Enclosure De-Rating

[richbogrow]

I am trying to determine if a Nema 1 disconnect is mounted to the outside of a Nema 12 enclosure, if that derates the Nema 12 enclosure to Nema 1. I cannot find anything in the NEC that specifies this, but I suspect it is true. Any thoughts would be appreciated.

 

[petersonra]

I am trying to determine if a Nema 1 disconnect is mounted to the outside of a Nema 12 enclosure, if that derates the Nema 12 enclosure to Nema 1. I cannot find anything in the NEC that specifies this, but I suspect it is true. Any thoughts would be appreciated.

I think you should stop using the term "NEMA type" and use the term "UL type" instead.

There is a chart in the UL508a standard that tells you what "type" of device can be used when penetrating a particular "type" of enclosure. You are generally correct that a type 1 device installed through the outer wall of a type 12 enclosure would effectively render the enclosure as a type 1.

However, if it is just bolted to the outside of the enclosure and the disconnect does not actually penetrate the enclosure, it may not have any effect on the enclosure type.

besides, what difference does it make in the vast majority of cases?

 

[Cow]

You are generally correct that a type 1 device installed through the outer wall of a type 12 enclosure would effectively render the enclosure as a type 1.

However, if it is just bolted to the outside of the enclosure and the disconnect does not actually penetrate the enclosure, it may not have any effect on the enclosure type.

This is what I was thinking.