Dear JIMMIE,
https://secure.wikimedia.org/wikiped...current_device
As I understand, a GFCI compares the hot and neutral currents.

Christopher A. Young
Learn more about Jesus
www.lds.org
..

"JIMMIE" wrote in message
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The GFCI breaker works by detecting leakage current on the ground
wire. It only needs to detect about 5ma to cause a trip.

Jimmie