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8.1.2
Reliability and Agency Requirements
The STS2 is designed for high reliability and high availability with a critical bus Mean Time
Between Failure (MTBF) exceeding 1,000,000 hours.
The STS2, Control/Power Module, and all its options are designed, tested and certified, where
applicable, to meet agency requirements as follows:
• UL 1008: Transfer Switch Equipment, for UL and ULc listing
• UL1459: Telephone equipment (Modem)
• NEC
• FCC Part 15 EMI emission limits for Class A computing devices.
The STS2 uses conservatively rated components, minimizing the need to go to maintenance bypass.
All maintenance and repair work can be done through the front panel of the unit. This access
makes repairs and maintenance easier.
Gating and control logic are partitioned so that failure of one source's gating or sensing logic does
not prevent the switch from transferring to the other source.
All control and logic components are mounted separate from the power components. The STS2 is
designed to minimize the exposure of hazardous voltages to allow safe servicing of the unit while
the load is energized.
All electrical components requiring normal maintenance are replaceable without de-energizing the
load, as long as one source is available. Solid-state switching devices are packaged to allow safe
repair of those devices without having to de-energize the load. All non-automatic switches or circuit
breakers are the plug-in or draw-out type to allow replacement without de-energizing the load. All
solid-state power switching devices are rated to prevent hazardous device failure in power systems
with available fault currents up to the defined limits, as listed in 15.1.5 - Electrical
Requirements on page 108.
8.1.3
Factory Backup and Service Assistance
Because improper installation can cause a system to fail, a Liebert Global Services or a factory-
trained service technician should thoroughly inspect the unit to ensure it is properly installed and
its operating parameters are properly configured.
Once the STS2 is properly installed, you, as the on-site operator, can easily monitor the unit's oper-
ation utilizing the touch screen or LEDs.
If you need assistance, or have questions, in the United States, call 1-800-LIEBERT
(1-800-543-2378).
Outside the 48 contiguous United States contact Liebert Global Services, if available in your area.
For international areas not covered by Liebert Global Services, the Liebert authorized distributor
can provide technical support.
8.2
Modes of Operation
8.2.1
Normal (Preferred Source)
Under normal operating conditions, the STS2 routes power from the preferred input source to the
output load. The unit monitors the voltage current and phase of each source to ensure that both are
operating within set tolerances, and that the alternate source is available, should a transfer be
required
8.2.2
Transfer
Should the preferred source fail or be outside acceptable voltage limits, the STS2 transfers the
input to the alternate source until the problem is rectified in the preferred source. The unit can be
set to automatically transfer the input back to the preferred source, or only allow the transfer to be
done manually.
52
Introduction to STS2 Operations
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