Emerson Liebert NX User Manual download pdf (Page 89)

Operation

Liebert

™

Maintenance Mode

For maintenance or repair, the Liebert NX may be operated in maintenance mode. To place the

Liebert NX in maintenance mode, the load must be transferred to bypass and the inverter must be

turned off. When those conditions are met, the CB3 may be turned on and the UPS may be shut down,

permitting disconnecting the batteries for maintenance.

NOTICE

Risk of improper operation. Can cause loss of power to the load and damage to the UPS.

The internal maintenance bypass must not be used when the UPS system is in a parallel

system. Doing so can cause a backfeed that can damage the UPS and interrupt power to the

load.

Parallel Redundancy Mode (System Expansion)

For higher capacity, higher reliability or both, the outputs of up to four UPS modules can be

programmed for directly paralleling while a built-in parallel controller in each UPS ensures

automatic load-sharing.

Frequency Converter Mode

The Liebert NX can be programmed into frequency converter mode for either 50Hz or 60Hz stable

output frequency. The input frequency may vary from 57Hz to 66Hz. In this mode, the static bypass

operation is disabled and the battery becomes optional, depending on any requirement to operate in

battery mode (stored energy mode).

Eco Mode

If ECO mode is selected, the double-conversion UPS operation is inhibited at most times for the

purpose of saving energy. In this mode of operation, not unlike UPS of line-interactive or stand-by

technology, the bypass is the preferred source, and only when the voltage and/or frequency of the

bypass supply is beyond pre-defined and adjustable limits is the critical AC load transferred to the

inverter. This transfer takes place with an interruption of less than 3/4 of an electrical cycle, e.g., less

than 15ms (50Hz) or less than 12.5ms (60Hz).

WARNING

Risk of electrical shock. Can cause injury and death.

The UPS input and output must be protected with external overcurrent protection devices. In

maintenance mode, the input and output busbars remain energized.

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Emerson Liebert NX User Manual Page 89