Pushbuttons

[zinc]

I am familiar with explosion proof pushbuttons and enclosures, but I am very unclear about pressurized enclosures!! Are standard pushbuttons permitted in a pressurized enclosure, with approved monitoring, in Class II Div 1?

 

[don_resqcapt19]

For Class II installations, you probably have no need of a pruged or pressurized enclosure. Standard pushbuttons are permitted in "dust-ignitionproof" enclosures.
If you are really asking about a Class I, Division 1 location, then, yes you can use standard pushbuttons in a pressurized enclosure, but you need more than just monitoring to change from Division 1 to non-hazardous. You need to have a an automatic disconnect of the power to the pressurized enclosure on loss of pressure. This relay or contactor will have to be in an explosionproof enclosure or installed in a non-classified area.

 

[zinc]

Thank you, Don. The installation is in China; the Local Design Institute is a bit anal about combustible dust; they have their own Zone Classification which is loosely based on other standards groups. I would just like to be able to point to documentation of this permission in NFPA. I can't find it in NFPA 70; is this (non-rated pushbuttons, etc.) specified in NFPA 496, would you know? Thanks again!

 

[zinc]

I would just like to be able to point out the documentation of this permission (non-rated pushbuttons, etc.) in NFPA. I can't find it in NFPA 70; is this specified in NFPA 496? Would anyone be able to answer this question?
Another vendor told me it was not permitted!
Thanks again!

 

[don_resqcapt19]

The NEC only requires that the enclosure for a push button or other type of switch be dust tight.

502.115(B) Class II, Division 2 In Class II, Division 2 locations, enclosures for fuses, switches, circuit breakers, and motor controllers, including pushbuttons, relays, and similar devices, shall be dusttight.