How does a GFCI work?
. (From: James Phillips (jamarno@juno.com).) I quit having GFCI trouble after I fixed all the bad wiring connections, and I haven’t had trouble at all with GFCIs and my workshop, which I wired myself. GFCI controller chips include a time delay to reduce false tripping. I used to think GFCIs always tripped at 5 to 6 mA, but the UL allows up to a whopping 200 mA if the GFCI stops the current within 30 ms, and 6 mA leakage is allowed to last 6 seconds. According to National Semiconductor, their GFCI chips will stop a 200 mA fault in 20 ms, a 6mA fault in .5 sec.
