18 Chapter 3 Electrical Installation
Liebert APM 90 Integrated Modular UPS User Manual
3.1.7 External Protective Device
It is recommended to install circuit breakers or other protective devices in the AC supply, external to the UPS.
This section provides guidelines for qualified installers, who must have knowledge of local wiring practices
pertaining to the equipment to be installed.
Rectifier and bypass input
1. Ov
ercurrent
Over-current protection must be installed at the distribution panel of the incoming main supply. The
protection must discriminate with the power cable current capacity and with the overload capacity of the
system (see Table 11-6 and Table 11-7). As a guideline, a thermomagnetic circuit breaker, with an IEC60947-2
trip curve C (normal) for 125% of the current listed in Table 3-1 is suitable.
Note
For IT power systems, four-pole protective devices must be used upstream of the input distribution panel, external to
the UPS.
2. Earth leakage
Any RCD installed upstream of the UPS input supply must:
Be sensitive to DC unidirectional pulses (Class A) in power distribution network
Be insensitive to transient current pulses
Have an average sensitivity, adjustable between 0.3A and 1A
RCCB must be sensitive to DC unidirectional pulses (Class A) in power distribution network, and insensitive to
transient current pulses, as respectively shown in Figure 3-1.
Figure 3-1 RCCB symbols
Battery
The battery must be fitted with a BCB to provide over-current protection for the battery.
UPS output
Eac
h route of the UPS output is fitted with an output distribution switch.
3.1.8 Power Cable Connection Procedures
Warning
Before cable connection, ensure that you are aware of the location and state of the breaker that connect the UPS input
to the mains distribution panel. Check that this breaker is off, and post any necessary warning sign to prevent
inadvertent operation of the breaker.
Important
The operations described in this section must be performed by authorised personnel. If you have any questions, please
contact the local customer service center of Emerson immediately.
Once the UPS has been finally positioned and secured, connect the power cables as described in the following
procedures.
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