Mike Dolt Enterprises
Mike Dolt Enterprises
User: brock.aslan, Location: Ohio
Asked on: Sunday, January 19, 2025 at 4:06 pm EST
Answered on: Thursday, March 6, 2025 at 7:30 am EST
Question: Hello! New to the community, and hoping to get another's interpretation of NFPA 70 (NEC) code; specifically, Article 505.9(C)(1) [2023].I am currently deepening my knowledge of protection and wiring methods for a Class I, Zone 2 hazardous location application. I am finding it easier to find components and devices certified to the Class and Division system, and these same device certificates tend to remain silent on their Class and Zone classification.My question, I think is hopefully a simple one: If the device has a certification from an NRTL for Class I, Division 2, Groups A, B, C and D, Temperature Class T3, is it fair to conclude from looking at Article 505.9(C)(1) that these devices are also able to be installed in a Class I, Zone 2 hazardous location, with a similar group and temperature class?Here is the text for those who don't have the code right in front of them:"Equipment identified for Class I, Division 1 OR Division 2 shall, in addition to being marked according to 500.8(C), be permitted to be marked with all of the following: (1) Class I, Zone 1 or Zone 1; Class I, Zone 2 or Zone 2 (as applicable)..."A final comment, my interpretation of the code from Article 500 to 505 leads me to believe that Division 2 and Zone 2 are fairly similar; however, it looks as though Zone 2 is less strict (I'm saying this given the many number of protection and wiring methods afforded to the designer under Zone 2 vs Division 2) than Division 2, meaning that if I was to design a system for Class I, Division 2, I would be able to install that same system in Zone 2, given the group and temperature classes are the same.
You're on the right track with your understanding of Article 505.9(C)(1) and the relationship between Division 2 and Zone 2. Let's break it down
Your Interpretation is Correct:
Yes, based on Article 505.9(C)(1) of the 2023 NEC, you can generally conclude that a device certified for Class I, Division 2, Groups A, B, C, and D, Temperature Class T3 is permitted to be installed in a Class I, Zone 2 hazardous location with the same group and temperature class.
Why This is the Case (Breaking Down 505.9(C)(1)) "Equipment identified for Class I, Division 1 OR Division 2..." This clearly states that equipment certified for either division is potentially eligible for Zone installation under this provision. "...shall, in addition to being marked according to 500.8(C), be permitted to be marked with all of the following: (1) Class I, Zone 1 or Zone 1; Class I, Zone 2 or Zone 2 (as applicable)..." This is the key part. It permits the manufacturer to mark the equipment for Zone use if it meets the necessary requirements. The "as applicable" is important – it means the marking needs to be accurate for the Zone requirements.
Therefore, in your case, a device already NRTL Listed to Class I, Division 2, Groups A, B, C and D, Temperature Class T3, would be also permitted to be installed in a Class I, Zone 2 hazardous location, with a similar group and temperature class. And, it would be permitted by the code to be marked in such a way.Important Caveats and Considerations
NRTL Listing is Key
The fact that the device has an NRTL (Nationally Recognized Testing Laboratory) listing for Class I, Division 2 is crucial. This listing means it has been tested and certified to meet the safety standards for that classification.
Temperature Class
You must ensure the T-rating is suitable for the specific Zone 2 environment. For example, if the Zone 2 environment has a gas with an auto-ignition temperature that requires a T4 rating, then a T3-rated device would not be acceptable.
Equipment Markings
While 505.9(C)(1) allows for dual marking, it doesn't require it. The manufacturer might not have chosen to add the Zone markings. The presence of the Division marking itself is sufficient for installation in Zone 2 based on the permission given by 505.9(C)(1).
Installation Requirements
Even though the device is listed for Zone 2 based on its Division 2 certification, you must still adhere to all other relevant requirements in Article 505 for Zone 2 installations. This includes wiring methods, grounding, bonding, and any specific requirements for the hazardous material present.
Specific Application
Always consider the specific hazardous material present and the conditions of the hazardous location. The Division 2 listing ensures a certain level of safety, but you must confirm that the device is truly suitable for the specific application in your Zone 2 environment.
Documentation
Maintain thorough documentation of the device's NRTL listing, temperature class, and Group rating to demonstrate compliance with the NEC and any applicable local codes.
The Authority Having Jurisdiction (AHJ)
Always consult with the AHJ in your area. They have the final say in interpreting and enforcing the code. While your interpretation and mine may align, the AHJ's opinion is paramount.
Division 2 vs. Zone 2: Your Assessment is AccurateYou are correct that Zone 2 is often considered less restrictive than Division 2. This is because Zone 2 focuses on infrequent release of hazardous materials, while Division 2 focuses on abnormal operating conditions. The NEC provides a wider range of protection methods for Zone 2, reflecting this difference in risk assessment.
In summary:A Class I, Division 2, Groups A, B, C, and D, Temperature Class T3 listed device is permitted to be installed in a Class I, Zone 2 location with similar group and temperature class, provided you adhere to all other applicable requirements of Article 505 and consult with the AHJ. Just because a device can be installed doesn't mean it should* be without considering all factors.Remember to always prioritize safety and consult with qualified professionals when designing and installing electrical equipment in hazardous locations. Good luck! Flag for review