Garbage disposal trips breaker when it is switched off
Are you in the USA?  The green screw should be Ground (green or bare wire), not Neutral (white).

Generally:


Line is "hot", with the active AC voltage present.
Neutral is the return path for the current.  All current should travel from Line, through the load, and then back through Neutral.
Ground is there for safety only. It should only carry current in the case of a fault.


In a standard circuit there is no indication that current is flowing through ground, as long as it's not enough to trip a breaker.  However, your garbage disposal unit is connected to a GFCI breaker.  This kind of breaker is specifically designed to open up when there is ground current.

It sounds like your circuit's Neutral is tied to the junction box.  The junction box is also likely grounded.  This ground connection is generally made by a bare copper wire attached to the back of the junction box.

At the same time, your disposal has a big motor in it.  When you turn off a motor it creates its own current for a small amount of time as it spins down.  Since this current can't return through the switch , it returns through ground.  This trips your GFCI.


First, verify the wiring connections. It is possible that the ground was wired correctly, but that someone did it with white wire (instead of green or bare wire) just to confuse everybody.  Ideally, there should be one connection from the green screw to the junction box, and a totally separate connection between the white wire from the breaker box and the white wire to the disposal unit.
If, in fact, all the white wires are tied together then you should disconnect your white wire from the green screw.  Then run a wire from this screw to the grounded junction box.