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Design Decisions: Choosing the Correct NEMA Enclosure

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William K.
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Selecting a Nema enclosure
William K.   12/4/2013 11:35:16 PM
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Both Hoffman and Rittal include good informationin their catalogs, at least they used to include it.

And I can easily imagine the aluminum of some types of buttons corroding away in justa few weeks of gulf salt spray. The problem is that not everybody advertises their non-corroding controls, and they do cost a lot more initially. 

Ann R. Thryft
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Re: Good info
Ann R. Thryft   12/3/2013 12:03:04 PM
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I agree, thanks for this excellent overview of NEMA enclosures.



Amclaussen
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Heavily damaged panels.
Amclaussen   12/2/2013 12:36:58 PM
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Probably, the worst panels I have seen ever, were at a couple of offshore platforms in Campeche Bay.  The panel components had suffered a terrible corrosion damage because of the marine atmosphere, but even worse: the pushbuttons had disintegrated completely, probably from UV light damage from the sun.  Selectors were completely stuck and couldn't be rotated at all.  All these damage was inflicted in less than two years of ambient exposition.

Those panels were to house the igniton system of the platform flare burner. Inside, we found that the ignition coil was too lightly constructed, and the manufacturer had placed a sticker (that was brown colored from oveheating) stating a Duty Cycle of only 30%, so that it required a cooling rest period after only two minutes of operation. I doubt the manufacturer did ANY calculations on temperatures inside the panel, that was a NEMA-7 Explosion-proof box, about 24" side square box.

Call that a completely "Monkeyish" design and execution.

naperlou
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Blogger
Good info
naperlou   12/2/2013 11:04:30 AM
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Pat, thanks for the clearly written article.  This is an area I see often neglected. 

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