Hopefully the 3 phase feeds for each controller come off of the same switch gear. Each controller will use a main transformer supplied buy its individual 3 phase disconnect. This controller transformer will typically take two legs of the 3 phase and convert that voltage to 120VAC for controller voltage. If one elevator is utilizing say, phase #1 and phase #2 of the 3 phase power supply, and the next elevator is utilizing phase #2 and phase #3 for its power supply, you now have a difference of potential between these two controllers. When these two controllers are connected via group connections, you have a doubling of voltage between the shared circuits.
Ah thanks mate now I understand what you meant. This is why I haven't come across this as, most of the time if you use a 3 phase step down transformer(ie you use the 3 legs), which we always do, you don't have these issues. Cheers mate.
