emergency shutdown

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petersonra

Senior Member
Location
Northern illinois
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Semi-retired engineer
The other day I got a drawing showing an ESD circuit - 120VAC - with a note that says both the line and neutral has to be opened. Are there any cases in the NEC where this is required? or even allowed? it appears like they want to tap off the control panel transformer to power up part of a fuel dispensing system from the sketch. don't do much in the way of fuel dispensing systems so maybe this is common in that kind of system.
 
The other day I got a drawing showing an ESD circuit - 120VAC - with a note that says both the line and neutral has to be opened. Are there any cases in the NEC where this is required? or even allowed? it appears like they want to tap off the control panel transformer to power up part of a fuel dispensing system from the sketch. don't do much in the way of fuel dispensing systems so maybe this is common in that kind of system.

Yes. See 514.11.
 
so what is the thinking on this? why would you need to open up the grounded conductor?
If you are working on the gas dispensing equipment you can create an arc if you cause the grounded conductor to make contact with the metal parts of the gas dispensing equipment. This can't happen if the grounded conductor has been isolated from the electrical system.
 
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