equipment grounding conductor

[electric291]

I just took a test that had two questions I'm not sure of. 1- an insulated copper conductor can carry 1 ampere per 42.25 cir. mils for 5 seconds before it fails. This is referred to as what. 2-A rule of thumb is that an equipment grounding conductor should have what percent capacity of the ungrounded conductor. I don't know where to find these answers. Any help would be appreciated. Thanks

 

[infinity]

I have no idea on #1. #2-the closest thing I can come up with is 12.5% which is the minimum sized bonding jumper permitted on a service. I guess that you could take the conductor values in 250.122 and try to come up with a rule of thumb. Not sure how accurate either method is.

 

[don_resqcapt19]

#1 tells you how much current an insulated conductor can handle without damage. It is not the failure point, it is the amount of current and time(ampere squared seconds) that will cause the conductor to reach a temperature of 150?C. There is more information about this in this document. It is sometimes called the conductor withstand rating.