Earthquakes happen every day in the United States. In fact, over 30,000 earthquakes have been recorded during 2024. Most of these events occur near the West Coast, but all 50 states have recorded these seismic events at some point in history. While most earthquakes do not exceed 3.0 on the Richter scale, many surpass the 3.0 level annually, and these are when humans can feel them and things start moving around.
This movement can be destructive, and the moments after the shaking stops can be chaotic and dangerous for those inside a structure. Emergency systems are relied on to assist decision-making and safe evacuation during these events. Keeping the lights on, plus identifying and illuminating egress paths, is the purpose of emergency lighting systems, and these collections of devices must be capable of surviving the violence of seismic shaking.
Designing and installing inverters and signs for seismic areas
The construction and installation of lighting inverters and exit signs must consider the seismic testing standards required in many areas. Seismic testing is required for emergency inverters to ensure they can withstand seismic events, such as earthquakes, without compromising their functionality. Emergency inverters are critical components of backup power systems, particularly in facilities like hospitals, data centers, and emergency response centers. Many jurisdictions require critical infrastructure to meet seismic standards. These details can be found on various agency websites, including the International Building Code (IBC), the American Society of Civil Engineers (ASCE), and the International Code Council (ICC). California has led the way with testing requirements through its Healthcare and Access Information (HCAI) department (formerly OSHPD), given the critical need for reliable power in medical facilities during an emergency.
In the aftermath of an earthquake, reliable power supply is crucial for life-saving equipment, emergency systems, and essential infrastructure. Seismic testing verifies that the inverter can continue functioning or restart quickly after a seismic event without failure. Seismic vibrations can cause internal components of inverters to loosen, break, or malfunction, potentially leading to system failure or safety hazards.
Emergency lighting Inverter seismic testing requirements
Testing ensures that the inverter’s design and mounting can withstand seismic forces. Seismically certified lighting inverters prevent power loss to essential systems like emergency lighting during earthquakes, reducing risks to human life and property. The level of seismic testing depends on the geographic location and seismic hazard. In high-risk areas, inverters must meet stringent seismic resilience requirements. Testing can certify that the inverter meets zone-specific standards, such as those outlined for California or other earthquake-prone regions.
Seismic testing for emergency inverters involves subjecting them to simulated earthquake conditions. These tests assess their structural integrity and operational functionality during and after seismic events. One of the primary methods of testing is the Shake Table. The inverter is mounted on a shake table that replicates seismic ground motions. The table moves in multiple directions (horizontal, vertical, or both) to simulate earthquake forces. The inverter must maintain mechanical stability, remain functional, and avoid excessive vibrations, displacement, or damage. Check out this Chalk Talk about seismic testing, which includes a video of a large lighting inverter on the shake table.
Tests like the shake table are based on peak ground accelerations (PGA) expected for the region. The PGA measures the maximum ground acceleration that occurs during an earthquake. The duration of simulations mimics the duration of typical earthquake ground motions. During the test, the inverter mounting conditions are the same mounting configuration used in the field to ensure realistic results.
After mechanical testing, the inverter’s electrical performance is verified to ensure it continues to operate within specifications. The system is tested under load conditions to ensure uninterrupted power supply.
Isolite products are built for strength and stability
Lighting inverters are composed of various electrical components, and they can weigh more than 3 tons due to the large number of batteries arranged on shelves inside the inverter case. If seismic activity starts to shake the inverter, these batteries and other components could “walk” around or break free from connection points. Battery security on the shelves, floor mounts for the inverter case design, and rack strength are just some of the design considerations necessary for seismic-rated lighting inverters.
Even though seismic testing is not required for items under 50 pounds, design considerations can also be included with emergency exit signs and lighting. The team at Isolite overbuilds the mounting mechanisms for these products to prevent them from being vulnerable to shaking, and internal batteries and transformers are hard-fixed rather than floating to ensure stability.
