I have a customer with ECS Gen3 EX300 wanting converting its current PDU (example: 3-phase Wye  to Single Phase). I did not found any documentation regarding this procedure.

It is just powering off ECS, changing it (following Installation manual) and powering up? No script to run on ECS so it "knows" it has another PDU? I am asking this because for VMAX/POWERMAX it is necessary.