Class II Division II purge

[Pat H]

I have heard conflicting information about Class II Division II purge requirements for a motor control panel.

My interpretation of the NEC 502.115 B is that a control panel needs to be dust tight for CII DII (Groups F&G) and doesn't specifically call for a purge. CI DI does specifically call for a purge unit.

The manufacturer of the purge unit tells me that you do need a purge unit for CII DII and the distributor say's you don't really need the purge, but its a good idea because the enclosure seal could wear out.

I build control panels and need to know if I am really required to provide a purge system when panel is going to be in CII DII (dust that is not normally present).

Can anyone offer any insight to this? Does some electrical code really specifically dictate that a purge unit is necessary in CII DII? If so, can you tell me what code that is? Are they just trying to sell me?

Thanks,
Pat

 

[rbalex]

Purging is not required in either Class II, Division 1 or 2.

 

[Smart $]

Purging is a permitted alternative to using the more stringent enclosure types for respective hazards. That is, purging is never outright required, but could be "necessitated" in combination with an enclosure that does not fulfill hazard mitigation requirements by itself.

The possibility or likelihood of enclosure seals wearing out is not such a "necessitation"... not to my knowledge anyway.