Tap rule for jockey pump

[cppoly]

What do you do when running a feeder to serve a very large HP fire pump with a small jockey pump where the jockey pump conductors are tapped from this feeder? For instance, if you have a 2000 amp OCPD and you need to tap this feeder to serve the jockey pump, you would then need 200 amp tap conductors just to serve a 3 HP jockey pump assuming <10'?

 

[gadfly56]

What do you do when running a feeder to serve a very large HP fire pump with a small jockey pump where the jockey pump conductors are tapped from this feeder? For instance, if you have a 2000 amp OCPD and you need to tap this feeder to serve the jockey pump, you would then need 200 amp tap conductors just to serve a 3 HP jockey pump assuming <10'?

Just because the OCPD is 2000 amps doesn't mean your taps need to be 200 amp. Remember, the OCPD (I assume this is a fused disconnect) is sized for the locked rotor current of the largest fire pump and jockey pump and the FLA of all other pumps, motors, and auxiliary loads. At 2000 amps, at 460 3 phase you have a fire pump at about 275 HP. The conductors will be sized for the fire pump, jockey pump (all at 125% FLA), and auxiliary loads at 100%.

 

[cppoly]

Thanks, but the tap rule for <10' indicates the tap conductors need to be sized at 1/10th of the feeder OCPD right? 2,000A OCPD would be 200 amp minimum conductor ampacity.