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Liebert® EXM™ UPS 20-100kVA, 50/60Hz User Manual |
16
3.2
External Protective Devices
For safety concerns, it is necessary to install external circuit breakers or other protective devices for the input AC
supply of the UPS system. This section provides generic practical information for qualified installation engineers.
The installation engineers should be knowledgeable about regulatory wiring standards and the equipment to be
installed.
To reduce the risk of fire, connect only to a circuit provided with branch circuit overcurrent protection in
accordance with NEC ANSI/NFPA 70.
3.2.1
Rectifier and Bypass Input Supply of the UPS
Overcurrents
Install suitable protective devices in the distribution unit of the incoming mains supply, considering the power
cable current-carrying capacity and overload capacity of the system. Generally, the magnetic circuit breaker with
IEC60947-2 tripping curve C (normal) at the 125% of the nominal current listed in
is recommended.
Split bypass: In case a split bypass is used, separate protective devices should be installed for the rectifier input
and bypass input in the incoming mains distribution panel. A shunt trip coil of 120V must be installed in the
bypass and rectifier input breakers if the system does not include a Liebert
®
Bypass Cabinet.
Earth Leakage, RCD Devices
Any residual current detector (RCD) installed upstream of the UPS input supply:
•
Must be sensitive to DC unidirectional pulses (Class A)
•
Must be insensitive to transient current pulses, and
•
Must have an average sensitivity, adjustable between 0.3 and 1A.
To avoid false alarms, earth leakage monitoring devices when used in systems with split bypass input or when
used in paralleled UPS configurations, must be located upstream of the common neutral sinking point.
Alternatively, the device must monitor the combined four-wire rectifier and split bypass input currents.
3.2.2
UPS Output
If an external distribution panel is used for load distribution, the selection of protective devices must provide
discrimination with those that are used at the input to the UPS (see
).
3.2.3
UPS Input Configuration
By default, the Liebert
®
EXM ships with internal links installed between the bypass input and main (rectifier)
input (single input configuration).
show the Liebert
®
EXM in a split bypass (single source dual-input) configuration. In this
configuration, the static bypass and the maintenance bypass lines are supplied by the same source using
separate feeds. Both feeds must be protected externally with properly sized protective devices.
Wire Liebert
®
EXM Input as Single Source Dual-Input
To wire the Liebert
®
EXM as a single source dual-input UPS, remove factory-installed links between rectifier and
bypass input busbar (see
NOTE
The rectifier input and bypass input must use the same neutral line.
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