Remote I/O in Class 1 Div 2 Area

[kcca]

I'm in the process of specifying a field enclosure which will contain a remote I/O subsystem located in a C1D2 rated area. There are 4 main components in the field enclosure: module power supply, communications module, remote I/O modules and a second 24 VDC power supply for the instrument loops. All 4 of these components are specified by the manufacturer as being rated for Class 1 Division 2. A NEMA 4 enclosure will be specified.

I will be connecting 120 VAC to both 24 VDC power supplies. An ethernet cable will be connected to the communications adapter.

The field instrumentation is all specified as non-incendive, rated for Class 1 Division 2. Hence, no IS barriers are needed.

Given that all of the interior panel components and instrument interfaces meet C1D2, per Articles 501/504, it is my understanding that I do not need to Z-Purge this panel or do anything beyond installing the components. It is also my understanding that I'll need to wire the 120 VAC to the power supplies in a manner to avoid the potential for an arc.

Does all of this sound feasible, or am I overlooking something here? Be kind, this is my first post in this forum - Thanks.

 

[rbalex]

Welcome to the forums.

You are correct; as you have described it, purging is unnecessary. As a matter of fact, IS barriers were probably unnecessary in any case.

 

[kcca]

Bob,

Thanks for the feedback. Really appreciate it. I expect that I will also need to pour a seal in the conduit within 18 inches of entering this remote i/o enclosure with the 120 VAC feed. Would you agree?

 

[rbalex]

If the remote I/O enclosures are required to be explosionproof, you will require a seal within 18" for the integrity of the enclosure. Other possible seal requirements will depend on potential boundary crossings.

 

[weressl]

Bob,

Thanks for the feedback. Really appreciate it. I expect that I will also need to pour a seal in the conduit within 18 inches of entering this remote i/o enclosure with the 120 VAC feed. Would you agree?

You already established that a NEMA 4 box without purging is adequate. What would you WANT to seal? What does a seal do? I think those two questions allow you to answer your own.