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1.1
Summary
These specifications describe the requirements for an automatic static transfer switch. The Liebert®
STS2 is a solid-state, three-pole, dual-position transfer switch designed to switch automatically and
manually between two synchronized three-phase AC power sources.
The input power shall be supplied from two different AC power sources, which are nominally of the same
voltage level, phase rotation and frequency. The primary purpose of the Liebert® STS2 is to allow virtually
uninterrupted transfer from one source to the other in case of the failure of one source or by manual
initiation for test or maintenance. The switching action shall not connect together the two sources of
power that would allow backfeeding one source to the other. The Liebert® STS2 shall allow for either
source to be designated as the preferred source. The switch will automatically transfer to the preferred
source and remain so until manually initiated to transfer or until the selected source fails. The Liebert®
STS2 shall be furnished with key-interlocked static switch isolation and bypass Molded-Case Switches
(MCSs) to each source, which allow uninterrupted manual transfer to and from either source for
maintenance.
1.2
Standards
The specified system shall be designed, manufactured, tested and installed in accordance with:
•
American National Standards Institute (ANSI)
•
Canadian Standards Association (CSA)
•
Institute of Electrical and Electronics Engineers (IEEE)
•
ISO 9001
•
National Electrical Code (NEC)
•
National Electrical Manufacturers Association (NEMA)
•
National Fire Protection Association (NFPA 70)
•
Underwriters Laboratories (UL)
•
EN 61000-6-4 & 6-2
The Liebert® STS2 shall be UL and UL listed per UL Standard 1008 for Automatic Transfer Switches or
1008S for Solid State Transfer Switches
The Liebert® STS2 shall comply with the latest FCC Part 15 EMI emission limits for Class A computing
devices and the emission limits of EN/IEC61000-6-4Class A.
The Liebert® STS2 shall safely withstand without misoperation or damage:
•
Transient voltage surges on either AC power input as defined by ANSI/IEEE C62.41 for Category
B3 locations (high surge exposure industrial and commercial facilities)
SL-20610_REV12_09-21
Vertiv™ Liebert® STS2
GUIDE SPECIFICATIONS
Automatic Static Transfer Switch
100A - 1000A
1.0 GENERAL
Proprietary and Confidential © 2021 Vertiv Group Corp.
1
Guide Specifications
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Summary of Contents for Vertiv Liebert STS2
- Page 1 The Liebert® STS2 shall safely withstand without misoperation or damage: • Transient voltage surges on either AC power input as defined by ANSI/IEEE C62.41 for Category B3 locations (high surge exposure industrial and commercial facilities) SL-20610_REV12_09-21 Guide Specifications Proprietary and Confidential © 2021 Vertiv Group Corp.
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Page 2: Modes Of Operation
Electrostatic discharges (ESD) up to 10 kV at any point on the exterior of the unit • Electromagnetic fields from portable transmitters that are not within 3 ft. (1m) of the unit The Vertiv™ Liebert® STS2 shall comply with the immunity requirements of EN/IEC61000-6-2 Class A. Definitions •... - Page 3 [(automatically) (manually)] reset after the current returns to normal to allow for continued protection against a source failure. 3. Manual Transfer (Optimized Transfer Disabled). The Vertiv™ Liebert® STS2 shall allow manually initiated transfers between the two sources, providing the alternate source has proper phase rotation and is within acceptable voltage and frequency limits and phase tolerances with the preferred source.
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Page 4: Performance Requirements
Regardless, the critical bus voltage is always maintained within the ITIC standard. Recommend contacting Vertiv for guidance if connecting to a rotational/regenerative load to the Liebert® STS2. - Page 5 No fuses are used to protect the solid-state power switching devices. Access The Vertiv™ Liebert® STS2 shall be designed for front access only. The Liebert® STS2 shall be designed so all installation, repairs and maintenance can be done from the front or top of the unit. The Liebert®...
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Page 6: Warranty
The system shall be designed, manufactured and tested according to world-class quality standards. The manufacturer shall be ISO 9001 certified. 1.7.2 Factory Testing Before shipment, the manufacturer shall fully and completely test the Vertiv™ Liebert® STS2 to assure compliance with the specifications. SL-20610_REV12_09-21 Guide Specifications Proprietary and Confidential ©... - Page 7 Fabrication 2.1.1 Materials All materials of the Vertiv™ Liebert® STS2 shall be new, of current manufacture, high grade and free from all defects and shall not have been in prior service except as required during factory testing. The maximum working voltage, current and di/dt of all solid-state power components and electronic devices shall not exceed 75% of the ratings established by their manufacturer.
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Page 8: Control Panel
Vertiv™ Liebert® STS2 2.1.6 Grounding The Vertiv™ Liebert® STS2 shall operate from sources that are solidly grounded or impedance-grounded (for 480V and below). The unit shall not be used on corner-grounded delta systems. The AC output neutral shall be electrically isolated from the Liebert® STS2 chassis. The Liebert® STS2 chassis shall have an equipment ground terminal. - Page 9 STS on alternate source Auto Retransfer Inhibit Heatsink Overtemp Transfer Inhibit An audible alarm shall be activated when any of the alarms occurs. All alarms shall be displayed in text form. SL-20610_REV12_09-21 Guide Specifications Proprietary and Confidential © 2021 Vertiv Group Corp.
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Page 10: Programmable Relay Board
2.3.4 Communications Board The Liebert® STS2 shall be provided with a Communications Board that can communicate with a Vertiv™ Liebert® SiteScan™ monitoring system. The Liebert® STS2 shall be equipped with an RS-422 communication port for communication to a Liebert®... -
Page 11: Remote Source Selection
Vertiv™ Liebert® STS2 2.3.6 Remote Source Selection The Vertiv™ Liebert® STS2 shall be furnished with Remote Source Selection board to remotely select the preferred source. Closure of one of the two N.O. dry contacts (by others) shall cause the selected source to be the preferred source to which the Liebert®... - Page 12 2.3.14 Factory Witness Test The owner and/or the owner’s representative shall attend a factory test of each unit. The factory will perform its standard witness test to demonstrate that the unit meets the Vertiv™ Liebert® STS2 specification. 2.3.15 Export Crating Heavy-duty solid wood crating with vapor barriers and desiccant shall be provided to meet international requirements regarding package strength and markings for overseas shipments.
- Page 13 Parts from the national parts center shall be shipped within 4 hours on the next available flight out and delivered to the customer’s site within 24 hours. SL-20610_REV12_09-21 Guide Specifications Proprietary and Confidential © 2021 Vertiv Group Corp.
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Page 14: Maintenance Contracts
Vertiv™ Liebert® STS2 3.2.3 STS Maintenance Training Maintenance training courses for customer employees shall be made available by the Vertiv™ Liebert® STS2 manufacturer. This training is in addition to the basic operator training conducted as a part of the system startup.
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