Sizing Service Conductors - 3 Phase

[blaze1389]

Would anyone have an example for sizing service conductors for a 3-phase over current protection device? I am looking specifically for 2000 amp systems. Thank you in advance. I am referencing table 310, but just want to run through the motion with an example question.

 

[don_resqcapt19]

Not sure what you are asking about. I don't find a 250.56 in my book.

 

[blaze1389]

Not sure what you are asking about. I don't find a 250.56 in my book.

Not sure what you are asking about. I don't find a 250.56 in my book.

Typo. Table 310 is what I meant.

 

[augie47]

Is there a calculated load and is there a main overcurrent device involved ?

 

[kwired]

Is there a calculated load and is there a main overcurrent device involved ?

That is about first thing needed to know. Single overcurrent device of 2000 amps - you must have no less than 2000 ampacity of conductor.

Multiple service disconnecting means supplied by one set of conductors (where permitted) you can have conductor ampacity that matches the calculated load, even if the sum of overcurrent protection is more than that supply conductor ampacity. Individual taps to each disconnect must still be in accordance with overcurrent rating of each device though.

 

[infinity]

Would anyone have an example for sizing service conductors for a 3-phase over current protection device? I am looking specifically for 2000 amp systems. Thank you in advance. I am referencing table 310, but just want to run through the motion with an example question.

Since you're over 800 amps you need a minimum of 2000 amps worth of conductors. We would use 5 sets of 600 kcmil copper (420*5=2100 amps)

 

[blaze1389]

Since you're over 800 amps you need a minimum of 2000 amps worth of conductors. We would use 5 sets of 600 kcmil copper (420*5=2100 amps)

Any reason you would not use 5 sets of 500 kcmil?

 

[don_resqcapt19]

Any reason you would not use 5 sets of 500 kcmil?

That is only 1900 amps....5 x 380

 

[infinity]

That is only 1900 amps....5 x 380

My reason exactly.
You would need 6 sets with 500 kcmil.

 

[kwired]

Any reason you would not use 5 sets of 500 kcmil?

As I mentioned earlier, for a single 2000 amp service disconnect you must have 2000 amp or more ampacity conductor.

But if you have 2-6 service disconnects that net at 2000 amps, you only need conductor ampacity (on a common supply conductor) greater or equal to the calculated load.