UL Ratings

Gentlemen, I am pushing my PLC Company to obtain a class 1 Div 2 rating by UL. They have come back an offer a TUV class 1 div 2 rating from Germany. I asking if anybody believes that this rating would be accept here in the US.


Mickey Moore

If I remember correctly, class 1 div 2 is "explosion proof". If you are looking at PLCs with relay outputs, the PLC will have to be manufactured with hermetically sealed relays. As relays get older, there tends to be an increased possibility for arching. With that said, I don't know if they would pass a relay output controller.

With triac or transistor outputs, you may have a better possibility. It will depend on the device that is handling the current load.

You will also have to take into account the power supply being used.

Is the mfg. going to charge you for this rating or is it something that they have already tested to?

Some of the testing agencies (UL, CSA, TUV) have reciprocal agreements with certain standards. So you may want to check with UL to see if the TUV rating they have offered is recognized by UL in the US.

If I am not too forward in asking, why do you require a class 1 div 2 rating for the PLC?

One other way that you can achieve explosion proof is puting the PLC in an explosion proof enclosure...but that will cost $$$$

In our 25 years, to our knowledge, we have not had a controller "explode". The majority of materials from the circuit board to the components have been tested and at worst have chared for various reason, but I believe they do use flame resistent material.

Hope this helps,

God Bless,

Stephen Luft

In our 25 years, to our knowledge, we have not had a controller "explode". The majority of materials from the circuit board to the components have been tested and at worst have chared for various reason, but I believe they do use flame resistent material.

Click to expand...

Just a clarification:

To the best of my knowledge, explosion-proof does not mean that the device will not explode, nor does it imply that the device is made from non-flamable materials. It means that the device can be installed in an explosive atmosphere (flamable gasses, dust) and not cause an explosion.

Steve,

Thanks for the clarification.

God Bless,

Stephen Luft

There is a huge difference between European and US standards on hazardous areas, intrinsic safety, etc. To the best of my recollection the TUV standards do not cross reference directly to the US UL or FM standards. I believe the IEC standards are based on but not identical with TUV.

Control Engineering recently had some articles on this subject, so you cold go to their site and do some searching. I also strongly reccomend you get in touch with a supplier knowledgable about hazardous areas - start with enclosure and/or intrinsic safety barrier guys.

I believe that the insurance underwriters, safety department or specifying engineers for the particular industry you deal with would have input as to what they would accept. Even certain industries have requirememts as to what they would accept (underground coal mining in the US usually requires MSHA approval).

TUV has a Nationally Recognized Testing Lab approval (usually mentioned as NRTL) which places their testing and approval on par with UL, CSA etc. you might want to verify that they are approved to test to UL 1604 which is the UL standard for Electrical Equipment in Class I and II, Div 2 hazardous locations.

I have still heard about specific requirements for either FM, UL, CSA or other alphabet agencies even though the NRTL process was put in place to make things easier (to further complicate things!) banghead .

UL standard site link:

http://ulstandardsinfonet.ul.com/

Bob

UL

First, thanks you for all your gentlemen inputs. The reason this has come up is that I'm down in here Houston, petrochemical/pipeline country. I have lost several jobs due to this rating. I have pushed them very hard for this rating and we currently carry UL508/CE, Nema 4x, and IP20/(IP65 mounted). Several of My customers are E/I firms and it’s their customers who are asking for this rating. I do believe that UL and TUV run parallel to each other, but I’m check on that for my PLC Company. Quite frankly UL is pain in the butt, but a necessary evil. Mr. Bailey is also right with correctly defining the classification. We have already been told by UL that they would like to see 2 amp relays instead of 5 amps relay out.

Schneider Electric has some UL listed Class 1 Div 2 modules in their Quantum family. You can look at their Momentum and Premium offerings also.
http://www.modicon.com/PLCIO/Quantum/Quantum_Agency_Approvals.htm