Ground as a Neutral

[Rotato]

Before I begin. I understand this is a big no no. Against code. For reasons. The reasons that I understand are the ground is meant to be a safety if a hot conductor were to touch a casing of a machine / device then a fault occurs which gets transferred from where the fault is all the way back to the bonding jumper at the source tripping the overcurrent device.

The question is this. How can I safely show somebody that using a ground as a neutral with no neutral at all present is incorrect and can potentially kill someone? What would it take to show them its not ok? Has anyone had to cross this bridge of explaining it to someone that is not grasping? Say scenario of 220V single phase with a couple of 120V devices (what the ground is for) inside.

 

[infinity]

Say scenario of 220V single phase with a couple of 120V devices (what the ground is for) inside.

You're correct, the EGC is only carrying current under fault conditions. Under normal conditions it is not to be used as a conductor for the neutral current. The loss of the neutral would allow all of the neutral to be flowing on the metal parts of the system creating a potential shock hazard.

I'm not sure what the 220V part of your question is referencing.

 

[Rotato]

You're correct, the EGC is only carrying current under fault conditions. Under normal conditions it is not to be used as a conductor for the neutral current. The loss of the neutral would allow all of the neutral to be flowing on the metal parts of the system creating a potential shock hazard.

I'm not sure what the 220V part of your question is referencing.

My apologies. I meant to say a 220V single phase machine with a couple of 120V devices (Contactors) inside.

So if I am able to mentally wrap my own self around this scenario. Lets add a situation where that machine is powered by a buss duct where it gets its EGC. All machines on that buss duct will have their EGCs now hot (0V but current carrying). If I am understanding this correctly?

 

[NEC Inspector]

I have heard of a man who got killed when he took apart a metal raceway feeding a well pump. The ground wire was tied to the neutral at the well pump, so the raceway was carrying neutral current. When he pulled the raceway apart, he became in series with the neutral current because he had one hand on the raceway carrying neutral current from the well pump and the other hand was on the raceway going back to the panel. He got hung up and was not rescued in time. Similar things happen to plumbers when they work on metal water mains, almost all of those are carrying neutral current.

This concept could perhaps be demonstrated a non-contact voltage detector, a wire jumper connecting the two sections with an amp clamp, a lightbulb in series, or the most dramatic would be some kind of fuse-like material (like aluminum foil) between two sections of raceway that are hooked up as the neutral to a device and letting it burn. Obviously, if you want to play with live voltage you need to be the one to figure out how to do it safely at your own risk. I have never tried these items, so I don't know what all you would have to do to get them to work.

Any metal appliance housing, metal raceway, metal panel, metal buss duct, etc, that is in series with neutral current could likely be separated and used in this way.

 

[Rotato]

Thanks for the input. Trying to make sure I don't stumble over my own explanation of "why".

I don't plan on doing a live demonstration with any AC voltage but maybe if I was to use a small 24V test box (w/batteries) and a relay coil. Maybe I can come up with something to get it sticking in their head.

 

[LarryFine]