Vertiv Liebert STS2 - Power and Control Wiring

Vertiv™ | Liebert® STS2/PDU
™
User Manual | Rev. 6 | 10/2017 8
4.0 POWER AND CONTROL WIRING
The input power busbars are accessible through the front of the unit. Liebert’s 250A units have PEM nut inserts
designed to allow one-handed tightening. Busbars in the 400-800A units are supplied with holes to
accommodate two-hole lugs.
Cables can be installed through the top or bottom of the unit through removable conduits plates. Units with
output inline panelboards are bottom exit only for output cables.
Unless otherwise labeled, use the recommended tightening torque shown in Table 30.
See Figures 12 through 21 for wiring entrance locations.
4.1 Input and Output Power Connections
The input power connections are made to the busbars provided inside the unit (see Figures 26 through 31).
These busbars are accessible through the front of the unit.
Output power connections are handled two different ways, depending on the type of distribution used. Power
connections on standard units with an output breaker are made to the busbars inside the unit. These busbars
are accessible through the front on 250A units and on the side on 400-800A units. See Figures 26 through 31
for details on the busbars. Power connections on units with panelboard distribution are made directly to the
panelboard breakers. Busbars are provided in the output cabinet for ground and neutral connections.
The two input power feeds (sources) to the Liebert STS2/PDU should be from two independent sources to avoid
a common source failure.
To ensure proper operation of the Liebert STS2/PDU, the two input sources must be the same nominal voltage
level and phase rotation.
For uninterrupted automatic transfer, the two input sources should be synchronized within 15 degrees.
NOTICE
The input sources to the Liebert STS2/PDU must be grounded-wye sources. Input sources other than solidly grounded-
wye sources may cause damage to the switch.
The Liebert STS2/PDU is designed for operation with three-wire, solidly grounded sources only.
WARNING
Risk of electric shock. Can cause injury or death.
This unit is supplied by more than one power source. The unit contains hazardous voltages if any of the
input sources are on, even when the unit is in bypass. To isolate the unit, turn off and lock out all input
power sources.
Verify that all input power sources are de-energized and locked out before making connections inside
unit.
Lethal voltages exist inside the unit during normal operation. Only qualified service personnel should
perform maintenance on the Liebert STS2/PDU.
All power and control wiring must be installed by a licensed, properly trained and qualified electrician. All
power and control wiring must comply with the National Electrical Code and all applicable local codes.
WARNING
Risk of electric shock. Can cause injury or death.
Verify that all input power and control circuits are de-energized and locked out before making
connections inside unit.