megloff11x
Senior Member
For enclosures in non hazardous locations, I favor one of those rotary switches (UL98) with the rod that goes to the fused switch block mounted to the back panel, or the knife switch - both interlocking the door.
Since an enclosure in a Class I Division 2 location is purged and pressurized, are these kind of switches still allowed, and allowed or not, is there a better way?
The differential pressure switch needed to sense pressurization isn't required to kill power for Division 2, just raise an alarm when pressure is lost. It can be assumed that the switch will open and any sparking will occur while the enclosure is still sealed & purged. And obviously you want a time delay after re-sealing to re-establish pressure and exchange any vapors that may have crept in, before throwing the switch again.
Is there a standard practice for setting one of these up? I could comply with each requirement of NFPA 496 several different ways, but the inspector won't fuss as much if your choice is what everybody else does, and uses components that everyone else uses.
Matt
Since an enclosure in a Class I Division 2 location is purged and pressurized, are these kind of switches still allowed, and allowed or not, is there a better way?
The differential pressure switch needed to sense pressurization isn't required to kill power for Division 2, just raise an alarm when pressure is lost. It can be assumed that the switch will open and any sparking will occur while the enclosure is still sealed & purged. And obviously you want a time delay after re-sealing to re-establish pressure and exchange any vapors that may have crept in, before throwing the switch again.
Is there a standard practice for setting one of these up? I could comply with each requirement of NFPA 496 several different ways, but the inspector won't fuss as much if your choice is what everybody else does, and uses components that everyone else uses.
Matt