When generators are installed, it is common to use four pole changeover switchgear or contactors when transferring from mains to generator, resulting in the traditional neutral-earth reference being lost during transition. This can cause the phase voltages to rise alarmingly and any sensitive single phase loads could be damaged. By adding a bypass isolation transformer it allows the electrical contractor to earth the UPS output neutral, thereby eliminating this problem. Single phase bypass transformers are also installed on small systems where the client requires the UPS output neutral to be earthed.