Installation Manual Liebert Hipulse E Chapter 2 - Installation Procedure
Single or '1+N' UPS System Installation (Electrical)
(07/04) Page 2-3
2.1.6 Protective devices
For safety reasons, it is necessary to install, external to the UPS system, circuit breaking protective devices in the input
a.c. supply and towards the battery. Given that every installation has its own characteristics, this chapter provides
general useful information for qualified installation engineers, with knowledge of operating practices, of regulatory
standards, and of the equipment to be installed.
Rectifier and Bypass input supply of the UPS:
Protection against excessive overcurrents and short circuits in the mains supply input:
These inputs must be protected, installing suitable protective devices at the distribution panel of the incoming main
supply, considering that the protection should discriminate with overload capacity of the system (see Chapter 5
Specification: - Electrical Characteristics).
Split bypass: in the case of a split bypass being used, separate protective devices should be installed in the incoming
mains distribution panel.
The protective devices must be selected for the nominal input current, with respect to the UPS rating and the input a.c.
supply voltage as given in table 2-1.
Protection against earth faults (RCD devices):
In the event of a differential (RCD) device being installed upstream of the input supply, one must take into account the
transient and steady state earth leakage currents that are produced during start-up of the UPS.
The presence of an RFI suppression filter inside the UPS, determines a residual earth current greater than 3.5 mA and
less than 1000 mA.
Residual current circuit breakers (RCCB) must be sensitive to d.c. unidirectional pulses (class A) in the network and
insensitive to transient current pulses.
They are identified by the symbols respectively:
These isolators must have an average sensitivity, possibly adjustable between 0.3 and 1A.
It is recommended that the selectivity with every differential switch be verified both upstream of the input distribution
board and downstream (towards the load).
Parallel 1+N:
Use of differential circuit breakers on UPS unit inputs in a configuration with separate inputs and one battery for each
unit requires installation of a common device only on the system bypass mains.
Use of differential circuit breakers on UPS unit inputs sharing a common battery requires installation of a device
common to all the input lines. If inputs are configured for separate mains, a common device will also be required for all
System bypass mains.
UPS Battery:
The UPS Battery is protected by means of a control circuit that operates the tripping mechanism of an automatic
circuit breaking device (having a variable trip setting). The tripping mechanism using an undervoltage release coil
that operates on a preset minimum voltage level.
The circuit breaker is essential for maintenance of the battery and is normally located near to the battery installation.
The characteristics and operation of the automatic circuit breaker are given in Chapter 3.
Output of the System:
In the eventuality that an external distribution panel is used for load distribution, the selection of protective device must
provide discrimination with those that are used at the input to the UPS module.
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