UL 98B vs. UL 1741: Why They Matter for Your Facility

If you manage electrical systems, automation equipment, or energy projects, you’ve likely encountered UL standards during equipment selection or installation. These standards are far more than regulatory red tape; they ensure safety and peace of mind by verifying that products have met stringent quality standards.

For manufacturers working with solar power, battery storage, or microgrid systems, two UL standards often come into play: UL 98B and UL 1741. At first glance, they seem to serve very different purposes, but the reality is that they overlap in some key areas.

Both standards can apply to enclosed or dead front switches, meaning either one could be relevant when selecting a disconnect for your system. The main distinction is that UL 1741 covers a much broader range of equipment, including power conversion systems and other key components in renewable energy installations.

Understanding this overlap and the broader scope of UL 1741 helps simplify purchasing decisions and ensures your project is both safe and compliant from the start.

Here at ASG, our two decades of industry experience have led us to work with a variety of UL standards. This article will explain what each of these two standards covers, how they fit into different types of projects, and why understanding these details are essential.

Understanding UL 98B: Safety for Photovoltaic Disconnect Switches

To understand UL 98B, it helps to first know a little about UL 98, its parent standard. UL 98 is the broad standard that applies to enclosed and dead-front switches—the types of disconnect switches commonly used to isolate industrial equipment from incoming power. These are the switches electricians rely on when locking out equipment before performing maintenance.

However, as solar power systems became more popular, the industry quickly realized that disconnect switches for photovoltaic (PV) systems required more specialized testing than standard UL 98 equipment could provide. Solar systems operate under higher DC voltages than typical industrial circuits and, in some cases, they experience current flowing in both directions, known as bidirectional flow between solar arrays and battery storage.

UL 98B applies directly to photovoltaic disconnect switches, ensuring they are built and tested to handle the unique characteristics of solar power systems.

For solar systems rated up to 1500V DC, the disconnect switches of the system can be certified to UL 98B. This certification ensures they can safely isolate the array for maintenance or emergencies while preventing equipment damage or dangerous arc faults.

Understanding UL 1741: Certification for Power Conversion and Grid Interconnection Equipment

While UL 98B strictly governs the disconnect switches that isolate solar arrays, UL 1741 has a greater scope and also includes devices that convert, control, and manage the power produced by those arrays. Specifically, UL 1741 focuses on inverters, converters, and controllers.

The primary focus of UL 1741 is ensuring that these devices not only operate safely within your facility, but that they also interact safely with the larger electrical grid. This is especially important if your system will send excess power back to the utility through net metering or participate in programs where onsite generation supports local grid stability. 

UL 1741 ensures that when disturbances occur—such as voltage fluctuations or grid outages—your system can respond appropriately without creating dangerous conditions for utility personnel or damaging grid infrastructure.

For example, UL 1741 requires that inverters automatically disconnect from the grid if they detect a loss of utility power. This prevents solar power from back-feeding into the grid when there is an outage. This can endanger utility workers who assume lines are de-energized when, in fact, they are not.

Beyond safety, UL 1741 also ensures that modern inverters comply with evolving grid-support requirements, such as those outlined in IEEE 1547. This means inverters are not just passive devices, but active participants in maintaining grid reliability, helping to support voltage and frequency stability when the grid experiences stress.

How These Standards Work Together

When it comes to solar installations, it’s easy to see why UL 98B and UL 1741 can be misunderstood. Both standards can apply to disconnect switches, and in many cases, they are interchangeable. This gives you flexibility when selecting compliant equipment for your system.

That said, UL 1741 goes beyond just disconnect switches. It also covers other critical components, including power conversion and management equipment, ensuring that these products meet performance and safety requirements when connecting to the grid.

If you’re installing solar panels at your facility, you’ll need to ensure your disconnect switches meet either UL 98B or UL 1741 requirements. And for power conversion and management equipment, UL 1741 certification is a must.

Together, these standards help create a robust safety and performance framework—covering both the equipment controlling power flow and the devices that disconnect it when needed, along with other essential components of your solar array.

Getting It Right: Partnering with Experts Who Understand Compliance

You shouldn’t have to become an expert on UL standards to complete a successful renewable energy project—but you do need to work with suppliers who understand the stakes. Selecting compliant equipment from the start saves you time, money, and headaches during installation and inspection.

At ASG, we combine our deep knowledge of industrial automation with a clear understanding of the renewable energy equipment many projects are now embracing. We can help you select the right disconnect switches, inverters, and controllers—ensuring that every component is fully compliant with UL 98B, UL 1741, and any applicable local requirements.

Whether you’re installing your first solar array or upgrading an existing system to add battery storage or grid support capabilities, we can guide you through the process, helping you choose products that are not only safe but future-ready for evolving grid standards.

Final Takeaway: Know the Standards, Protect Your Project

Understanding UL 98B and UL 1741 isn’t just about ticking a regulatory box. It’s about ensuring the safety of your workforce, the reliability of your system, and the long-term success of your investment.

When you know which standard applies to which part of your system, you make smarter equipment choices, avoid inspection and approval headaches, and give your project the best chance of achieving its sustainability and resilience goals.

If you’re planning a new renewable energy project—or even just upgrading existing electrical infrastructure to accommodate future solar or storage—reach out to ASG today. Our team is ready to help you navigate the standards and select the right products for your project to ensure compliance, safety, and confidence.