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NEMA 4 Enclosure Installation Best Practices
How to install Free Standing Nema 4 Enclosure on concrete pad, with bottom entry conduits, while maintaining NEMA 4 Rating?

Problem: Industrial Free standing NEMA 4 Enclosure installed on concrete pad. Conduits turned up in concrete and enter through the bottom of the enclosure.

Interested in best practices, watch-outs, and products (general). There is no skirt kit available. Not sure what would be acceptable.

I have extensive experience with the installation of this type of equipment in indoor industrial and manufacturing settings. I am struggling with how to maintain the rating of the enclosure in this case. Seen other applications where a rectangle hole is cut to match the outside perimeter of the conduits and the enclosure edges are sealed once the enclosure is in place. This doesn't seem very professional.

By Bob Peterson on 4 February, 2016 - 1:43 pm
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I prefer type 3R enclosures. They often come with the whole bottom open. Cut what you have to and then seal the box to the pad. Expanding foam works pretty well.

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You cannot mount it flush to the floor and penetrate up the bottom with conduits while maintaining the Type 4 protection level. The only way to avoid violating the Type 4 integrity is to use a type 4 conduit hub or cable sealing device. I would build a base and raise it up of of the floor, then use one of those methods.

Another possibility is that if this is outside, the reason a Type 4 enclosure was specified was only because they needed an outdoor rating, and Type 3R was was not acceptable for some reason, such as because they wanted the door sealed. In that case you could appeal to whomever specified it and ask if the sealing to the concrete is an acceptable adaptation.

Technically however, it would not meet Type 4.

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Nema 4 rating is maintained on enclosures, indoor or outdoor for bottom entry by gland plates and every cable entering being glanded off.

As stated above the enclosure should be on a plinth. If you can't obtain one - have one made to fit.

Cables leaving the enclosure through the concrete pad should be sealed with expanding foam or similar to prevent gas or vermin from reaching the enclosure underside.