Sorry to beat this dead horse again guys, but, went to a presentation on AFCI's tonight put on by Cutler-Hammer(maybe Eaton-Yale elsewhere.) They had a piece of NMD 90 wired off a 15 Amp AFCI breaker to show how little of an arc was generated on a short circuit fault as comapared to a regular breaker. Being as inquisitive as we are we tried just touching the neutral and ground together to see what happened, the AFCI tripped every time. My question is why? Of course the guy they send out is a salesman and not a technician so we didnt get a very good answer from him, so I was just wondering what you guys thought.