E Stop Requirements NEC 514.11

mtdt

New User
Here’s my question:

We have multiple state owned & operated self serve fuel dispensing sites. According to 2014 NEC 514.11 all power, communication, etc needs to be shut down when the emergency stop is activated. We accomplish this with a contactor that disrupts power (& neutral) to the power panel that supplies all the circuits to the fuel island. The E stop switch keeps the contactor energized and, when activated, de-energizes the contactor.
We also have a fuel equipment/tank monitoring system that monitors tank levels, leak detection, etc. This TMS uses intrinsically safe field wiring and sensors. The design folks have powered the TMS from the fuel system power panel. When the Estop is activated the TMS is also shut down which causes us to loose all ability to know what's going on at the fuel equipment. My view is that since the TMS field wiring is intrinsically safe, it should be exempt from the shutdown requirements in 514.11. Neither this article or article 504 (intrinsically safe systems) address this. What is your interpretation? I believe the2017 NEC may clarify this.
Thank you for your generous contribution the the electrical trade with all the resources you provide.
 

don_resqcapt19

Moderator
Staff member
Location
Illinois
The 17 code added an exception for IS circuits.
Exception: Intrinsically safe electrical equipment need not meet this requirement. [30A:6.7]
NFPA 30A, Code for Motor Fuel Dispensing Facilities and Repair Garages is the controlling document. This exception came from 30A. The exception has been NFPA® 30A since before the 2012 edition of that document. The numbers in brackets following this exception tells you that the rule came from section 6.7 of NFPA 30A. When the NEC brings the rules in from the controlling standard, the NEC cannot make changes in the rule. It probably should have been added to the NEC right after it was added to 30A.

Based on the rule in NFPA 30A and in the 2017 NEC, maybe your AHJ would permit you to use the exception and not disconnect the IS circuits.
 
Top