One leg of main drops, other goes up.

[Krush]

Hey guys, I'm familar with wiring etc, but I have a question that maybe ya'll could help me out with before I call the power company. I recently aquired an old barn that has power service to it and I've been wiring up the inside.

Everything worked until I accidently had a short wired in. I flipped the breaker for that circuit and got an arc and the breaker tripped (note, the main did not trip). Now here is my problem: I went to plug in a saw and use it and everything died.

Doing some testing with my multimeter (after turning all circuits off) I get 120v on each leg coming in to neutral and 240 hot to hot. When I plug in a hairdryer, the motor will run, but the voltage on that leg drops to 80v. When I turn the heat on the dryer own, the motor stops and the voltage goes to 2 v...conversly the other leg jumps up to 230v. I've read elseware that this is signs of a bad neutral connection or something. I do have a decent ground rod going into the ground (shouldn't this take care of a bad neutral for testing sake?).

Question...is the problem in my box or on the pole transformer (do I need to call the power company?). I have single phase.

 

[hbiss]

Re: One leg of main drops, other goes up.

Sorry, we don't give advice to do-it-yourselfers. I suggest you call a licensed electrical contractor to diagnose your problem.

-Hal

 

[don_resqcapt19]

Re: One leg of main drops, other goes up.

I've read elseware that this is signs of a bad neutral connection or something. I do have a decent ground rod going into the ground (shouldn't this take care of a bad neutral for testing sake?).

You have a high resistance connection on the neutral on the line side of the point where you are testing the voltages. No, the ground rod should not and will not take care of this problem. The impedance of the path back to the transformer grounded conductor via the grounding electrode system is too high to take care of an open neutral problem.
Don

 

[Krush]

Re: One leg of main drops, other goes up.

Originally posted by don_resqcapt19:
You have a high resistance connection on the neutral on the line side of the point where you are testing the voltages. No, the ground rod should not and will not take care of this problem. The impedance of the path back to the transformer grounded conductor via the grounding electrode system is too high to take care of an open neutral problem.
Don

Thanks! This is what I figured the problem was, so I'll get on the horn with my power company.

Thanks for the info, and for the record, I may be a DIY'er but I'm also a mechanical engineer that used to work at a power plant.

Edit: I just realized why I can get a reading to ground on the meter...it bascially lets no current pass thru it so the potential difference between the line and ground shows, but the ground is not a good conductor back to the pole. I was using a measuring point on the neutral wire coming from the meter, so this shows that my problem is not in the box. Thanks again.

[ January 08, 2006, 05:30 PM: Message edited by: Krush ]

 

[charlie b]

Re: One leg of main drops, other goes up.

Originally posted by Krush:. . . I may be a DIY'er but I'm also a mechanical engineer that used to work at a power plant.

Which is to say that you are not an electrician, and you are seeking assistance with performing electrical troubleshooting and repair. The Forum rules prohibit us from giving you that assistance. Our concern is that you may get only the answer to the question that you ask, and get no answer to the thousand other questions that you should have asked, but did not know that you needed to ask. The thousand of other questions are the ones that electricians, electrical engineers, and other professionals in the electrical industry would have known about, and would have understood the answers to, as part of their years of training.

?A little knowledge is a dangerous thing.? The Owner and Moderators of this Forum do not wish to risk allowing you and your family to be placed in danger, by giving you too little information.

I am closing this thread.