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The Liebert UPStation S™ Maintenance Bypass
Cabinet allows the customer to completely isolate
the UPS for repair and/or preventive
maintenance. A rotary switch provides a make-
before-break system that enables a transfer to
and from maintenance bypass without
interruption to the load.
There are two sizes available; the VM12000
series for the 8-12 kVA units and the VM18000
series for the 15 -18 kVA units.
Weights/Dimensions
The maintenance bypass cabinet is a wall-mount
system. Dimensions and weights depend on the
KVA rating and options installed. Use the
following table to determine the weight of your
maintenance bypass. Dimensions can be found
on page 20.
Approximate Weights in Pounds
Model Number 125 175
VM12000
VM18000
Standard Features
• A locking handle prevents unauthorized
access.
• A holder for the User’s Manual and any site
documentation is provided on the inside
cover of the door. This enables the
customer to keep all documentation relating
to their UPS and maintenance bypass with
the unit.
• Auxiliary contacts, rated at 15 amps and 600
volts, are available if the customer requires
remote monitoring of the maintenance
bypass.
• Conduit knock-outs for power wiring and
control wiring are prefabricated into the
enclosure, allowing for top or bottom
entrance.
Modes of Operation
The are three modes of operation on the
maintenance bypass; On-Line, Test, and
Maintenance Bypass. There are two major types
of maintenance bypass cabinets and Liebert
UPStation S™ units when referring to the one-
line diagrams and power flows.
On-Line
When the rotary switch is placed in the On-Line position, contacts A and C are closed with contact B open.
The standard Liebert UPStation S™ is powering the critical load as illustrated below.
UPStation S™