Sizing The Input Breaker Feeding A Liebert Nxl Ups; Power Cable Connection Procedure - Emerson Liebert NXL Installation Manual

2.3

Sizing the Input Breaker feeding a Liebert NXL UPS

Nominal input current (considered continuous) is based on full-rated output load. Maximum current
includes nominal input current and maximum battery recharge current (considered noncontinuous).
Continuous and noncontinuous current are defined in the NEC. The Rectifier Input Feed Breaker
must be set to withstand the Liebert NXL transformer inrush of up to eight times the nominal
current.
Maximum input current is controlled by the current limit setting, which is adjustable. Values shown
are for maximum current limit. If a smaller input feed breaker is used, the input current limit can be
adjusted; see your Emerson representative for more information. The input current limit should not
be set less than 105% of the current needed to support the inverter at full load for normal operation.
This results in sufficient power to recharge the battery in a reasonable time and to operate over the
published input voltage range.
2.3.1

Power Cable Connection Procedure

The rectifier input, bypass, output and battery power cables (all require lug-type terminations) are
connected to busbars in the I/O sections (refer to 4.0 - Installation Drawings).
Equipment Ground
The equipment ground busbar is in the I/O sections as shown in (refer to 4.0 - Installation
Drawings). The grounding conductor must be connected to the ground busbar and bonded to each
cabinet in the system.
All cabinets and cabling should be grounded in accordance with local regulations.
NOTE
Proper grounding reduces problems in systems caused by electromagnetic interference.
WARNING
!
Failure to follow adequate grounding procedures can result in electric shock hazard to
personnel, or the risk of fire, should a ground fault occur.
All operations described in this section must be performed by properly trained and qualified
electricians or technical personnel. If any difficulties are encountered, contact Emerson
Network Power. See the back page of this manual for contact information.
The grounding and neutral bonding arrangement must be in accordance with local and
national codes of practice.
Once the equipment has been positioned and secured, connect the power cables as described below
(refer to the appropriate cable connection drawing in 4.0 - Installation Drawings):
1. Verify that the UPS equipment is isolated from its external power source and all the UPS power
isolators are open. Check that these supplies are electrically isolated and post any necessary
warning signs to prevent their inadvertent operation.
2. Open exterior and interior panels on the front of the I/O sections.
3. Connect the ground and any necessary main bonding jumper to the equipment ground busbar
located in the I/O sections.
4. Make power connections and tighten the connections to the proper torque.
Ensure correct phase rotation.
WARNING
!
Risk of electrical shock. Can cause injury or death.
If the load equipment will not be ready to accept power on the arrival of the commissioning
engineer, ensure that the system output cables are safely isolated at their termination.
WARNING
!
Risk of electrical shock. Can cause injury or death.
When connecting the cables between the battery extremities to the circuit breaker, always
connect the circuit breaker end of the cable first.
8
UPS Electrical Installation