Exposed service drop

[BARRY ADAIR]

Found this yesterday

Is there any way for that bare aluminum conductor to be completely broken (two ends hanging separately on the utility company side of the connection) and still detect neutral at the receptacles?

[John Arnold]

I inspected a house where the service neutral had been cut on purpose and the receptacles still tested ok. If there is an intact grounding conductor and electrode at the house and also at the transformer, then there is a path back to the transformer through the earth. Not a good path, but a path.

[Jerry Peck]

Yes.

Checking circuits for grounding only checks back as far as the service equipment where the neutral is bonded to ground.

From there back to the transformer, you are checking nothing.

Also, the grounding electrode system at the service equipment, and at the pole/transformer, are both grounded into the same earth, and the neutral is bonded to that ground, thus, you are conducting the neutral (grounded) current back to the transformer through earth.

Not the low resistance path it is seeking, but a path back nonetheless.

[Thom Walker]

Jerry and John,
Thanks for that answer. I had my first severed one last week. One question:

Are you saying that the only value of the neutral back to the transformer is "least resistance" and that it could be eliminated? Not that it would or should, but COULD, with no potentially adverse effects on the system as a whole?

What would be your suggested wording on a report? Okay, that was two questions.

[John Arnold]

No, it can't be eliminated. The "low resistance" path it provides is much much lower than the earth path we described. It would create a very dangerous condition to eliminate it - the low resistance path back to the source (transformer) allows sufficient current flow during a ground fault to trip a breaker.

[BARRY ADAIR]

John and Jerry,

Thank you for the explanations.

[Thom Walker]

What Barry said.

[Jerry Peck]

Think of it this way.

When you have a dropped or loose neutral, the voltages on the two phase conductors to the neutral connection in the panel now varies depending on the load on each phase conductor (because the neutral is not creating the grounded center point).

That means that when the 120 volt toaster kicks on, the voltage on that side of the neutral will drop (higher current through the resistance of the neutral drops more voltage there), leaving higher voltage on the other phase conductor.

Let's say that the voltage drops 50 volts (not at all uncommon with a neutral problem - I've seen it many times), that means one side of the panel now has 70 volts on its 120 volt circuits ... not too bad you say? BUT ... the other side of the panel now has 170 volts on its 120 volt circuits, and that is not a good thing for equipment designed to operate at 120 volts (neither is 70 volts, but that's a different effect than that much over-voltage).

Now, if (*IF*) there were *only* 240 volt circuits, no problem.

Plus, with that current flowing back to the transformer through the ground, you could wind up with all kinds of stray voltage problems, energizing TV antenna masts, playground sets made of metal, metal fences, etc.

Consider that there is a chain link fence running alongside the property line, the transformer is in that back corner, the electrical service is at that rear corner of the house, the fence turns back to the house from the side fence.

Loose or have a bad neutral and the neutral current is going to take all available paths back to its source (not just the path of least resistance, *all* paths). Now consider that the chain link fence may actually be the 'path of least resistance', the current will go through the ground back to the transformer, but a lot may also go back through the fence, the path of least resistance.

[Thom Walker]

That example you gave nearly matched the house where I was. Good explanation!