Why is Earth Fault relay tripping?

Question

We have installed 3 Aircondition package type big units.when we started the units earth fault relay is tripping.we can run 2 AC units at the same time, but when 3 rd AC unit switch on EFR is tripping. 2 units can be run at the same time but not three. EFR wiring is checked. EFR is set for 2 ampere delay time 1 second.but There is no chance to earth fault.

Answer 1

My guess it is because there are not enough amps in the building for 3 ACs this is more of and engineering, electrician, or electronics question.