05' Nec 250.122(b)

[dcspector]

Correct me if I am wrong. Example: Elevator disconnect 200 amp OCPD. For whatever reason they installed 750 kcmil Al with a #4 Al EGC. VD is not an issue. They could have used per 310.16 250 kcmil AL with a #4 Al EGC per 250.122. I took The circular mils 750 divided by 250 circular mils=3.0 then #4 EGC circular mils(41740) x 3.0=125220 circular mils which per Tbl. 8 that is greater than a 1/0 so one would use 2/0 EGC.

Thanks all.

 

[iwire]

IMO you are correct

 

[dcspector]

Thanks Bob.....EC installed and EE approved. I cited it and left it up to the EE. I wanted to make sure.

 

[mdshunk]

I've seen a good many elevators served with really oversized conductors when it's not all that far to the service equipment. Do they do this to help prevent winking the lights when the pump comes on?

 

[iwire]

I've seen a good many elevators served with really oversized conductors when it's not all that far to the service equipment. Do they do this to help prevent winking the lights when the pump comes on?

Actually that is more likely to cause voltage dips on the service then if they ran 'just big enough' conductors for the elevator feeder.