Control Cabinet penetrations - esp. NEMA 4, etc.

[Chuk Gleason]

Have a general question about electrical control cabients, NEMA 4 & similar ratings.

If you're designing a controls cabinet with operator controls on the front door, what are the important points about maintaining the NEMA 4 rating even with the penetrations for things like pushbuttons, switches, HMI screens, etc? The little bit I've been able to decipher is that making a penetration pretty much voids the NEMA 4 rating, unless there are certain guidelines observed, and proven to be followed?

Yes, there's a story behind the question, which will become apparent later. And I'm just the FNG (funny new guy) so I don't have the street cred to ask too many very pointed questions. But where can I point my mentors to information that they really should know? The general question comes up because of an HMI screen installed in a NEMA 4 cabinet, in an outside environment, but the HMI material says OK for "NEMA 4X (indoor use only)"

 

[LionelHutz]

It's rather simple. If the cabinet is Type 4 then every hole must be filled with a device that is also Type 4 rated or else the cabinet drops to the rating of the lowest installed unit.

That HMI probably has issues with either cold or sun. It's likely not Type 4X listed if if can't be outside.

I write Type instead of NEMA because Type is what listing agencies will call the rating. Anyone can say something is NEMA rated, but that's not a tested and listed rating that listing agencies will recognize.

 

[Chuk Gleason]

Noted on the usage of the word "Type"

Yes, issues with sun shining on the display, plus water intrusion.

Back to the generic discussion, to control buttons, switches, etc. have to be appropriate Type. So that should be on the datasheets for those items?

During or after a control panel construction, is there some sort of acceptance testing or inspection? Or is it assumed that if the panel is built with all properly type-listed components, that it still meets the overall Type listing?

 

[LionelHutz]

You need a listed enclosure and listed devices and then you follow the ratings on all to get the overall panel rating. It's considered listed if you're build a listed product following your own file or a panel file such as UL508A. You should also look for any special notes or requirements pertaining to the device rating.

 

[djs]

Please note that Type 4/4X is not totally waterproof. The rating is basically for wash down. A type 4/4X enclosure placed where rain or water can fall on it, will get water inside it. Seems illogical but there are reasons.

 

[jraef]

Please note that Type 4/4X is not totally waterproof. The rating is basically for wash down. A type 4/4X enclosure placed where rain or water can fall on it, will get water inside it. Seems illogical but there are reasons.

No, not at all true. Type 4 or 4X is indoor, outdoor, water tight to exclude water entry from the force of 60PSI from a 1" nozzle. If water cannot get in from a 60PSI stream, it cannot get in from falling rain.

What Type 4/4X does NOT do is allow any INTERNAL condensation to drain out, BECAUSE water tight works both ways. So if there is a possible air exchange, i.e. via conduits coming from another area that is open to atmosphere, then moisture in that air can condense in the enclosure and not escape.

There ARE Type 4 breather/drain accessories that can go on the bottom of the enclosure that take care of this, or you can seal the conduits with duct sealing compound.

As LionelHutz said, any penetration to the enclosure must be used with a device of the same or greater rating. So Type 4, 4X, 6 or 6P pilot devices in the door will maintain the Type 4 rating of the assembly.


" We are all here on earth to help others; what on earth the others are here for I don't know." -- W. H. Auden

 

[ScottyUK]

Some NEMA 4X equipment - A-B's PanelView series of HMI's for example - meet the water-resistance aspects but (used to) fare really badly in UV light. The 'indoor use' qualification may apply to something other than purely the enclosure rating.

 

[controlsdude]

Look up Meyers hub for all conduit penetrations since its washdown. Different connectors for different levels of nema ratings.

https://www.eaton.com/us/en-us/catalog/fittings/myers-hubs.html

http://www.cooperindustries.com/con...mmercial-products/catalog-pdfs/myers-hubs.pdf

https://www.galco.com/shop/MYERS-HUBS-Crouse-Hinds-Conduit-and-Cable-Connectors-Fittings