Vertiv™ | Liebert
®
STS2
™
100-1000A, 50/60Hz User Manual | Rev. 12 | 11/2017 9
5.0 POWER AND CONTROL WIRING
All power and control wiring should be installed by a qualified electrician. All power and control wiring must
comply with the NEC and applicable local codes. Unless otherwise labeled, use the recommended tightening
torque as shown in Table 20 - Torque tightening.
The busbars are accessible through the front of the Liebert STS2 and designed to allow one-handed tightening.
Cables can be installed through the top or bottom of the unit through removable conduits plates.
See Figures 4 through 9 for wiring entrance locations.
Input wiring also can be installed under a raised floor to optional input junction boxes and cables, when used.
5.1 Input And Output Power Connections
If the unit is furnished with input junction boxes, the input power connections are made to the input power
terminals located in the junction boxes. Input power cables, furnished with the input junction boxes, are shipped
unattached to the unit for connection between the junction boxes and the bus bars provided inside the unit.
Input junction box installation is discussed in 6.12 - Input Junction Box Installation—Optional on page 16.
If input junction boxes are not furnished, the input power connections are made to the bus bars provided inside
the unit. These bus bars are accessible through the front of the unit.
Output power connections also are made to the busbars provided inside the unit. These bus bars are accessible
through the front of the unit. See Figures 13 to 18 for details on the bus bars.
Aluminum or copper-clad aluminum wire can be used for equipment ratings 400A and above. Follow minimum
wire size ratings provided in submittal drawing PS214004.
5.1.1 Grounding
The Liebert STS2 operates from sources that are solidly grounded or impedance-grounded. The unit must not
be used on corner-grounded delta systems.
The AC output neutral is electrically isolated from the Liebert STS2 chassis. The Liebert STS2 chassis shall have
an equipment ground terminal.
The two input power feeds (sources) to the Liebert STS2 should be from two independent sources to avoid a
common source failure.
To ensure proper operation of the Liebert STS2, 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.
The Liebert STS2 is designed for operation with 3- or 4-wire, solidly grounded sources only.
For 4-wire operation, the common source neutral must be connected to the Liebert STS2. See Figure 2 on
page 10 for a typical one-line diagram. Refer to Figures 13 to 18 for electrical field connections on all units, with
both single and dual output breakers.
WARNING
Risk of electric shock. Can cause equipment damage, injury and death.
Verify that all input power and control circuits are de-energized and locked out before making
connections inside unit.
CAUTION
Risk of unit damage.
The input sources to the static switch must be grounded-wye sources. Input sources other than solidly
grounded-wye sources may cause damage to the switch.
To Next Page
Loading...
