PLC in Class 1 Div 2, cooling options


Thread Starter



We need to put a PLC control panel in a Class 1 Div 2 location. Unfortunately the location is fixed, there is no way we can put this panel in a non-classified area.

The plant is in Texas and the PLC's got to withstand brutal heat. What would be our options for cooling? I believe we might be able to use a NEMA 4X panel rated for Class 1 Div 2.

I know you cannot use NEMA 4X for Class 1 Div 1, but you might be able to do it for Class 1 Div 2 if you use intrinsic safety barriers. Is my understanding correct? Has anyone done this before? This will be first time for me.

Also can you put a closed loop cooling system and still have the panel retain it's Class 1 Div 2 rating?

Thanks in advance..

If you have a source of dry compressed air, these are very good coolers:

There is a heat load sizing calculator available on the site.

You could also check with Hoffman Enclosures about their recommendations, accessories and experiences:

(Remove any spaces inserted by the forum software when pasting into your browser.)

Check with your preferred control panel supplier, also, for their recommendations.

Let us know what you find out!


I'm no expert but I have heard if you can create, and guarantee, positive air pressure in the control cabinet you don't need anything else. It does two things. 1) keeps the hazardous material out; 2) cools the cabinet. Sounds like both things would be beneficial to you.

Possibly some of those older and wiser members of can chime in and confirm or deny this assertion.

Bob Peterson

something in EXe will do you no good in an area classified to Class/Area standards.

Vortec type coolers work ok, but air is an extremely expensive utility.

There are air conditioners available in both explosion proof configuration and rated for class I division 2 areas.

many components such as PLCs and their I/O cards are specifically listed as suitable for use in CID2 areas, and some general purpose equipment is specifically allowed in such areas by the NEC. Take a close look at article 501, paragraphs 100 through 150.

This is not something someone can learn about by asking random people on the Internet. You should really have someone who is competent in this area help you, as there are a lot of non-obvious things that need be considered.

If it were me, my first pass at it would be to design the control panel so I didn't have to do anything unusual. Just because it is hot does not mean it has to have any cooling. Even if it is outside, you can shade it from direct sunlight to reduce heat gain, and use enclosures that are painted white or made of reflective metal to also reduce heat gain.

If you are clever, most times you can completely avoid the need to use any special components as well, but you need to know just what you can, and more importantly, what you cannot do.

agreed vortex coolers have a place, but not a good means for cooling a panel. If you use one, you need to install a muffler system to limit the noise.

we've used explosion proof a/c, but you have to be careful to avoid condensation in the cabinet when exposed to ambient air when it is opened, and all the conduits properly sealed.
I&CAdvisor... If you intend to use cooling-air, its source must be from an unclassified area!

In addition, the flow of air must be exhausted into an unclassified area!

Regards, Phil Corso