emergency shutdown

[petersonra]

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.

 

[texie]

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.

 

[petersonra]

Yes. See 514.11.

so what is the thinking on this? why would you need to open up the grounded conductor?

 

[texie]

so what is the thinking on this? why would you need to open up the grounded conductor?

Not sure but it has been there since dirt was invented I think. It is an easy one for me only 'cause I used to do a lot of gas stations.

 

[don_resqcapt19]

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.

 

[hillbilly1]

They even make breakers that have a contact built in that breaks the nuetral.

 

[Cow]

They even make breakers that have a contact built in that breaks the nuetral.

One of our supply houses calls those 2 pole switched neutral breakers "gas pump breakers".