party yesterday

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petersonra

petersonra

Senior Member
Location
Northern illinois
Occupation
engineer
I was at a party yesterday.

I walked outside and happened to see the electric meter. Next to it is the telephone interface box. There is a green (maybe #10) green wire coming out of the telephone box and appears to disappear into the meter.

A closer look though shows the end of the wire has burnt though and is not actually connected to anything. The burnt insulation shows something was very hot there.

How in the world would you ever get enough current flow through that path to melt a #10 wire?
 
How about a 10 wire coming in contact with a 10000 amp unfused xformer supply?? That is my guess. I have heard of guys using 12 wire for a 200amp fuse I dont know what 10 will melt at. This wire was put in for lightning protection so maybe it was a lightning strike as my second guess.
 
peter d said:
Perhaps an open neutral and the current tried to return to the source via that conductor?
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That would be my guess. That is also why the NESC is requiring a #6 Cu. to be used for inter-system bonding. I believe this has been approved and is in effect for the 2007 NESC. I have a copy of the 2002 but not the 2007 NESC. :smile:
 
charlie said:
That would be my guess. That is also why the NESC is requiring a #6 Cu. to be used for inter-system bonding. I believe this has been approved and is in effect for the 2007 NESC. I have a copy of the 2002 but not the 2007 NESC. :smile:
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how would it do that through the telephone box?
 
petersonra said:
how would it do that through the telephone box?
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Open neutral, return current takes all paths back to the source but no longer has the low impedance path of the neutral so it now returns through the earth, telephone ground, CATV ground, gas pipe, etc. From what I have seen, return current is not picky and can burn up small conductors. My CATV shield was connected to my water pipe with a #14 Cu. until I changed it to a #10 several years back. :)
 
charlie said:
My CATV shield was connected to my water pipe with a #14 Cu. until I changed it to a #10 several years back. :)
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Did your picture quality improve any? :grin:
 
LarryFine said:
Did your picture quality improve any? :grin:
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:rolleyes:
aetsch013.gif
:D
 
wind storm

wind storm

This reminds me of a trouble call I received from a rental property owner at a duplexe. It was a year and half ago. Property owner tells me that he had a fire and a tenant saved the structure! We had a wind storm and a dead pine tree's top popped out and landed at the gable edge of roof. One piece fell across mast and broke. Second piece of the tree fell down and took out the meter at socket. Fire broke out in attic space and one tenant happened to be at home and entered the attic and fought the fire with a small extinguisher after calling fire department. After looking through out the entire system I discovered that there was several different fires, maybe 6 that had burned in the attic. About three different places in the SE cable had burned up! Every place that there had been a fire I noticed a #12 wire scortched!There was a few of these #12 single solid conductors running about the attic??? After further investigation I traced these all back to the catv interface. Ground conductors. I went on the roof to look around at service head. I noticed one of poco's lines at the service drop where they make the crimps did not have a "snap cap" insulator on terminal! So what happened was first contact of tree slapped drip loop into the neutral and energized it! Sending voltage down to ground and over to catv box and back through attic! At the point that the #12's ran across the rafters was a fire! And the fire burned SE cable! Ran new SE to one panel and checked the panel and the other service on other side of duplexe. After further inspection and having inspector call the poco we still had problems. Poco's lineman discovered crazy voltages at meter can. I thought maybe damaged line in mast?? Come to find out he had a burn at top of transformer also! Voltage ran up neutral to transformer.He repaired damage there and then did a load test at meter socket. If the guy living there had not been at home, the duplexe possibly would have burned down!
 
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