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Weird One #72527 12/01/06 05:43 PM
Joined: Oct 2002
Posts: 482
Zapped Offline OP
I'm wondering if any of you have seen something like this and can guide me in the right direction.

Here's the situation: A 100A power pedestal at the entrance of a gated community with loads including 2 gate motors and controllers, an irrigation pedestal, and area lighting.

They had a company come out and install holiday lighting. One of the lighting circuits now draws about 16.4Amps and the other draws about 6.7Amps.

They had problams with the gates - and one of the control transformers ends up being baked. I ran a voltage check and found that the baked control was getting 151VAC. The motor on the other phase was getting about 80VAC.

I went back to the pedestal (panel) and got the same readings at the phase busses (150 on one leg and 80 on the other).

I deactivated all circuits and the voltage went back to about 120 on each phase. Through deduction, I found that the circuits for the lighting were causing the problem. When activated alone, the low load circuit would bring the voltages of the phases to 110 and 130. When I activated the high draw circuit alone, or both together, the voltage would go to 80 on one phase and 150 on the other.

The two lighting circuits are on a single tandum breaker, so I put the breaker on the other phase and got the same results, with the voltage differential on the phases switched (of course).

It seems that the amperage for the holiday lights is too minimal to cause load-balancing problems on a 100A service, and the other phase jacking up when one drops is throwing me off.

I'm sure the infinite wisdom on this forum can shed some light on this. Thanks in advance!

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Re: Weird One #72528 12/01/06 05:52 PM
Joined: Apr 2005
Posts: 27
Rich R Offline
Sounds like a bad neutral opening up, Problem has probably been there for a while but is now worse because of the additional load of lights.

Look for a burnt neutral connection at meter can or at main etc..

Re: Weird One #72529 12/01/06 05:59 PM
Joined: Oct 2002
Posts: 482
Zapped Offline OP
Thanks Rich, that was my first guess, but there is nothing obviously visible on the neutral bus on the load side of the pedestal.
No burns and I snugged everything up and the problem persisted.

Is it possible that the PoCo's neutral has been disrupted somehow? Or do you think it could be hidden on my side?

Re: Weird One #72530 12/01/06 06:01 PM
Joined: Jan 2006
Posts: 558
Rewired Offline
I call a bad neutral somewhere between the 'Ped and its source of supply. Could be as far upstream as where the service connects to thee PoCo.


Re: Weird One #72531 12/01/06 06:06 PM
Joined: Oct 2002
Posts: 482
Zapped Offline OP
Thanks gentlemen. I wanted your educated opinions before I invloved the PoCo (and had to wait for them to respond). Very much appreciated.


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