Three Key Takeaways:
- UL 508A is the Underwriters Laboratories standard for general-purpose industrial control panels and covers roughly 90 percent of the panels Adgo builds.
- UL 698A is a stricter, specialized standard for panels used in hazardous (classified) locations where flammable gases, combustible dusts or ignitable fibers pose an ignition risk.
- If any field wiring from your panel enters a classified hazardous area, UL 698A applies, and every intrinsically safe barrier in the panel must be rated to the specific class and group of that area.
If you are specifying, procuring or approving a control panel for a facility with any classified hazardous area, knowing the difference between UL 508A and UL 698A is not academic. It determines how the panel is built, labeled and tested, and whether your installation will pass inspection.
Most industrial control panels in North America are built to UL 508A. A smaller subset, those whose field wiring crosses into a hazardous classified location, must be built and labeled to UL 698A with specific intrinsically safe barriers rated to the class and group of the area.
Getting this wrong has real consequences: A panel with the wrong rating can fail inspection, force rework, delay startup or in the worst case, contribute to a preventable safety incident in an area where a spark could ignite the atmosphere.
What Is the Difference Between UL 508A and UL 698A?
UL 508A is the standard for general-purpose industrial control panels. UL 698A is the standard for industrial control panels that interface with hazardous (classified) locations, such as areas containing flammable gases, combustible dusts or ignitable fibers.
The practical difference comes down to where the panel connects. If any wiring from the panel runs into a classified hazardous area, the panel must be labeled to UL 698A and include intrinsically safe barriers rated for that area’s class and group. If the panel lives and connects only in general-purpose environments, UL 508A applies.
Both standards require the panel builder to be a UL-certified facility, to use UL-certified components as required and to follow the specified enclosure type ratings.
What Is UL 508A?
UL 508A is the safety standard for general-purpose industrial control panels. It sets requirements for how the panel is assembled, which components can be used inside, how terminations are torqued and which enclosure types are acceptable for a given environment.
UL 508A is the most commonly applied panel standard in North America. At Adgo, roughly 90 percent of the panels we build are UL 508A.
Key requirements include:
- Using UL-certified components where the standard calls for them (not simply UL-recognized).
- Following manufacturer-specified torque ratings so terminals are neither under- nor over-tightened.
- Matching the enclosure type rating to the installation environment.
- Maintaining full bill-of-materials documentation that can be reviewed at the UL audit.
A UL 508A label tells the inspector, the authority having jurisdiction and the end user that the panel has been built by a qualified shop following a documented, repeatable process.
What Is UL 698A?
UL 698A is a safety standard that goes a step further than UL 508A. It applies to panels interfacing with hazardous classified locations where a spark could ignite the atmosphere. Typical applications include gas compressor stations, chemical plants, solvent handling, grain and feed, and any area classified under the National Electrical Code.
The core of UL 698A is the intrinsically safe barrier, or ISB. An ISB is an interface between the control panel, usually mounted in a safe area, and the field wiring that runs into the hazardous area. The barrier limits the energy in that wiring so it cannot produce enough spark or heat to ignite the atmosphere under normal or fault conditions.
UL 698A panels must be labeled as such. Every intrinsically safe barrier inside the panel must be rated for the specific class and group of the area it protects:
- Classes cover the type of hazard: Flammable gases and vapors (Class I), combustible dusts (Class II), and ignitable fibers (Class III)
- Groups classify material types: The specific gases, vapors or dusts present in the area
Unlike UL 508A, which receives regular updates, UL 698A does not change often. That stability is useful for long-term installations, but it also means specifiers must pay close attention to the class and group of each wiring run going into the field, and to any NEC changes that affect how those areas are classified.
Key Differences Between UL 508A and UL 698A
The table below summarizes how the two standards compare across the factors most often asked about by engineers and project managers.
| Factor | UL 508A | UL 698A |
|---|---|---|
| Application | General-purpose industrial control panels | Panels interfacing with hazardous locations |
| Typical share of Adgo builds | ~90 percent | Specialized subset |
| Intrinsically safe barriers | Not required | Required, rated to class and group |
| Panel label | UL 508A | UL 698A |
| Update frequency | Updated regularly | Updated rarely |
Both standards require the panel builder to maintain UL facility status, pass UL audits every two years and keep a UL-certified staff member on site.
