I have a 200 amp gould electrical panel. I am installing a 20 line with NM 12/2 wire in my basement for 9 electric plugs in my workshop. Current city code requires a gfci circuit in basements. I tried first a siemans gfci breaker then a square D breaker. Both trip- the siemans immediately and the square D in about 10 to 15 seconds, even if the circuit wire is disconnected from everything at the first junction box. The polarity on all plugs has been checked and I have checked that there are no grounds in the system (between the white and black wires). The junction boxes and outlets are grounded with the ground wire in the cable which is attached to the ground bus in the main box. When I install a regular (non GFCI) 20 amp breaker in the circuit, everything works fine.
The main breaker box has a number of circuits, since it supplies all the circuits in the house (furnaces, washer/dryer, etc.) I am stumped, since even when the wire for my new circuit is completely disconnected from everything at the first junction box, the GFCI still trips. There are no other GFCI breakers in the main panel.