Emerson Liebert NX 480V - Manual (Page 21)

Electrical Connections
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2.1.5 Safety Ground
The safety ground busbar is located below the Maintenance Bypass circuit breaker as shown in
Figure 4. The safety ground cable must be connected to the ground busbar and bonded to each cabi-
net in the system.
All cabinets and cable conduit should be grounded in accordance with local regulations.
2.1.6 Protective Devices
For safety, it is necessary to install circuit breakers in the input AC supply and external battery bat-
tery cabinets, 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 prac-
tices, 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 5.4 - UPS Elec-
trical Characteristics and Table 9 for overload capacity.
When an external battery supply not made by Liebert is used, the customer must provide overcur-
rent protection for the battery circuit.
• Dual Input
When wiring the UPS with dual inputs, the Rectifier input and the Bypass input must be pro-
tected separately. Size the breakers according to the input currents shown in Table 8. In dual
input configuration, the neutral wire of each source should be connected together to guarantee
dual source has the same voltage potential to earth.
!
WARNING
Failure to follow proper grounding procedures can result in electric shock hazard to personnel
or the risk of fire, should a ground fault occur.
NOTE
Proper grounding significantly reduces electromagnetic interference problems in systems.
NOTE
The ground busbar is easily accessible when the lower protective cover plate is removed.