Problem solved
Myself and another electrician took another look at it this morning. We traced the wiring coming off the "On","Off", "Bypass" switch and found that it went to the E-Stop. I checked the resistance of the conductors going back to the E-Stop while the other electrician operated it. I was getting strange results where the readings fluctuated up and down rapidly. We decided to open the E-Stop housing and test the conductors after isolating them at that end, too. As soon as my co-worker opened the housing a significant amount of water ran out onto the floor. The NC contact was corroded and the wiring was wet. Once this E-Stop was cleaned up and the damaged part was replaced we tried to run the fan motor and everything worked as it should.
How the water got inside the E-Stop is a mystery. And how did this cause the 125A fuse on the one phase of the line side to blow? Have some ideas but I'm not certain of anything.
