Vertiv Liebert EXM - 3.2.8 Protective Devices

Vertiv™ | Liebert® EXM
™
50-250kVA, 480V, 60Hz User Manual | 31
3.2.8 Protective Devices
For safety, it is necessary to install circuit breakers in the input AC supply external to the UPS
system. Given that every installation has its own characteristics, this section provides guidelines
for qualified installation engineers with knowledge of operating practices, regulatory standards
and the equipment to be installed.
UPS Rectifier and Bypass Input Supply
Protection from excessive overcurrents and short circuits in power supply input
External overcurrent protection for the AC output circuit is to be provided. See 7.3 - UPS Electrical
Characteristics and Table 23 for overload capacity.
Overcurrent protection for the battery circuit must be provided by the customer when using an external
battery cabinet not manufactured by Vertiv
™
.
• Dual Input Single Source
When wiring the UPS with dual inputs but with a single input source, the Rectifier input and the Bypass input
must be protected separately. Size the breakers according to the input currents shown in Table 16.
Fuses
The Liebert
®
EXM’s
™
main input and bypass input busbars are equipped with fuses (six locations; see
Figure 24). The type is Bussman, rated 450A for 50-200kVA units (170M4463 for main input and 170M4465
for bypass input) and rated 550A for 250kVA units.
NOTE
For single or dual input, a 480V shunt trip coil(s) is required when a breaker is supplied by the
customer. See Figures 8 for details.