Vertiv Liebert EXM - Torque Requirements; 3.2 External Protective Devices

Vertiv™ | Liebert® EXM
™
50-250kVA, 480V, 60Hz User Manual | 20
Torque Requirements
Refer to Tables 2 and 3 for lug size and torque requirements.
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 Table 16 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 480V
must be installed in the bypass input breaker if the system does not include a Liebert
®
Bypass
Cabinet. Refer to Figure 7 for more details.
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 UPS.
Alternatively, the device must monitor the combined three-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 Table 21).
Table 2 Busbars (for power wiring)
Bolt Shaft Size Lb-in (Nm)
1/2" (M12) 428 (48)
Table 3 Terminal block with compression lugs (for control wiring)
AWG Wire Size or
Range Lb-in (Nm)
#22 - #14
3.5 to 5.3 (0.4 to
0.6)