All conductors including the Grounded conductor Must be broken. 480 Volt 3 phase (Transformer mini power center) to 120-208 volt secondary Panel that feeds pumps & dispensor circuits. Shunt trip the Primary (480 volt 3 phase) thur Emergency stop button. Completely Shuts dn Panel feed to 120/208 volt off. Does this meet the intent of the code? (Never saw it done this way )??
I'm with vindiceptor. Killing the source of the primary does not disconnect the grounded conductor on the secondary side. 514.11(a) also refers to the "source of supply". In a separately derived system that's the secondary coil, not the primary.
Vin: We have to debate the word 'breaking' as in the opening of a knife switch, as opposed to 'de-energizing' all conductors.
Greg: Yes, there is no physical disconnection of the grounded conductors, but there also is no voltage potential within the fictious panel.
As I said above, "seems to, sort of'. Would I accept this setup IF prsented on a set of PE/EE signed and sealed plans? I cannot say that I would or would not at this time.
Note that in the 2011 this section was modified to:
514.11 Circuit Disconnects. (A) General. Each circuit leading to or through dispensing equipment, including all associated power, communications, data, and video circuits, and equipment for remote pumping systems, shall be provided with a clearly identified and readily accessible switch or other approved means, located remote from the dispensing devices, to disconnect simultaneously from the source of supply, all conductors of the circuits, including the grounded conductor, if any.
The wording "or other approved means" IMHO will result with a manufactured control panel that will 'kill' everything within the dispensers.
I don't think we have to debate the word at all. According to the section you posted above, it doesnt matter which method is used to "disconnect simultaneously from the SOURCE OF SUPPLY, all conductors of the circuits, including the grounded conductor, if any." Opening the circuit on the primary side of a transformer does not disconnect the grounded conductor from its source of supply, which is the secondary coil. The fact that there is no voltage potential when the primary is disconnected is not germain to the question.
The Source of the Grounded conductor is on the Load side of the transformer. The Grounded conductor does not exist on XO till the 120/208 exist. A Grounding conductor existing on the Primary feeder side but NOT a grounded conductor.
I believe the reasoning for disconnecting the grounded conductor was required to prevent any possibility of electrical energy to be present within the dispensers. Hence, the availability of a cb with the facility to 'open' the neutral conductor.
The assured elimination of all electrical energy within the dispenser is, IMHO the intent of 514.11. Both for service and maintenance of the dispenser, via the circuit breaker for the dispenser/item requiring maintenance AND in emergency situations, the EPO which kills ALL power to the fuel islands. We seem to agree on this.
The OP leads me to follow the scenario for the EPO, which, again IMHO should be compliant via the termination of the transformer primary. This method must not affect any life safety items when the EPO is activated.