Sizing Equipment Grounding Conductor Wire

[aramg83]

Hello,

If you were told to size the equipment grounding conductor wire to and from a 400A disconnect switch with a 250A fuse would you size it based on the switch rating or the fuse?

If I had to guess, I'd say the fuse for the current installation, but what about future consideration? If it were your building, would you prefer the egc be sized for the full 400A in case you later wanted to swap the fuse for a larger one?

Thanks

 

[Dennis Alwon]

T. 250.122 will show you that the EGC is based on the OCPD rating. In your case 250amps

 

[Keri_WW]

Size to the 250A fuse. You would not size your feeders for the 400A frame size on the disconnect (or for panelboards, etc.), not to mention the GEC.

 

[dcspector]

Hello,

If you were told to size the equipment grounding conductor wire to and from a 400A disconnect switch with a 250A fuse would you size it based on the switch rating or the fuse?

If I had to guess, I'd say the fuse for the current installation, but what about future consideration? If it were your building, would you prefer the egc be sized for the full 400A in case you later wanted to swap the fuse for a larger one?

Thanks

Just don't forget about 250.122 (B) If you sized the ungrounded conductors for the 400 amp OCPD. Just a thought.

 

[bphgravity]

Equipment buss / frames are quite often rated higher than the feeder(s) and/or branch circuits supplied. EGC's are based on overcurrent protection rating of the circuit in question.

 

[dcspector]

Equipment buss / frames are quite often rated higher than the feeder(s) and/or branch circuits supplied. EGC's are based on overcurrent protection rating of the circuit in question.

Bryan was that meant for me?