Emerson Liebert NX 10-30kVA - Manual (Page 17)

Electrical Connections
9
2.0 E
LECTRICAL
C
ONNECTIONS
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.
2.1 Power Cabling
2.1.1 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 27, 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 27, with respect to the unit rating and the output AC voltage.
• Battery cables - Each UPS unit has its own internal batteries factory-wired. If 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 27, with respect to the unit rating.
The power cables can be sized to suit the UPS unit rating according to Table 27.
Lug Size and Torque Requirements
Refer to Table 33 for lug size and torque requirements.
!
WARNING
Before connecting input power to the 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 27 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.