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Shake, Rattle, and Roll - Seismic Options for ASCO Transfer Switches

ASCO Transfer Switches are available with ratings for use in locations of higher seismic risk. The following sections explain why they are needed and provide an overview of available options.

Regions of Elevated Seismic Risk

Some regions of the United States present elevated risks for seismic activity. Commonly, people first think of California with its history of significant earthquakes along the San Andreas Fault. But other areas of the USA also present elevated seismic risks (Figure 1).i These include locations near Saint Louis, Missouri, and near Charleston, South Carolina.
Other regions of the world also present elevated seismic risks. India, Japan, and Indonesia are a few of the areas highlighted in Figure 2.ii
Building Codes

To mitigate seismic risks, building codes set forth specific standards that equipment must meet in areas at risk for earthquake activity. The International Building Code sets forth seismic guidance for the United States.iii Other countries have adopted corresponding codes.

These standards require designers to consider not only the risk of earthquake occurrence for a particular geographic location, but also the effect of equipment position within a building. Because undulations can amplify movement with increasing height from the ground surface, regulations require consideration of the building height and the height of equipment within that building. For an overview of these and variables, review the ASCO Power Technologies report entitled Seismic Certification and the Consulting Engineer.

Typically, building codes require the use of equipment with seismic readings that are appropriate for the application. These codes specify the types of building movements that installed equipment must withstand. To prove that equipment can survive these movements, it must be tested according to the requirements of the prevailing test standards for the jurisdiction. The following table identifies seismic codes for equipment for a sampling of countries.
Seismic Testing of Equipment

Manufacturers that choose to specify seismic ratings for their equipment must subject it to seismic vibration testing to demonstrate compliance with prevailing codes. Testing is typically conducted by a laboratory using a triaxial shaker table to which the manufacturer's equipment is mounted. During the test, the shaker table simulates building movement during an earthquake by subjecting the equipment-under-test to a sequence of movements specified by industry-accepted test methods. If the equipment does not initially pass seismic tests, then the manufacturer can modify the design and retest the product. Common enhancements include:

• Gusset plates to add rigidity to equipment frames
• More robust hardware for securing enclosures and equipment to framework and bases
• Enhanced latches and other devices for securing doors and panels

Seismic Documentation and Labelling

When a product complies with test criteria, a laboratory will issue a test report that identifies the standard(s) with which the equipment complies and corresponding seismic forces that were used during testing. An equipment specifier will use this information to select an appropriately rated device to install at a particular location in a facility. An excerpt from an ASCO seismic rating certificate is shown in Figure 3.
At the job site, seismic-rated equipment must be labeled so that interested parties, including Authorities Having Jurisdiction, can verify that the proper equipment has been installed. This label presents key information that summarizes the seismic conditions a device has been verified to withstand. It will list key parameters such as ground acceleration according to the definitions of applicable standards. Figure 4 presents a label from a seismic-rated ASCO transfer switch.

When specifying backup power equipment and other types of devices, the seismic risks that may be present at both the geographic location and the equipment position within the building must be understood. It's important to verify that selected equipment has seismic ratings suited for the application. ASCO Power Technologies offers a range of transfer switches and paralleling switchgear with standard or optional seismic ratings. For additional information on the seismic capabilities of specific models, contact a local ASCO representative or ASCO Customer Care.


For additional reading:

ASCO Power Technologies:
White Paper - Seismic Certification and the Consulting Engineer
White Paper - Can Building Codes Ensure Power Reliability?


i United States Geological Survey. 2018 Long-term National Seismic Hazard Map. https://www.usgs.gov/media/images/2018-long-term-national-seismic-hazard-map. Accessed November 2, 2021.
ii Silva, D. Amo-Oduro, A. Calderon, J. Dabbeek, V. Despotaki, L. Martins, A. Rao, M. Simionato, D. Viganò, C. Yepes-Estrada, A. Acevedo, H. Crowley, N. Horspool, K. Jaiswal, M. Journeay, M. Pittore (2018). Global Earthquake Model (GEM) Seismic Risk Map (version 2018.1), DOI: 10.13117/GEM-GLOBAL-SEISMIC-RISK-MAP- 2018.
iii International Code Council, Inc. 2021 International Building Code®. October 3, 2020.
iv Jeff Gatscher, Schneider Electric. Standardizing Equipment Compliance Validation for Critical Infrastructure Across Global Seismic Codes. June 4, 2021. p.2.