ATEX device use in machine to be NRTL certified

[JovialBulge]

I have a machine where the end user is looking to having the electrical system NRTL certified in the end and I want to make sure I am starting off of the right path here while determining the components that I will use in the machine on the automation side. With regard to proximity sensors, transducers, pressure switches, safety sensors, magnetic reed switches; I assume that I must only use devices that are UL, FM or ETL certified in order to adhere to the NRTL requirement is that correct? If I were to find a device that is say only listed with an ATEX Zone rating I should stray away from using that since, based on my limited understanding, that’s not covered under the NRTL umbrella.

 

[petersonra]

I think you are on the right path here.

 

[suemarkp]

Does it have to be NRTL certified, or can a local Field Evaluation Body certify it? Here in WA, the state maintains a list of approved local Field Evaluation Bodies (FEB) who can put their stamp of approval on things. This evaluation is required for anything electrical that isn't listed or have a NRTL marking (we had to call them whenever we moved something like a drill press from the 1940's that wasn't NRTL listed and it changed locations (meaning a different street address). Once it had the FEB marking, we could use it anywhere in WA.

If a Field Evaluation Body can be used, and ATEX may be a more specific subcategory that not all FEBs can evaluate, I would choose one and ask what they need for them to put their label on it. The earlier you work with a NRTL or FEB, the better. It certainly helps to use UL Recognized components (the RU marking). But other components with known specifications may be acceptable, and general rules may be able to be used if some details are not documented. Chinese stuff with no documentation, or obvious fake/lie documentation, may not work.

There are also many more NRTLs that the three you mentioned. OSHA maintains a list: https://www.osha.gov/nationally-recognized-testing-laboratory-program/current-list-of-nrtls

 

[DukeB]

If you are using the intrinsically safe protection method, a device categorized as a "Simple Apparatus" by the NEC does not need to be rated for a hazardous location. Read NEC 70 Article 100 Simple Apparatus and NEC 70 Article 504. Informational examples given for passive components are switches, connectors and resistance temperature devices.

 

[JovialBulge]

If you are using the intrinsically safe protection method, a device categorized as a "Simple Apparatus" by the NEC does not need to be rated for a hazardous location. Read NEC 70 Article 100 Simple Apparatus and NEC 70 Article 504. Informational examples given for passive components are switches, connectors and resistance temperature devices.

So I get a bit turned around when it comes to switches, as in operator interaction switches and push buttons. I have read about the “simple apparatus” designation in the past but then I have also come across buttons, from say Allen Bradley, that are rated to be installed within a Class I Division 2 location. Are these buttons carrying this rating so they don’t need to be installed on an IS barrier and somehow still comply?
I would assume I could take a non-rated push button, consider it to be a simple apparatus, install it in the hazardous location with the signal going to and from it on an IS barrier, and be fine, is that correct? If so, how does one do the calculations that you would typically do on a rated device installed in the hazardous location that’s on an IS barrier to ensure the circuit as a whole based on installed cable length is still IS?

 

[DukeB]

I don't have experience with C1D2 so you would have to check the details of how the switch is rated for C1D2. My guess is it's rated non-incendive by virtue of sealed contacts and not by IS.

Having said that, you could use that switch or an non-rated switch with appropriately rated IS in C1D1.

However, you do need to assess whether a device can be considered a simple apparatus. The NEC 504.1(D)calls for assessing the temperature classification (thermal ignition) based on the characteristics of the device and how it is used. The NEC does not appear to address spark ignition compliance.
The informational note for Article 1 Simple Apparatus refers to ANSI/UL 913 and ANSI/UL 60079-11. I do not currently have access to those but IEC 60079-11:2023 address both thermal ignition compliance, spark ignition compliance as well as a host of other requirements. Note that UL 60079-11:2023 was adopted from IEC 60079-11:2011 with National differences and some revisions along the way. To my knowledge, UL 60079-11:2023, IEC 60079-11:2023 and NEC 70:2023 may result in differing temperature classifications for a switch.

As for a switch's entity paramters for selecting an Zener-type IS barrier , I've seen Ui = switch voltage rating, Ii = switch current rating, Pi = switch power rating, Ci = 0 and Li = 0.