Enclosure Door Interlocking

[mcs666]

We use a lot of two door enclosures, with overlapping doors, usually installing the disconnect handle through the master door. Is it necessary to mechanically or electrically interlock the other door? I would think this is the case being the master door could be closed while the other door is open. This would allow the disconnect to be turned on with the other door open. Not sure how to interpret NFPA79 in this area.

 

[jraef]

I don't have my NFPA79 on me, but I believe it only addresses OPENING the enclosure, not what happens when it is already open and you choose to energize it afterward. But along that line, one thing that was added a few years ago was that you must have a means of disconnecting the power even if the door is open. That's why most of the people selling rotary through-door disconnects now have what they call an "NFPA79 handle" that is permanently attached to the shaft. If you are using a flange mount disconnect, that's inherent.

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[jraef]

5.3.1.4 and 6.2.3 are the relvant sections.

As I suspected, no mention of what is required once the door is opened in terms of leaving the door open. I would however put a sign on every bay that says "Close all doors before energizing equipment."



"Dear future generations: Please accept our apologies. We were rolling drunk on petroleum."
— Kilgore Trout (via Kurt Vonnegut)
For the best use of Eng-Tips, please click here -> faq731-376