Class II Division 2 junction box/terminal blocks

JovialBulge

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Location
New England
Occupation
Programmer
When it comes to installing a junction box on a piece of equipment within a CIID2 area, NEMA 4X rated. Which will be used to house only DIN mounted terminal blocks so that there are connection points from the devices on the machine, which would be intrinsically rated sensors and CIID2 rated AC motors controlled by VFDs, to the MCC; do the terminal blocks themselves need to be rated for the CIID2 environment?

It’s my understanding that if there are any electronic devices within the enclosure in the hazardous area that they need to be rated for the area, so say you can’t put a network switch in the NEMA 4X cabinet unless it’s rated for CIID2, or a remote IO rack. However the terminal blocks I can’t determine a good answer for.
 

don_resqcapt19

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Illinois
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retired electrician
Class II is all about heat...you can put pretty much anything you want into a dust tight enclosure in a Class II, Division 2 location, as long as the outer surface does not get too hot for the dusts that are in the area.
Terminal blocks are not an issue even in a Class I, Division 2 location.
 

JovialBulge

Member
Location
New England
Occupation
Programmer
So I was under the impression that something like say a VFD, which is not rated for the environment at all, would not be able to be installed within a dust tight enclosure since it’s not rated for the environment. Unless of course the enclosure is purged. Is that incorrect? As in, so long as it’s in a dust tight enclosure it’s ok for CIID2.
 

rbalex

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Location
Mission Viejo, CA
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Professional Electrical Engineer
There are actually two issues here. Don is correct that pretty much anything may be installed in an otherwise correctly installed dustight enclosure in Class II, Division 2 as long as it doesn't create an excessive surface temperature on the enclosure. However, a VFD manufacturer may object if their product is installed in an inadequately ventilated enclosure.
 

JovialBulge

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Location
New England
Occupation
Programmer
There are actually two issues here. Don is correct that pretty much anything may be installed in an otherwise correctly installed dustight enclosure in Class II, Division 2 as long as it doesn't create an excessive surface temperature on the enclosure. However, a VFD manufacturer may object if their product is installed in an inadequately ventilated enclosure.
I will be honest and say that I am a bit shocked at this just from my previous reading. I am no expert by any stretch here which is why I asked the questions in the first place. I was under the impression that if I had a NEMA 4X cabinet, which is considered dustight from what I understand, and I installed a PLC inside of it; said PLC would need to be rated for the CIID2 location. What you’re saying is that is not the case. Since the device is within a dustight enclosure then it’s considered ok.
 

rbalex

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Location
Mission Viejo, CA
Occupation
Professional Electrical Engineer
I will be honest and say that I am a bit shocked at this just from my previous reading. I am no expert by any stretch here which is why I asked the questions in the first place. I was under the impression that if I had a NEMA 4X cabinet, which is considered dustight from what I understand, and I installed a PLC inside of it; said PLC would need to be rated for the CIID2 location. What you’re saying is that is not the case. Since the device is within a dustight enclosure then it’s considered ok.
Almost, but not quite. It is OK as far as Class II, Division 2 is concerned IF it doesn't cause an excessive temperature on the enclosure's surface. The device(s) must still be suitable to be enclosed in a Type 4X enclosure no matter the location's classification.
 

JovialBulge

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Location
New England
Occupation
Programmer
Almost, but not quite. It is OK as far as Class II, Division 2 is concerned IF it doesn't cause an excessive temperature on the enclosure's surface. The device(s) must still be suitable to be enclosed in a Type 4X enclosure no matter the location's classification.
So to determine that it would be on the devices specification sheet?
As an example.
These aren’t rated for CIID2 but their temperature range is listed.
 

rbalex

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Location
Mission Viejo, CA
Occupation
Professional Electrical Engineer
OK, Let's go from the NEC itself. Read Section 500.8 (i.e., read it all) with special emphasis on Subsections 500.8(B)(1), (C)(4), (C)(6)(b), and (D)(2). In addition, read all of Section 502.10(B) with special attention to Subsection 502.10(B)(4) and read all of Article 502, Part III. [beginning with Section 502.100] with emphasis on the various Class II, Division 2 Subsections. [NOTE: The devices you are referring to are technically Utilization Equipment (defined in Article 100) made up of various components in the rest of Part III]

We aren't going to do your engineering for you; we will help interpret the NEC.

BTW, "These aren’t rated for CIID2 but their temperature range is listed." is meaningless with respect to your Class II, Division 2 issues. The temperatures listed are operating temperatures for the components, not necessarily the temperatures they generate.
 
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