Liebert NX 30 User Manual

12 User Manual 10H52192UM60 - Rev. 1 - 09/2011
Liebert NX Installing the UPS Module
1.6.1 Rectifier and Bypass Input
Overcurrents
Common bypass: Install suitable protective devices on the incoming mains supply distribution system, taking into account the
power cable current-carrying capacity and overload capacity of the system (see Table 8-6). Under normal circumstances, we
recommend magnetic circuit breakers with IEC60947-2 tripping curve C (normal) at 125% of the current listed in Table 1-1.
Separate bypass: In the case of separate bypass supply, install separate protective devices on the bypass input lines in the incoming
mains distribution panel.
Note
1. The rectifier input and bypass input must use the same neutral line.
2. For IT power systems, four-pole protective devices must be used upstream of the input distribution panel and output distribution
panel, external to the UPS.
Earth Leakage
The residual earth current generated by the RFI suppression filter inside the UPS is greater than 3.5 mA and less than 1000
mA. It is recommended that the sensitivity of all differential devices be verified upstream of the input distribution panel.
Use of Differential Protective Devices (RCCBs or RCDs)
The UPS does not require RCCBs or RCDs to be connected upstream, however, when these are fitted in order to comply with local
regulations it must be remembered that separate RCCBs or RCDs in the rectifier and bypass supply lines may trip incorrectly,
interrupting the power supply to the unit. Therefore, if unavoidable, only one differential protection should be used for both
rectifier and bypass input.
An RCCB or RCD installed on the input bypass supply senses the sum of all earth leakage currents in both the UPS and the load it
supplies. To avoid incorrect operation, the following must be taken into consideration when selecting RCCBs or RCDs for
installation at input supply:
1. The nominal value of ID must take into account the earth leakage current of the UPS and the load, in normal operating
conditions: ID = ID
UPS + load leakage current.
(The maximum limit for UPS earth leakage current is 5% of the nominal input current. See EN62040-1)
2. It must be of a delayed operation type (greater than 300 mS).
3. The type of RCCB or RCD used must conform to product regulation EN62040-1.
In the case of systems distributed in parallel, a single, common RCCB or RCD is to be fitted upstream of the point at which the line
divides to supply the bypass inputs of the UPS. Installation of separate devices in other configurations can result in incorrect
operation.
In order to guarantee correct current distribution in the neutral cables, installation personnel are to ensure that the lengths of the
cables are as equal as possible. If, however, the bypass lines are drawn from sources that are galvanically isolated from each other,
an RCCB or RCD may be installed on each line. (In this case, and in cases when the load is supplied from the bypass via the bypass
static switch, the isolated sources are connected in parallel. It should be evaluated on an individual basis whether any resultant
imbalance between the currents on the bypass lines is compatible with the respective protective devices.)
1.6.2 External Battery Circuit Breaker
The UPS and its associated battery are protected against the effect of overcurrents by a fused switch, mounted on the external
battery cabinet. For internal batteries, the battery fused switch is integrated in the UPS.
The voltage of the battery overcurrent protection device is greater than 500 Vdc, and its DC breaking current is more than 8 kA.
1.6.3 UPS Output
The UPS output distribution must be fitted with a protective device. This device must be different to the input distribution
protection switch and must be able to provide overload protection (see Table 8-6).

Liebert NX 30 Specifications

General

Brand	Liebert
Model	NX 30
Category	Power Supply
Language	English