Mechanical Installation
5
1.4.3 Raised-Floor Installations
If the equipment is to be located on a raised floor, it should be mounted on a pedestal suitably
designed to accept the equipment point loading. Refer to the base view to design this pedestal. The top
of the pedestal must be solid.
1.4.4 Kick Plate Installation
Kick plates must be installed. If the unit is to be installed in a position that does not permit access to
rear kick plates, then the kick plates must be installed before the unit is placed in its final position.
1.4.5 Special Considerations for 1+N Parallel Systems
Consider the grounding configuration of your system before finalizing module placement See 2.6 -
Configuring Neutral and Ground Connections.
Emerson Network Power recommends matching the impedance in the bypass path of paralleled
systems as closely as possible.
The impedance mismatch can be minimized by controlling the wiring length of each unit. The design
and the layout of the UPS system and associated panels and cabling should be examined closely to
ensure that cable lengths and impedances are closely matched. The Liebert 1+N UPS module is
supplied with a sharing reactor to minimize the impact of cable impedance mismatch.
The cabling impedance must be carefully controlled to ensure good bypass current sharing.
For Liebert NXL Systems, the cabling impedances must be within 10% from maximum to minimum.
If the cabling impedances need to be greater than 10%, contact your Emerson representative to
calculate whether the system will result in an overload condition when operating on bypass.
When bringing the 1+N system online for the first time or after removing one unit, Emerson
recommends checking the bypass current mismatch. To check the bypass current mismatch:
1. Place a load on the bypass of each UPS module.
2. View the output current of each unit.
The accuracy of the currents displayed on the UPS module is sufficient for this check. If the
mismatch is greater than 10%, the bypass impedances must be balanced or the load must be
limited to less than the maximum rating.
1.5 System Composition
A UPS system can comprise a number of equipment cabinets, depending on the individual system
design requirements: e.g., UPS cabinet, battery cabinet, maintenance bypass cabinet. In general, all
the cabinets used in a particular installation are of the same height. Refer to the drawings provided in
4.0 - Installation Drawings for the positioning of the cabinets as shown in Figure 1.
NOTE
The UPS must be placed on a solid surface. There must be no openings in the surface except
those required for conduit landing areas. All provided kick plates must be installed.
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