UL-508A Design Considerations

October 1, 2019 / by Chad Charman

UL-508A certification for industrial control panels is a requirement in most jurisdictions and a standard many OEMs voluntarily choose to follow. There is a common misconception that a UL-508A certified panel shop can certify any panel they build. However, panels must also be designed to UL-508A standards to be certified. Because of this, it’s important to make sure your design is compliant with the 508A standard before approaching a panel shop to build and certify it. Here are a few things to consider to ensure your design is UL-508A certification ready.

First, it’s important to understand that the purpose of UL certification is safety related. A UL-508A sticker certifies that the panel uses components appropriate for the application and that those components are used in a manner consistent with their designed purpose. The two primary areas of focus in a UL-508A design are component selection and panel design.

 

Component Selection

UL certifies individual components as either UL Listed or UL Recognized. There are dozens of UL standards, and components used in a UL-508A panel must be certified under the UL-508 standard.

UL-508 listed components can be used freely in a UL-508A panel design. These tend to be components that are designed so that they will be safe no matter how they are hooked up (within reason). Examples would be DC power supplies, industrial PCs, and PLC components.

UL-508 recognized components can be used in a UL-508A design, but only within the manufacturer’s installation specifications. These are components that cannot protect themselves such as terminal blocks, fuse blocks, and power distribution blocks. When used consistent with their design, these components are certified to be safe.

Non-listed components or components that are listed only under different UL standards are not permitted in a UL-508A design unless the UL-508A panel shop has been granted a specific exception. For example, Vertech’s shop is permitted to use ground bars normally used in breaker panels.

 

Panel Design

Design requirements for UL include the proper use of UL recognized components along with labeling and documentation requirements. All components in the panel must be incorporated into the design as specified by the manufacturer. This includes considerations like physical spacing, overcurrent protection, and wire sizes.

UL requires that panels have drawings (seems obvious) and that all wires and components have labels. Design drawings must include FLA (full load amps) for all active components and call out wire sizes and fuse sizes. When built, wires and devices must be labelled to match the drawings.

Other labeling requirements include a replacement fuse chart, and standardized labeling that includes environmental (IP or NEMA) rating, short circuit rating, wire type specifications and more.

UL-508A Panel

This picture shows the UL certification label, panel-specific labeling, and an enclosed drawing set.

Getting it Built

A properly designed UL-508A panel must be built in a certified UL-508A panel shop. Certified panel shops go through an initial certification process that includes extensive training from UL, and regular quarterly inspections are required to ensure continued compliance. Prior to shipping, the panel shop will certify the panel by applying a serialized UL-508A sticker provided by UL.

 

The most important thing to take away is that a UL-508A shop cannot just certify any panel they build. The panel design must meet the standard for components and labeling. If you are in need of a panel, a lot of time can be saved by having the engineers at Vertech design your panel from the ground up to meet the standard.

 

Learn more

To see an example of a recent Vertech control system upgrade, including new panel design, at two wastewater treatment facilities, read this case study

 

Topics: Control Systems

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