Selective Coordination OCPD 200 amp dialed down to 80 amps.

[Gategator37]

This applies to emergency power on a backup generator.

I have an 80 amp OCPD feeding a downstream 200 amp OCPD (selectively coordinated) which is dialed down to 80 amps. Since the 200 amp OCPD has the possibility of being dialed back to the full 200 amps do the feeder conductors have to be sized to 200 amps (#3/0) or can they be sized at 80 amps (#3)? I cannot find a code requirement for this type of question.

 

[zog]

Look at 240.6(C)

 

[Gategator37]

Thanks. That is exactly what I was looking for.

 

[david luchini]

The conductors are protected at the point they receive their supply with an 80A OCPD. The conductors need only be sized for the 80A, regardless of whether the downstream OCPD is dialed up to 200A. The conductors downstream from the 200A c/b will have to comply with 240.6(B) or (C).