3 occurances of dropping one leg of 240V


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Old 02-09-11, 07:51 AM
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3 occurances of dropping one leg of 240V

2 weeks ago, one leg of my 240 dropped out. My heat pump was struggling and half the house power went off. The other "half" of service never flinched. This happened 2 times within an hour and lasted a minute or so each time. I went straight to basement to cut off heat pump. All breakers and wires including main were cool to touch. I didn't think about it much more until it happened again yesterday. I had the Power Co. out here at 10PM last nite after I called a neighbor to ask if he had an weird electrical experience at same time as me. He described the exact same instance without promting him. I "assumed" he was on the same transformer as me, lost "half" his service at the same time so I called the Power Co. as the first step. This is where it gets tricky. It was quickly discovered by Power Co. Technician that my neighbor is on a different transformer with underground service from high-voltage line to a above ground transformer near his house. The Power Co. guy said it was not possible ("one in a million chance") for both of us to have a half service loss at the same time being on different transformers, but my neighbor assured me it happened. My transformer checked good: 123V X2 @ 246V total and he pulled the meter base and said it looked fine in there. I am extremely concerned at this point as to my safety but at the same time thouroghly confused by the chain of events. I have 200A Crouse Hinds box installed in 1985. Murray breakers are all I can/have interchanged. Any suggestions would be greatly appreciated. I apologize for the length but kept post as short as possible.
 
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Old 02-09-11, 09:04 AM
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Originally Posted by linesider
The Power Co. guy said it was not possible ("one in a million chance") for both of us to have a half service loss at the same time being on different transformers, but my neighbor assured me it happened.
I agree it would be very unlikely. The only thing I could think of would be some type of transient/surge/sag event on the higher voltage distribution system that caused bizarre side-effects for both of you. If you have different transformers, then your hot and neutral conductors are all separate so there could be no common cause that I could think of other than the higher voltage system.

My transformer checked good: 123V X2 @ 246V total and he pulled the meter base and said it looked fine in there.
If they checked out your transformer, meter pan and you checked out your main panel, then I'd say you're in good shape. There's nothing more you can do at this point other than keep an eye out for other anomalies and report it to the power company if it happens again.
 
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Old 02-09-11, 09:14 AM
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My father had this happen a year ago, over a period of several weeks. Half his service went out, he has an overhead drop also. Clearly, a case of a bad connection. The POCO was called, and since the problem was intermittant they didn't fix it. I happened to be outside actually looking at the line secondary connections, when it happened. I saw a spark that led the POCO, 2nd visit, to the exact connection that was bad. But, no, it didn't involve his neighbor.
 
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Old 02-09-11, 05:24 PM
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Next time it happens, measure voltage from A leg to neutral, B leg to neutral, and A leg to B leg, inside your breaker panel. tHIS IS TO TRY TO NARROW DOWN WHETHER THE PROBLEM IS IN YOUR HOUSE OR OUTSIDE.
 
 

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