Originally Posted by jaketoby
The non incendive wiring going to the switch has inductance and capacitance associated with the wiring. Is this a concern? The energy going to the switch is not limited by a Class 1 2,or 3 circuit. This system , the voltage and current could surge above the switch limit. The switch is in a class 1 div 2 group A.
If it weren?t for the Group A, I wouldn?t even bat an eye; as it is, batting an eye is still all I would do.
Assuming the location is properly classified ?Division 2? and the wiring and components are consistent with the concepts of ISA 12.12.01 then it is irrelevant whether the system is powered by a Class 1, 2 or 3 power supply or not. In fact, none of the wiring methods described in Article 725 make an inherent difference at all since they must still comply with Articles 500 through 516. They may be low powered with regard to general shock and fire hazards, but they still are fully capable of being an ignition source for Classified materials, especially Group A. See Sectin 725.3(D).
Philosophically though, if Division 2 is the proper classification, and the various nonincendive protection techniques legitimately applied, the amount of energy the system could deliver under unusual conditions is not a reason for concern. Under Division 2 concepts, the ignitable mixture
should not be present under normal conditions, so an uncommon condition in the protection technique still has nothing to ignite. If there is reason to believe the events would be simultaneous, then it would be a Division 1 location and nonincendive an inappropriate protection technique.
BTW ? I?m out of the country ATM and don?t have access to my regular library. So I may or may not be able to respond quickly to any followup questions.
__________________
"Bob"
Robert B. Alexander, P.E.
