2008 NEC 240.13 - Ground Fault Protection of Equipment

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lmcgill

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Hello All, I was wondering if someone could help me. I hope I posted this in the right forum. Anyway, I am an electrical designer, and working on a project that needs a new 480V - 1200A service. Based on NEC 2008 240.13 - the service needs ground fault protection. So, if I specify a SQ D Micrologic 6.0A trip unit in the 1200 amp main breaker for the new service, what would you recommended for the trip settings?

? Long time pick up
? Long time delay
? Short time pick up
? Short time delay
? Instantaneous
? Ground fault pickup
? Ground fault delay

Any help would be appretiated. Thank you.
 
lmcgill said:
Hello All, I was wondering if someone could help me. I hope I posted this in the right forum. Anyway, I am an electrical designer, and working on a project that needs a new 480V - 1200A service. Based on NEC 2008 240.13 - the service needs ground fault protection. So, if I specify a SQ D Micrologic 6.0A trip unit in the 1200 amp main breaker for the new service, what would you recommended for the trip settings?

? Long time pick up
? Long time delay
? Short time pick up
? Short time delay
? Instantaneous
? Ground fault pickup
? Ground fault delay

Any help would be appreciated. Thank you.
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Has a coordination study been done?

There is no one size fits all answer here, there are countless variables that go into those settings.
 
As Bob has said, there are many variables into setting a GF system up, the last one we were involved with was at a theater and they had the manufacture schedule an engineer who was familiar with doing coordinated studies, the object is to get all the breakers to work together so that when a low amperage circuit down stream in a sub panel faults to ground it don't take the main GFP out shutting down the whole system, so this is why it requires an engineers stamp otherwise your putting allot of liability on yourself.
 
lmcgill said:
Thanks guys, a coordination study has not been done, so I guess I'll look into that. Thanks,
Click to expand...

Have you looked into the possibility of using two 600 amp mains in lieu of a single 1200 amp main? By doing this, you can avoid the additional cost of the GFPE and the sometimes very difficult device coordination.
 
How about a MLO panel with no more than (6) breakers and none 1000 amps or larger ?
 
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