Originally Posted By: bbadger
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Thank you Patrick.
Robert while you are correct that a 480 volt service has higher arc fault potential a simple 240 house service can make conduit and wires disappear.
The POCO simply does not protect the secondary wires running to a house, if your lucky the connection between the utility wires and the home owners service conductors will burn clear.
If it does not burn clear nothing will stop the current from destroying what ever is "in the way"
Have you ever welded?
If so you know how much metal you can melt with 100 amps @ about 70 volts.
Now think about a 1000 amps (or much more) @ 120 volts (the voltage to ground) believe me no metal raceway will contain the fault.
We will have to agree to disagree on this one, ![icon_smile.gif](upload://b6iczyK1ETUUqRUc4PAkX83GF2O.gif) maybe some others will jump in on this.
Back to the higher current services.
We had a good one on a 1200 amp 480 service, it melted all three 4" rigid metal conduits back toward the transformer like a wick for about 30'
luckily this was on the outside of a block building.
The utility fuse did not blow until the oil in the transformer boiled over
and the primary winding in the transformer melted.
Electrical Construction & Maintenance
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