Right - the issue is with the original PDU, which Ian specifically said they did not rewire. That means one neutral, both inside the PDU, in the power cord, and in the power plug. The loads inside the 780 (which are single phase, as Ian said) have nothing to do with the issue. So, the 780 PDU has a three phase wye power cord (five conductors, including ground). I'm betting that they have a 220V split phase circuit to run it from, so they've wired two of the three phases together for one side of the 220V circuit, and the third phase to the other side. Best case, assuming the loads inside the 780 are balanced, that would make the neutral current the same as one of the phase currents. But that's not really a safe situation - if any of the internal loads within the 780 is turned off, disconnected, or blows its own breaker, then the neutral current will _increase_ due to the imbalance. Worst case in this situation the neutral current would be 2x normal. They probably get away with this because the PDU isn't loaded to anywhere near it's rated capacity. And let's hope they really aren't running it from three separate circuits on the same phase. Were it my 780, I'd rewire the PDU to be 220V split phase (just redistribute the third phase's outlets amongst the other two). The result would only have 2/3rds the current carrying capacity of the original, but it'd be a safe arrangement. Bob