Specifications

Liebert Nfinity UPS Guide Specification
4kVA –20kVA (208/120 or 240/120) 4/03 Rev 2
SL-23956
7
2.2.5 Remote Emergency Power Off (REPO)
The remote emergency power off function (REPO) allows the user to disable all UPS outputs in an
emergency situation. The REPO, in order to be flexible, will be able to interface with either normally
open (N.O.) or normally closed (N.C.) systems. The REPO is activated when a pair of „SELV‟
contacts, external to the UPS, are activated. The REPO connection is through a simple terminal block
type connector.
The REPO function will not operate if no system control modules are present in the UPS or if the
manual bypass switch is in the bypass position. The user must supply a means of interfacing with the
REPO circuit to allow disconnecting the UPS input feeder breaker to remove all sources of power to
the UPS and the connected equipment to comply with local wiring codes/regulations.
Regardless of the UPS mode of operation when the REPO is activated, the UPS output will not be re-
enabled until the following occurs:
REPO contacts are reset (closed if N.C. contacts are used and open if N.O. contacts are used)
Input circuit breaker is closed
Control enable switch is turned on
User interface on/off switch is depressed
2.2.6 Bypass
A. General
A bypass circuit is provided as an integral part of the UPS. The bypass has an overload rating
of 300% rated full load for 10 cycles and 1000% for sub-cycle fault clearing. The bypass
control logic contains an automatic transfer control circuit that senses the status of the
inverter logic signals, and operating and alarm conditions. This control circuit provides a
transfer of the load to the bypass source, without exceeding the transient limits specified
herein, when an overload or malfunction occurs within the UPS.
B. Automatic Transfers
The transfer control logic automatically activates the bypass, transferring the critical AC load
to the bypass source, after the transfer logic senses one of the following conditions:
Inverter overload capacity exceeded
Inverter over temperature
UPS fault condition
For inverter overload conditions, the transfer control logic inhibits an automatic transfer of
the critical load to the bypass source if one of the following conditions exists:
Inverter/Bypass voltage difference exceeding preset limits (±15 % of nominal)
Bypass frequency out of preset limits (± 5 % of nominal frequency)
C. Automatic Retransfer
Retransfer of the critical AC load from the bypass source to the inverter output is
automatically initiated unless inhibited by the manual control. The transfer control logic
inhibits an automatic retransfer of the critical load to the inverter if one of the following
conditions exists:
Bypass out-of-synchronization range with inverter output
Overload condition exists in excess of the inverter full load rating
UPS fault condition present
D. Manual Transfer
In addition to the internal bypass function, the UPS has a manual bypass function. The
manual bypass function is provided via of a switch mounted on the bottom-front of the UPS,
removal of the lower front bezel is required. The actual AC break time between inverter and
bypass is less than four milliseconds.
The manual bypass provides a partial „wrap-around‟ bypass, and is configured to wrap
around the rectifier, battery charger, inverter, and battery in the same manner as the automatic