Loss of Neutral @ Service Entrance

[djnjpi]

Here is a hypothetical with it's roots in reality. A house is undergoing major renovation with all wiring disconnected. Temporary wiring is then run from the panel by the contractor and utilized for all tools and site needs.One line also feeds the work trailer with a small refrigerator which is on constantly. The main panel box is not grounded, and the grounding clamp on the grounding rod is loose. Sometime during the night, the neutral conductor at the service point drops out due to a faulty, substandard connection utilizing an undersized and dissimilar metal connector. Will the temporary wiring be energized at 240v? Please explain the sequence of events as they relate to fire potential.
Don

[ October 21, 2003, 11:00 PM: Message edited by: djnjpi ]

 

[dereckbc]

Re: Loss of Neutral @ Service Entrance

Originally posted by djnjpi:
Here is a hypothetical with it's roots in reality. A house is undergoing major renovation with all wiring disconnected. Temporary wiring is then run from the panel by the contractor and utilized for all tools and site needs.One line also feeds the work trailer with a small refrigerator which is on constantly. The main panel box is not grounded, and the grounding clamp on the grounding rod is loose. Sometime during the night, the neutral conductor at the service point drops out due to a faulty, substandard connection utilizing an undersized and dissimilar metal connector. What can we expect?
Don

Trouble. I closed your duplicate post. Sorry to be vague, but it reflects the details you posted

 

[insptr]

Re: Loss of Neutral @ Service Entrance

I guess you could expect spoiled food!

 

[hurk27]

Re: Loss of Neutral @ Service Entrance

And your grounding voltage would be elevated so I wouldn't touch anything that is bonded by this service/panel unless there is a seprate grounding wire ran.

 

[brian john]

Re: Loss of Neutral @ Service Entrance

With out a neutral single phase 3 wire circuits
(1 phase/hot, neutra/grounded, GEC) and any multi wire circuits (2 hots,1 neutral/grounded conductor, GEC) with apliances connected could expierence a voltage above 120 vac (nominal) depending on their impedance/resistance and could be damaged.

 

[Ed MacLaren]

Re: Loss of Neutral @ Service Entrance

djnjpi,

Here are sketches of a "hypothetical" 3-wire circuit that might help illustrate what happens to the load voltages when the neutral conductor is opened, and the load is unbalanced.

It supports the other arguments in favor of spending some time to balance the loads on a multi-wire circuit, especially a service.

Ed

 

[brian john]

Re: Loss of Neutral @ Service Entrance

ED:

Only thing missing from your drawing is the SMOKE.

 

[kupiec]

Re: Loss of Neutral @ Service Entrance

What would be the prudent steps to take if this
situation *HAS* actually happened? I'm speaking about checking wiring/breakers/outlets.

 

[djnjpi]

Re: Loss of Neutral @ Service Entrance

In this case the house was a total loss due to the subsequent fire.

 

[hurk27]

Re: Loss of Neutral @ Service Entrance

By:kupiec
What would be the prudent steps to take if this
situation *HAS* actually happened? I'm speaking about checking wiring/breakers/outlets.

The first thing would be to remove all power to the service pronto!

Then only turn on A phase breakers this will allow you to trouble shoot the lost neutral without the danger of over voltaging one of the phases. But remember if the grounding is also bad everything connected or bonded to the grounding could have elevated voltages on it so care must be taken if others are on the job site.