Purged and Pressurized Enclosures

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Anyone know about NEMA 3R enclosures in a class I div I area and with arcing and sparking devices inside of said enclosure. Are these to be monitered at all times by an attendant? Such as at a Natural Gas Compressor Station? I think they are.
 
html said:
Anyone know about NEMA 3R enclosures in a class I div I area and with arcing and sparking devices inside of said enclosure. Are these to be monitered at all times by an attendant? Such as at a Natural Gas Compressor Station? I think they are.
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I don't think a NEMA3R enclosure would qualify for purging/pressurization. They generally are not gasketed, and that is one of the requirements.
 
petersonra said:
... They generally are not gasketed, and that is one of the requirements.
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What Standard does this come from? It is neither an NEC nor NFPA 496 requirement.
 
html said:
Anyone know about NEMA 3R enclosures in a class I div I area and with arcing and sparking devices inside of said enclosure. Are these to be monitered at all times by an attendant? Such as at a Natural Gas Compressor Station? I think they are.
Click to expand...
What you are describing sounds like a ?Type X? system in NFPA 496. There are some very rigorous requirements, but being constantly monitored by an attendant isn?t one of them ? because it isn?t good enough.
 
rbalex said:
What Standard does this come from? It is neither an NEC nor NFPA 496 requirement.
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I wonder if he means more of a practical reason? There is a door gasket on a NEMA 3R CB panel, but the rain lip is not gasketed. Hard to maintain pressurization, but not impossible if you add some filler/gasket/caulk to the gaps.
 
It isn't worth the risk to just put on a gasket and call it a day. Use a Nema 4 or 4X, get a listed Purge controller, bring some air to the unit and keep safe. Eliminate the possibility of human error so you won't be in the newspaper. I have used Type X purge controllers in Cl. 1, div 1 areas. They are easier to work on, maintain and populate than a Nema 7. It is not worth taking shortcuts.
 
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