OK. It's an emergency requirement. If it were only for maintenance, it would be a general requirement throughout hazardous locations - at least for Division 1.
Originally Posted by Dr Duke
Basically, in an emergency all conductors to a dispenser must be isolated. The theory is there is a potential "surge" backfeed through the grounded conductor which could possibly arc in the Division 1 location. (Remember, the possibility, not necessarily the inevitability, of an arc is all that matters in Division 1.)
Where you are right is the pushbutton itself need only be the actuator for the device(s) that actually perform the "means" for isolating the conductors.
It should be noted this is a residual philosophy from the NFPA 30A Technical Committee and its predecessors and has been for many decades. Code Making Panel 14 has little control of the content of Article 514. They can only make sure it is not in direct conflict with the rest of Articles 500 to 504. See Sections 510.1 and 501.2.
Robert B. Alexander, P.E.
Answers based on 2014 NEC unless otherwise noted.