So i go on a service call for a AAON rooftop not cooling (460volt/3 phase) hi rise residential building in nyc. Blown condensor fan contacor burnt to all hell. (they have 3 fans tied into 1 contactor). I replaced the contactor and amped it out.. It was high so i was cheking terminations and voltage.Found getting 460 across the board but to ground was getting 28 volts on one of the legs.. The 460 volt main transformer feeds all the equipment on the roof. I checked out all the other equipment voltage and it was the same (460,28,460). To make a long story short it turned out to be a shorted wire in the conduit from the MCC panel to one of the exhaust fan motors (water in the conduit). All the motors are fed from a 460v MCC panel,with starters. So there was a short but how come the fuses didnt pick it up and blow it instead it went through and backfed the transformer causing a voltage drop for everything that was tied into it?