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Electrical Connections
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3.1.4 Cable Connections
The rectifier input, bypass and output are easily accessible from the front of the unit for installation.
All require lug type terminations. They are connected to busbars on the front side of the Liebert
®
NX
™
and below the circuit breaker, as shown in Figure 3. These busbars are accessible when the front
side panel is removed. Busbars to connect external batteries are accessible from the front of the UPS.
3.1.5 Safety Ground
The safety ground busbar is located below the Maintenance Bypass circuit breaker or to the right of
the UPS Output breaker for 160-200KVA models as shown in Figure 3. The safety ground cable must
be connected to the ground busbar and bonded to each cabinet in the system.
All cabinets and cable conduit should be grounded in accordance with local regulations.
3.1.6 Protective Devices
For safety, it is necessary to install circuit breakers in the input AC supply and external battery
battery 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 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 6.4 - UPS
Electrical Characteristics and Table 9 for overload capacity.
When an external battery supply not made by Liebert is used, the customer must provide
overcurrent protection for the battery circuit.
• Dual Input
When wiring the UPS with dual inputs, the Rectifier input and the Bypass input must be
protected separately. Size the breakers according to the input currents shown in Table 8.
NOTE
External connection access requires removal of a protective panel on the lower front of the UPS.
NOTE
There is no battery fuse in the UPS; the battery cabinet must include a circuit breaker
to cut off the current in case of short circuit. Refer to Table 8 for current ratings.
!
WARNING
Risk of electrical shock from ground fault. Can cause injury and death.
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.