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15.2 System Components
All Liebert STS2 models provide two static transfer switches within one enclosure, with the ability to
transfer between two input sources to a single output.
All Liebert STS2s are configured with either an LCD Color Graphical Interface touch screen display
or LEDs for monitoring and configuring the unit.
This section lists the common components and the differences for both types of units.
15.2.1 Frame and Enclosure
The complete Liebert STS2 is housed in a freestanding enclosure. The cabinet is a NEMA type 1
enclosure and meets IP20 requirements. The cabinet is structurally designed to handle lifting from
the base. The frame is designed to accommodate floor stands.
The distributed floor weight for Liebert STS2 is less than 150 lbs./sq. ft. (660kg/m²).
The required service access is only from the front of the unit.
The Liebert STS2 can be tipped 15° in any direction without falling over.
15.2.2 Casters, Leveling and Seismic Anchoring
The frame includes heavy-duty swivel casters for ease of installation, plus permanent leveling feet for
final installation.
The unit also can be fastened to the floor using optional seismic anchors to meet seismic Zone 4
requirements. See 4.0 - Locating the Liebert STS2 and Figures 11 through 13 for instructions and
details for installing seismic anchoring.
15.2.3 Cooling
The Liebert STS2 100 – 600A units utilize convection air cooling for the enclosure with forced air
cooling of the heat sinks. The 800-1000A units are fan cooled using low-velocity fans to minimize
audible noise. All fans are redundant so that a single fan failure cannot cause temperatures to
increase beyond acceptable limits.
Air intake is through screened protective openings in the front of the unit. A standard furnace filter is
installed behind the openings.
By opening the front door, the filter can be changed easily without exposing personnel to high voltage.
The size of the filter is 1 in. x 25 in. x 25 in. (2.54 cm x 63.5 cm x 63.5 cm).
The air exhaust is through the top of the unit.
Table 20 Frame sizes
Rating Width Depth Height
100 – 250A 3 pole 30 in (76 cm) 32 in (81 cm) 76.77 in (195 cm)
400 – 600A 3 pole 38 in (96 cm) 32 in (81 cm) 76.77 in (195 cm)
800 – 1000A 3 pole 84 in (213 cm) 32 in (81 cm) 76.77 in (195 cm)