Most industrial infrastructure requires isolation switches to safely isolate circuits. Whether used for maintenance, emergency shutdown, or regulatory compliance, these switches play a critical role in ensuring system safety and maintainability. Schneider Electric's TeSys VLS isolation switch features a compact modular design with rated currents ranging from 25 A to 125 A, meeting UL 508 and UL 98 application requirements. It is commonly used for motor isolation, feeder disconnection, and electrical panel protection.
As part of the TeSys motor control and protection product line, the VLS series supports industrial and commercial systems in various application areas, including material handling, HVAC, pumps, solar energy, and mining. These switches come in two forms: DIN rail and door mounted, and can be equipped with auxiliary contact blocks (as shown in Figure 1), padlock handles, fourth poles, and terminal shields to meet specific safety and regulatory requirements.
Picture of Schneider Electric TeSys VLS auxiliary contact block
Figure 1 Schneider Electric TeSys VLS auxiliary contact blocks provide status indication or interface with safety and control systems. (Image source: Schneider Electric)
The TeSys VLS series has passed UL, CSA, and IEC standard certifications, providing consistent installation dimensions and expandable options that simplify panel design and reduce component variation.
This article reviews the practical differences between UL 508 and UL 98 standards, with a focus on common use cases in applications such as HVAC, material handling, solar energy, and energy. It also outlines how the TeSys VLS modular architecture enables flexible installation and configuration. At the same time, it also discussed how accessories such as padlock handles, auxiliary contacts, and interlocking devices can assist in achieving safety functions and complying with the tagging protocol. Finally, it was explained how standardized components and consistent external dimensions can help panel manufacturers and system integrators simplify shell design and reduce inventory complexity.
Isolation switches and standards: UL 508 and UL 98
Industrial isolation switches must comply with standards that reflect their expected functionality in electrical systems. UL 508 covers motor controllers for load side applications, while UL 98 defines universal switch requirements for disconnecting feeders. The application scope, performance requirements, and fault handling capabilities of these standards vary.
UL 508 is suitable for manual motor controllers used for load side disconnection, typically used for isolating motors or equipment within local areas of the panel. These switches are typically used for individual loads such as fans or pumps and do not require disconnection in the event of a complete failure condition. The UL 508 model has a short-circuit rated current of 5 kA, a size of 36 mm, a compact structure, and is most suitable for applications with limited space.
UL 98 is applicable to universal switches intended to disconnect the entire feeder or used as panel main disconnect devices. These models must meet stricter performance requirements, including a 10 kA fault current rating and higher load durability. UL 98 switches typically adopt a larger 70 mm external size to support higher current carrying capacity and fault interruption capability.
UL 508 and UL 98: TeSys VLS Technical Specifications
Schneider Electric's TeSys VLS series includes both UL 508 and UL 98 certification options, enhancing design flexibility while maintaining consistent mechanical dimensions. UL 508 models, such as TeSys VLS 25A isolating switch (as shown in Figure 2), 32A model, and 40A variant, support compact panel layout and branch circuit protection.