActionDave]

Earth connection will not help you from getting a shock either, unless one of the electrodes is a very low impedence path back to the source like a metal water pipe connected to another service. In that case, the lost neutral may not be noticed for years. But dirt will not lower the potential between the service with the lost neutral and ground any significant amount unless you are standing right on the electrode.

Let's try it this way....

In the case of a line to earth fault anywhere in the system, yes you would have to be standing right on the ground rod to not get a shock but, an open neutral at the service I don't think you would get much of a shock at all. An open neutral at a sub-panel where the neutral is not isolated can give you a nasty shock.

 

[don_resqcapt19]

Yes, and along with that, you wouldn't have to lose a neutral to be shocked. Current will flow on both the neutral and any metal it is connected to. So if you touched the EMT and something else that is grounded it will shock you. That is if the neutral and ground were bonded again at the subpanel.

Not likely unless the neutral and the conduit both are high resistance paths. The only voltage that is available to drive a shock is the voltage drop on the parallel path that consists of the neutral conductor and the conduit. If the wire is in a good condition, then there will be only a few volts, at most, to drive the shock.

 

[don_resqcapt19]

Let's try it this way....

In the case of a line to earth fault anywhere in the system, yes you would have to be standing right on the ground rod to not get a shock but, an open neutral at the service I don't think you would get much of a shock at all. An open neutral at a sub-panel where the neutral is not isolated can give you a nasty shock.

Why can't an open neutral at the service give you a shock? If you have an open neutral and a single 120 volt load the load end of the open neutral will be at 120 volts.

 

[Ground Loop Guru]

SUBPANEL

It's this voltage drop that's "very small and imperceptible" in the context of lights and motors and electric shock that drives so-called "ground loops" in AV systems (causing hum and buzz) and putting "glitches" into the grounding system of computers, making them do unexpected things.