Service entrance wiring burned but breaker didn't trip

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Old 08-10-15, 12:53 AM
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Service entrance wiring burned but breaker didn't trip

I would like to ask on how it happened that the wire burned and the breakers did not trip. The loads are welding machines and grinders. One thing that I thought is that the ampacity of the wire was not able to hold the current, for short, an under rated wire. Could you share your opinions regarding this incident?
 
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Old 08-10-15, 01:17 AM
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If it's actually the service entrance, in the US it wouldn't be your problem...but I would guess either the correct torque on the connections or no anti-corrosion paste used? Scorched connections won't necessarily make a breaker trip.
 
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Old 08-10-15, 01:36 AM
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Sorry sir but it is not in the U.S. It is from Philippines. The service connection wires are burned but the main breaker did not trip. The load side wasn't damaged too. I am thinking what is the cause of this incident. I think the connections are good because they have used it before.
 
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Old 08-10-15, 03:02 AM
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What size service do you have, what is your main breaker size and what is the size of the entrance cable? If the cabling was too small for the load and the breaker was too large for protection of the cable, then the cable becomes your "fuse" and will burn before the breaker trips unless there is a direct short.
 
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Old 08-10-15, 04:03 AM
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A breaker will trip on overload which is normally due to too much current flowing through the breaker. Heat is also a contributing factor.

Wires that are burned is almost always due to a poor connection. Poor connections can create a lot of heat, but depending on where it might not be enough to trip a breaker, especially on a main breaker with 100-200 amp rating.

Are the wires aluminum? If so, is there anti-oxidation past on them? A picture would be helpful.
 
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Old 08-10-15, 06:23 AM
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If you run welders, you know how much damage an arc can do even from a small welder. A loose wire in the electrical service works the same way. All it takes is for the connection to be a little bit loose, an arc forms, heat builds up, bigger arc, more damage, bigger arc... Significant damage can occur before there is enough amperage drawn to trip the breaker.
 
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