UL Certified vs. UL Recognized: A Distinction That Matters
When you build to either standard, the components inside the panel must also carry the correct UL mark. UL Certified and UL Recognized are not the same thing.
- UL Certified: Tested as complete, standalone products under a standardized procedure
- UL Recognized: Tested only for use as part of a larger assembly, under specific conditions
For UL 508A and UL 698A-labeled panels, using UL-certified components where the standard requires them is non-negotiable. That includes honoring the listed torque ratings so terminals are not under- or over-tightened, and selecting enclosure types that match the environment:
- Type 1: Basic indoor applications with minimal protection needed
- Type 3R: Outdoor installations (Adgo’s minimum rating for any outdoor enclosure)
- Type 4, 4X: Watertight and corrosion-resistant applications
The enclosure type must match the application environment, and choosing the wrong type is one of the most common reasons a panel fails field inspection.
How to Know Which Standard Your Panel Needs
Specifying the right standard starts with a classification review of the installation environment. From our experience with customers, we know a few practical questions get you most of the way there:
- Does any wiring from the panel enter a classified area? If yes, UL 698A and intrinsically safe barriers are almost certainly in scope.
- What are the class and the group of the hazardous area? Each ISB has to be rated to match. If you do not know the classification, work with the facility engineer or the AHJ before releasing the panel design.
- What is the enclosure environment? Indoor, outdoor, washdown, corrosive or explosion-prone, the type rating has to match.
- Are all components UL certified where the standard requires? Many field failures can be traced back to this requirement.
Running this checklist before submittal saves rework and keeps the inspection clean. In our experience, most resubmittal problems on hazardous location projects stem from missing or misrated barriers and enclosures that do not match the field environment.
Why UL Certification Is an Ongoing Commitment
Being a UL-certified panel shop is not a one-time achievement. UL facilities must pass testing and audits every two years and keep at least one UL-certified staff member on site at all times. Documentation has to be updated as standards evolve, which happens more often with UL 508A than with UL 698A.
Adgo has maintained UL facility status for decades across both standards. Every UL 508A and UL 698A control panel we label carries the weight of that program behind it: the audits, the certified staff, the component library and the documentation that keep it valid.
The Next Step
The difference between UL 508A and UL 698A comes down to where your control panel lives and what it connects to. UL 508A is the standard for general-purpose industrial control panels. UL 698A is required whenever your panel’s field wiring crosses into a hazardous-classified location, and it imposes specific requirements for intrinsically safe barriers rated for the class and group of that area.
If you are designing, specifying or reviewing a control panel for a hazardous location or a critical process, Adgo can help you determine which standard applies and build a panel certified to it. Contact us with your questions today.
FAQ
Is UL 508 the same as UL 508A?
UL 508 and UL 508A are related but not identical. UL 508 is the broader standard for industrial control equipment and components, while UL 508A is the specific standard for complete industrial control panels. When people ask about the difference between UL 508 and UL 698 for panels, they are almost always comparing UL 508A and UL 698A.
Do I need UL 698A if only part of my panel connects to a hazardous area?
Yes. If any wiring from your control panel enters a classified area, the panel typically must comply with UL 698A and include intrinsically safe barriers rated for the area’s class and group. The rest of the panel can be located in a safe area, but the labeling and barrier requirements still apply to the entire assembly.
What enclosure type does Adgo build to?
Adgo builds to whichever enclosure type matches the environment. Type 1 for basic indoor applications, type 3R as our minimum rating for any outdoor installation and type 4 or type 4X for wet, washdown or corrosive locations. The application drives the rating.
What is the difference between UL certified and UL recognized components?
UL certified components are tested as complete standalone products under a standardized procedure. UL recognized components are tested only for use as part of a larger assembly under specific conditions. For a UL 508A or UL 698A-labeled panel, you need UL certified components where the standard requires them.
How often does UL 698A change?
UL 698A updates infrequently compared to UL 508A. That stability is helpful for long-term installations, but specifiers still need to pay close attention to how the NEC classifies each field-wiring run and to the class and group ratings of every intrinsically safe barrier in the panel.
