Emerson Liebert NX User Manual download pdf (Page 23)

Electrical Connections

Liebert

™

3.0 ELECTRICAL CONNECTIONS

The UPS requires both power and control cabling once it has been mechanically installed. All control

cables must run separate from power cables in metal conduits or metal ducts that are electrically

bonded to the metalwork of the cabinets to which they are connected.

3.1 Power Cabling

3.1.1 Cable Rating

The main factors affecting the choice and size of cable are voltage, current (also taking into account

overcurrent), room temperature and conditions of installation of the cable.

The power cables of the system must be sized with respect to the following description:

• UPS input cables - The UPS input cables must be sized for the maximum input current, includ-

ing the maximum battery recharge current, given in Table 8, with respect to the unit rating and

the input AC voltage.

• UPS bypass and output cables - The bypass and output cables must be sized for the nominal

output current, given in Table 8, with respect to the unit rating and the output AC voltage.

• Battery cables - When connecting an external battery cabinet, the battery cables must be sized

for the battery discharge current at the end-of-discharge voltage, as given in Table 8, with

respect to the unit rating.

The power cables can be sized to suit the UPS unit rating according to Table 8.

Lug Size and Torque Requirements

Refer to Table 34 for lug size and torque requirements.

WARNING

Risk of electrical shock. Can cause injury and death.

Before connecting input power to the Liebert NX, ensure that you are aware of the location

and operation of the overcurrent protection devices that connect the UPS input/bypass supply

to the power distribution panel.

De-energize and lockout or tagout all incoming high- and low-voltage power circuits before

installing cables or making any electrical connections.

NOTE

Table 8 gives nominal currents for determining the size of UPS power cables. Other important

factors to consider include cable route length and coordination with protective devices.

NOTE

When installing a Liebert NX with Softscale

™

capability Liebert recommends sizing the input,

bypass and output cabling for the UPS’s maximum rating. Properly sizing the cable will

reduce the work required to upgrade the UPS.

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Emerson Liebert NX User Manual Page 23