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#68643 - 08/11/06 11:03 PM Re-posting high and low voltage problems  
billy6139  Offline
Joined: Mar 2006
Posts: 8
Carson,Ca. USA
Reposting because topic was lost. I received one answer from Roger.

Scenario:Mobilehome park with 192 units. Main distribution is 240/120 3 wire from Edison. All main feeders are 100A 2 pole breakers feeding 4 to 8 pedestals with 50A mains. All distribution wiring is direct burial 1/0 aluminum, no conduits.
Problem: flucuating voltage. When loads are present(at times) voltage (between neutral or ground) on 1 leg lowers to 90 vbolts, while the other side increases to 140 volts. Voltage line to line is approximately 245 volts and fairly steady. This problem exist about 4 to 5 hundred feet away from main distrubution panel where voltage on the losd side of the breakers(at main distribution panel) remains 240/122, steady as a rock.
Has anyone ever experienced this? Any solutions?

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#68644 - 08/12/06 02:15 AM Re: Re-posting high and low voltage problems  
Larry Fine  Offline
Joined: Feb 2005
Posts: 693
Richmond, VA
This is definitely an open neutral problem. The normally-zero-volts-to-ground on the neutral is being forced away from zero due to normal neutral current.

It can be a hazard because what should be grounded surfaces are instead being fed by the 25-or-so volts, and must be repaired ASAP.

Troubleshooting this would start with isolating the section with the broken line by finding the last point where the problem doesn't exist and the first point where it does.

Then start digging.

Larry Fine
Fine Electric Co.

#68645 - 08/12/06 11:09 AM Re: Re-posting high and low voltage problems  
e57  Offline
Joined: May 2003
Posts: 2,876
I had the EXACT SAME PROBLEM, AND SCENARIO ten or so years ago.

I used to service work and had this, in a trailer park in Concord CA. Turned out to be a U/G direct burial feeder had a nick, and the AL conductor rotted over time.

To save on digging, put a tracer on the neutral and hope you get a dead end to the signal from both sides near the same spot. If you do thats were the Christy box goes. Becacuse it is intermitant they is no real guarantee it will would but well worth the shot!

Another method is to TDR the run, or use a pulse generator on the run. If you dont have any of the varied expensive equipment to find it, there are companies that specialize in it that you can sub it out too. Or you can rent it...

Mark Heller
"Well - I oughta....." -Jackie Gleason

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