3 Phase 800A Service Feeder Sizing per load

[husmball1974]

3 phase system 480vac
Two independent loads coming from same pad-mount transformer.
Each Load has a Main Breaker @ 800A .

One load is 280A with 800A Main Breaker
One load is 357A with 800A Main Breaker

Naturally thinking that parallel runs of 3c 500 MCM for each unit (2 - 3c cables per each breaker)
But with the oversizing of the Main Breakers as compared to the lighter load, 1 cable to each Main would be sufficient for continuous current carrying capabilities but I am not 100% if it is up to code or not.

 

[augie47]

If your service conductors terminate on an overcurrent device they must have an ampacity based on the rating or setting of that device. 230.90
Unless you can change the rating plug of that breaker or adjustment {per 240.6(C)} you will need to base your ampacity on the 800 amp breaker.

Is it a 480/277 pad ??

 

[kwired]

If your service conductors terminate on an overcurrent device they must have an ampacity based on the rating or setting of that device. 230.42(B)

If they terminate on individual OCPD.

If you paralleled service conductors but made taps to the two individual devices each tap still would need to be an 800 amp conductor but the common conductor when more than one service disconnect only needs sized to load calculation.

 

[husmball1974]

Thanks augie47
yes 230.42(B) says directly what needs to happen.
Thanks again !!