Loss of 1 Phase

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jmellc

Senior Member
Location
Durham, NC
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Facility Maintenance Tech. Licensed Electrician
Sorry if this has been addressed before, I found no other posts at the moment.

Customer has lights going out at times. He turns on the range and lights come on, though flickering and dim. It happed for just a few seconds while I was there. I ran to panel and checked, had only 1 leg. Ran out to meter and it was good there, but also good back at panel. Happened too quickly.

I think phase A is dropping out, killing the lights. Turning on the range connects A to B through the burners, giving partial power back to A for the lights.

I tightened the fuse block clamps (old fuse panel) and called Duke Energy to check outdoors for anything starting to give out. Haven't heard back from them yet.

Anyone else had a similar problem?
 
This is a very common problem. You diagnosed it correctly. I usually find the problem is with the poco. It can be tricky as you may find proper voltage at the meter, however under load you will probably see the voltage drop to zero on one phase.
 
I agree with Dennis.
Lights dimming or becoming usually bright often indicates a neutral problem. Flickering or going out all together, often a phase problem (not to discount the neutral)
On the old fusible mains I have found the stabs on the pullout sometimes don't make good contact with the "socket".
 
While your trying to find the problem it is important to remove electronic equipment and any other voltage sensitive equipment from the trouble circuits.
 
This is probably not the culprit, but we did have this happen in a home just before turkeyday. After some troubleshooting and going down the list, we found that within the main disco for the house, the "teeth" if you will, that close upon contacting, had come loose on one phase. When I went to take it off the wall the whole thing just fell out. Needless to say, after replacing the disco, all was functioning as normal. Good luck.
 
Problem Found

Problem Found

Just heard back from the customer. Power Co. told him they replaced 2 weatherheads somewhere outside. I think of a weatherhead as the cover on a riser at the service drop. They must mean something else, such as a splicing device? I knew it was most likely something outside, as I was missing voltage on 1 leg coming to panel, ahead of the loose fuse block.

Thanks for the feedback.
 
Just had a similar trouble call. Dim lights, and changes when stove is turned on. .. And I had read this post just the night before. So the stove thing was no surprise. I found a bad feeder breaker to the apartment panel. A decomposed mouse was laying on top of the breaker. I'll say the acids from the mouse ate away one stab!
 
ok here it is !!!

ok here it is !!!

I am having the same or close to these problems but not until after replacing the service meter box and the mast

1. At the meter socket line side 240 line to line, 122 Line to neutral each leg

2. Plug in the meter at the load side 240 line to line , line to neutral on one leg 116v the other leg 140v this is after the main breaker was turned on. this test was on the line side of the main breaker.

3. So when I turn on the garbage disposal one leg gains voltage and the other leg drop about 6 to 10 volt difference, if the refrigerator starts and the same effect. you can see the fluctuation of the motor in the lights.

4. I have double checked all my connection and all is good.

5. the lighting is old bx and knob and tube. I ran a new grounded plug circuit and plugged a lamp into it and it has the same effect as the knob and tube circuit.

6. the old meter mast was like se cable with a cable weather head and the strike knob had been pulled free from the house and I had to cut back some trees and pull the service entrance back up to re-attach the knob. did doing this loosen a connection at the pole?

7. is it a power company problem?
:-?:-?:-?:-?
what is the answer?:-?:-?:-?:-?
 
Most likely a POCO problem. Bad neutral conductor or connection. Especially since the neutral conductor may have been stressed when the attachment knob was pulled out of the house.

Call `em right away, and tell them you have a bad neutral situation.
 
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